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V-Twin '55-57 Transmission Alignment To Rear Axle Plates

Posts: 1536
Location: S.Calif.

Here's an exchange between myself and Don from Corbin-Gentry. He's in another position with the company now, but was head of the frame dept. in 1997. I sent my #1107 back three times for adjustment. Now I'm checking to see that the trans. and rear axle plates are in alignment:

hi don,
I have that rigid Pan frame #1107 that we adjusted the motor mounts and bottom gas tank mount bracket re-positioning.
Then I found the 5th mount stood too high, and met the bottom of the transmission boss too early. I stripped the top laminate plate off the 5th mount and ground, and flat-filed it to provide a .004-.025 clearance between the 5th mount and trans boss for a shim. All is okay now.

Now, I'm assembling the motor and trans into a rolling chassis w/ brakes (that work). Standing up above the machine with the tanks and fenders off, and looking down at the top of the chain, it looks like the trans. main shaft might be directed a little more towards the rear wheel, than at 90-degrees to the trans. like it should be. The trans sits flat in the cradle of the base plate. It looks like I should twist the trans. counter-clockwise, but of course I can't, since the base plate is installed, and even with the 4 trans. stud nuts loose, I can't spin the trans. sideways at all to compensate.
When I look at the rear chain from above, it looks like maybe the mainshaft is pointed to the rear slightly.
Do you have any suggestions for checking the alignment of the trans. mount to the rear axle plates? - Plumber

Don's reply:
I would be more inclined to think your rear wheel isn't in the proper position left to right. This will also cause the chain to be at an angle as you see it. There should be an 8-7/8 inch space between the rear axle flanges. Half of this (4-7/16) inch space should be at the center line of the frame. Check to see if you have this. If not, then one or both of the axle flanges is off position to the left or right. If these dimensions are correct, then you are correct that the transmission is turned. This can be fixed by elongating the base plate holes. Not what you want to do, but it is a solution. Let me know what you find.
Don, I checked the measurements and there is a 8-7/8" space between the rear axle flanges. There's 4-7/16 " hub center (of zerk fitting) to side axle plate distance. Both dim's are as you stated.
I have a 4-link-too-long, and straight, 530 chain lying between the sprockets right now. So, I'll remove 4 links and put a master link on it and then spin the wheel and watch the new rear chain track. So far the news seems to be good. Can't beat that!
If it turns out that I have to elongate base plate holes (right to left), Stett can do that on a Bridgeport.
I think I'll install the motor, when Stett finishes new pistons and rings, and start it up and see if it throws a primary belt. If so, then I guess I'll need to remove the trans. base plate and elongate the 4 holes. Thanks again, Plmbr.

Posts: 123
Location: Mpls. area
Plumber, I had an alighnment problem on my 51, when I sent the frame in to the frame shop they used a jig which had the engine mount and tranny plate locations on it to check those locations on a suspectedly bent frame. (mine) As was suspected, she was at some point, slid into a curb at a damaging rate of speed, cocking the front engine mounts down a bit (possibly explaining the broken front engine bosses) and pushing the tail section over a bit (explaining the bad tranny alighnment). After the frame was checked and repaired I have had no alighnment issues, belt or drive chain. Mike

Posts: 1536
Location: S.Calif.

Thanks. I'm so far into making the Pan run now, that I have to bolt it together and kick-it over and check it out.
I'm putting the Knuckle together as a chain primary. The knuckle frame is OEM and it's rolling with brakes, so both, or one of them will make it to the road.
Here's the transmission and chain in alignment. Looks pretty good. Don knows his stuff about frames.

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