I have a 92 evo that I recently rebuilt. Upon start up, it ran but I could hear a tapping sound coming from the motor. I pulled the push rod covers and found the rear intake pushrod was loose and rapping around inside. I tightened it up, started it and it ran fine. The next day I started it blew out a puff of smoke. I revved it up and still smoked until I went for a ride and it disappeared. When I came back, I left it running and leaned it on the kickstand and it started again. The crankcase breather runs to a separate filter so it's not going back to the carb. Someone told me it could be the valve spring seal on the head that may have been smushed down. I hear that's a tough job replacing those springs. Before I try that method, do you guys have any other thoughts or suggestions i could try first? Thanks.

 

Sounds like oil is "puddling" in one or both heads, causing the head to become over full with oil that should be running down to the crankcase.

Since it started up again when you leaned the bike over on the jiffy stand and it didn't do it when the bike was upright I would look to the return(s) being clogged or the valve cover/cylinder head gaskets being installed incorrectly.(or wrong gaskets)

If to much oil accumulates in the head the valve seals will leak, especially after setting a while.

Check the plugs for signs of oil contamination and this may help you identify which head is the culprit.

 

The bike is a 92 with original seals. It sat for two years in pieces with no oil or anything. I know they're cheap, but how expensive is it to have a shop install them if the other things you mention are ok?

 

When I first got my bike is was a freshly remand motor from the factory.

It would smoke just a little from the rear jug but it wasn't much and it only did it cold so I didn't worry about it.

It eventually stopped and doesn't do it any more.

 

Sounds to me like valve guide seals or some process that would, as Kabear said, cause oil to puddle in the rocker box.

 

Valve seals are an expensive job I'm told no?

 

I've never had that job done to a bike, but I had it done to a V-8 and it was only $35 or so. It is really simple, just requires the special tools to compress the valve springs.

I kind of agree with Texas, if the bike sat awhile it might be worth the wait and see.

But, from what you said and then added to I'll bet on an exhaust seal gone bad/broken and that is what is plugging the oil passage and allowing oil to drip into the exhaust and burn on start-up. Exhaust pressure will keep the oil in the valve cover once it is running. Where as an intake seal gone bad would be "sucking" oil in on every stroke.

Look for oil in the exhaust pipe after the bike sits for a couple of days. Running it like this won't hurt it because the "leak" is after the fact, not in the combustion chamber. If it is an exhaust seal gone bad.

 

You say rebuilt. But it really doesn't sound to me as though it's rebuilt. My definition of rebuilt would be, well, rebuilt. Anything that is serviceable, is serviced and /or replaced.
So if it's not a complete rebuild, what is it? If you did a ring job, it could be that the rings haven't seated yet. Cast rings seat pretty fast if everything is perfectly round. Moly rings can take a good amount of miles before seating.

 

I'm still an amateur at this so bare with me. Although I did replace all the rings and gaskets from the base gasket up. The thing that I find weird is that when the rear intake pushrod was loose, the bike still ran it just had a rattle to it. When I tightened it up, that's when the smoke began coming out of the rear cylinders exhaust. The bike still runs good and has plenty of power, I just hate that smoke. Like I said it smokes at start up then goes away. When I return from the ride and put it on the kickstand, it really starts smoking. What do you guys think I should do. The reason I believe it could be the valve seals is from that bouncing around of that pushrod on the intake side may have smashed it which in turn is allowing oil in.

 

OK, did you have it running prior to the tear down and rebuild??? If so did it smoke then??? Did you change anything, like the cam?? Are you sure all the gaskets are on right and the drain holes are lined up???
John