Right Exhaust on Mk3 Smoking After Engine Stop

glcaines · Jun 20, 2022

I have a 1975 Commando Mk3. The motorcycle runs really well. There is no visible smoke out of either exhaust while riding or while the engine is idling. The engine idles great it runs very smooth and strong. I have never had to add any oil and the engine has excellent compression. The spark plugs look great with no oil on either plug. The problem is that when I shut down the engine after it has been running more than 2 - 3 minutes, a large amount of smoke comes out of the right exhaust. No smoke comes out of the left side. It is a very light-colored smoke which continues to come out for about 3 - 5 minutes. I'm at a loss as to the cause. I've put around 500 miles on the bike since I purchased it and this has only developed recently.

Shelby-Right · Jun 20, 2022

It might be oil getting down from the valve guides , also if you do a big de-throttle down a hill ,ask your mates of there is a puff of smoke .cheers.

chaztuna · Jun 21, 2022

Check to see if the right side intake valve seal has come loose from it's valve guide. See posts #3 & #18 linked below. FYI, the valve spring can be removed without removing the cylinder head.

https://www.accessnorton.com/NortonCommando/teflon-seals-and-valve-stem-wear.32167/

Valve Seal Installation Tool info

https://www.accessnorton.com/NortonCommando/valve-guide-seal-mod-2016.21481/

chaztuna · Jun 21, 2022

Download the attachment on post #28 of the link below for Ludwig's DIY "in situ" valve spring removal tool.

https://accessnorton.com/NortonComm...al-tool-brilliant-2005.690/page-2#post-393677

marshg246 · Jun 23, 2022

glcaines said:
It is a very light-colored smoke which continues to come out for about 3 - 5 minutes.

Blueish or white? Feel the inside of the muffler when cold - is it oilier than the other side? Does it do it after a longer run too? If the smoke is white, it may be condensation, but I can't imagine on only one side.

Torontonian · Jun 23, 2022

marshg246 said:
Blueish or white? Feel the inside of the muffler when cold - is it oilier than the other side? Does it do it after a longer run too? If the smoke is white, it may be condensation, but I can't imagine on only one side.

Fit new Teflon intake guide seals . You likely will have to pull the head which is a big job. Don't use O.E.M. rubber seals.

Shelby-Right · Jun 23, 2022

I have done seal and spring changes mainly on cars with chainsaw pull rope, feed a good amount in then bring that cylinder to TDC , you might need to make a special lever and cut away pipe to assist in getting valve spring compressed , keepers out , pull that rocker shaft 1 st of course , might be worth a crack ? maybe someone who has had a go could chime in , otherwise its as torontonian suggests .

chaztuna · Jun 24, 2022

glcaines said:
I have a 1975 Commando Mk3. The motorcycle runs really well. There is no visible smoke out of either exhaust while riding or while the engine is idling. The engine idles great it runs very smooth and strong. I have never had to add any oil and the engine has excellent compression. The spark plugs look great with no oil on either plug. The problem is that when I shut down the engine after it has been running more than 2 - 3 minutes, a large amount of smoke comes out of the right exhaust. No smoke comes out of the left side. It is a very light-colored smoke which continues to come out for about 3 - 5 minutes. I'm at a loss as to the cause. I've put around 500 miles on the bike since I purchased it and this has only developed recently.

Please check your "conversations" [aka private messages]. Sign in and click the envelope icon at the top/right of any page. See posts #67 & 70 linked below for more info.

https://www.accessnorton.com/Norton...manual-parts-catalog-errors-2017.23083/page-4