Very Old Motorcycle possible stuck oil scraper ring, suggestions?

[Hugh R]

I have a 1930 motorcycle which I don't run enough. I started it up last week and it's smoking like crazy, didn't smoke six months ago when I started it. Single cylinder 4 valve head with open valve springs, so oil is not coming in from the valve guides. I think I have a frozen oil scraper ring. I'm thinking of dumping a 1/2 ounce of Marvel Mystery oil in the spark plug hole, letting it sit overnight and then turning it over bunch of times with the plug out. It might work, if not, I'm in for pulling the jug and replacing the ring(s). Any other suggestions? PB Blaster instead of Mystery oil?

[Steve Carlton]

Many years ago I had heard great things about the 502 engine oil improver. I can't see how it would hurt to try.
http://www.swepcousa.com/lubesite/add.htm

[304065]

Hugh,

What color is the smoke? You might try a decoking procedure with a spray bottle of water before anything else.

MMO is great and you should be able to buy gallon jugs at Wal-Mart. The great thing is your cylinder is near vertical, so you should be able to pull the plug, set the cylinder to BDC, pour COPIOUS MMO in through a funnel and then let the weight of all that oil work its way down through the gaps in the various rings and then into the case. You could then turn the thing over a few times to see what happens. About the only damage you could do would be to hydrolock it somehow but with the spark and drain plugs out I would think you would be OK.

Or you can use Automatic Transmission Fluid, but I bet MMO is a lot cheaper.

[dhoward]

Seafoam.
http://www.seafoamsales.com/

[Hugh R]

Thanks all, John, you make sense about putting a lot in so the weight of the oil will "push" it into and around the rings. The cylinder is vertical and it's a dry sump design, so no hydrolocking issues with the spark plug pulled.

[Tim Hancock]

Penetrating oil, MMO, ATF, kerosine..... any of these might help to loosen a stuck ring if soaked overnight. You say it is a dry sump, so this next idea might not be plausible, but I thought I blew up my Interceptor 500 last year as after sitting for about three months, I started it up one morning and it blew a ton of smoke. It ended up being shiit gas causing the float needle to leak which ended up allowing a tank of gas to fill the crankcase with oil thus diluting the oil and raising it's level such that it was easily going past the rings and smoking like crazy. The crankcase was fill nearly to the top with diluted gas/oil!

[Joeaksa]

Hugh,

We use MMO on antique airplanes all the time. It "frees things up inside" and keeps valves and such from sticking.

Would put a couple of ounces in a gas tank with a gallon of gas, agitate a lot then put in the bikes gas tank.

Put a couple of ounces in the oil for the bike and run it for a while, maybe drive it a couple of miles. Then change oil and see what happens.

Sure works on airplanes so hope this helps.

Joe A

[kmhemi]

you need to post some pics of that ole bike so the rest of us gear heads can enjoy it too. I love old bikes...old planes are cooler but bikes are cool.

[Hugh R]

Click on the link in my signature and you can see an article about the bike.

I went on the Rudge BBS and was told it doesn't have an oil scraper ring, only two compression rings. I'll try running it some more, I put some Marvel Mystery Oil in the cylinder and will let it sit overnight then blow the oil out the sparkplug hole and try running it some more to see if it clears up. The plug hole is enormous, as is the plug, so can't use a conventional compression gauge. Also, no kick start, only a compression release. I suppose I could put it in fourth gear and try and spin the engine over by turning the rear wheel. I'll let you know what happens.

[johnco]

let your wife tow you behind the 911 with a rope. that ought to get it spinning hehe

[SLO-BOB]

Bike like that I would probably pull the jug and inspect the pistons and rings. Not that much work really and better than really screwing things up.

[Porsche_monkey]

Kerosene. GM has a procedure for Cadillac engines.

[1967 R50/2]

Several things come to mind.

1. Are you certain oil is not coming from the valve side? Your Rudge has exposed valve gear , but I am assuming there is some type of lubrication, at least for the exhaust valve? Is it smoking on start-up? If so, that may mean oil is already in the combustion chamber when you kick it over. Obviously, oil can't travel upward when it has been at rest, so it must be traveling DOWN past the valves...just a thought. Not knowing the Rudge lubrication system, it is tough to say.

2. Old metallurgy is, well, old, and by modern standards, pretty bad. Therefore it is more likely to be affected by changes in temperature. If you are starting it in the middle of winter, chances are the tolerances are much different than in the summer when you last started it. Let it warm up a bit and see what happens. If it continues to smoke, then you need to determine if it is the valves or the rings.

3. To be certain whether it is the valves, rings or both, do a leak down test. You may have to make some kind of adapter for your plug hole. That is where you normally pump the air in.

4. In the end, you may discover it is neither. Perhaps a blown head gasket is letting in oil? Again, not knowing the Rudge's lubrication system, this may not be the case, as I have no idea whether the oil pathways are internal or external.

If you do have to replace the rings, you'll likely need a rebore as well. You'll have to measure the bore to be certain, of course.

I would look to use a modern 3 piece, continuous ring set to eliminate blow by. I've purchased from here. http://www.cyclewerks.net. Ed Korn is a class guy and even though he mainly deals in BMWs his rings should fit just about anything.

'Fraid I can't make any recommendations on an overbore piston though.