Smoking

[bazz]

My xs650 engine is smoking
I bought it around 10 years without knowing any of its history
I made a test rig for it at the time so I could fire it up to test and I do not remember it smoking
But recently I've been running the engine a fair bit and it's smoking all the time as soon as you start it
Is it likely to be the valve guide seals gone hard?
Or more likely the piston rings?

 

[Jim]

As a general rule, smoking at idle and on decel is valve guides. Smoking all the time is rings...

 

[Jim]

Sitting for 10yrs... good chance it's stuck rings. I'd be tempted to pour a little penetrating oil down the plug holes and let it sit for a week or so.

 

[bazz]

Sitting for 10yrs... good chance it's stuck rings. I'd be tempted to pour a little penetrating oil down the plug holes and let it sit for a week or so.

I should add compression seems ok
It's 132psi both sides

 

[jetmechmarty]

There is a procedure for replacing the valve seals without pulling the engine. (If you come to that.)

 

[bosco659]

There is a procedure for replacing the valve seals without pulling the engine. (If you come to that.)

Been there, done that. A finicky process but saves pulling the motor.

 

[bazz]

I should add that after riding the bike a couple of times times the smoking has got a fair bit worse
IE when you start it it belts the smoke out immediately
I'm guessing this is more likely rings than seals or guides

 

[Its been a long time]

I should add that after riding the bike a couple of times times the smoking has got a fair bit worse
IE when you start it it belts the smoke out immediately
I'm guessing this is more likely rings than seals or guides

Sounds like might be time to open it up for a look?

 

[bazz]

Sounds like might be time to open it up for a look?

Yep I reckon so
I've no Idea of the engines history
It sounds pretty quiet and runs quite well
It starts immediately etc
It's just the smoke
I bought a spare barrel and pistons in really good order a couple of months back as a backup plan
Unfortunately I won't be able to work on it for a few weeks
I have a full gasket and engine seal set including valve stem seals
So I'll stick some photos up when I pull the engine
What's the consensus on changing the cam chain and tensioner whilst I'm in there?

 

[Its been a long time]

Yep I reckon so
I've no Idea of the engines history
It sounds pretty quiet and runs quite well
It starts immediately etc
It's just the smoke
I bought a spare barrel and pistons in really good order a couple of months back as a backup plan
Unfortunately I won't be able to work on it for a few weeks
I have a full gasket and engine seal set including valve stem seals
So I'll stick some photos up when I pull the engine
What's the consensus on changing the cam chain and tensioner whilst I'm in there?

Everyone has a different viewpoint of course. For me, on an engine with little or no known history I would be inclined to replace the known service items whilst in there. Good luck with it.

 

[jetmechmarty]

I had a smoker. I had the bike since new. Here’s the thread.
https://www.xs650.com/threads/sensible-engine-decision-now-top-end-refresh.57859/

 

[Jim]

What's the consensus on changing the cam chain and tensioner whilst I'm in there?

For me, on an engine with little or no known history I would be inclined to replace the known service items whilst in there. Good luck with it.

My rule of thumb: If you have to pull the engine to replace it, replace it while the engine is pulled. The chain and guide don't really add much cost to the rebuild in the grand scheme of things. I'd change 'em.

 

[Its been a long time]

My rule of thumb: If you have to pull the engine to replace it, replace it while the engine is pulled. The chain and guide don't really add much cost to the rebuild in the grand scheme of things. I'd change 'em.

100% agree. Small beer in the overall scheme.

 

[Grimly]

My rule of thumb: If you have to pull the engine to replace it, replace it while the engine is pulled. The chain and guide don't really add much cost to the rebuild in the grand scheme of things. I'd change 'em.

Yep, it's a pain in the arris to have to pull it apart again.

 

[bazz]

Stripped my engine today hoping to find the cause of all that smoke but no smoking gun as yet
The cam chain tensioner guide was totally worn out and a bit of wear on the bores but nothing major
The valve guide seals weren't too bad and zero wear on the valves and guides
I was really hoping to find the valve guide seals hanging off but they weren't that bad
Where else should I be looking?
Cheers

 

[Jim]

Where else should I be looking?

Pistons, rings and bore, obviously.
Also, it's very rare, but look the head over real good for cracks that go up towards the rocker box. Oil can make it's way into the exhaust/intake ports that way.

 

[bazz]

Got my xs motor back together today after fitting new rings, giving the bore a light hone, new valve guide seals fitted,new cam chain and guide
The engine fired straight away and held an idle but as it started to warm up it started smoking
The smoking was mainly on the right cylinder
The hotter the engine got the worse the smoke got
When it was apart the bores looked pretty good
There was less than 4 thou between the pistons and barrel
And I have certainly seen a lot worse than this without any smoking!
The smoke was neither blue or black I'd call it more grey
Is it possible it's running too rich and causing smoke but not enough for black smoke?
It doesn't smell rich
I'm pretty gutted

 

[bazz]

Got my xs motor back together today after fitting new rings, giving the bore a light hone, new valve guide seals fitted,new cam chain and guide
The engine fired straight away and held an idle but as it started to warm up it started smoking
The smoking was mainly on the right cylinder
The hotter the engine got the worse the smoke got
When it was apart the bores looked pretty good
There was less than 4 thou between the pistons and barrel
And I have certainly seen a lot worse than this without any smoking!
The smoke was neither blue or black I'd call it more grey
Is it possible it's running too rich and causing smoke but not enough for black smoke?
It doesn't smell rich
I'm pretty gutted

I stripped it down because of the smoking and the main difference now is before the strip down the motor would smoke as soon as it was started
Whereas now it seems to smoke as it heats up
Also when I pulled the plugs to take a look there was wispy smoke coming out the spark plug holes! Would burnt oil do this?

 

[bazz]

Pistons, rings and bore, obviously.
Also, it's very rare, but look the head over real good for cracks that go up towards the rocker box. Oil can make it's way into the exhaust/intake ports that way.

I couldn't see any cracks when it was apart
But I'm now thinking it's a possibility

 

[bazz]

I'm wondering if the carbs are running rich enough to cause the smoke
But not rich enough to cause black smoke?