poor tick over (pilot) inlet valve.

karl johnson

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hi guys and can i have advice please.
my comet is running on a fairly new 229f. when i tune the carb to achive a tick over (going through the usual pilot inward throttle stop down ) i am finding that the best i can get is when the pilot is all the way inward which i know aint right. despite the plug not too sooty and golden. the burn looks to me ok. with the pilot more than a quarter of a turn open its regular spitting.

tick over the bike will miss a beat (if i can use that word) then spit at the carb and die.so i keep blipping the throttle to avoid a cutout. on start up its been pointed out to me that their is a very very fine petrol mist comming out of the bellmouth suggesting a inlet valve problem.( he was watching me start it) is this a symptom of so called leaky valve stem. ive not a clue. i did hylomar and gasket the manifold to the head and the carb is nice and tight on the manifold..... any opinions please. any major work ille get done at the end of season.

cheers guys
 

timetraveller

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If it is a valve problem then that should be obvious when you kick the bike over. Can you stand on the kick starter and if so for how long? If you have Mk 2cams fitted then you will get blow back from the carb until about 4,000 rpm. If the inlet valve is leaking then if you can get someone to help you they can stand on the kick starter on the compression stroke and you can put your head near to the carb and hear the air leaking out.
 

Gene Nehring

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What carbs are you running?

Poor idle tick over can be as a result of wrong pilot jet size.

This is a good place to start as there are allot of good minds that can help out.

Best,

Gene.
 

karl johnson

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thanks time traveller

i am a fairly strong guy so i can put pressure on the kick start (as you quoted) for about five seconds before it goes over tdc. ive just done a compression test too and its 70lb i dont know on the cams in my machine. and i am positive with help ive just had i cannot hear any tel tale hissing.
 

karl johnson

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What carbs are you running?

Poor idle tick over can be as a result of wrong pilot jet size.

This is a good place to start as there are allot of good minds that can help out.

Best,

Gene.
229f i bought it new from burlen..... pilot screw
 

BigEd

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.... ive just done a compression test too and its 70lb i dont know on the cams in my machine. and i am positive with help ive just had i cannot hear any tel tale hissing.
Compression test 70 psi sounds low. How did you do the compression test?
 

davidd

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VOC Member
Karl,

In a contest between the new carb and the compression at 70, I think the poor compression wins. A leak-down test would tell you more specifically whether it is the intake, exhaust or rings (or all of them), but if you don't have a leak down tester, you need a friend with one. I would guess that you need a top end rebuild.

I know that you don't know what cams you have. If you want to know what the cranking PSI should be you would need to know what cam you have and what piston compression ratio you have.

Who is around to help you out?

David
 
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