Please help YZ85

[outlawtubbywales]

I just bought my son a 2004 yz85, the bike runs great until the upper rpm band. It hits the pipe good, pulls great to a certain rpm and lays down, in all gears. If he keeps it on a tight track, or off the straightaways it's okay. I have changed fuel, cleaned carb, changed fuel lines etc.... it doesn't smoke any more or less than comparable bikes. I am running 32:1 with Redline and Premium unleaded. Air filter good, fuel flow into carb good. I have mechanical ability, but this one is kicking me in the backside.
Please Help!!!!

 

[IndyMX]

little too rich on the main most likely.

 

[outlawtubbywales]

SO buy and try the next size smaller jet correct???

Thanks for the input, Indy MX

 

[_JOE_]

How old is the top end? Silencer packing?

 

[outlawtubbywales]

I don't know, just bought the bike. It seemed to run fine when we bought it (test rode it). I got it home and it started laying down at higher rpm under a load.

Thanks for the interest.

 

[_JOE_]

You should at least check the compression. It can be extremely frustrating to try to tune a worn engine.

 

[JD-250]

Once the bike is warmed up, find a straightaway and wind it out in 3rd or 4th and while your at max rev's for a second or two, push the kill switch and pull in the clutch. Check the plug and that might give you a better idea on what's going on.

 

[outlawtubbywales]

Cool- Thanks for all the help guys. I will try all that this weekend and and follow up with ya'll.
I got 4 smokers now, I better learn em inside and out.

 

[Rooster]

I had to chase a similar problem on an old KX125. The previous owner swapped out jets with no rhyme or reason. I cleaned out the carb, and re-jetted to original, which was still a bit rich, but then it was easy to fine tune. It was struggling pretty bad on the main circuit before I did this.

 

[outlawtubbywales]

Okay, I tried everything mentioned. Repacked silencer, replaced bent pipe with perfect factory pipe, one jet up/down, new plug(s), new air filter, drained/cleaned tank, cleaned carb, installed new choke assy, tried 32-1 and 40-1. It is like bike has a rev limiter, it gets to a certain rpm and cuts out, with or without load. It seems to be electrical, will the cdi box cause this, it pulls strong until a certain rpm. I haven't ran a compression check yet...

 

[outlawtubbywales]

04 YZ85 w/rev limiter???

Okay, I tried everything mentioned. Repacked silencer, replaced bent pipe with perfect factory pipe, one jet up/down, new plug(s), new air filter, drained/cleaned tank, cleaned carb, installed new choke assy, tried 32-1 and 40-1. It is like bike has a rev limiter, it gets to a certain rpm and cuts out, with or without load. It seems to be electrical, will the cdi box cause this, it pulls strong until a certain rpm. I haven't ran a compression check yet...

Please help. :bang:

 

[sick 96 250]

compression check it and refer to your other thread

 

[outlawtubbywales]

Compression checked at 135psi with no leak down, is that high enough reading?

 

[sharky243]

Change the reeds. Even if they look ok, they might be week and not sealing off well.

 

[outlawtubbywales]

They are V-Force 3 carbon fiber reeds, they were on the bike when I bought it.
I will change them out and give it a try.
Thanks.