The BSA A7-A10 Forum

Technical => A7 & A10 Engine => Topic started by: a101960 on 30.10. 2009 10:03

Title: Pinking (pinging)
Post by: a101960 on 30.10. 2009 10:03
Does anyone have any ideas or observations about eliminating pinking (pinging)? I have an  ally big valve head, a 389 carb fitted with 23 pilot, 420 main jet .106 needle, and a number 3 slide. I have retimed the engine so many times now that the mag drives jumps off the shaft just by whistling at it! At 35 degrees (15/16) BTDC the engine is way over advanced, and the same applies at 34 degrees. I have tried 32 degrees BTDC and there is no pinking but the engine is flat and has no performance. Today I intend to set the timing up at 33 BTDC. I have tried it at this setting before but it still pinked on gradients. This has been an on going problem for ages and I can honestly say that it is detracting from the pleasure of riding the bike. I am paranoid about damaging the engine. I have considered swapping to a manual mag. This would allow some adjustment but, I am beginning to wonder if the compression is to high. I do not know what pistons are fitted, but they have slightly raised crowns and are flat topped with small cut outs in them, so I am guessing that they are probably  eight twenty five to one. Before I go to the expense and all the hassle of fitting new pistons does anyone think that this might be worthwhile? While I realise that fettling is part of the territory that goes with owning an old bike, I am getting a bit tired of constantly playing with the timing and getting nowhere. When the engine is set at 35 degrees BTDC it goes like?.er?a rocket, but the engine always feels harsh, it also intermittently kicks back when starting. To not put to finer point on it I am getting so fed up with it that I am contemplating getting rid of the bike and buying something that is a bit less of a Prim Donna. By the way I always run on 99 RON petrol.
Title: Re: Pinking (pinging)
Post by: a101960 on 30.10. 2009 10:16
Some additional information: I have had the mag and auto advance unit checked out by Tony Cooper ( I actually visited him) and he said to me that he would be quite happy to fit the mag and A/R unit to his bike, so a clean bill of health on that then. The plugs I use are either Champion N4C or B7ES.
Title: Re: Pinking (pinging)
Post by: Josh Cox on 30.10. 2009 10:20
Do not claim to be an expert, but if it was me, I'd:

Ensure the fuel is less than 12 months since purchase ( preferably highest octane at the bowser ),

Screw the mixture "full Rich" (screw all the way in ?),

Clean and regap plugs.

Does the the pinking happen when the engine is cold or hot, or both ?.

Is the pinking both cylinders ( run the engine at rpm, spray CRC or similar of the top of the exhaust pipe at the cylinder head, if one cylinder is running hotter than the other, the burn/smoke difference will be noticable, you could use an infared heat sensor to tell you this, CRC is more fun).

Does it pink at a certain RPM, at any stable RPM or whilst varying RPM ?.

Look forward to your response, don't give up on the old girl, this is her having PMT.
Title: Re: Pinking (pinging)
Post by: a101960 on 30.10. 2009 10:34
The pinking happens under load, going up gradients for example when I open in top gear to maintain speed. If I change down then it seems to go away. I use the highest octane petrol that I can get my hands on. The exhaust pipes are still chrome with no discolouration. After a run there is a very slight yellowish discolouration that vanishes once the motor has cooled down. The plug colour looks O.K. to me (coffee colour). Incidentally when I set the timing up I use an electronic LED module so it is about as accurate as could be reasonably expected. I am running the mixture a bit on the rich side. I am totally stumped!
Title: Re: Pinking (pinging)
Post by: A10Boy on 30.10. 2009 11:16
When was the last time it had a de-coke?
Title: Re: Pinking (pinging)
Post by: RichardL on 30.10. 2009 11:37
Is "15/16" at 35 deg. a typographical error? I can't say I know the angles that go with the distances, but "5/16" is more likely. If you are timing near 15/16" BTDC, it sounds like you might have the timing wheel incorrectly attached. Since you seem to have eliminated the usual suspects, another thing that comes to mind is the possibility of timing gears being off a bit, maybe one tooth.

One thing I am rather certain of, your bike is not haunted. There is, indeed, a reason for the problem and you will eventually find that reason. Maybe someone who is not guessing, as I am, will give the exact answer while I'm typing. There are lots of bikes out there with higher compression than yours that don't ping (I am in the U.S., after all, so, not "pink"). Mine is one of them at 9:1. I think I can speak for a lot of members here in saying, "hang in there, we enjoy the company."

