Running in after rebore and new piston

M

Mtoliva

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Location
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My 1974 1000 3c was running fine but has now started to run rich on all three cylinders and using huge amounts of oil which seems to be coming out of the exhausts and mixing with carbon to form a oily wet black paste inside the exhaust outlet.Plugs are black but not wet.

The engine has had major work over the last few thousand miles including new valves, followers and guides, pistons may have had some attention, new rings and honing ( not sure how good , suspect fairly basic)

The bike runs fine without any problems, any suggestions aside from another engine rebuild
 

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The bike was fully restored over the past 20 years, including carb refurbished with Dellorto stock parts, I’m not sure what jets were used but the bike ran fine , ie clean plugs for the first 500miles I owned it then something changed. Very vague and I haven’t directly answered your question.
 
Main jets are easy to review. Just open the lower plugs of the carbs and take one out.
But at low revs the small jet is important and needle, kind and position and needle jet.
Check choke and will the rubbers at the end of the choke cable close the choke jets?
 
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I’d estimate a litre over the last 200 miles, White smoke yes but not as bad as a two stroke, most of the time its not really noticeable
 
Oh, that does not sound so good. Engine needs a check by a specialist.
Compression check, is the oil blown in the air filter? Was to much oil in the case?
Good luck
Andre
 
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1 litre in 200 miles???? Something has gone wrong, first check the engine breather there is a little ball that sits in the housing that the hockey stick hose connects to.
Then if you look up into the exhaust ports with the headers removed see if its wet with oil in there.
 
Checked the engine breather, the ball moves freely and looks in good condition,

checking the exhaust ports sounds like a good idea, if there is oil there, what does that suggest?
 
Glazed bores - was it or is it running on synthetic oil since the rebuild?
Broken / incorrect piston rings.
A leak down test will reveal more than a compression check.
 
Mtoliva said:
Checked the engine breather, the ball moves freely and looks in good condition,

checking the exhaust ports sounds like a good idea, if there is oil there, what does that suggest?
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It could suggest that the copper sealing gaskets between the head and header pipes is not doing it's job and is sucking oil through the exhaust valve guides. Check the gaskets are in place and header pipe clamps are tight. Happened to me years ago.

Another cause of oil in my pipes was when a workshop filled the oil to the dip stick level when it was screwed in at an angle and not hanging vertical as per the book, resulted in way too much oil in engine and it came out through the exhaust valve guides as well. The rag I wiped the pipes out with way back then (1979) looked as oily as yours does now.

There must be something in common causing this to happen suddenly in all 3 cylinders.

Having said that, 1 litre of oil is a lot to lose in 200 miles considering they only hold about 3 litres.
 
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Thank you all,

The last service was in January 2022 when Ged at GCS changed the oil, I‘m sure he didn’t use synthetic oil.

I‘ll check out the header pipe caskets and arrange a leak down test, won’t be until, early August, I’ll report back in case anyone is interested
 
I would start as Rob suggested - leak down test. The testers are quite cheap from ebay. Don't get hung up on the cheapo gauge results/accuracy - just pressurise the cyl and listen for wehere the escaping hiss is coming from.
 
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