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riderman329

compression test

7 posts in this topic

i did a compression test on my 04' 450f and i got 30 psi is that right? i can't seem to find anything in the owner book about it at all!

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You can do a compression test, but you have to disable the decomp mechanism to make it meaningful. Remove the cam cover. Insert a piece of card stock such as a matchbook cover under the flyweight on the exhaust cam so that it will hold the weight in the full out position against spring pressure, and so that it will not fall out and escape into the engine. Do your compression test and be sure to remove the wedge when you're done.

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most enigines w/ compression releases have specs in the 50 - 100 psi range.

i have an 03 450, i checked mine recently and got ~70 psi. yamaha is the only manufacturer tha does not give a spec for comp. pressure in their service manuals. with comp. release dissabled a would expect a reading more like 175- 200psi.... but 30 seems waaaay low.

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