HEADS UP!!!

Site upgrade in progress... Core site functions are working, but some non-critical features/functions will be temporarily unavailable while we work to restore them over the next couple of weeks.

Please post any bugs you encounter, but before you do, check to see if it's already listed.

Thanks for your patience while we work to improve the community.

Sign in to follow this  
Followers 0
blu400f

YZ 400F Loss of compression

5 posts in this topic

I just got done cleaning the carb, replacing the throttle cable and changing the plug on my 99 YZ 400F. After I got it all back together and went to fire it up I had a huge loss of compression, it will kick all the way through with little resistance like a 125. Before I could not get it to turn all the way through without using the compression release, the plug is tight and the compression release is not stuck open. Anyone else have any idea of what it could be???

Share this post


Link to post
Share on other sites

Was it running before doing the carb clean ?? Sounds like you might have jumped time or have bent a valve....Why did you decide to clean the carb ?

Share this post


Link to post
Share on other sites

Try to bump start the bike to get it running again. Ride for a sec and then shut it off and see if you have compression again. After doing the BK mod on my bike the same thing happened. I bump started and it has been normal since.

Share this post


Link to post
Share on other sites

I just thought I would give it a good cleaning while I was replacing the throttle cable. I have owned it for a year now and never done it. It ran fine before. I will try bump starting it tomarrow and see what happends

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!


Register a new account

Sign in

Already have an account? Sign in here.


Sign In Now
Sign in to follow this  
Followers 0