08 wr450f no compression

Ok, a I've recently been doing work on the wr and have ran into problems. I have the fmf powercore4 slip on w/ stock header and have recently taken it off to get to my linkage & replace bearings. Anyway, after reinstalling my fmf I had an exhaust leak at the mid pipe connection. That caused popping and backfiring until it finally cut out all together. Well I went back with a hammer and got a better seal I thought, bike ran fine for a little over a week until the same thing happend, popping & motor cuts out. I've put her in the garage and removed the fmf pipe & reinstalled the stock exhaust to see if it was an exhaust problem again. Now I've got no compression when I kick the motor there's nothing there. I can crank it over with my hand & the battery is dead from trying to use the e-start too much. Any help trouble shooting my problems would be appreciated.

I hate to tell you this but if nothing went bang it can only be a probate with a valve not closing

A 08 shouldn't have any issues. They all can pop on decel it's normal. Make sure if you have no compression? If none pop off the top of the valve cover and see if you lost a valve. One of the springs will be popped up.

...or your auto decompressor is stuck shut. The lever should move with your fingers.

 

Decel popping is more likly a fuel screw not adjusted or leaking from a bad oring

Edited by KRANNIE

I remember that week it was running that it would idol high. I could pull in the clutch & it was almost at 4k on my tach. & the decomp lever is free and working properly. So valves huh :/

Not to be a dick but are you sure there is zero compression ? 

 

Does it sound normal when trying to E-start it , as in was it spinning faster than normal ?

I can rotate my motor by hand with the kick start but It hurts like a bitch .

 

 

Your first issue sounded more like an electrical problem to me .

 

Have you checked for spark ?

 

 

A valve lash check should show signs if it's actually valve issues  .

Edited by still2smokin

Quick follow up on my dead WR. Took the top off the motor they were all dead on in spec (.10 in & .20ex) I got the .23 under on ex valve once but it was hard as he'll to do & I couldn't really get it when I double checked everything.

Replaced spark plug & tried to fire the motor still nothing, pulled the coil with the plug still in it to check for a spark hit that ignition switch and gave myself a good shock so we're all good there.

As for compression I can move the kick start full circle with my hand but after one crank when it comes back to the top it's like I never moved it so I didn't know if that was normal for the motor to auto decompress after every crank I thought it would build up more than that.

Ps. New air filter + clean gas are being used

One of the valves must be leaking

You said you have a dead battery in your first post. Replace it.

Battery isn't ruined it's just drained from trying to start the bike over & over. & wouldnt i still be able to kick start with no battery?

How would I check for a valve leak? I don't even know where to start for that...

If you have the head off, turn it over and pour gas into the combustion chamber.....it shouldn't pour through....

I guess when I get off work I will ohm out the ignition system pet the manual and report back with the results there.

I haven't taken the head off. I just took the case off to reveal the cam shafts and measured the gap under each lobe. Are you saying to pull all that & put gas on the piston and see if it filters through?

Sorry about so many questions but this is my first bike & first real problems I'm having with it.

I haven't taken the head off. I just took the case off to reveal the cam shafts and measured the gap under each lobe. Are you saying to pull all that & put gas on the piston and see if it filters through?

Sorry about so many questions but this is my first bike & first real problems I'm having with it.

Take the head off, turn it upside down and pour gas in combustion chamber, if gas leaks past the valves then you will know the valves are not seating properly.

You may consider taking the bike to someone that is a good mechanic for diagnoses. Hopefully there is something minor you have overlooked.

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