140YX Suspect Low Comp

[beccsptyltd]

Hey Guys,
i have looked around on the forum for some compression results but allas i was unable to find any.

Just did a comp test on the 140yx and it only came up to ~60psi.

Have checked valve clearances and are .003 and .004 thou.

Has anyone else checked there comp or know the result that i should be getting from this engine?

Kick starter has very little comp and could almost start with your hand if it wernt for the random kick back, lol...

Thanks in advance fellas

JB

 

[Moto99]

On my yx140 i had no compression untill i found out it had a bent vavle
Might need new piston, and rings?

 

[beccsptyltd]

On my yx140 i had no compression untill i found out it had a bent vavle
Might need new piston, and rings?

was your bike running correctly though? the bike seems to be running great

 

[Moto99]

nahh wasent running at all, untill i replaced it and now it has loads of compression

 

[beccsptyltd]

Does anyone else have any ideas? Checked the comp on another YX 140 and it was up around 90psi.

As i have said the bike seems to run fine, just kick starting really has NO comp, have checked valve clearances.

Would have a big bore twin exhaust reduce compression because it can breathe easier?

 

[sean01]

most yx140's have an auto decomp on the camshaft.. most of the time they work when they want too.
but it seems yours is working properly..

if it isnt blowing smoke/using oil then i wouldn't be too concerned, unless you know for sure something isnt right..

oh and are you doing the compression test with the throttle wide open?