I just got it used it has a 13.1 jd piston just reringed and sleave pressed timing chain advanced 1 tooth (exhaust I think) at idle it seams to knock at first I thought it was a fuel knock so I put it up to 104 octane runs great but still knocks at idle. I thought the crank could be going though I can't realy pin point where its coming from I also have some gas in my oil but i figured that was from running 93. if its gonna pop so be it i have a 471 stroker kit for it. is it safe to ride 12-15 mile trips any thoughts thanks.

 

First, the Yamaha 450 tends to have a lot of engine noise compared to others. Before you get to crazy, is there a good running example you could compare it to(could be a dirtbike too?) Otherwise, I would probably have replaced the piston vs re-ring. The whole top end wears out quickly on these.

Gas in the oil has nothing to do with octane, but you may have a float issue, or maybe the piston is out of spec. Somehow gas is likely getting past the carb and your piston/rings.

 

my brother inlaws friend has the same modle and mine just seams to have more of a knock he said it could just be the high compression piston with the stock crank I have a 470 stroker kit waiting just don't want to rip apart a good engine thanks

 

If you already have the parts to rebuild, I would do that. We have a high comp and a stock comp YFZ. My brothers(hi) has always been a bit louder than mine, but when it was noticeably louder it was due to his piston being worn out/top end needing replaced.

 

Just got a manual this thing looks fairly easy compaired to my old 700 sportsman. I'm gonna check the valves this week end and change the oil and filter if it is a lower bearing making the noize I would have a power loss shouldn't it? or if its coming apart is the filter a small enough micron to catch flakes? In the first post I said reringed it's suppose to have a new piston/rings and sleeve installed. it also doesn't seam to blow any smoke either.
Thanks
Matt

 

changed my oil today I guess we are tearing down its got a funny silver tint to it awfully shiny to I'm guessing flakes off of the rist pin or crank bearings have you ever split the lower case on one these (scooter86). I'm an engine mechanic but I'm used to ones without spark plugs.
just wondering what I'm getting into. I never split the lower case on anything I owned.

Thanks
Matt

 

Funny you ask, because I haven't. Mine is waiting to be done though, a lonely bottom end sitting on the dining room table, lol. There are a few vids of people doing it online. The big pain looks like the trans and keeping it all sorted out.

 

I'll dig in and let ya know I prob. start next week see if it will pop till then right before spring realy starts that sucks

 

almost done just waiting on cams ready to ride sucks waiting