The BSA A7-A10 Forum

Technical => A7 & A10 Engine => Topic started by: Hubie on 17.06. 2010 23:18

Title: Running out of puff
Post by: Hubie on 17.06. 2010 23:18
G'day all,

Have been reading with interest the problem child a10gf of a10sausage.   I note with interest how his bike is pulling strong uphill at 70mph.  My bike revs very cleanly and well throughout the range in the first three gears and will sit on 60 in top fairly well but try and give it any more wellie and progress is very slow to increase.  I know I have my carb jetted right but I am wondering why I run out of steam beyond 60.  The bike should cruise pretty easily at 70.

I have a mk1 concentric on it with a 230 main jet which according to what I have read is about right.  If I turn the air lever open while riding, it slows it down so the bike is not too lean, nor is it too rich.  Standard magneto with the timing properly set up.  It is a one kick start every day and runs fantastically except for when described above.

Any thoughts would be appreciated.

Cheers,


Dave.
Title: Re: Running out of puff
Post by: trevinoz on 17.06. 2010 23:33
Have you tried changing down to third and opening it up? If so, does it accelerate?
Do you still have the 24 tooth engine sprocket fitted? If so, top gear is now like an over-drive and your engine will probably struggle to accelerate.
Trev.
Title: Re: Running out of puff
Post by: muskrat on 18.06. 2010 09:32
I think Trev hit the nail on the head. With a tall primary even my fire breathing cafe has to go back a gear at 60 to accelerate quickly.
Cheers
Title: Re: Running out of puff
Post by: Hubie on 18.06. 2010 13:14
Now that I have the rest of the bike sorted, will have to do some playing and see what happens.  Will post on my progress.

Cheers

Dave.
Title: Re: Running out of puff
Post by: BSA_54A10 on 19.06. 2010 13:00
Quote
Standard magneto with the timing properly set up.  It is a one kick start every day and runs fantastically except for when described above.

As BSA instructed for the fuel that was available when it was new or slightly further advanced to compensate for the light fuel oil that we get now days ?

Try changing the points to change the timing.
Rule of thumb .001" = 2 deg.
Close it down to advance
Open it up to retard.

A lot easier for experimenting than pulling the timing gear off.
Title: Re: Running out of puff
Post by: a101960 on 19.06. 2010 15:00
An interesting topic. I have an RGS  and the recommended ignition setting is 3/8 BTDC. At this setting there is no doubt about it, it goes very well, but it pinks under load. I use 99 octane petrol. Backing off to 5/16 reduces the the tendency to pink, but also reduces performance. What is interesting is the fact that the road test published in the 'Motorcycle' magazine back in the sixties comments on the tendency of the engine to pink even on 5 star petrol. Now,I have no wish to burn holes in my pistons, or to knock out my bottom end, so I run my engine on the 5/16 BTDC setting. It would seem to me that the price of of opting for more go is a shorter engine life due to the stress imposed by more advanced ignition. I am not one of those people that enjoy stripping down and rebuilding engines. I just want to ride the bike. The late Bob Currie wrote about how BSA twins did not like pool petrol, and how they tended to run on and pink. http://tetraboost.com/ is one product that is available that can provide genuine leaded fuel. But be aware this is not a cheap option. I have tried using this product, and I could not determine any real difference (at 3/8 BTDC). The engine still pinked under load.

John
Title: Re: Running out of puff
Post by: muskrat on 19.06. 2010 21:00
G'day John,
                   that stuff sounds great, but down here any lead additive is illegal (bloody tree hugers). They are even taking standard unleaded off the market and replacing it with E10. I use Nulon octane boost and a smig of R30 oil.
 Try going a little richer with the carb settings eg. from #3 1/2 slide to a #3, raise the needle 1 notch. You may need a hotter plug, from B7ES to a B6ES, but you will be able to advance back up to 3/8". Worked with mine.
Cheers
Title: Re: Running out of puff
Post by: bonny on 19.06. 2010 22:51
what is the speed an a10 in standard flash tune will sit comfortably at on the road with out shaking itself to bits ? 
Title: Re: Running out of puff
Post by: trevinoz on 19.06. 2010 22:58
Bonny,
               That will depend on how well your engine is balanced.
             
                          Trev.
Title: Re: Running out of puff
Post by: bonny on 19.06. 2010 23:03
Bonny,
               That will depend on how well your engine is balanced.
             
