I have a 1995 yamaha ovation 340cc fanner, and I want to know if it' s normal to have a low compression reading when cold? Also, does this motor have a decompression valve? My gauge is only hitting 30psi, and not holding it, but exactly the same on both cylinders.
When i do a compression test i set up my gauge pull the motor over 3 times with the throttle wide open (kill switch and key in off position) gonna need 100psi minimum. Your gauge should hold the pressure untill u release it by pressing the decompression button on the gauge. A lower psi is normal when cold but still should be 100+ psi. I own a defective compression gauge that dosent save the psi reading and always reads low. I went out and got a new 1 for around 20 bucks and was alot happier with the reading i was gettin. It went from around 60psi on both holes with the old to reading a solid 127 with the new 1. Hope this helps you out
On a fan 340 the compression will lower when cold , If it still starts good cold and hot than you are probably ok
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