factory cast iron piston types

[Steve Swan]

hello All ! i would like to be schooled on factory cast iron pistons. here we have pistons with 2 rings and pistons with 3 rings. are these differences between years (earlier vs. later) or differences between models. i can tell you the pistons attached to rods are the pistons that came with my lower end, 27 JD13514. i do not know what model of twin or J-type model the other set of pistons were associated with.... why would the one set have no 3rd ring (oil control?) and the other piston set has what i assume is an oil control ring?

s-l1600 (3).jpgs-l1600.jpg

also, what diameter rod was used for 1914 fender braces?

Thanks in advance!

[TechNoir]

Hi Steve, just checking in after a little while off here and noticed this question. The type with 3 rings are the same as fitted to my 1920 bike.

John

[Steve Swan]

Great to hear from you John! and doing CPR on this thread! I wonder what machines or applications cast iron pistons with 2 rings were used...

[TechNoir]

I wonder what machines or applications cast iron pistons with 2 rings were used...

Me too. I am reasonably sure that my pistons are original so "J" 1920 bikes used 3 rings. I seems that perhaps 1927 "JD" bikes had 2 rings? Somewhere in between they swapped between the two configurations and it would be interesting to know..

A selection of parts lists would help. My up to 1921 list shows a picture of the 3 ring type,access to later lists would identify when the design changed.

I had a look around on here and didn't find much although this thread has some debate over the number of rings.

John

[Steve Swan]

Me too. I am reasonably sure that my pistons are original so "J" 1920 bikes used 3 rings. I seems that perhaps 1927 "JD" bikes had 2 rings? Somewhere in between they swapped between the two configurations and it would be interesting to know..

A selection of parts lists would help. My up to 1921 list shows a picture of the 3 ring type,access to later lists would identify when the design changed.

I had a look around on here and didn't find much although this thread has some debate over the number of rings.

John

Yes, there are quite a different piston/ring configurations used during all the IoE twin years.... the parts book tells some of teh tale, but i don't thinks so much on the number of rings on different pistons

[aumick10]

The Inside harley davidson book by Jerry Hatfield mentions a change from 3 rings to two rings in October 1927, for 74" only.

[Steve Swan]

Mick, Thank you for your reply! The cases i am using for my rider are 27JD 13514; these 2-ring pistons were on it when i got it.

s-l1600 (8).jpg

[aumick10]

Steve,
I have some info that says the total twin production in 27 was just under 20,000.
making allowance for the 61" models and magneto models, I would call your cases as very late 1927.
Maybe wrong but it seems right.
Cheers.
Mick

[Steve Swan]

Mick, i would agree! I do know one of the differences between early and later '27 cases is the early '27's fitted a smaller diameter nipple that connected the oil pipe from hand pump, the later '27's had a larger diameter nipple, same for the diameters of the oil pipes and different check ball valves.

[Steve Slocombe]

This piston was found on 30VL4899. The casting number inside is 317-30D, suggesting the JD ones are different. It has three compression rings and no oil control ring, which might explain why we have problems setting up the oil pumps when using modern replacement pistons.