Richard L.
Title: Re: Pinking (pinging)
Post by: Triton Thrasher on 30.10. 2009 14:49
Have you tried raising the needle in the throttle slide?
Title: Re: Pinking (pinging)
Post by: groily on 30.10. 2009 16:22
Would it be worth running the thing up a hill at speed under load to promote the pinging, cutting it dead while it's doing it and doing a plug chop roadside? If they're far off the coffee colour you describe, then it might well be worth raising the needle a notch. Could also try B8s or N3s I guess, but doubt it would make much odds.
No air leak at carb to head, deliberately arranged to fool you because it only causes grief when the motor's sucking hard? No funny gizmos in the plug leads sold by snake-oil persons as spark-enhancers?
Like Richard, also wondered about your 15/16ths - which would account for no end of hassles, including trying to break your leg when starting. But if you're using a timing disc anyway, does look like a misprint.
I wouldn't put on a manual mag with the deliberate intention of running it at less than full advance most of the time, as the spark weakens appreciably as you retard it. Manual ones are set up to spark best at full advance, fixed ones always spark optimally. Better to do the 'Orabanda slotted-hole mod' (see recent threads) to get some moderate (few degrees) adjustment?

Title: Re: Pinking (pinging)
Post by: chaterlea25 on 30.10. 2009 17:30
Hi, a101960
My Super Rocket behaved very much like yours for a long time
I would feel BSA fitted a manual mag to the SR etc for a reason!!!! (mine has)
If your bike is kicking back it means the A/R mech is not doing what it should

You are saying you are using 99 octane petrol
Personally I dont believe such a product exists!!! I believe the oil companies dish out any old crap and charge a premium for calling it 99 octane.

To stop my SR from pink(g)ing I used to add octane booster,
I did not find valvemaster plus much good at the recommended dose!! so I upped it 2 or 3 times the reccomdation this gave some improvement,
I had better results using Acetone with a wee drop of 2 stroke oil mixed in
maybe 50ml to a tank full.

The final cure came when I changed out the Lucas mag to a BTH (manual)
This is not a straightforward job,  see the post I put here on the forum.

I really dont know for sure why the BTH cured the problem????????
But it gives a way better spark at low revs (kicking over)
and way better acceleration and power, with the same timing figure, 35degrees

I'm just thinking as I write this, have you connected a strobe to your bike
Its a good way to see if there are any misfires when you rev the bike it will also check how well the A/R  unit is working
I have sorted out quite a few mysterious problems on various bikes /cars just by looking
at the strobe light pattern, its very easy to see erratic behaviour on one cylinder at a time
What about the tension on the points spring? maybe the points are floating a bit when the revs are up causing over advanced timing????
HTH
Regards
John O R


Title: Re: Pinking (pinging)
Post by: muskrat on 30.10. 2009 18:55
G'day A101960, like John O R says strobing is the best way to time the spark. Pinging and kick back is caused by too much advance at both ends of the curve. I run 31 deg on the A7 with 8:1 and 33 on the A10 with 10.5:1. I also boost our premium (98oct) unleaded with Nulon pro octane boost to about 105 and add a cap of R30 per tank (mmm that smell). A bit of a pain but the ride is worth it. most old bikes will ping on unleaded, even my Rhonda Whore had to be retarded by about 4 deg. Richening the needle & main jet may also help. All the replies have merit, just work your way through them, don't give up. The ride is worth it.
Cheers
Title: Re: Pinking (pinging)
Post by: Richard on 30.10. 2009 19:15
John
Dont bother mucking about with it any more, you know its not worth it, give it to me it likes my garage anyway.
Retime it to 32/33 degree's meet up with us on Saturday at the Esso garage at Chisledon tomorrow (Saturday) at 11am  for the Fish and Chip run and then let me see how it goes and you can try my Super Rocket which does not have the big valve head but the standard vales for a S/R then at least we will have something to go by and if it goes as well as mine at 32 or 33 degrees without pinking then you have nothing to worry about.
bring some basic tools and if needed we can raise the needle by one notch which will if I am correct give more fuel when you open the throttle to go up inclines which should stop the pinking if it is fuel related.
Ring me and let me know if you will be coming
Richard
Title: Re: Pinking (pinging)
Post by: a10gf on 30.10. 2009 21:11
Be 200% sure the auto advance behaves properly, to eliminate it completely form the equation.

groily:
Quote
I wouldn't put on a manual mag with the deliberate intention of running it at less than full advance most of the time, as the spark weakens appreciably as you retard it.
I'm no expert, but seems to me that with a mag in decent condition the spark will always be strong enough as long as timing is roughly within spec (but very high compression could have an impact, am on 7.5. No spark problem at full retard, would not start if so). So IMO, no harm in trying out manual control.

Title: Re: Pinking (pinging)
Post by: BSA_54A10 on 30.10. 2009 21:16
Get a new slide with a small cut away.
Run up your "test hill " .
If it pinks then pull the slide and increase the size of the cut away.
Repeat till pinking stops.

The original carb was designed to work with "real" petrol which modern "fuel" bears only a vague resembelence to, so all of the factory settings should be regarded as a starting point for tuning and not the correct "set in concrete" correct settings.

Do not use a bunch of different slides unless they are all brand new because different wear in the slides will change the volume of air drawn down the sides so you could end up with more than one variable and these problems are only soluable by changing one thing at a time.

The cut away acts as a acceleration pump and enritchens the mix as you open the throttle.
It is a right royal PIA job to do but worth while .

