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Post Info TOPIC: Low compression after standing for months


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Low compression after standing for months
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Hi all,

Just wondering if anyone else has experienced this. 
When I have not started by TTR for a few month. when I come to start it it turns over easily but doesn’t show any hint of wanting to start. I then try it on the kick start and there is very little resistance. after 20 or 30 kicks resistance builds up and it will then start first push of the starter button (Ive  ever had much luck start it on the kick start)

On starting it smokes for about 10 seconds, the back to normal until left for many months again.

It has continued to do this after a top end overhaul.

 Not really a problem (must remember to kick it over while it’s not being used)

Anyone else experienced this?

Lama



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Super Guru

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Sounds like a sticky valve maybe?

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Mines done this twice in the last 18 months, drag the bike along with rope and it should sort it out if its a sticky valve like Simon suggests

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Thanks

Daniel Lee



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I would have thought that a single cylinder engine would come to a stop on compression, with all valves closed, so don’t think a valve is sticking open. Plus all the smoke at start up makes me think that the piston rings aren’t sealing. But I’m no expert.

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Well, when you spin the engine over to start it, the valves open. If one is then not fully closing you will lose compression. Has it been fully run-in since the rebuild? New rings and valve stem seals?

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As Simon advised me before, set the engine tdc and check the valve clearances. If ones larger than normal suddenly that valve is sticking. Really quick thing to check. Good luck. :)

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Thanks

Daniel Lee



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Thanks both for your thoughts.
It does seem more likely that that much compression loss would be caused by a valve not closing rather than past the rings.
Not sure how it explains the oily smoke at start up though.
Good call on checking the valve clearances ext time it happens.
Cheers

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did you fit piston rings & hone bore with cross hatch if so it needs some hard work to bed the new rings into the bore may be worth doing a compression test if its low pour little oil into cylinder it will tell you if its a ring it will build up compression if its a valve they will be no difference thats what i would do its up to you your decision

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yamalama wrote:

Thanks both for your thoughts.
It does seem more likely that that much compression loss would be caused by a valve not closing rather than past the rings.
Not sure how it explains the oily smoke at start up though.
Good call on checking the valve clearances ext time it happens.
Cheers


 Smoke on start up only = valve stem oils seals problem



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