                          Trev.
only had a few quick blasts on my a10 before i dismantled it for restoration , but it seemed to be smooth enough trev.
Title: Re: Running out of puff
Post by: a101960 on 20.06. 2010 00:02
Muskrat, my friend. There is no doubt about it. Tetraboost is good stuff, and it is legal in the U.K. as is leaded petrol. Yes that is right leaded petrol can be legally sold in the U.K. It is bloody hard to find though, because it is expensive due to the high tax rate imposed on it. I do not know how the Ausie customs operate, but in the U.K. as an example you cannot operate a radio transmitter without a license. However you can legally buy and own one as long as you do not use it. That in its self is no deterrent. There is a whole sub culture  here in the U.K. that buy transmitters and set up radio stations. The authorities then hunt them down, but it is a losing battle. When the operators are caught the equipment is confiscated. So, what do the operators do? they go on air again with new equipment. As I say, weather your customs could impound Teraboost at the point of entry I do not know. Do not mention tree huggers to me. All these self righteous enviromental barstewards are very good at complaining. How many of them are prepared to give up their cars or live without gas or electric power? And Interestingly enough, unleaded petrol is a greater health hazard than leaded petrol. Why so? Benzene and tuoline. Both substances being highly carcinogenic. You don't even have to ingest the stuff by breathing it in Benzene can be ingested by contact.On that cheery note I will say good night.

John
Title: Re: Running out of puff
Post by: Hubie on 20.06. 2010 00:24
It's a bit wet here at the moment but that will give me some time in the garage to close up the points a little and raise the needle one notch.  I already have the timing more advanced as it was actually coughing and choking under load from being too far retarded.  I have since sorted that and I am not after a race bike, I'd have bought something else for that.  I just want it to perform the way it was designed to. Will see how it goes.

Cheers,

Dave.
Title: Re: Running out of puff
Post by: chaterlea25 on 20.06. 2010 02:13
Hi All,

BSA_54A10,

""""Try changing the points to change the timing.
Rule of thumb .001" = 2 deg.
Close it down to advance
Open it up to retard.""""

I believe you are mistaken with the quoted information above!!
Opening the gap advances the ignition
the cam has to open the points gap further so it must start sooner, ie advance

HTH
John O R
Title: Re: Running out of puff
Post by: Hubie on 20.06. 2010 08:58
Timing is nice, the bike pulls like a 13 year old boy in third up to 60mph with a bit more left.  I think Trev is right that my engine sprocket is too big.  The only reason for my scepticism was putting a 22 tooth gearbox sprocket on my meteor up from 20 and it transformed the machine.  I might get myself a 22 tooth engine sprocket (up 1 from standard) and that should do the job. 

Might also try out that extralube zx1 stuff from a post by a10sausage just to see how it goes.

Cheers

Hubie.
Title: Re: Running out of puff
Post by: Hubie on 21.06. 2010 06:11
Also on this topic, does anyone have a 22 tooth 2 lobe engine sprocket they want to part with??

Cheers,

Hubie.
Title: Re: Running out of puff
Post by: A10Boy on 21.06. 2010 12:07
Adding two teeth to the engine sprocket is a whole different ball game from adding two to the gearbox.
Title: Re: Running out of puff
Post by: Hubie on 22.06. 2010 03:44
I have been pondering that Andy and although I would have thought the overall result would be the same, perhaps it is not.  Can someone explain the difference to me??

Also I have one of those 4 spring triumph style clutch centres on my bike too, and could not get it off with a puller from an earlier attempt, what is the best way to do it, will applying some heat cause to much trouble?
Title: Re: Running out of puff
Post by: dpaddock on 24.06. 2010 21:34
Andy - given the typical sprocket teeth numbers involved, an incremental change to either of the driving sprockets will result in the same change in ratio.

Hubie - assuming you're using the centre extractor made for this job; screw it in, tighten the bolt and hammer it lightly. A little heat from a torch will help.

