Like you may have read in my previous posts, my Zilla has developed a noise, and will not rev past 4-5K RPM, will sputter and pop and not rev anymore.

I pulled the flywheel, and noticed one of the wire wraps is kind of loose. I found out form Ricky Stator that it is just a lighting coil, and has nothing to do with engine operation. hmm.. I then grabbed the crank and wiggled it up and down... play.

Not a whole lot, but there is a little bit there. Does this mean that the seals are bad and the motor is severely leaning out and therefor not revving? Could this be the noise I was hearing? Now someone tell me this. Is there ANY way to tell if my Zilla has the machined bearing boss's from what I am looking at? (the outside of the left main) Thanks for any help, people.

 

When my big end rod bearings went on my QR250 it made a pant load of noise, but it reved fine. From what I am told of my buddies zilla when the mains are going you have no performance loss, as a matter of fact it usually will rev out of control if it goes lean due to a bad bearing or seal. If the rod lets go you (and the whole neighborhood) will know it.

 

350X,
It's a common problem bud! and frankly, I'm not surprised.
I've owned mine since it was new, and it's really been pampered... Happened to me too!

When mine got loose, the crank seals weren't doing a really good job thus creating a really lean condition. I didn't burn it down because I'm quite sensitive to my jetting. I went up 5 sizes on the main jet to keep it running for the rest of the weekend. (not recommended)
I never noticed any noise from mine, but it's certainly a possibility.

A possible reason it won't rev would be the severely lean condition. (Wild guess here)
As friction increases, the ability to rev would decrease... usually you don't get much notice before the piston is melted into the bore.

There is NO way to tell if it's already had the boss inserts without disassembly, but chances are it doesn't... the brass inserts are usually a permanent fix to the problem.

The best advice I can give is to find a reputable shop that's done a bunch of these, and get it taken care of... Otherwise, you're sitting on a time bomb.
Do you research!! and find a reputable shop! (I could make some recommendations for you, but it's best that you draw your own conclusions)

Good luck!