compression PSI

[h450rider]

Hello I want to know if someone of you have the exact compression in psi of a stock 450r motor
Thanks!!

[Trx450always]

it should be 108 psi.

[fasterz]

Originally posted by Trx450always
it should be 108 psi.
are you sure, that seems awful low. The 450r does have a very low compresion ratio stock so mbey you are right. I havent checked my stock motor for psi so im not sure and it doesnt matter since its all getting rebuilt this winter any way.

[Trx450always]

yes that is stock pressure. becuase it has decomp it is low. And i know its right, because its right out of the manuel.

[andrew24]

I tested my 06 and I got 40 but runs good is it realy 108

[soyo]

depends on where the decompresser is set. i set my mine to 60 psi with the electric start.

[andrew24]

Is that the factory setting

[d3ktrix]

The spec in the manual is for the decompressor adjustment.
It is not the total cylinder pressure.

I'm guessing you are trying to do a compression check to check your rings/valves?
Won't work on these bikes since they have an auto decompressor on the exhaust valve.

And good luck getting it to turn over with the decomp disabled.

[andrew24]

Thanks for your help how can I tell when **** starts going down

[rt20ps]

Leak down test!

[andrew24]

What's a leak down test

[Sjorge450R]

instead of measuring pressure, it measures how much pressure is lost. the tool you use is simular to a compression tester and you are supposed to set you piston to TDC so that the exhaust valves are closed and the intake valves are fully down. Then I believe you are supposed to use an air compressor and put a certain amount of pressure in the cylinder and see how much is lost in a period of time.

I have never done this so if I am wrong someone please correct me.