The BSA A7-A10 Forum
Technical (Descriptive Topic Titles - Stay on Topic) => A7 & A10 Engine => Topic started by: derek taylor on 09.06. 2014 19:55
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engine is pinking when you accelerate under load when it is hot i have put a fuel cat in the tank, its not made any difference it still pinks.
had a look at the points they are clean and at 12 thow plugs are L82C and look rich if anything, bike hase only done 1400 since rebuild? :!
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G'day Derek. Is it auto or manual advance? You'll need to back the timing off a degree or two. If you have manual, use it to retard a bit when it pings. If auto you can close the points a thou" or two to test it, if better reset points and re-time it.
1400 miles is just enough time to start building carbon deposits on the piston and comb chamber. This leads to hot spots and pre-ignition.
Cheers
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thanx it's auto advance/retard
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I like timing a magie like most here like rockerbox's. If you have it set at 3/8" go back to 5/16".
The only other thing that can help is to richen the mixture, but with sooty plugs already, I wouldn't.
Cheers
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Hi Dave
Fuel cat - well there are a lot of such things around, not sure I have much faith in them and in any case your engine probably doesn't need lead additive.
However what is does need is Octane, I use Castrol valvemaster plus, it has a lead replacement but more important an Octane booster, this brings your modern fuel back to the levels of bangyness it had in the days your bike was made, £15.00 a 250 mil bottle at Halfords but you only use 1ml per litre so it will last a long time.
Sooty plugs are not always an indication of over rich mixture with today's fuel.
If this is a sudden change of running then Muskrats tips are the way to go I reckon but the Valvemaster will do no harm and might well help
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Good catch Bill.
Yes raising the octane from 91 to 95 or 98 will also help.
Cheers
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Sooty plugs can indicate a rich idle mixture or slide cutaway, while using the wrong notch in the slide needle or a too-small main jet could still make it pink under load.
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thanks lads all taken on board
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Derek,
If the timing/fuel tips above to not correct the problem, a possible cause of racket from the upper cylinder is a bad wrist pin bushing. I once had one start wearing against the aluminum rod at just a 1000 or so miles after a rebuild. Unfortunately, removing the cylinders is the only way to make that diagnosis.
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right then not done anything about the pinking yet but gunna start on it tomorrow, just been reading the bible and it says tighten the unit
on the magneto shaft without the shaft moving. when i take it to bit's and see how it all works it will most probably all fall into place, but if not how do you hold the shaft without it all turning?
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Press the drive gear hard onto the magneto shaft with your thumbs, before tightening the nuts. The taper should grip it.
Doesn't always work, so check the timing afterwards..
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Dont forget to wedge the auto advance unit in the fully advanced position when you set the timing.
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thanx lads
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I always remove the earth screw on the magneto and put a bolt in to nip the armature and hold it where I've set it, before fitting the pinion. I think the bolt is 5/16 cycle thead
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ok checked the timing, the points just part as near as dam it 5/16 btdc.
i don't think that is to far advanced?
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G'day Derek.
Next will be increasing the octane of your fuel a few #'s or lift the needle a notch and main jet by 1 size.
Cheers
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the points just part as near as dam it 5/16 btdc. i don't think that is to far advanced?
is this with the a/r unit jammed in advance as Brian advised (a wedge jammed in to keep the bob weights out)
for reference - when checking the timing with the timing case on and the engine not running the points should open (roughly) around TDC
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yes a/r unit fully open
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these are the plugs (see pick)
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allowing for today's fuel, they look pretty normal
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They look too "white" for today's fuel.
I would do as Musky suggests, as your timing is right, fuel needs looking at.
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will lift the needle up a notch see what happends
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Definitely too weak a mixture.
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seems like I'm outvoted on this one
Maybe I run my bikes a bit on the weakside dunno or could be my eyes, but think if runnng weak some of that black (I know it's not soot these days) would have been burnt off.
