WR450f Compression Test

[craigeyz250]

Hey guys,

I'm going to have a look at an 06 WR450F (to replace my old YZ250). I'm buying it privately and wanted to do a compression test on it to ensure the the engine is OK. Does anyone know what the compression should be on the 06 Models (is it also the same on the 04/05 models)? Also is it as simple as putting the compression tester in and using the electric start to check, or is there a decompression switch I need to turn off to get an accurate reading?

Also if you can suggest any other specific things to check for that would help a lot!

Cheers!
Craig.

 

[derek145]

Hey guys,

I'm going to have a look at an 06 WR450F (to replace my old YZ250). I'm buying it privately and wanted to do a compression test on it to ensure the the engine is OK. Does anyone know what the compression should be on the 06 Models (is it also the same on the 04/05 models)? Also is it as simple as putting the compression tester in and using the electric start to check, or is there a decompression switch I need to turn off to get an accurate reading?

Also if you can suggest any other specific things to check for that would help a lot!

Cheers!
Craig.

if its used listen for the valves its an expensive fix , radiator, suspension and seals, and compresion (expensive fixs) then the little stuff wont break ur back

 

[craigeyz250]

Thanks for the tips. What's the best way to check the compression?

 

[Matt90GT]

You cannot check the compression. The exhaust cam has an autodecompression mechanism. basically it pushes down the exhaust valve when you try to start it releasing the compression making it easier to start.

If you want to check the motor, you need to do a leak down test.

 

[craigeyz250]

Thanks Matt

 

[Matt90GT]

keep in mind that all Yamaha YZFs have the auto decompression cam starting on 2003+, all other CRF RMZ KXFs all had them from day 1.