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Smoking 650SS

Submitted by andrew_teague on Wed, 22/02/2012
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Heavy Twins

Does any one have any ideas as to a resolution of the following problem.The backgrouund is that the engine has been in the hands of a well known Norton man to rectifiy an engine rumble.The crank was reground,new gudes,valves & springs and new piston rings.This was about 5 years ago.I only refitted the engine at the end of last year(naughty boy!)The engine started easily 2nd kick,mechanically very quite, but smoked heavily.I checked the oil retun which was ok.It was filled with grade 50 oil.I suspected maybe oil pressure build up in the crankcase,I drained the oil out of the sump and tried again.Oily soke and oil dripping out of the scilencer,exhaust pipe joint.I spoke to the engine builder who suggested that a ring may have stuck,run it for 10 minutes,this didnt cure the problem.

The whole bike was returned late last year.The engine i'm told has been apart,bores measured and within tollerence,new rings installed,still smoking,(the silencers have been cleaned to remove oil residue)A further set of new old stock rings installed only the top and oil control where available,the silencers removed(to remove doubt about trapped oil) and run again,still smoking!!!The engine builder is at a loss,so am I as I'm merely a home mechanic.I'm convinced that it has to be the bores/piston rings as there is oil litterally seeping out of the exhaust systemwhen the engine is run.

I am considering going to +20 and getting new pistons and rings.Before I take this expensive action does anyone have any bright ideas please?

Many thanks Andy Teague

Submitted by tony_ripley on Wed, 22/02/2012

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Hi,

If it smokes badly at tickover can you remove the rocker covers and see if the head isfloodingwith oil ? If the valve guides are not quite as they should be oil could be finding its way down between the head and the guide or if the oil is deep enough it could be running down the valve inside the guide.

I think it would beunlikelyto be pistons / rings if unburnt oil is coming out theexhaust. More likely top end.

Regards

Tony

Submitted by Xanna_jeannett… on Wed, 22/02/2012

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Hello - Have you looked at the pressure relief valve, it may be sticking open!Also did you clean out the drain hole from the inlet valve side and down the back of the barrel then in the crankcase there is a elbow this gets blocked up with gunge, it comes out into the timing side , and you should be using a good 20/50 same as Austin mini oil made for ball and roller bearings, as Mini's have their gearbox under the engine hope this may do some good.

Submitted by anthony_duffield on Wed, 22/02/2012

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Andy,

Check the crankcase breather, remember pistons and bores are splash lubricated, standard lube system for the rocker gear etc is fromthe oilscavanged from the sump.

If there is that much oil being expelled from the exhausts you have a serious amount of oil getting past the rings, excessive crankcase pressure just might be the answer.

Good Luck

Tony

Submitted by eugene_brolund on Wed, 22/02/2012

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Hi Andrew,

I had a similar situation on an 850 Commando I used to have & it was a stuck pressure relief valve, but checking the rocker covers for oil flooding seems like a good idea also, as that could also cause some oil in the exhaust. The bit about the oil is a hot topic here :0 I use straight 50 weight, my bike has no filter (yet) so I use non detergent, but in any case I am fairly certain that your issue has nothing to do with whatever oil you use.

Skip Brolund

Submitted by colin_sharpe on Thu, 23/02/2012

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I had a very similar problem on my '69 S. The problem turned out to be that when the old, worn out valve guides were removed, the hole in the head was scored, allowing oil to run down the outside of the guide into the combustion chamber.

Submitted by Xanna_jeannett… on Sun, 26/02/2012

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Previously wrote:

Hello - Have you looked at the pressure relief valve, it may be sticking open!Also did you clean out the drain hole from the inlet valve side and down the back of the barrel then in the crankcase there is a elbow this gets blocked up with gunge, it comes out into the timing side , and you should be using a good 20/50 same as Austin mini oil made for ball and roller bearings, as Mini minors have their gearbox under the engine hope this may do some good.

Hello Yes a lot of you may have hit the nail on the head , I been checking my bike and found a broken valve guide in the right exhaust port . I will have to wait , until after the Hobbies Exhibition In Goole And Then We take a good look at it. ? I will let you know what I find ???? your Anna J

 


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