David
Title: Re: Running out of puff
Post by: bsa-bill on 24.06. 2010 22:10
I did have a spreadsheet someone kindly sent me that let you input the sproket sizes and it worked out the final ratio, can't find on this computer at the moment but the link below might be useful

http://www.mez.co.uk/mezporting/gearratio2.html (http://www.mez.co.uk/mezporting/gearratio2.html)
Title: Re: Running out of puff
Post by: wilko on 24.06. 2010 23:34
That's a handy link Bill, i've kept that one. I don't have to use my brain!
Title: Re: Running out of puff
Post by: Hubie on 06.07. 2010 07:09
Had a good chance to give the bike a run today.  Got the original gearing back on it and it goes fine through the first three gears, but approach a hill and it is slower getting up there than my old bullet used to be.  Do I have a problem with carb settings or is it valve timing?  I am at a loss as to why it is fine through gears 1 to 3 and then has nothing up top in 4th.  After having a bit of a read on the forum I am confident my valve timing is not correct.  Next step is to learn how to check and adjust it.  Any help would be very much appreciated.

Cheers

Dave.
Title: Re: Running out of puff
Post by: bsa-bill on 06.07. 2010 09:04
Difficult to see what could move though Dave however to check that the dots and dashs on the timing gears line up, means removing the outer timing case cover, the dynamo drive chain and large sprocket and then the inner timing case cover (four screw).
Then trun engine over ( could be up to 70 odd times ) to see if they all come together ( when they do the engine is at top dead centre)

To set it up so they do with out all that turning over -
best to remove the rocker box or screw out the tappets so the valves remain closed and remove spark plugs so your not fighting compression.
Then slide out the idler gear and turn the engine and cam shaft so that you can line up the dots on the crank pinion and idler gear and the dash on the cam gear and idler gear.
Title: Re: Running out of puff
Post by: Hubie on 06.07. 2010 09:28
Thanks Bill,

I am thinking that I am on the right track though.  I cannot think of what else could cause such a loss of power up top.  I have not checked it since I bought the bike either.

Cheers

Dave.
Title: Re: Running out of puff
Post by: muskrat on 06.07. 2010 10:33
G'day Hubie,
                    Bill is correct, but to save un-doing the tappets turn the motor to bottom of stroke then remove the idler. Now turn the cam so the dash is pointing towards the center of the idler hole. Now turn the crank till the dot is towards the center of the idler hole. Now insert the idler and it should be only a little tweak to line it all up and push the idler home. The only way cam timing can be out is if it was set up wrong in the first place or the key in the cam or crank pinion has sheared.
 Double check the ign timing, if it's retarded it will spin in lower gears but loose out in top. Too advanced it will ping under load.
Cheers
Title: Re: Running out of puff
Post by: Hubie on 06.07. 2010 11:37
Thanks mate,

Definately doesn't ping, and that's after i've advanced up the timing.  I have never checked the cam timing since I've had the bike so it's a least worth a check.
Title: Re: Running out of puff
Post by: Hubie on 09.07. 2010 06:38
Before I go this far, can someone tell me if I am on the right track?  I have the standard gearing, good power through gears 1-3 but in top when climbing a hill it runs out of steam and slows right down feeling suffocated/stifled.  Does it sound like cam timing?  I am happy with the ignition timing and can't get it to ping even though I have the timing advanced a tad more than standard.

Cheers,

Dave
Title: Re: Running out of puff
Post by: Stu55Flash on 09.07. 2010 07:13
Hubie

Have you checked the obvious stuff like air filter restrictions and full fuel flow to the carb?

Stu
Title: Re: Running out of puff
Post by: Brian on 09.07. 2010 07:26
What you describe Dave can be caused by the cam but also other things. Lack of top end can be due to carburettion or low compression, gearing etc. If you are sure all is well then maybe a check of the cam is worthwhile.

It is unlikely that the cam timing is wrong as has been stated as long as the dots and dashes line up then it should be right. You may have read that I had a issue with my Star Twin but I am certain that is due to a incorrect part that I will look into when that motor is apart again oneday.

If your problem is cam related it is more likely due to a worn cam or one that has been reground incorrectly. Just for an example here is a picture of a cam that had been ground incorrectly, it has lost 1/8" of lift and ground to the wrong profile. You will see that the heels have been completely removed and the timing on this cam was way out.