All of the other stuff, in particular the freshness of the fuel and the addition of acetone are all to be considered.
Basically the compression ratio and combustion chamber shape in your engine are not compatable with modern fuels.
And the same applies to the magneto. It only just has enough power to ingnite the current fuels that have a much lower amount of high volatiles so require a lot more energy to ignite and do not atomize properly in the carb as they are designed  to be pressure injected into engines that operate at much higher cylinder temperatures than your BSA can cope with.
  
Title: Re: Pinking (pinging)
Post by: mike667 on 30.10. 2009 22:57
Have you tried raising the needle in the throttle slide?

this what i did  and cured my pinging  too, which was occurring similar to yours on my A10. I also had a similar problem in my commando and put in the next size bigger needle jet  - worked beautiful on that also - both changes enriched the mixture, although in different ways

 
Title: Re: Pinking (pinging)
Post by: Triton Thrasher on 31.10. 2009 08:10
Get a new slide with a small cut away.
Run up your "test hill " .
If it pinks then pull the slide and increase the size of the cut away.
Repeat till pinking stops.
  

Increased cutaway weakens the mixture, which raises temperature, making pinking worse.

A weak slide doesn't usually cause serious pinking, because it is only controls mixture  up to about 1/4 throttle, or maybe less.  Bad pinking is that which is persistent at moderate rpm (and higher rpm) while the engine is pulling.  Your engine can be damaged badly.
Title: Re: Pinking (pinging)
Post by: beezalex on 31.10. 2009 11:51
First of all, we need to clear up what CAUSES "pinging".  What we're really talking about here is detonation and it occurs when the combination of pressure and temperature in the combustion chamber exceeds the spontaneous ignition point of the fuel.  To prevent the fuel from detonating you can do three things:  Lower the pressure, lower the temperature or change fuel to one that has a higher ignition point.   Lean mixture causes excess heat, so you first need to make sure that your mixture is correct...mainly on the needle. Going too rich can alleviate pinging, but it's a formula of diminishing returns and eventually causes carbon buildup which causes an even higher propensity for pinging.  Get your timing right (too much advance can also raise heat), get your mixture right, then if it still pings, decarbonize and polish piston crowns and combustion chamber.  Also, remove any sharp edges from around the valve cutouts on the piston.  This removes localized hot spots and origin points for detonation.  This has worked for me 100% of the time that I have done it.  If, however, this still doesn't do it, you can lower the compression ratio by either changing pistons, installing a spacer under the barrel or installing a thicker head gasket.  1 mm lowers compression by about 1 point.  This has also worked for me in the past until I realized how effective massaging the chamber was.

Good luck.
Title: Re: Pinking (pinging)
Post by: mike667 on 31.10. 2009 16:37
First of all, we need to clear up what CAUSES "pinging".  What we're really talking about here is detonation and it occurs when the combination of pressure and temperature in the combustion chamber exceeds the spontaneous ignition point of the fuel.  To prevent the fuel from detonating you can do three things:  Lower the pressure, lower the temperature or change fuel to one that has a higher ignition point.   Lean mixture causes excess heat, so you first need to make sure that your mixture is correct...mainly on the needle. Going too rich can alleviate pinging, but it's a formula of diminishing returns and eventually causes carbon buildup which causes an even higher propensity for pinging.  Get your timing right (too much advance can also raise heat), get your mixture right, then if it still pings, decarbonize and polish piston crowns and combustion chamber.  Also, remove any sharp edges from around the valve cutouts on the piston.  This removes localized hot spots and origin points for detonation.  This has worked for me 100% of the time that I have done it.  If, however, this still doesn't do it, you can lower the compression ratio by either changing pistons, installing a spacer under the barrel or installing a thicker head gasket.  1 mm lowers compression by about 1 point.  This has also worked for me in the past until I realized how effective massaging the chamber was.

Good luck.

 excellent points as always alex!
Title: Re: Pinking (pinging)
Post by: muskrat on 31.10. 2009 19:15
Good one Alex, indexing the plug can also help.
Cheers
Title: Re: Pinking (pinging)
Post by: nigeldtr on 01.11. 2009 18:17
I hope this fits with the thread ? if not sorry!

I have been looking around to buy a Road Rocket, but I have been put off a little by the problems associated with high compression, and racy cams. Does it really make that much difference to performance (cam ? compression) especially as I will probably not keep the engine bubbling at the sort of revs where a racy cam comes into effect?

Your experiences and advice on what to look out for would be greatly appreciated.

