Engine flush

I would just refill with oil and disconnect the return pipe to the tank and run the motor till clean oil appears. Flushing oil may carry rubbish into the crank. You should do a crank strip and clean if the motor has stood for a long time as dried out sludge in the crank trap may shift and block the crank.

Previously robert_tuck wrote:

I would just refill with oil and disconnect the return pipe to the tank and run the motor till clean oil appears. Flushing oil may carry rubbish into the crank. You should do a crank strip and clean if the motor has stood for a long time as dried out sludge in the crank trap may shift and block the crank.

And I confirm Robert hypothesis you need to dismantel the engine and clean inside the sludge trap . and check any ware on the large end journial and replace the large end shells, also check the main bearings as well yous anna j

There is a fair chance that your crank sludge trap has a fair amount of gunge in it. If you have been using your bike regularly and it's otherwide fine, just make sure you keep changing the oil regularly. Do that and the crank shouldn't build up any more gunge and you should be ok until the next overhaul when a crank strip will be required. Clean out your oil tank of course.

Ditto that, Clive, I have split a crank and the sludge trap was FULL, how any oil got through at all was a mystery, if yours is, and you start running a high detergent flushing oil through it, it will start to dissolve the mass of sludge, and then you will have a lot more work than just a strip down to do.

I wouldn't necessarilydismantle it down just to check, but if you don't want to, just carry on running it with whatever oil you were using before, until such time as you need to take it down for something else.

Cheers,

Niall

If a sludge trap fills just half way it will close off the oil feed to the big ends. That is where the oil holes are.

Having dismantled and cleaned out the sludge, use a modern oil with good dispersancy and detergency to ensure that the engine internals stay clean. Also make sure you change the crankshaft oil seals and the oil pump output conical seal. These have almost certainly hardened. Again modern oils like Mobil 4T 15W50 are much superior in seal compatability tests, as well as dispersancy and detergency, than the so called classic oils.

OK Charles, but what oil do you recommend for a Norton twin with no external filter but clean inside?

My local Motor spares shop is now stocking Morris 20/50 golden film, seems like a good time to try a multigrade, My motor is in the same position as Neil's, what do you say Charles?.

I can see no reason for preferring a low dispersancy, low detergency and often low wear protecting,classic oil over a modern high performing oil. The problem as to which one to chose comes down to availability, price and specification. It is harder now to find a high spec 20W50 car oil than it was 5 years ago so motorcycle oils have diverged from car oils. All the major oil marketers offer 15W50 or 20W50 motorcycle oils and some 20W60 grades. Opie oils website is worth a visit, I have used Mobil 4T, Motul , Shell and Castrol products but many others are no doubt as satisfactory. since all were customers of my pension provider, who was jointly owned by ExxonMobil and Shell, I had better not recommend one over another.

Remember detergents keep engines clean and dispersants stop sludge and soot from agglomerating into lumps large enough to cause real problems.

Thanks Charles, sticking with twins with no external oil filter, I believe what you are saying is that a modern multi oil with its detergents is fine inside a clean engine with regular oil changes. That being the case I'll try it. & Good luck to Robert.

PS: I use straight oil in my singles and never seen any sludge, must be doing something right!

I can see no reason for preferring a low dispersancy, low detergency and often low wear protecting,classic oil over a modern high performing oil. The problem as to which one to chose comes down to availability, price and specification. It is harder now to find a high spec 20W50 car oil than it was 5 years ago so motorcycle oils have diverged from car oils. All the major oil marketers offer 15W50 or 20W50 motorcycle oils and some 20W60 grades. Opie oils website is worth a visit, I have used Mobil 4T, Motul , Shell and Castrol products but many others are no doubt as satisfactory. since all were customers of my pension provider, who was jointly owned by ExxonMobil and Shell, I had better not recommend one over another.

Remember detergents keep engines clean and dispersants stop sludge and soot from agglomerating into lumps large enough to cause real problems.

and has ball and roll race bearings

how I hope this help out, yours Anna J