Giving Frankenstein a Transmission

Previously, CCM Team Member Brent Mayfield had been updating us on the extensive modifications needed to make the 1930’s Harley VL motor fit into the smaller 1920s JD Frame. Now with his front fork, motor mounts, and both front and rear axles set up to accept the flathead motor and Bultaco wheels, Brent details his progress in choosing the proper transmission to put the power to the rear wheel…

Hi Team,

photo.23

Cleaning up case threads for the transmission mounting bolts

The last 2 updates covered changes I made to the 25/27 J frame & fork. While there is still some work to be done to those 2 items, there is other work that needs to be done first. If you remember, in my first report I had mentioned that I had purchased 2 transmissions when I thought I would be building a 28 JD; One was a 27 J trans and the other was a 30 V trans.

The 27 trans had been used in a board track style racer and was supposedly to have been rebuilt with newer sealed type bearings.The 30 trans had not been in usage for a really long time, was very greasy, dirty and smelled bad but had good gears and I got it at a reasonable price so I figured I could use it for spares.

The 27 Trans :

Testing the fit of the main shaft and slider gear

Testing the fit of the main shaft and slider gear

Outwardly this trans looked good and was the one I was going to use in the JD.It had the early side kicker cover but did not have a kicker arm. Since this had been in a racer, the kicker arm and gears, including those on the main-shaft, had been removed and a plug put in place of the kicker arm. When I took the trans apart for inspection, it was in good shape and did have sealed bearings on both ends of the main-shaft. The main-shaft was also the later version with the bronze bushing in the drive gear instead of the 2 piece soldered unit on the shaft. The bearing surface of the main- shaft where the clutch hub rides is also in very good condition. The gears did show wear, as you would expect, but were in good condition. The bearing surfaces in the countershaft cluster gear was also very good. There was excessive end play on the cluster gear and some wear on the countershaft bearing surfaces. I replaced the countershaft, roller bearings and end thrush washer. I set the end play at .013″. I also installed a later style (31/36) style kicker cover, kicker arm and gears so there is less chance of broken gears due to kickback and no need to use the gear alignment plunger. I installed new bushings in the kicker cover and in the main-shaft kicker gear. The throw-out bearing and clutch rod were also in good condition. I cleaned and blasted the case, powder coated the top and side covers and had the hardware cadmium plated.

Installing new kicker bushing

Installing new kicker bushing

 

The 30 Trans :

I originally bought this trans because I got it at a good price and figured I could use the internals for spares. When I took it apart, all the gears and main-shaft were in very good condition. Sometime over the years, this trans had already had the newer style main-shaft, kicker side cover and kicker gears installed. I figured if I could find an earlier J case, I would build a complete spare transmission. Note : The main difference between a J and V case is the V case has ears extending from it to attach to the inner primary and the adjusting screw is moved 1/2″ farther out to the side. I found a really nice late J case at Davenport this summer so I was ready to build a complete spare trans. I replaced the countershaft, rollers and thrush washer. I also used new style sealed bearings on the main-shaft. I put new bushings in the kicker cover and main-shaft kicker gear. Two of the mounting stud holes were stripped out so 2 stepped studs had to be made. I cleaned and blasted the case, powder coated the top and side covers and had the hardware cadmium plated.

In addition to new bronze bushings in the kicker cover, Mayfield also installed one in the main shaft kicker gear

In addition to new bronze bushings in the kicker cover, Mayfield also installed one in the main shaft kicker gear

Not sure yet which trans I’ll use in the VJ as they are now both in really good shape but no matter which I use, I will have a good spare.

Clutch :

Since I am using a V series motor, I needed the stronger V series clutch (more plates, springs & double row primary) which I did not have. I called Jon Neuman and he brought one to Davenport for me.  It was complete with good primary teeth and pressure plate.  While the original clutch plates look OK, I will install new plates and springs and use the old ones for spares. I also installed new rollers in the clutch hub bearing race.

Trans Drive Sprocket :

photo.28While I am using a standard 28 tooth drive sprocket, it needed to be modified. The drive sprocket on the rear wheel I am using (Bultaco) uses a 520 chain which has the same pitch as a 530 but is narrower and uses a .235″ thick sprocket whereas 530 chain uses a .340′” thick sprocket. The drive sprockets are extremely hard and I could not touch it with my tooling and lath. I gave it to a friend of mine and he ground it down to the appropriate thickness and put the leading bevel back on the teeth.

 

 

 

Quite a bit of work, but the final product is quite pretty

Quite a bit of work, but the final product is quite pretty

This pretty much covers the transmission and clutch so till next time,

Old #77

Brent