Ironhead 1981 Sportster Won't Shift Into 4th

[doodah man]

Check how much slop exists between the cam plate axle and the shift tower bore where the cam plate rides inside. The spring loaded cam follower is always pushing the cam plate away from the trap door. If there is too much clearance in the tower bore to axle fit the cam plate will turn off axis and wear the top hats down or crack them. You’re lucky that broken piece didn’t travel between meshing gears!!

[Yamalol]

New problem: I put everything back together (details below) and went for a ride. I can shift into 4th now without issue, but as soon as I let the clutch out I can hear chatter from the trans and get a lot of jerkiness like it's popping in and out of gear. I adjusted the clutch per the manual, and it was fine in gears 1-3.

Any ideas?

Instead of replacing the top hat, I replaced the entire shifter assembly with the one from my parts transmission. Looked to be less wear, and the tophats had a little less play. All of the gears looked fine. No noticeable wear or chipped gears.

[Gold Member]

Did you take the gears off the shafts and give them all a good look over?

[Yamalol]

I did, nothing had any noticeable wear, and definitely nothing as noticeable as chipped teeth.

[doodah man]

How fast are you traveling when you shift into 4th? I do north of 50mph when I upshift to high gear… try another clutch adjustment and see if it still does it?

[joe s]

If this was a BT 4-speed trans I'd ask if the new shift yoke had the same shims as the old? IDK if that applies to sportster?

[Yamalol]

Alright, I pulled the transmission again and found some very noticeable wear on one of the shift forks. I made a video to make it clearer. Linked below. Any help greatly appreciated.

https://www.youtube.com/watch?v=DSWU3MfAGAY&t=12s

[Yamalol]

Ok I kind of answered my own question. I didnt notice on the video, but the dogs on the clutch gear and female side of the 2nd gear arent great. I'm going to replace both, but is there any thing else I should take note of?

[Gold Member]

Thanks for putting that video up. That clutch gear does look sketchy to me.

[brucstoudt]

you didn't notice likely because you're inspecting your trans. parts while they're still covered in oil.that should all be removed before inspecting.i'm going to come back later and have another look at your video.