The BSA A7-A10 Forum
Technical (Descriptive Topic Titles - Stay on Topic) => A7 & A10 Engine => Topic started by: RoyC on 19.08. 2018 09:52
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Started my bike up for the first time in two months, went second kick.
I have a popping sound in the left silencer, had it for quite a while.
Could this be due to tight rocker clearances ?
New carb and plugs, none resistor type leads.
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Exhaust popping or banging usually caused by unburned fuel detonating in the exhaust. Maybe your left pot runs a bit richer?
Does it pop when opening or closing the throttle?
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Does it pop when opening or closing the throttle?
No, most noticeable on fast tick over,
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Leaking exhaust valve?
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Can be weak mixture. Maladjusted pilot screw, blocked pilot jet or slide wear.
Air leaks into the exhaust pipe, at the cylinder head, usually cause banging on the over-run.
All this assumes that your engine gets serviced according to the schedule. I don’t have much sympathy for people who ride around until the valve and points gaps close up and then moan on the Internet.
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Leaking exhaust valve?
This could be too tight a setting on exhaust valve. I will have to look at it.
I don't ride the bike, just start it up occasionally.
Brand new carb, so no wear on slide. All set up for me as per BSA factory specs.
https://surreycycles.com/carburettors/amal-monobloc-376-389/
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If the problem arose after fitting a new carburettor, suspect a too-big slide cutaway.
Also check for inlet manifold air leaks by spraying WD40 or something on the carb to manifold joint while the engine is idling. If rpm changes, there’s a leak.
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If the problem arose after fitting a new carburettor, suspect a too-big slide cutaway.
Also check for inlet manifold air leaks by spraying WD40 or something on the carb to manifold joint while the engine is idling. If rpm changes, there’s a leak.
It was there before the new carb (one reason that I replaced the carb).
Already checked the for leaks.
I am still going with valve not closing properly.
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Hi Roy,
All set up for me as per BSA factory specs.
Those settings were for the fuel available at the time, this is only a very distant relation to the crap sold now *sad2*
Any new carb that I have had to look at after being fitted to old bikes has run lean on the factory settings *conf*
Starting up a bike without riding it and getting everything up to working temp's will cause all sorts of issues
John
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A valve not sealing will show up on a compression test.