please help

Hey everybody,

I need some help with my 80 xj650. Here is a little back story. I have gone through the entire bike, modified the frame, built a new wiring harness, painted it, you name it. I took the top end of the engine apart about six months ago because the bike appeared to be burning some oil (exhaust smoke with an oily smell, enough to clear out the garage). Since then I took the engine down, put new pistons rings in it and gave each cylinder a good hone, and put it all back together. I am still burning oil I think. I know my carbs need to be adjusted some more because the bike is running rich and the throttle tends to "hang" but i dont think that is the sole cause of any smoke coming from the exhaust. I have only run the engine for about 10 minutes total since the rebuild and smoke starts pouring out about 2 minutes into it running. So I am kind of stuck here. I looked into new oversized pistons for the thing but I was surprised to find that there are few available and the ones I have found are incredibly expensive. As of now im thinking that my cylinders are egged and oil is blowing by the rings. ( forgot to mention that I changed all the valve seals and did a valve adjustment during the rebuild as well). I put 10w40 oil in the bike each time. My question really is that if i am burning oil with new rings, what are my options to get this thing running clean again? I don't have a ton of money to throw at this and I am looking for some alternative to throwing a bunch of cash at it. Has anyone ever changed the cylinder sleeves? Is there somewhere I can get a piston kit? Should I look at trying to find a used set of jugs that are standard size and in good shape? Any tricks or anything im overlooking that could be the root of this problem? Please help. Thanks.

 

A fresh rebuilt engine may smoke awhile when first started up.The rings need to seat in , if all was reassembled correctly. When I do my VW engines run it about 3000 rpm for 15 minutes I don't want it idle but bring it down to 2000 rpm for another 10 min. The whole time cking for leaks and run it back up to 3000 rpm for 10 minutes. ( neighbors love me) then let it idle....it sometimes look like a mosquito fogger. Shut it down ck oil level and ck for leaks. You need to run your engine a little before tearing it down again. Good luck cheers

 

Thanks Jetfixer, I will try to let it run for a while tomorrow and see where I'm at. It is just not my luck for this to be as easy as to let it work itself out. Thanks for the tip, I hope that's all it is.

 

don't run it 3K for that long without a good fan on it

 

I will probably put it on the dyno and let it break in on there.

 

Let's say that giving the engine time to break in isnt enough. Where would you go from there? Like I said, I don't have a lot of money to dump into this thing now that i've done everything else. Is it possible to put 750 pistons in and bore to that size?

 

Replace valve seals?
Worn dry or cracked valve seals will cause smoking on start up.
Alan

 

maybe a dumb question, but when you replaced the oil ,did you fill to the window on the clutch case, or could you have gas leaking into the crankcase, via a stuck float needle . overfilling can cause smoke.
stu

 

Compression readings ?

 

+1. I was thinking the same thing - first thing I would want to know with a possible engine issue are the compression values. If it's burning oil, then it could be coming in via leaking valve sleeves or rings. st Doing a compression test can tell me which.

 

Compression test to come, but I think you are referring to a leak-down test which I will also do this week. I adjusted the carb some today and it helped out a lot with the smoke. After the bike gets warm there still is smoke coming out of the tailpipe though. I did change all the valve seals and did a valve adjustment during the last tear down. The engine sounds smooth while running. I need to get it up on the dyno and sync the carbs to alleviate any symptoms of that being confused with burning oil. I will post back after I check all these things. Thanks guys.

 

I bet you just need the rings to seat, a few blast of 10- 15 seconds in 3rd gear of full throttle , then no throttle for 15 seconds , would likely seat them, but get it tuned as well as possible before hand.
Alan
I always did that on car engines I rebuild , small block Chevys, Ford 2.3 etc .
They all were strong engines afterward

 

I should midifie that go from about 2000 rpm to 8000 rpm T full throttle, slow with engine( no brake or clutch), about 6-8 runs , that will seat the rings in,,, 10 seconds would be way over redline

 

You should have 20w 50 motorcycle oil in it

 

all the seafoam burned out yet? that makes the smoke when you treat the cylinders with it.
ride it slow for a while following factory break in period

 

ALRIGHT GUYS GOOD NEWS. PUT THE BIKE ON THE DYNO AND LET IT RUN AT ABOUT 2500-3000 RPM FOR ABOUT 15 MINUTES AND LIKE A SWITCH, THE SMOKE WAS GONE AND THE RINGS FINALLY SEATED IN. WHAT A RELIEF. I HONESTLY THOUGHT THAT I WAS GOING TO HAVE TO GO BACK INTO THE THING. THANKS TO EVERYONE FOR THE INPUT AND HELP. WHEN THE BIKE IS COMPLETELY FINISHED I WILL POST PICTURES AND ANSWER ANY QUESTIONS ABOUT THE BUILD. THANKS AGAIN FELLAS.