Regards

Nigel
Title: Re: Pinking (pinging)
Post by: muskrat on 01.11. 2009 19:13
G'day Nigel,
                It does make a difference to performance BUT. A highly tuned motor puts more stress on its components and needs a bit more fettling to stay tuned. Factory settings go out the window.
Start with a std model and work your way up if you want more go later.
Cheers
Title: Re: Pinking (pinging)
Post by: chaterlea25 on 01.11. 2009 19:18
Hi Nigel,
Dont worry!
Normal well tuned and sorted Rockets and Super Rockets are extremely flexible and willing!
Mine will pull away from low revs in top gear without complaint.
They are nowhere as fussy as a tuned single cylinder bike
HTH
John O R
Title: Re: Pinking (pinging)
Post by: a101960 on 01.11. 2009 20:00
Agreed. the engine is not some highly strung inflexible unit that is a liability for every day use, but it is quite noticeable when it does come on cam. Regarding my own engine I have today removed the 420 main jet and fitted a 430 that I have yet to try out (the weather today has precluded that). I will let you know what improvement there is or not as the case may be as soon as I get the opportunity.
Title: Re: Pinking (pinging)
Post by: Richard on 01.11. 2009 22:45
dont forget to mark the 1/4 incriments on the twistgrip
Richard
Title: Re: Pinking (pinging)
Post by: a101960 on 06.11. 2009 21:02
(https://www.a7a10.net/forum/proxy.php?request=http%3A%2F%2F&hash=d56b4b7995135993e6b438e299f2e6c5)
Following on from from what I originally said about the pistons in my engine here is a picture of them from when I stripped the top end down to de-coke it. What compression ratio do you think that they are? could they be 9:1? I know that it might be hard to say from a picture, but I thought that it might be worth asking the question anyway.
Title: Re: Pinking (pinging)
Post by: Brian on 06.11. 2009 21:24
To quote from the Hepolite catalogue,

6.5 - 1      Concave
7.25 - 1     Flat with valve pockets
8.5 - 1      Flat bevelled with valve pockets
9.5 - 1      Dome stepped with valve pockets


Yours are 8.5 - 1 
Title: Re: Pinking (pinging)
Post by: chaterlea25 on 06.11. 2009 21:32
Hi, a101960
The pistons look like the GPM pistons???, I think they are 8.25 or 8.3 to 1
More importantly it looks like one cylinder is running differently to the other???
The nearest to the camera is black and sooty while the other is not!
Check the ring gaps, even though there is no evidence of blow by on the photo
Check the valve guide clearances, look for oil leaking down a guide in the ports,or for a loose guide in the head
Also check if the ignition timing is the same on both cylinders
HTH
John O R
Title: Re: Pinking (pinging)
Post by: a101960 on 06.11. 2009 22:30
There was indeed a problem with the valve guides. The inlet guide was lose in the head. The head has now been overhauled by the Cylinder Head Shop. The valves and guides were replaced and new seats fitted. That is why there was such a build up on the crown. Oil was getting in due to the lose guide. You might not be to amazed to know that before the remedial work on the head was done there was a lot of blue smoke emitted from the exhaust pipe, and oil consumption was quite high. The smoke has now gone and oil consumption is virtually nil. I very rarely need to top the oil level up now. I have still not had a chance to see how the bike goes on the 430 main jet. I must say that it is a relief to learn that the compression is relatively modest. I am not sure what make the pistons are. What I do know is that they are Italian. Thanks for your help.
Title: Re: Pinking (pinging)
Post by: Brian on 06.11. 2009 23:35
If they are Italian there is a very good chance they are GPM and GPM pistons are amongst or even arguably the best you can buy.
Title: Re: Pinking (pinging)
Post by: chaterlea25 on 06.11. 2009 23:50
Hi again, a101960
You may find that a reduction in jet size will be in order!
This is because the new guides will have a much closer clearance to the valve stems
this very much reduces air leaking down the guides,
Did you get the guides with the oilseals fitted?
Cheers
John O R
Title: Re: Pinking (pinging)
Post by: a101960 on 07.11. 2009 09:30
The reason that I have fitted a 430 main jet is because no matter what I do with setting up the timing it pinks under load most specifically when going up gradients. What happens is I will hit the gradient in top gear doing about fifty or sixty say, and as I open up to maintain speed then the pinking starts. As I said at the start of this thread I have altered the timing so many times now without relieving the problem that I am totally lost as to what to do about it. It just seems logical to me to try the next size up main jet, especially in view of the fact that I always fill up with premium 99 octane petrol.
Title: Re: Pinking (pinging)
Post by: a10gf on 07.11. 2009 10:49
This must be a major irritation!

Still my only suggestion, triple check magneto and auto advance, things may happen as rpm rises, may look ok when setting timing and at idle\low rpm. Maybe borrow and fit a set in known perfect working condition, if only to completely eliminate the ignition as the possible cause.

Had uneven L\R timing and points 'bouncing' at higher rpm, not found before doing this (http://www.a7a10.net/forum/index.php?action=dlattach;topic=1375.0;attach=3134;image) and this (http://www.a7a10.net/forum/index.php?action=dlattach;topic=1375.0;attach=3136;image)

e
Title: Re: Pinking (pinging)
Post by: a101960 on 07.11. 2009 11:31
Quote
This must be a major irritation!
You have hit the nail on the head! The problem is I have had the mag and the A/R unit checked out by an acknowledged expert and he said they were both O.K. Now, that is not to say that he could be wrong, but the chap has a excellent reputation as being the best that there is for magneto work. I am reluctant to mess about with it myself on two counts. I do not really have much mechanical aptitude, and I therefore do not have the confidence to carry out this kind of work which would require a high degree of accuracy. I am beginning  to think that there is something fundamentally wrong with either the mag or the A/R unit, the problem is where do I get an a accurate diagnosis from?
Title: Re: Pinking (pinging)
Post by: RichardL on 07.11. 2009 13:16
John,

