Whoops

[Deleted User]

For reasons otherwise, I have not put many miles on the poor old thing, we are now at 47 —
Well, before I could think “its nipping up” it did. Had to sit in the sun till it cooled down then with prodigious prodding it reluctantly came to life and got me home, I had opened the pilgrim just in case.
So, now without the plugs it spins fine, but starting is not good, timing is still spot on 1/4″ BTDC.
I have checked the bores through the plug holes, they look fine, without lifting the barrels of course, but I do wonder how high the oil level should be in the crankcase, at present levels the big end is well dipped and the oil is nearly to the level of the door aperture.
I am also finding oil in the right hand inlet trumpet due to spit back.
Forgive a muppet, but how much oil should remain in the wells?
😳

[Deleted User]

They are always full, the engine will burn off the excess oil, that’s the trail of smoke you see in your mirror. 😀

You probably have a timing issue, was the rad boiling off when it nipped?

[Ian Parsons]

It’s possible that the seizure has caused the rings to nip up in their grooves. Seizing can be due to insufficient clearance as well as lack of lubrication. I have found that Scotts run well with worn bores but with good rings so a generous clearance is better than too little.
Although the compression seems good it is good suction that is crucial to easy starting and good running.

[Deleted User]

No the rad was not boiling, and when it had cooled down and the engine free to rotate, the level was where it normally sits, about 1″ down from the bottom of the neck.
The engine now turns freely with the plugs out and I seem to have compression. Also nice “plops” when turned over. It seems to be kicking back more often though, just like when it was first started after the rebuild, so I do not think more advance is needed. Also I do not have an advance retard on this bike, I have one of the newfangled BTH magnetos.
I am thinking that the clearance at the piston skirt may be a little less than generous and that was the cause of it.
One plug was oiled the other fine, so that probably didn’t help, plenty of oil in the wells but not a huge amount of smoke.
So whether to lift the barrels for a peak or see what happens next, that is the thorny question!

[Ted Robinson]

I had my 1949 scott for 36 yrs. and made sure it was well lubricated, one of the things I checked when I first had it was the amount of oil in the wells after a run. I removed the drain plugs and there was exactly 17ml. in each side. I would have thought if the oil was up to the doors it would have oiled the plugs up. The only way the oil level will increase is when it is ticking over for a long period but it soon drops to normal when you are moving and the cloud behind returns to a faint wisp.

[BRIAN MARSHALL]

The piston clearances for DPY Powerplus engine were stated by the factory as follows :-

Top land .012″ to .014″

Top of skirt .0085″

Bottom of skirt .0055″

Those clearances were for the period Hepolite pistons of course.

The piston ring gap should be .005″ and vertical play .0015″ to .0025″ max.

Brian

[Deleted User]

Hmm, the clearances were less than that when assembled.
it was a rather warm day and I feel that a combination of factors conspired to create trouble.
So, what I have now is polished piston sides with minor vertical scratches, I have checked the rings can move (only one per piston) and without the plugs it spins well.
I am running a 4.3 to 1 reduction unit for the Pilgrim, this gave a gentle haze but during the running in process I may have been a little optimistic in its setting.
I will now rebuild and increase the oil flow, this does rather bugger up the running, but hey, when settled it should be fun.
Here’s hoping —

[Deleted User]

The plugs normally give a guide to the pilgrim setting. The crankcase wells take
about an egg cup of oil each . the carb main jet is usually increased by 10% with
modern unleaded, which aids cooling. This hot climate of our will increase the
oil flow through the pilgrim if using 40 SAE. Best of luck.

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