slight pop from number 4 cylinder??

[DAVEKWAK9?]

Hi people hope you can help got a slight pop from number 4 cylinder every now and then? got new plugs filter and oil and oil filter.
no smoke at all ticks over lovely any thoughts peeps ?

[warren3200gt]

Air leak in no 4 exhaust joints some place maybe especially if it's most evident on over run.

[DAVEKWAK9?]

thank you ill have a look tomorrow

[gray]

Agreed, you might need to look very closely at No 4 exhaust where it seats into the cylinder head - might be its not quite snuggled down tight on the gasket ( maybe a bit of old hard exhaust gasket cement in the way?) or it's just marginally loose cos the copper gasket has compressed a bit, or the steel collets aren't sitting just right, to press the gasket into the recess

[DAVEKWAK9?]

thank you will check tomorrow

[DAVEKWAK9?]

no sorry peeps not blowing at all at the cylinder but it pops at the rear of the exhaust. mmmmm got me lol

[warren3200gt]

Your not looking for it blowing. The theory of an air leak is that on over run unburnt fuel is expelled into the the exhaust. The exhaust SHOULD be full of exhaust fumes with zero air thus the unburnt fuel can't combust as it has no air. "IF" there is an opportunity for air to get sucked in by venturi anywhere along the the entire exhaust it allows the fuel vapour to mix with the air which gets ignited by the next exhaust cycle creating a exhaust popping.
Another possibility is a poorly seated exhaust valve but a compression / leak down test would show if that was an issue.

[DAVEKWAK9?]

oh thank you know what you mean now thank you will do more investigation is that on tick over aswell that what it does it on m8 cheers

[gray]

a pop when you ride along and close the throttle ( ie on the over-run) suggests air leak. An occasional pop at idle suggests HT lead or spark plug or pilot jet or pilot passages to me .
swop No 1 spark plug over with No 4 and see if the pop moves to another pipe. If it moves you've found the problem.
if that doesn't make a difference, take the tank off and swop No1 HT lead and No 4 HT lead and see if it moves. Make sure the plug caps are screwed in tight to the HT leads
That's the easy steps.
After that its a carbs off job , drop the No 4 float bowl and remove the pilot jet to see if its partially blocked, and while the jet's out use carb cleaner up the pilot passage , from airbox side . And do a reverse flush through the tiny holes in the carb throat into the float bowl . Put kitchen roll on the bench so you can see if you've dislodged anything

[DAVEKWAK9?]

Thank you Gray that is so help full thank you for your time will give all that a try