Smokin' Rebuild

[Shaw520]

Ok, in a previous thread I noted that I was doing a topend rebuild on an 05 TTR 125E. I went with a 55mm bore, (bored by reputable source) installed Wiseco piston/Rings, had the head redone,(guides, valves, seals) by the same source, checked ring end gap, assembled according to wiseco's instructions (ring cap spacing, manufactures mark on ring 2 is facing up, ect.) It runs like a top!... but it smokes on exceleration, I thought I mistakenly installed a ring upside, down are mis-aligned ring end gap, so I disassembled and checked everything, everything was fine, reasembled (made sure the oil ring was 'butted' and not overlapped) and it's still burning oil. I mean a little oil,... I would figure the rings just need to seat in,.. but this thing is seriously fogging when excelerating. something is not right. Its got me stumped. Compression is good, and it runs awesome. It doesnt smoke on decel or at an idle, so Im guessing the valve guides and seals are good, only on excel. I have checked the crank case vent, any suggestions greatly apprecieated.

 

[whenfoxforks-ruled]

Got to go with the valves Shaw. Seems a simple compression check would show the air escaping from the point of issue. I had a guy do a head for me, one of the valves was not seating correctly.

 

[Shaw520]

Got to go with the valves Shaw.

Im not thinking so,... improper guide/stem clearance or bad seals could cause oil consumption,.. but likely more prevelent under cylinder vaccum, like during decel, (going down a hill with throttle chopped).
Its not smoking a bit under these conditions,.. its smoking during combustion which would indicate rings/cylinder clearance. Ring end gap is at .010,.... I dont know, I will disassemble again tomorrow.... :|
Thanks WFF-R

 

[JunkmanDT250]

Some type of vent for the crankcase? perhaps it may be plugged causing oil to be drawn into the cylinder under accelleration. I know it sounds stupid but you did get the correct size piston right?

 

[Shaw520]

Crakcase vent is fine, Ive checked while running and I can feel the air moving in and out the vent tube as it should.
When I get a chance this week I will disassemble and take more measurements, like piston/cyl clearance, ring end gap, ect... is it possible wiseco sent me a bad ring? I know the #2 ring is supposed to be beveled with manufatures stamp facing upwards, but I've looked at it with a magnifing glass and cant see a bevel.

Any other ideas,..... Eric, Rich ?

 

[Rich Rohrich]

Shaw - The second ring being improperly marked (i.e. upside down), or just plain bad is certainly something to consider. It's rare, but it does happen.

Assuming the bore is round and straight, the bore surface finish is correct, and the piston to wall clearance is in spec I think you have to look at the second ring, the scraper rails and the expander (check for edge overlap) as possible culprits.

It certainly sounds like you have done proper due diligence up to this point in identifying the known good parts of the system.

 

[Shaw520]

Shaw - The second ring being improperly marked (i.e. upside down), or just plain bad is certainly something to consider. It's rare, but it does happen.

I think you have to look at the second ring

Yea, for what its worth I think I'll just replace those rings, while looking closely at the 2nd ring I noticed a sort of 'burr' on what they claim would be the upper side, (according to the manu. mark) and something just didnt look right with it.

Thanks Rich :cool: