XR smoking after full rebuild

[winter_rules]

My XR 250 was burning a touch of oil after it got fully warmed up a year ago so I decided to have it rebuilt before the problem got worse and while I had the money. After $1000+ I got it back and it STILL smokes!! It's a blue smoke...I'm almost positive it's oil. I brought it back to the dealer and they tore it all apart again but didn't find anything wrong. Since then I've decided to just ride it, if it blows it blows. With a labor rate of $80/hr I can go through a bit of oil. However, with spring and new riding season coming underway it's bugging me a lot. I usually lead my brothers on their four-wheelers but once it gets smoking I end up following them so they don't have to deal with it. This the #1 reason I bought this bike over a KDX 220...no smoke! Do you guys have any thoughts of what it might be? Thanks a lot! :cool:

 

[SpeedyManiac]

Did the valve seals and seats all get replaced? Also, that's where my money would be if the bike was properly broken in with a new piston and cylinder.

 

[fiejasgr]

sometimes it takes a little while to get the rings in the cylinder to seat and seal like they should, not sure how many hours you have on the bike since the rebuild.

otherwise it could be due to valve seals (more than the seats) like Speedymaniac metioned above, another possibility is that the cylinder wall is not exactly true, which might be why it smoked from day one. did you have it bored and honed.

hopefully it is just valve seals. Goodluck. :cool:

Jake

 

[winter_rules]

It has about 150 miles of mainly 1st-3rd gear riding since the rebuild. I'm not sure what they changed with the valves, but when I brought it back they checked everything and adjusted the valves for me. I would think (hope) that they would have replaced them if something was in question. It was overbored as part of the rebuild. Thanks guys!

 

[BadgerMan]

Did they double check the oil ring assembly to ensure it was installed correctly? It's pretty easy to get the ends overlapped.

 

[Uchytil]

A full rebuild should have included a piston to cylinder clearance. Ask them what the readings were for the bore. See if there is a bore diameter, out-of-round, and taper spec. If these readings were out you may never get a correct ring set. If the bore is bad a rebore or something else may be required (sleeve/new cyl). The piston should have been measured and/or replaced. If everything was cool a good petroleum based oil is best for inital ring set. The valves may also be a problem (seals or guides). Usually they (unless really bad) smoke upon initial start up from oil passing into the CC when it sits overnight and sometimes clears up after a little while (not always the case though). What year is the bike? Get a manual and check what's been told to you by the shop. Maybe there is a DRN'r that lives nearby that can help you out.