It might help if the members offering suggestions knew who your expert was. I realize that you are being appropriately diplomatic in not mentioning the name, but others here may have expereince with, or even be friends with him. No one would deny that you have have been most repectful of his name and expertise. Nevertheless, there are folks here with a lot of experience who might have other opinions of him. Otherwise, knowing the person, they might be able to pose the right questions for you to ask or, even, intercede on your behalf. (I would not be among those who know the man, being that I'm in Chicago.)

Richard L.
Title: Re: Pinking (pinging)
Post by: a101960 on 07.11. 2009 13:40
Richard,

No secret about who the man is: Tony Cooper. Tony has a enviable reputation and the general concensus is that he certainly does a good job on magneto overhaul and repairs. As it happens I have just been out for a quick ride (not far because the sky is looking very leaden). The exhaust note has lost the sharp bark that it had before but it seems to go reasonably well. Because the forecast is not to Kosher I did not have time to ride out to my nemesis: the infamous hill that gives me all this grief ( Richard from Mintey knows it well). Anyway I did not have any pinking but the acid test will be the this particular hill. I just hope that there is some clear weather before the local authority start putting grit on the roads.
Title: Re: Pinking (pinging)
Post by: Triton Thrasher on 07.11. 2009 13:54
Have you tried raising the needle in the throttle slide?
Title: Re: Pinking (pinging)
Post by: a101960 on 07.11. 2009 14:01
Triton Thrasher,

Yes I have tried raising the needle in the throttle slide and to honest I could not detect any difference.
Title: Re: Pinking (pinging)
Post by: RichardL on 07.11. 2009 14:06
We are going to have 67 deg. F. today in Chicago and I plan to take advantage of it.

As soon as I read the name, I recognized it from accolades here on the forum, and a search turned up a lot of them.

Richard L.
Title: Re: Pinking (pinging)
Post by: a10gf on 07.11. 2009 14:22
Quote
I do not really have much mechanical aptitude
After having sorted out this problem, you will!
"Problems are sources of knowledge"  ;)
Title: Re: Pinking (pinging)
Post by: Triton Thrasher on 07.11. 2009 17:55
Conventional wisdom says that if you're sure the mixture isn't weak and you're sure th timing is correct at all rpm, you may be using a compression ratio too high for your engine with the fuel you're using.
Title: Re: Pinking (pinging)
Post by: RichardL on 07.11. 2009 19:13
TT,

I seems hard to imagine that the 8.5:1 pistons are too much compression with the 99 "RON" petrol a101960 says he's using. Now, I'm not that familiar with the "RON" system you use in the UK. In the U.S., "regular" unleaded gasoline is 87 octane. I see that "ordinary" unleaded in the UK is 95 "RON". So, maybe this means the 99 RON is not so high in "octane" as the number implies. I look forward to being set straight on this.

Richard L.
Title: Re: Pinking (pinging)
Post by: Richard on 07.11. 2009 21:27
Richard
http://www.csgnetwork.com/octaneratecalc.html
Will this help
R
Title: Re: Pinking (pinging)
Post by: a101960 on 07.11. 2009 23:18
Richard,

99 RON = 99 octane   95 RON = 95 octane. 95 is regular petrol 99 is premium. We also have 97, and 98 and 100 octane lead petrol is on sale still at a few outlets. The problem is that it is the small independent guys that stock it, and they are becoming fewer and fewer because low volume sales make it uneconomic to stock. There is a very heavy tax penalty which makes it expensive. I always used to use it when my local filling station had it, but it is now no longer sold there.

John
Title: Re: Pinking (pinging)
Post by: Josh Cox on 07.11. 2009 23:34
100 Low Lead is easily available at any light aircraft airport, AVGAS.
Title: Re: Pinking (pinging)
Post by: muskrat on 08.11. 2009 07:28
Josh uses the enema tube to syphon his plane to fuel his bikes. Percs (sic) of the trade !
Title: Re: Pinking (pinging)
Post by: Triton Thrasher on 08.11. 2009 09:22
TT,

I seems hard to imagine that the 8.5:1 pistons are too much compression with the 99 "RON" petrol a101960 says he's using. Now, I'm not that familiar with the "RON" system you use in the UK. In the U.S., "regular" unleaded gasoline is 87 octane. I see that "ordinary" unleaded in the UK is 95 "RON". So, maybe this means the 99 RON is not so high in "octane" as the number implies. I look forward to being set straight on this.

Richard L.

I agree.  I'd have thought you'd maybe get away with "ordinary" unleaded at 8.5:1 in a 650 with alloy head.  I suspect something is making the engine overheat.

Timing should realy be checked up to high rpm with a strobe, which is a bit of a fiddle on a bike like an A10.  Points on a loose pivot can make the timing do strange things at speed.


