Oil and smoke in right-side exhaust

cbertels

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Long time lurker, first post. I just wrapped this one up and have a ton of smoke coming from the right side exhaust. It kicks and fires up after 3-4 kicks. Oil is getting into the right side somehow. In searching it looks like it’s typically rings, valve stem seals, valve guides, or some combination.

I did a top end rebuild that involved all new gaskets, cam chain and guides, new rings, valve guide seals, and other typical consumables. During tear down nothing seems concerning. Spot build up but not a ton. No damages to cylinders or pistons. Valve train looked fine too. Nothing way out of spec.

For diagnosis I got 145 on both cylinders. No visible oil leaks outside the engine. The right exhaust is about 1-2 tablespoons of oil in it. I added some to the tappet cover to see if it’d drip down the valve stem but nothing visible. I’m assuming I’m looking to do valve seals again since it’s the easiest but looking for guidance or other diagnosis steps to take.

Thanks!!
 

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I had same problem with my KZ305 after a top end rebuild, smoking out of one pipe. It turned out I damaged 1 intake valve seal when reassembling.
I was able to replace the damaged seal by stuffing the cylinder with nylon cord and not removing the head.
 
As a rule of thumb, smoke on startup and decel is valve seals.
Smoke constantly is rings.
That’s what I’ve gathered. The smoking was bad enough I haven’t had a chance to take it for a ride. Idling a little high ATM too but need to tackle the smoking before that.

Any reason not to start with seals first? I did them and the rings when the top end was off but I guess something could have gone wrong.
 
Took forever to get seals and plan on tackling the job with the motor in and see how it shakes out. The writes ups are incredibly thorough and seems straight-forward enough.

Anyone have a similar issue and it be from the intake side rather than the exhaust side? Figured I’d start on the exhaust side since that’s where the oil seems to be pouring out of and if no improvement, try the intake side. I have enough to do all four but since the left side is fine (so far), I’ll leave it be for the time being.
 
Took forever to get seals and plan on tackling the job with the motor in and see how it shakes out. The writes ups are incredibly thorough and seems straight-forward enough.

Anyone have a similar issue and it be from the intake side rather than the exhaust side? Figured I’d start on the exhaust side since that’s where the oil seems to be pouring out of and if no improvement, try the intake side. I have enough to do all four but since the left side is fine (so far), I’ll leave it be for the time being.
Personally, I'd have suspected the inlet valve stem seals as being of much more importance in reducing oil ingress to the combustion chamber. Certainly as a general rule in IC engines that is the case. Others with more experience of the XS650 engine may know more than me. Good luck with it.
 
Personally, I'd have suspected the inlet valve stem seals as being of much more importance in reducing oil ingress to the combustion chamber. Certainly as a general rule in IC engines that is the case. Others with more experience of the XS650 engine may know more than me. Good luck with it.
Agreed
 
Given the amount of oil in the exhaust itself, I figured it was leaking past the value and I to the pipe. Wouldn’t expect that from the intake just based on its orientation.
 
Given the amount of oil in the exhaust itself, I figured it was leaking past the value and I to the pipe. Wouldn’t expect that from the intake just based on its orientation.
To be honest, I think that's very unlikely you will solve your problem.

The inlet valve guide and stem seal is subject to vacuum on engine inlet stroke. The exhaust valve isn't. On a closed throttle, quite high vacuum is pulling oil down the valve stem.

Without seeing this, it's hard to say, but I suspect you have worn valve guides as well as bad seals.

Personally, I don't hold out much hope, if any, of an improvement by just changing exhaust valve stem seals.
 
To be honest, I think that's very unlikely you will solve your problem.

The inlet valve guide and stem seal is subject to vacuum on engine inlet stroke. The exhaust valve isn't. On a closed throttle, quite high vacuum is pulling oil down the valve stem.

Without seeing this, it's hard to say, but I suspect you have worn valve guides as well as bad seals.

Personally, I don't hold out much hope, if any, of an improvement by just changing exhaust valve stem seals.
I’ll do both since it was only about an hour’s worth of time now for the exhaust side. Just wasn’t the side I would have expected.
 
So this fix may have worked and I’m pretty surprised. Did both the intake and exhaust on the offending side. Process was easy thanks to the guides from members. I’m still getting what seems like a sooty residue after starting when cold but I think it’s a tuning issue or old oil burning off from the older leak.

I went with a set of VM34s and don’t have any experience with them yet buts another thread.
 
So this fix may have worked and I’m pretty surprised. Did both the intake and exhaust on the offending side. Process was easy thanks to the guides from members. I’m still getting what seems like a sooty residue after starting when cold but I think it’s a tuning issue or old oil burning off from the older leak.

I went with a set of VM34s and don’t have any experience with them yet buts another thread.
You shouldn't be surprised if you changed the inlet valve stem seals. Sucking engine oil down the inlet valve guides into the combustion chamber is extremely common due to the suction on the induction stroke. Well done if you fixed the problem.
 
I’m surprised only because it had new guide seals to begin with. I replaced them and all the wear items in the top end and a few case seals where it appeared oil was leaking from the prior owner. Maybe I botched them or had crap replacements the first time.

I think it goes without saying replacing them with the head off is far easier than the hack with it on. Since I couldn’t fully see the seal I was skeptical that it was on fully or sealing well. I Had it idling for about 5-10 mins and it was markedly improved prior to the repair. I’ll need more run time to know for sure but I think I’m making progress.

Thanks everyone again for the help.
 
I’m surprised only because it had new guide seals to begin with. I replaced them and all the wear items in the top end and a few case seals where it appeared oil was leaking from the prior owner. Maybe I botched them or had crap replacements the first time.

I think it goes without saying replacing them with the head off is far easier than the hack with it on. Since I couldn’t fully see the seal I was skeptical that it was on fully or sealing well. I Had it idling for about 5-10 mins and it was markedly improved prior to the repair. I’ll need more run time to know for sure but I think I’m making progress.

Thanks everyone again for the help.
As you've found out, not all valve guide seals are created equal. I hope you've sold the problem.
 
How does a valve seal get damaged during reassembling?
Lack of knowledge and carelessness.
It's quite common to seat the seal then ram the valve up through the guide with scant attention paid to safeguarding the lip of the seal as the collet groove passes it.
First thing you know about it is on start-up and it smokes like a bandit. There's no short-cut but to re-do it again, and if you're unlucky your engine won't be one that allows in-situ access to the seal like shown above.
I always put the valve through, then put a piece of polythene over the stem before putting the seal down, that way it's protected.
Never had one fail, and have been especially careful of the Viton seals because of the cost of them.
 
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