E: Engine Oil Consumption: 100 Miles Per Pint…

Bill Thomas

Bill Thomas

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VOC Member
When getting an engine going after a long layoff,
WD40 down the plug hole frees rings etc off , If you are lucky.

Every now and again , My Comet has lost compression,
After a kickback from winter layoff,
Maybe too much coke on a valve stem ?,
Plug out quick squirt and no more trouble that season !.

They use it a lot in USA when getting cars going after long layoff.
 
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lee_812d

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No chance of WD40 curing this one. The piston is a Hepolite and as reported in KTB "the oil control ring groove was not adequately supported and often tightened on the ring, which seized" exactly what happened to mine - it's basically trapped by the groove as the groove is only supported at the gudgeon pin area and that's the only place where the ring is now free to move.
 
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lee_812d

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The piston is 0.060" oversize so probably not original(?) It might we worth comparing against some known items that are stamped. The bike went reasonably well with it and would have been better without the faults.
 
Bill Thomas

Bill Thomas

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lee_812d said:
No chance of WD40 curing this one. The piston is a Hepolite and as reported in KTB "the oil control ring groove was not adequately supported and often tightened on the ring, which seized" exactly what happened to mine - it's basically trapped by the groove as the groove is only supported at the gudgeon pin area and that's the only place where the ring is now free to move.
Click to expand...
Yes they were not the best,
I built my Blue Twin in 1970 with them , Took it apart for something else and found a Crack !,
So ever since have only used Old Specialloids.
 
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oexing

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Stuck rings may show the oil to have been a poor choice. Modern oils are supposed to have detergents , especially for Diesel engines, and should prevent carbon deposits like here. Try cleaning pistons and check ring grooves for sizes. I do not share the idea of deformation from heat or whatever.

Vic
 
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lee_812d

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When I pulled the oil ring off I did clean the oil ring groove of carbon, in fact I took a file to it as I had already decided I was going to replace the piston, so now it is definitely clean of deposits and the oil ring is still a very tight fit at the fore/aft points. For interest reasons I was going to file it out until it fit but I got bored of that, my file is not that sharp.
Anyway, the measurements (using non digital calipers, feeler gauges and my poor eyesight) are oil ring 0.124", the groove above the pin hole 0.126" and at the 90deg points about 0.123" maybe 0.124" - the ring can be forced in here but not all the way. It definitely wont be moving about much.
The piston has the slots down the side and it is tight from approx 1cm past this point around to the same point on the other side. I too find it hard to believe it has deformed as there is substantial amount of piston skirt but it must have.
It is true that GP50 oil might not be the best choice. I will consider something else - I bet there are loads of opinions on oil. Currently I'm using the felt filter, I think my oil chamber suffers the map of Australia on the end so the paper filter might need some work to fit.
I think this issue was there from the past and as it is documented in KTB must have some credibility.
 
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lee_812d

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The engine is now back together with new barrel / piston, nearly everything in the head replaced due to being worn or previously butchered, and new cams and followers as they were showing some wear. I've made a reed valve based on Vic's pictures on another thread and attached it to the end of the standard breather pipe which is timed in the standard way. The oil filter chamber has no issues in taking a paper filter so I switched to that from the felt one I was using. I decided to use Valvoline VR1 20w50 oil as it has had some decent comments on here.
So far I have done only 70 miles but the oil has not dropped to allow the cross piece in the oil tank to be seen yet, the smoking has been fixed, and no measurable amount of oil has gone into the primary case (yet). Easy to start, sounds a bit smoother and maybe quieter, plus no leaks around the engine. Early days, but so far it's going well. In the past it would have needed 3/4 of a pint by now!
 
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