Incidentally, isn't USA fuel rated by the MON octane number?  Which means your 87 might be our 95?

Just googled it and it might even be PON!


http://www.btinternet.com/~madmole/Reference/RONMONPON.html (http://www.btinternet.com/~madmole/Reference/RONMONPON.html)
Title: Re: Pinking (pinging)
Post by: RichardL on 08.11. 2009 13:28
Well, I don't know if it's really helping a101960, but I'm learning a lot, having read the whole Wikipedia topic "Octane Rating" ( http://en.wikipedia.org/wiki/Octane_rating#cite_note-6 ). I see where the 99 RON corresponds to the typical U.S. premium gas that I use with 9:1 pistons. As to the name of the method used for determining U.S. "octane", I found this:

"...in the United States, Canada and some other countries the headline number is the average of the RON and the MON, sometimes called the Anti-Knock Index (AKI), Road Octane Number (RdON), Pump Octane Number (PON), or (R+M)/2."

However, we just say "octane."

John (a101960),

I see that BP is trial marketing BP Ultimate 102 at a very limited number of outlets but I don't know if any of these are close to you. Nevertheless, I would not think that you should actually need to go that high in RON rating to cure the pings. It's the other possible causes that need to be eliminated.

While I think timing, mixture or coke are still the most likely culprits, I amuse myself by trying to think of obscure causes for problems. I wonder if anyone here has seen examples of head gaskets not quite made correctly, wherein a small bit overhangs the cylinder. (I can't say I've seen it.) Such an intrusion could cause detonation or pre-ignition.

Finally, for now, I think you were being too modest or, maybe, tongue-in-cheek, when you said you were not mechanically inclined. I went back and looked over several of your historic posts and I would have to say they show a lot of knowledge, interest and mechanical understanding. Maybe it's this sticky problem making you less "inclined" to dig into the engine, yet again. Hang in there.

Richard L. 
Title: Re: Pinking (pinging)
Post by: a101960 on 08.11. 2009 15:15
Richard,

I am O.K. with electrics, it's my job - aircraft electrician. I am O.K. stripping down and re-assembling (just a matter of common sense) however, machining and such stuff is way out of my league. I am a firm believer in not messing with tasks that are beyond my capabilities. I truly admire some of the projects undertaken by some of the members of this board, but I am only to aware of my limitations. Returning to the issue of pinking, I noticed that when "The Motorcycle" magazine road tested the RGS back in 1962 when 5 star leaded petrol was freely available the tester commented even than that the RGS was prone to this problem. I have also read somewhere that the A10 cylinder head design leaves much to be desired.

John
Title: Re: Pinking (pinging)
Post by: chaterlea25 on 08.11. 2009 17:14
HI John,
If the problem still exists after you have decoked the engine, try the simple solutions first,
add some octane booster,
I still wonder if the 99 octane petrol you buy has been sitting there too long due to not enough customers for it, it goes off fairly quickly
Try some colder running plugs  NGK B8's or equivalent.

Another thought does your bike have a siamise exhaust system and Goldie type silencer?
make sure there are no leaks on the exhaust system, (a bugger with the siamise setup)
I just wondered are you hearing the "goldie twitter"? or blow at a joint due to vibration/ stress at a certain speed

Have you checked the fuel flow from the tank / taps, carb banjo, etc to make sure you have a good and constant flow to the main jet,

I remember having to rebuild a Triumph T140 which holed a piston because the owner had'nt switched on the second petrol tap before going on a long dual carriageway journey,
Apparently at a certain speed /vibration level, fuel was not reaching the carb farthest away from the one tap that was on!
HTH
John O R
Title: Re: Pinking (pinging)
Post by: t20racerman on 22.08. 2011 19:23
Now that my A10 is run in and being thrashed I think I can add some thoughts and observations.

My bike has 9.1:1 pistons, spitfire cam, SRM crank, polished rods, nitrided crank etc and it has always been ridden hard. It has been off the road for 11 years, until recently, and always used to pink under load but not at constant fast cruising speed (70-85mph). I used to use normal 4* and simply stopped the pinking by backing off the manual timing a bit when loading it up.

It is now rebuilt but with gas flowed head and bigger 32mm concentric Carb.I took it for its first long and quick run this weekend and the pinking was awful. I too used 99 octane fuel. Without a manual advance and retard mechanism it would have been totally unrideable! (You need to get manual).

When cold it loves full advance and doesn't pink for the first 8-10 miles. After this it pinks badly under load AND at constant cruise mode too. To really accelerate fast you have to retard the ignition big time as you give it a handfull. You can then accelerate very quickly indeed - flying past cars, trucks etc. To maintain a fast speed you have to leave it retarded a fair bit too.

However when you slow down it coughs and splutters due to the retard and you have to advance the timing to ride slowly in traffic.  Seems odd, but for slow running I have a lot of advance, and a LOT of retard for high speed.

Seems to me that your only solution is the manual advance and retard - and like me you'll have to adjust the timing all the time on the move, and move it the opposite way to which you might expect!