It is not too difficult to check the cam timing and you only need a couple of basic items the main one being a degree disc. It also helps if you know what cam is in the motor but that is not essential. You do need to understand how to read the degree disc, ie. before top dead centre, after bottom dead centre etc. Your motor will probably have either a 334 or a 356 cam. The figures for these are as follows.
67-334   inlet      opens 30d BTDC and closes 70d ABDC
            exhaust  opens 65d BBDC and closes 25d ATDC

67-356   inlet      opens 42d BTDC and closes 62d ABDC
            exhaust  opens 67d BBDC and closes 37d ATDC
  
Title: Re: Running out of puff
Post by: Hubie on 09.07. 2010 07:32
Thanks Brian,

I have a monobloc on a super meteor i might try on it to rule out carburetion.  It is fine and the meteor pulls like a train.  Then I will go to a motorbike mate and have him show me how to properly check the cam timing.

Cheers,

Dave.
Title: Re: Running out of puff
Post by: bsa-bill on 09.07. 2010 11:26
Hubie I can't see anywhere you say what gear you have on the gearbox, the reason I ask is because  with a 24 tooth on the engine ( which you have now changed) and the rest of the gears standard, I'm thinking it would be quite feat to kick it over.
Anyway some overall ratio choices assuming you have a 19 tooth on the gearbox

standard   21 engine, 43 clutch, 19 gearbox, 42 wheel = overall ratio 4.53
Yours       24, 43, 19, 42 = overall 3.96
Sidecar     21, 43, 18, 42 = overall 4.78 or 20, 43, 19, 42 = overall 4.75
Yours now 22, 43, 19, 42 = overall 4.32

mine to get just a tad more acceleration 22, 43, 18, 42 = 4.56

4.32 is still a good bit higher than standard ( 4.53 ) a difference of 0.21, consider that sidecar ratio is a difference of 0.22 or 0.25, so you are still as much higher than side car gearing is lower, also consider that added to all this is you gearbox ratios which help your engine in the lower gears but by the time you get to top the full effect of your overall ratio will become more pronounced

As per usual my maths are open to scrutiny
(another pet hate - why all of a sudden has it become MATH in place of MATHS)
Title: Re: Running out of puff
Post by: alanp on 09.07. 2010 16:01
Bill, you're quite right, it is mathS, as a short version of mathematicS. 
Regards
Alan
Title: Re: Running out of puff
Post by: MG on 09.07. 2010 21:20
Bill, your maths are absolutely correct, but I don't think it will make such a huge difference in top gear performance.
According to my self-made gear-ratio - speed - rpm Excel spreadsheet, the standard gearing (21T-43T-19T-42T) would result in 4050 rpm @ 60mph in 4th gear (4900 in 3rd). Hubies 22T engine sprocket will result in 3860 at the same speed (4680 in 3rd). You might have to stay in third a bit longer, but still it should be pulling well enough in 4th I would think.

All values assuming a STD clutch basket and g'box sprocket is fitted.
Title: Re: Running out of puff
Post by: Hubie on 10.07. 2010 01:47
I am running completely standard gearing on the bike now but still have nothing left in top gear.  I am leaning towards cam timing but am still unsure.  I made new rocker box covers last night and now there's no compression and the bike will not start.  I will have to re do the valve clearances it would seem and then go from there.  I made doubly sure that the pushrods are all in position and re checked again this morning.

The saga continues.  I would just like the bike to have the go it is supposed to have.

Cheers,

Dave.
Title: Re: Running out of puff
Post by: trevinoz on 10.07. 2010 03:44
Dave,
            Have you ever thought why the previous owner got rid of the Flash?
Check your compression and have a look at the timing marks, as Musky suggested.
Another little thing to check is that the correct idler pinion is fitted.
Count the teeth between the dot and the dash.
It is not unknown for an early long stroke pinion to be fitted.
Trev.
Title: Re: Running out of puff
Post by: Hubie on 10.07. 2010 08:19
Thanks again Trev,

I will check that in due course, though I have just reset the valve clearances and the bike is running again.  Not only that but it feels as though there is a stack more power available.  In the past when the bike was revved on the centre the vibration higher up in the rev range would cause the bike to drag backwards along the ground.  Now a blip of the throttle and she rockets backwards.  Perhaps the beast has been awoken.  It has just started to rain here so a test ride when weather and time permits is going to be very interesting.

Thanks to all for their continued advice and support.

Dave
Title: Re: Running out of puff
Post by: bsa-bill on 10.07. 2010 10:12
yep mine does that, I use the throttle to move it about the garage.
Well good luck with it when you get it out on the road, it's rained hear in Northumberland through the night, supposed to get sunny this afternoon though