YZ - Hybrid problems

[brian250racer]

Has anyone had this problem? 1998 yz400f motor w/420cc big bore. Ran awesome last year, but has gone downhill since. The motor sounds like it is hitting the rev limiter at about half throttle. I rebuilt the motor, changed valve springs, swapped carbs, and it still runs the same. I am running out of time/money trying to find the problem. PLEASE HELP!!

[bwamos]

Sounds like your not getting enough juice from the stator to keep the spark hot when its in the high rev's.

Check your stator voltages, or have a shop check it for you. Also make sure all your bolts are tight on the stator.. sometimes one backs off causing you to loose a ground to some windings.

[brian250racer]

Thanks for the reply. I just went thru the yfz450 pages and found someone with similar problems. They changed the flywheel/stator and it cleared up. I just did the same to mine tuesday, now it runs perfect again!! The part that gets me though is everything was passing the Ohm/resistance checks the service manual has..Oh well. it's alive atleast!!!!:D

[whoamack22]

how does it run though, i might be getting me a yz400 hybrid , how you like it ? does it run with 450's or more in the z400 range?

[brian250racer]

It runs really good, but I can't compare it to other hybrids around here. I built this motor myself and put it in a Banshee frame. It fit in there alot easier than I expected. Without all of the twin cylinder stuff to deal with, it lost alot of weight. I race MX and Harescrambles with it, and it has been VERY good to me. It has definately had it's fair share of holeshots.

Motor mods: 420 big bore
13.5 comp piston
YZ450F exhaust cam
Port work on the head
other stuff I can't remember

Runs more along the lines of a slightlymodded 450. (pipe, cam mod, mild head work, etc)

[brian250racer]

http://img.villagephotos.com/p/2004-10/865257/241.jpg

Kind of a fuzzy picture, but, you get the idea...