Incidentally, my racing two strokes all have ignitions which retard as the revs rise.

EDIT
One other thing - I'm using the B10 something-or-other plugs out of my TZ350 as these are much cooler. I'm going to investigate cooler plugs that help prevent pinking in the near future.
Title: Re: Pinking (pinging)
Post by: A10Boy on 22.08. 2011 20:42
Totally different opinion.

The best solution in my view would be to ditch the 9:1 pistons and fit some nice 7.25:1 pistons and that's that. Way high compression in ancient engines with modern fuel just doesn't work.
I wonder why anyone would build an engine for road use that is virtually un rideable and would destroy itself with excessive detonation, it's beyond my understanding to be honest.  *conf*
Title: Re: Pinking (pinging)
Post by: bsa-bill on 22.08. 2011 20:59
Not un ridable Andy, my project went through a bit of pinking but mostly I managed to tune it out, but I have ditched the 9:1 in favour 8:5 mostly to try to get the thing to reliably start, this again is I reckon down to a maggie not being up to full spec.
There can't be any combinations of pistons, cam, whatever that have not been done over the years to these bikes but to a new owner (or not so new) it still a thrill to do it your own way - because you can
Title: Re: Pinking (pinging)
Post by: t20racerman on 22.08. 2011 21:32
Not un ridable Andy, my project went through a bit of pinking but mostly I managed to tune it out, but I have ditched the 9:1 in favour 8:5 mostly to try to get the thing to reliably start, this again is I reckon down to a maggie not being up to full spec.
There can't be any combinations of pistons, cam, whatever that have not been done over the years to these bikes but to a new owner (or not so new) it still a thrill to do it your own way - because you can

Agree with that Bill - not unrideable at all - just takes a bit more fiddling with and the end result is that I have a VERY quick A10 with the low down grunt of a tractor, which is exactly what I wanted. My 300 mile round trip this weekend seems to refute the 'unrideable' tag as I had a brilliant time.  *smile*

I like to ride my bikes hard and fast and if to do this I have to fiddle with the advance and retard mechanism, so be it. Certainly cheaper than a new pair of pistons.  *smile*
Title: Re: Pinking (pinging)
Post by: BSA_54A10 on 23.08. 2011 11:52
And I bet you were all waiting for me to say it so here it is;-
Fuel is not petrol
Petrol as we knew it no longer exists
Fuel is designed to be burned in computer controlled fuel injected engines
Not in viscosity/volume controlled motorcycles.

In a large part, fuel contains most of the hydrocarbon byproducts that are no longer allowed to be used in industry.
The composition can vary day to day.
The only stable consistent "fuel" is avgas
Title: Re: Pinking (pinging)
Post by: A10Boy on 23.08. 2011 12:59
t20racerman
Quote
Without a manual advance and retard mechanism it would have been totally unrideable! (You need to get manual).

Just offering the other opinion, you dont necessarily need to get a manual if you use pistons with a CR more suited to todays fuel. Its a matter of choice of course and that would be my choice. Having said that, I have an AJS CSR with high compression pistons and a Manual mag and it's great fun.  ;)



Title: Re: Pinking (pinging)
Post by: t20racerman on 23.08. 2011 13:48
The only stable consistent "fuel" is avgas

Very true. Use it in both my racebikes, and the A10 ran superbly on it. Only problem is that it is almost unobtainable in the UK now - being illegal to sell it to anyone other than those directly filling up an aeroplane!

I'm going to try to richen it next by raising the needle and fiddling with the jets and slide cutaway. A powerjet Carb might help as well..  I'll keep you posted  *smile*

Title: Re: Pinking (pinging)
Post by: Topdad on 23.08. 2011 14:33
This may sound daft but do you live near an airfield with light aircraft? If you do give any of the operators a call and see if they will sell you some avgas . As near to "proper petrol " as you could get and if it still pink's it's head off and you've checked out what the other guy's have suggested then you've got to  have a look at the top end or valve timing for a problem, regards BobH.
Title: Re: Pinking (pinging)
Post by: A10Boy on 23.08. 2011 20:01
Trev

I would have put money on it !!!  *smile*
Title: Re: Pinking (pinging)
Post by: Rich on 23.08. 2011 20:35
To get back to the original post, going up a hill at 50 to 55 in top and opening the throttle to maintain the speed is probably the reason why A101960 bike pinked in the first place, surely a gear change would have been more appropriate to maintain the revs so as to lighten the load on the engine.
Timing wise we have set it up from 31 degrees through to 35 degrees in stages using a timining disc making some difference to the overall preformance.
I have a similar engined bike (super rocket) be it a bit more run in than John's but I do not load the engine going up hill in top when I can fly up the hill in 3rd.
On another note is John still about? I have not seen a post for from him for some time
Title: Re: Pinking (pinging)
Post by: cyclobutch on 25.08. 2011 19:01
Thinking that I might be getting a little pinking off my iron head when at lower revs, in lower gears. I've covered 1300 miles or so now since it was all put back together. I run the highest octane I can find at the pumps and also add Castrol valve master with octane booster. Seems OK in top gear. I certainly didn't notice anything amiss in the first 1000 miles or so although I have been taking it easy running it in. I've got a concentric fitted, but all in I'd have to say she's running very well.

