JH or JDH twin cam?

[silentgreyfello]

I have a two-cam project that I am trying to sort out...

The left case was replaced at some point and the s/n is JD1419. Obviously not correct.

The fins are tapered towards the bottom. I have been told that this was a feature of the JH model (61ci) but not the JDH (74ci). I have also been told that they cylinders are Ricardo cylinders. Anyone know the difference?

I haven't pulled a cylinder to check the bore/stroke yet, but plan to.

I have limited knowlege of this era, and most of my reference books don't offer much.

Here are some pix.

[silentgreyfello]

rh side

[silentgreyfello]

top

[silentgreyfello]

The cylinders have spacers under them...

[silentgreyfello]

bottom

[Tommo]

If you haven't already got it, get a copy of Jerry Hatfields book "Inside Harley-Davidson" and read the second chapter that covers the 1916-1929 period in detail.
Page 68 has good photos of "Riccy chips"(the insert that turned the combustion chamber into a Ricardo style combustion chamber)
and gives you a good photo of what we over here call "Chicago barrels or Pineapple barrels". These barrels were generally recognised as racing 61 cu in barrels but they were also used on the 1928 JL models.
I'm not going to steal Jerrys thunder here as his descriptions in the book are excellent and it would take pages and pages on this forum to include all the info that one chapter has.
I will say it looks like your timing side case is a direct action 1928
two cammer case but without better shots of the lifter blocks I can't be sure.
Hope this helps.
Tommo

[silentgreyfello]

I cleaned it up a bit... hopefully these pictures show enough detail.

[silentgreyfello]

Please note the brass spacers under the blocks???

[silentgreyfello]

rear block

[Tommo]

The lifter blocks have the raised oil drains that was introduced in 1928 so you have a 1928/29 two cammer timing side crankcase.
If those cylinders are 61 cu in and are original to the crankcase you may have the bones of a 61 cu in racing engine. If they are original 61 cu in cylinders and have been bored out to take 74 cu in pistons they may be getting very thin around the base flange area.
You really need to get in touch with Jim Lattin,Danial Statnekov,Mike Lange, Dale Walksler or someone similar and let them physically see it and they should then be able to tell you exactly what you have.
It seems strange to me that the only response you have is from a Kiwi on the other side of the world when you have numerous very knowledgeable guys over there in the States.
Hope this helps anyway.
Tommo

[silentgreyfello]

Thanks Tommo!

Wish I had the Hatfield book.. I'll have to find it. I live quite a ways from those guys you mention, but will send some pictures.

Is there an easy way to tell the 61 cylinders from the Riccardo cylinders?

[AdminGuy]

Don't you mean Ricardo heads?

It is sad that no one else has responded given the depth of knowledge in this club. Thanks Tommo.

[Tommo]

The Ricardo chip was a sloping slug that was held in the top of the cylinder by the mounting bolt at the top of the cylinder. If you remove the top cylinder mounting bolt the slug will drop out if it's not too carboned up.
The "Riccy Chip" as it was known was an early way of introducing a squish style of combustion chamber and is easily identified by looking into the cylinder from underneath.
This design takes it's name from the inventor, Sir Harry Ricado, an Englishman whose patent of the idea made him a very wealthy man.
Paul, pop-up pistons don't work in F head designs as all they succeed in doing is obstructing the flow of gas from the valves so this is where the riccy chip came in.
The sloping form of the chip helped raise the compression by filling the space on the side of the chamber furthest from the valves and leaving the inlet and exhaust space unobstructed.

silentgreyfellow, some of Harleys cylinders were made with the Ricardo style combustion chamber cast into them and once again look up from the bottom and you should see the chamber sloping down towards the valve chamber

I hope this is not all as clear as mud but if you are still puzzled just ask and I'll try to explain better.

[silentgreyfello]

Thank you for the info! I'll pull a cylinder the first chance I get and will also attempt to take a photo of the inside.

[AdminGuy]

It didn't dawn on me that the barrel and head are cast as one. Lack of head bolts should have been a good clue.

It's very clear -thanks Tommo. Looking forward to seeing inside of that barrel now silentgreyfellow.