Hi All, I need your advice please. I recently replaced the piston rings on the above engine. Everything was fine for a while but now oil is leaking out from the spark plug and the plug is very oily. I get the engine going for about half hour before I have to clean the spark plug. Have I put too much oil in the sump or is it a problem with the rings please? Regards, Ian.
Most likely over-oiled but did you hone or rough up the bore, to de-glaze it, before fitting the new rings? New rings will not bed in to an old bore. To check for oil level simply remove the level cap under the wing nut on the base. Whatever runs out is surplus :-) ttfn Roland
Gentlemen, What amazes me is how it gets there as it not a pressured crank case, you would think it would scrap back down again.
Martin P
I was a bit puzzled by this the first time round and wondered then if we were missing something. I sold my "D" some months ago, so cannot check, but I am right in thinking that the crankcase breaths up the pushrod "tubes" and out of the top lid, aren't I?
If not, how does it maintain atmospheric or negative pressure?
Regards,
Kim Siddorn,
Ian has mailed me but I think this is a potentially interesting thread so will continue on group. As always corrections welcome :-) First is the bore badly worn? In the absence of a bore gauge or internal mike that can be checked by feeler gauges between (rings removed) piston and bore. Measure at the third land since the top two lands are normally slightly smaller dia to allow for extra expansion near the heat. Measure at both top and bottom of bore and the difference is the wear. Anything over say 0.015" might be considered excessive in a Lister D. Are the ring gaps the right size? Checked with the piston around the lower limit of its travel these should be around say 0.008-0.010"? Are the rings bedding in? My reading and experience says that rings and bore need to bed in together and that won't happen if the new rings are simply skating over an already glazed bore. The glaze needs to be removed although its a tiny amount of metal, say 0.0005". Before I had a hone I got good results with a home-made flap wheel. A hardish sponge cut roughly round and slightly oversize is fixed with large washers on a length of studding. A slit holds one end of a length of 120 grade alu paper which is then continued round to slighly overlap the inserted end. Slow speed in a drill with up and down movement soon produces a cross-hatched appearance. WARNING - the engine must be very thoroughly cleaned after this procedure as you don't want the particles of metal and Alu Oxide stayinmg in the engine!! just my 2p Roland
Sounds like a glazed bore? did you use a glaze buster or hone in it before putting newly ringed piston back in? New rings will not bed into an un-de-glazed bore.
Tim..
How do I glaze the bore please? I didn't do this as I thought (incorrectly!) that it wasn't that critical!
Thanks, Ian.
Another Question!
I think I know how to "hone" the cylinder wall now. Do you think I need slighlty oversized rings (+20")for a good fit? As you can see I'm new to all of this but it's a pleasurable learning curve. Regards, Ian.
I need new piston rings for my D - any suggestions where to get some ?
Also - what spark plug does it need ?
No, DE glaze the bore. i.e. rough it up with a glaze buster or similar so the new rings will bed in.
Ideally you'd assemble it, run it up to operating temp, then place it under varying load at varying speed for about 30mins or so to run it in. From about 10% upto 90% load and from 1/2 speed upto full chat.
No load and low speed running after a rebuild and you're going to have severe oil use problems.
Tim..
No. You only fit oversized rings when the engine is rebored and a new piston is fitted. I would try honing the bores. The method described should work. You want to aim for scratch marks at 45 deg to the bore. That means a slow electric drill and fast up and down movements. If there is a wear lip at the top of the bore, the engine may need a rebore. The other problem is that the new rings will hit the ridge and could break. That may be your problem.
John
it takes a 18mm plug , a 8COM made by champion is a good one , and if you can get an old stock one, it may be one that can split in half
-just like the old ones . i bought two myself yesterday at a bring and buy here in ireland for 15 euro each ,both were in good cond in their boxes and worth the money . regards , john
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