2005 trx450r burning oil

[nizzer450r]

I have just rebuilt my 05 trx450r new piston , rings crank and main bearings . I stripped it because it was burning oil . Put it back together and it is still burning oil . Swapped the head for a head that came off a motor that didn't smoke . Still doing it I am lost NEED HELP !!!!!!!!!!!!

[Scro]

Well, there's two ways for oil to get into the cylinder. It's either going past the rings, or it's leaking through one of the valve seals. Are sure it's oil burning, and not maybe coolant?

[nizzer450r]

No it's definitely oil site glass is empty after 15 minute race , all rings are in correct position and gapped , only thing I didn't do when I rebuilt the motor is de-glaze the cylinder. Any suggestions ??

[Scro]

I'm not sure if it would be causing the problem, but I always lightly deglaze the cylinder when putting in new rings. Some people won't because of the nikasil. I think it helps the rings to seat. How long has it been running since the rebuild? A little smoke is normal right after a rebuild, but it shouldn't be enough to cause the oil level to drop that much. Also, it's unlikely, but measure to make sure your cylinder isn't ovalled. I've heard of that happening before.

[nizzer450r]

My mechanic has just done a compression test and it is only 48psi he also said there is no decompressor clearance ! . Could the decompressor cause it to use oil ?

[Scro]

No, the decompressor is spring loaded. When the bike is running, the cam is spinning fast enough to overcome the tension of the spring, and disengage the decompressor arm (think centrifical force). But when you are kicking, it's not spinning over fast enough to disengage it (hence less compression in the cylinder...easier to kick over). With no decompressor clearance, it will seem very easy to kick over, and cause a low reading on the compression test. Not to mention, make it harder to start. I don't think that could cause the oil problem, but I would set that up correctly before trying anything else.