MK3 smoke out of one muffler

Hi all. Fairly new to the board but have been getting a ton of help and information on small learnings so thank you for that everyone. I've been noticing smoke coming out of my right muffler only at idle sitting at a red light after riding the bike around for a bit. Cold start idle and for the first couple minutes of riding, there is no smoke at all. I have a MK3 with the single mikuni carb with unbalanced pipes and peashooter mufflers. The peashooter mufflers and unbalanced pipes are new on the bike but the smoke still was happening prior with the balanced pipes and bean can mufflers.

Any idea what the issue might be?

Worn valve seal and/or guide on the intake valve? The high vacuum at idle could be pulling the oil through the guide. When cold, the oil would not be as thin and might not get pulled through the guide. What does it do when warm and using the engine compression to slow down at closed throttle?

Dan1950 said:

What does it do when warm and using the engine compression to slow down at closed throttle?

Click to expand...

That's what I was gonna ask too. Decel draws a lot of intake vacuum.

maylar said:

That's what I was gonna ask too. Decel draws a lot of intake vacuum.

Click to expand...

Sometimes the smoke will not appear on deceleration until the throttle is opened. Then there will be a large puff of smoke. That is a sure sign of valve guide/seal issues.

Also potentially a slow oil drain from the rocker box. As oil builds up, it could then exploit a weaker intake valve seal on the right side.
When my 850 had similar smoke puffs on left, I changed out the two inlet vavle seals (with head still on and engine in frame) the original seals just crumbled away as they had perished from time. Fit Viton seals and noted immediate improvements. Still got some puffs at times and then cleared the drain drilling at edge of right inlet valve spring seat edge, by running a long wire down to timing chest and blowing through with air or WD40. No more smoking.

Dan1950 said:

Worn valve seal and/or guide on the intake valve? The high vacuum at idle could be pulling the oil through the guide. When cold, the oil would not be as thin and might not get pulled through the guide. What does it do when warm and using the engine compression to slow down at closed throttle?

Click to expand...

not entirely sure since I'm not looking at the muffler during a slowdown. Here is a quick video of the bike after a spin around town.

seoulshakers said:

not entirely sure since I'm not looking at the muffler during a slowdown. Here is a quick video of the bike after a spin around town.

Click to expand...

Looks like a head removal job comin' up.
Recommend fitting Kibblewhite solid Teflon seals.
Check the head gasket for any leakages into the offending side.

seoulshakers said:

not entirely sure since I'm not looking at the muffler during a slowdown. Here is a quick video of the bike after a spin around town.

Click to expand...

Since it is unlikely for a valve guide to be worn on just one side, I would lean towards a bad valve seal. Replace seals on both sides since the other one would be likely to fail soon.

Number one rule in repair is to opt for the cheapest/easiest fix first.

See https://accessnorton.com/NortonComm...al-tool-brilliant-2005.690/page-2#post-393677 for valve spring removal with head on. Or you could try the rope down the plug hole trick.