Piston replacement ?

[cubman]

After getting my 1934 HD model B (21 c.i.) running I am not happy with the amount of blue smoke. We thought the existing rings were proably going to be alright so we went ahead. Now I think I need to replace those rings but as you all well know parts for these old singles are tough to find. Any ideas where to start looking for rings for this old single? Thanks Mike

[denismccarthy]

Hey Mike

When you guys pull it back down, would you give me the measurments of the rings. I will need cylinder bore size you are going to use, piston size you are going to use, ring groove height for all rings, ring groove depth. Before you toss the old rings, measure their end gap. Just curious. Also, is the piston and bore rough? Did you guys just hone or was the cylinder bored? Is it round? Would like to help if I can! It would be nice to run a bore gauge down the hole. Three spots is usually enough. Oh also, check the valve guides. How loose are they? This can be a source for excessive oil in the bore too ya know...

See ya

Denis

[exeric]

Not to divert the course of this thread but I have a question that I've never got a satisfactory answer for. If your pistons are stock cast iron and you're bore is still okay; could you widen the ring grooves in the piston and use 2 modern rings in place of the single wide H-D piston ring ? The alternative is new aluminum pistons and all of your clearances, and flywheel balance values change. Just wondering if the 2 ring option is viable.

[denismccarthy]

Um good question Eric

We usually change pistons. 9 times out of 10 we go aluminum. The only time we stayed with original cast iron was when I restored a 1915 Sears Dreadnaught. We found (believe it or not) a guy that had vintage steep bevel edge rings that would fit the bore and the pistons! By steep edge, I mean the ring ends came to a point at one angle, like the original Spacke rings. We still use the old bore formula for the ring gaps, on modern rings and pistons, usually around .010 for the gaps for a bore thats in the 2/2.5 inch range. I guess I see your point about final crank balance issues with a lighter piston, but we don't spin our engines to 10k do we? For something this old, we're just glad its running!! If your really worried, take out the difference from the cast piston to the aluminum piston from the counter weights. That should make it ok...

More to your point, I've never heard of, or have I ever tried to put two piston rings in one piston groove. I'm not too sure what would happen if you tried that. You might be faced we a "mechanical conflict" as a Pro-Stock Drag Bike friend described a recent connecting rod departure his engine had pointed out! "It might work, then again it might just freackin explode!" So... explore this at your own risk!

Interesting!! Take care

Denis

[cubman]

Piston replacement

I will get the measurements when I open it up, hopefully this week.
We did replace the valve guides, we had to make them though. We also replaced the valve seats and put new valves in. We had to take 45 valves and cut the shoulders down and cut the stems off.
According to the 1934 HD parts book the original piston is supposed to have two rings and a conical top. This piston does have two rings but a flat top. What is the difference between flat and conical?
The original was a Dow metal piston where this one is aluminum.
Thanks Mike

[RPjr]

Piston Rings

Egge made a piston for me, but did not give me useable rings, thought about it a few days, check out Hastings web site, lots of rings of all sizes.

[kg993]

If Hastings doesn't have it try Total Seal. They have a huge selection in sizes.
Eric, I've gone the other way put wide EL rings in my BSA single to fix the land clearance. A long time back I made a set of rings for my Firestone outboard motor. If all else fails I think that would be the best solution, although I can't think of any reason stacking the rings would do any harm in a low speed motor.
Kerry

[exeric]

Thanks Kerry. Like I said, it would be nice to use the original iron pistons for flywheel balance. Also, cast iron pistons are suppose to be very gentle on cylinder walls. My '16 J is and old lady and needs gentle treatment.

[Tommo]

If you want GENUINE HD rings give me a call.
I've attached photos of some of the stock of rings I have.
Perhaps the boxes are worth more than the rings, especially the pre 1920 plain packaging.

[Tommo]

Sorry it's not a good close-up photo.
Since my stroke my eyes don't see as good as they used to.
I'll have to get someone else to do my photography.
Sorry chaps.

[Bills37]

Not to worry Tommo. If they click on the pic it enlarges enough to see what's going on. By the way, nice little stash of rings you got there.