Back in the day the bike had a tendency to blow head gaskets, slightly concerned that the noise I can hear might be that - it always first started manifesting itself in that way i.e under load. Checked the points and all looked clean and gapped OK. I gather that if I want to speculatively back the ignition off a little (auto advance on my mag) I have to go in through the timing side. I guess I could tighten the points gap a little.

Plugs in the bike are B6HS, Haynes says B7HC, should I consider changing these perhaps?
Title: Re: Pinking (pinging)
Post by: t20racerman on 25.08. 2011 22:53
Plugs in the bike are B6HS, Haynes says B7HC, should I consider changing these perhaps?

That seems a very hot plug to me! With NGK the higher the number the cooler the plug. B6 seems way too hot. Try B8HS if you think your engine is pinking. I run B10s in mine!
Title: Re: Pinking (pinging)
Post by: orabanda on 25.08. 2011 23:51
For my rigid AND plunger framed engines, we found on the dyno runs, that a B7Hs in the left cylinder and B6HS in the right cylinder, was the best combination. The hotter plug in the RH side helped correct the richness on that side that all of my A10's seem to have. An induction bias (tapered) spacer between the carb and head also helped. Both of these actions helped to even up the mixture in both pots.
Richard
Title: Re: Pinking (pinging)
Post by: trevinoz on 26.08. 2011 02:20
Richard,
             Have you thought about having a head gas flowed to see what is happening?
Possibly a little work on the ports may cure the induction bias.

     Trev.
Title: Re: Pinking (pinging)
Post by: orabanda on 26.08. 2011 04:16
Hi Trevor,
You have raised this very good point before, but I will not bother unless I have to remove the heads from the engines.
However, I will go to the trouble next engine I re-build.
Thanks for the tip,
Richard
Title: Re: Pinking (pinging)
Post by: muskrat on 26.08. 2011 22:29
I agree t20, our bikes do run better on colder plugs with the modern wee water. The only down side is they can be a little harder to start when cold, and when started must be run up to temp. If started and stopped as soon as the choke is off plugs will foul.
 I'm running 9's in mine and backed off the timing to 28 degrees as well as a super rich mix and it still pings. I do as Rich and throw her back a gear or two.
Cheers
Title: Re: Pinking (pinging)
Post by: Slymo on 25.01. 2019 20:12
Just took my 9:1 Super Rocket for 180 mile ride. It went well but was prone to pinking (does anyone but Aussi's call it pinging?) Im running N4 Champions so should probably change to N3's
Title: Re: Pinking (pinging)
Post by: muskrat on 26.01. 2019 00:00
G'day Slymo.
I've found changing plugs in winter (hotter) and summer (colder) helps a little.
What grade fuel are you using? Higher octane takes longer to burn, higher compression quickens the burn.
If the plugs show a good colour I'd back the timing of a couple of degrees.
The slightest bit of pinging (detonation, pinking, stick in a can rattle) can have serious consequences.
Cheers
Title: Re: Pinking (pinging)
Post by: Tomcat on 26.01. 2019 05:18
G'day Slymo, I run my bikes on 95 petrol as 91 always pings. Perhaps try 98 as well?
Title: Re: Pinking (pinging)
Post by: muskrat on 26.01. 2019 06:27
G'day tc.
That's odd as the opposite should apply.
Suppose depends on the brand of fuel *dunno* and the comp ratio.
I find the A7 with 7.5 runs and doesn't ping on anything but dish washing liquid  *whistle*
 *beer*
Title: Re: Pinking (pinging)
Post by: Triton Thrasher on 26.01. 2019 06:53
Quote from: Tomcat
G'day Slymo, I run my bikes on 95 petrol as 91 always pings.


G'day tc.
That's odd as the opposite should apply

What do you mean, Muskrat?
Title: Re: Pinking (pinging)
Post by: muskrat on 26.01. 2019 08:24
G'day TT.
Higher octane needs the ign timing advancec. Higher compression needs the ign timing retarded.
I was outwitted with my Cafe seeing 10.5:1 comp and 105 ocft fuel to go for std timing.  *problem*.
Still had to retard timing to 32 degrees.
Cheers
Title: Re: Pinking (pinging)
Post by: Triton Thrasher on 26.01. 2019 10:58
Using petrol of lower octane than you need, causes pinking.
That’s why they call octane rating “anti-knock.”

Yes, higher octane fuel burns more slowly than low octane, requiring more spark advance for best running, all other things being the same.
Title: Re: Pinking (pinging)
Post by: Slymo on 28.01. 2019 03:00
Ive had a thought that it might be something to do with one set of rings not bedding in. I seem to be making smoke from the rhs pipe and the oil level definitely dropped over the 180 miles. Might have to pull the head off and have a look.