YFZ 450 Help

My Cousins 04 YFZ450 Raptor and it runs great but recently started burning oil in larger amounts, and smoking blue heavily, but still running great. There was a good amount of oil coming out of the exhaust. I just took the motor apart to rebuild the top end to replace the piston and rings. But to find it was a 97mm big bore piston kit "ESR" and piston looks great and rings look fine. I dont know if it is just the rings or the valve seals to be replaced. Not sure whether to run the big bore kit with a new set of rings or just get an oem cylinder and piston.

 

Time to sell that piece of shit and buy a honda.

 

I did try that seems that no one cares anymore . LOL

 

A yfz450 raptor? Is it a yfz motor in a raptor? Why would he do that?

Sorry for the off topic-ness, just kinda curious.

 

just because the rings "look good" doesn't mean they are. Any blow by on the piston skirt? I agree, a leakdown test is the best way to diagnose.

 

i say new rings and new seals for the ESR piston if you arent looking to burn a lot of money, otherwise your gonna need new piston and jug, and to dyno tune and re jet for the new piston and compression ratio. by the way, if it is a hi comp piston in there right now you need to run race fuel in it, anything above 13:1 or so. if at all possible finding out exactly what piston ratio it is will get you in the right direction. on the other hand, if the rest of the bike is mostly stock, then the rev happy motor seems a little flat when you only put a big bore kit on it. i have a 98mm bored and stroked YFZ and until you add cams and some head work with the bigger jug, it doesn't flow right. i've built two YFZ's since they first came out, an 04 and my current 05, if you wanna chat, ive been inside and out of that motor a lot. PM me for my number if you want.

 

I knew i shoulda done a leak test but i didnt have a tester. I already got the OEM piston and rings and gaskets. I know where to get a good used oem cylinder for a good price.

No blow by on piston skirt.

 

I knew i shoulda done a leak test but i didnt have a tester. I already got the OEM piston and rings and gaskets. I know where to get a good used oem cylinder for a good price.

No blow by on piston skirt.

 

Sounds like an expensive issue, did you have the right amount of oil in it?

 

Think so , not exactly sure its not my quad.