Didn't realize Champoin were made in France, probably made everywhere
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Didn't realize Champoin were made in France,
If that's how they spell it, then 'so be it'.... *conf*......Bill, yer eyes are better than mine- but then I didn't look.... *smile*
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you have to stand on your head Dutch *smiley4*
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seems like I'm outvoted on this one
Whether a piston gets holed or not, is not decided by a democratic process.
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Whether a piston gets holed or not, is not decided by a democratic process.
*smile* I have no problem belong to a minority party and never have had a piston holed
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i'v lifted up the needle a notch will see how it goes. oh and shall i turn the pick upside down?
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While you're at it, Derek, make sure that you are not sucking air around the carby gasket.
Is your carby set to factory specs?
They usually run OK at that.
Trev.
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oh and shall i turn the pick upside down?
nah - actually the pics were pretty good
lets see how the richer setting works
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yes all to factory spec
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i was having the same problem and indications of a rich mixture, mine was caused by a distorted float bowl which was sucking in air so the fuel was not atomizing correctly. i have an Amal concentric fitted.
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Sorry for hyjacking this thread a bit, but can anyone explain the term 'pinking' to me? I haven't heard it before. Does it have something to do with backfiring?
Thanks!
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Pinking - also Pinging - is also pre-ignition although I think that might be something else really.
anyhow as I understand it, to much advance and the spark try's to knock the piston back the way it came sort of, results in a metallic click sound, can do lots of damage if left.
goes hand in hand with higher compression and advanced timing and hills (so sporty models have manual advance/ retard )
I did have it with my RGF but cured it with electronic ignition (better advance/retard curve I guess)
Excuse any lack of technical terms - sure someone will explain better
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Nearly right Bill. It is sort of like pre-ignition in that a burn is started without a spark (hot spot). This burn travels across and collides with the normal flame front produced by the spark plug. This collision creates a much higher pressure and occurs faster than normal so in effect peak combustion occurs too early.
A good read here http://en.wikipedia.org/wiki/Engine_knocking
Most commonly heard going up hill under load on an opening throttle. Hemi heads with high top pistons are the worst. Quick fixes are retard the timing or richen the fuel air ratio. It must be addressed, a holed/melted piston or worse (broken rod) WILL eventuate.
Cheers
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Sorry for hyjacking this thread a bit, but can anyone explain the term 'pinking' to me? I haven't heard it before. Does it have something to do with backfiring?
Hi Pim, the Dutch word for pinking is''pingelen'' Does that ring a bell? (pun intended)
Backfiring is when the combustion blows back through the carb instead of taking the normal route via the exhaust. May happen if you start her up with a bit to much of ignition advance. Can put your bike on fire if you're unlucky...
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I see.
Well i heard of it Morris, but have no prior experience with the innerworkings of petrol engines. I know the basics but the devil is in the details:)
So am i correct by saying you have to set the fuel mixture a tad ritcher so it cools the engine more and the pinking should stop? as an imidiate/temporary fix?
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And retard the timing a tad. Usually only a problem with our A's once the compression ratio gets above 8.5-9 : 1.
The best quick fix is to throw her back a gear and rev it, don't labor.
Cheers
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i was having the same problem and indications of a rich mixture, mine was caused by a distorted float bowl which was sucking in air so the fuel was not atomizing correctly. i have an Amal concentric fitted.
Hmmm.. never heard of a distorted float bowl sucking in air ? Could you re-phrase that please?
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Hi,
I haven't read through all of this, so apologise if I've already commented, or its been said. I had terrible problems with pinking and plugs dying on my road rocket when I first got it running. Spent an age mucking about with ignition timing, carb settings and the like. Completely went away when I got my magneto rebuilt.
Cheers,
iain
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i was having the same problem and indications of a rich mixture, mine was caused by a distorted float bowl which was sucking in air so the fuel was not atomizing correctly. i have an Amal concentric fitted.
Hmmm.. never heard of a distorted float bowl sucking in air ? Could you re-phrase that please?
Happens a lot on Amal Mk1s. Air is drawn into the pilot fuel passage at the float bowl to carb body joint.