According to this JIMS trap door with 2 diffrent bolt patterns only the 2 upper bolt holes differ between newer and older covers:
https://www.jpcycles.com/product/603...sion-trap-door
Is it really necessary to change the trap door or can something else be done here?

 

I think you will find that even if you drilled the holes...there is no gasket surface...so you would have a major leak.

To drill the holes and not get metal in the trans...you would need to remove it...while you have it off...why not change it out for a $25 ebay part and save yourself a lot of grief.

 

I changed my 85 Flhtc over to the ball and ramp setup a few years ago. Still trouble free

 

Has anybody made or found instructions how to actually do the swap? I believe there's some special tactics needed with bearings and shafts...

 

as dr. hess mentioned on an earlier post,you need to properly adjust the clutch as per manual. I too had a broken fork but its been 10 yrs since.

 

Multibagger Like I said its been a few years since I changed mine out. Actually all the parts I used were donated from friends except the new bearings I installed on the trap door. The trap door came off a superglide and the new clutch cable was from a softtail and I don't recall what the ball ramp set-up came from. I made a tool to pull the trap door off the side of the transmission, never removing the shafts or gear sets from the tranny or bike. I think I heated the bearings to get them t slip on the shaft.

 

Look at these tools:
620120
620130

http://www.georges-garage.com/trans_pre_o7.htm

In a nutshell:

After removing trap door bolts and shaft nuts, remove trap door using 620120.

Remove and replace bearings in new trap door using 620120

Pull trap door onto shafts using 620130

If your new trap door is a `99 or later, use tool 620140 instead of 620120, because the bearings are a different size.

 

Ok I think I got it now. Thanks guys! I hope this helps others too...