81 XJ650 - The dreaded “falling out of 2nd gear” problem

Been having a well known issue recently and it’s seriously bumming me out. My bike will occasionally fall out of second gear and into neutral, while under power. It seems to happen at random. Sometimes I can rev to 7k with no problems, sometimes it will fall out while puttering around at 3k RPM in traffic.

I understand this is a common problem caused by worn shift dogs in the transmission, and I’ve heard it’s impossible to fix without splitting the case. However, I wonder if there might be something else I can try first. The thing is, I only started having this problem after installing the performance shifter pawl and replacing the springs under the shifter cover. Second gear was still temperamental before (hence why I did the mod), and it would sometimes fall into neutral when down shifting from 3rd to 2nd. This felt different though, and it would never happen under power.

So, is there any way this problem could arise from messing something up in the shifter mechanism? Or does it have to be the dogs because the other gears are totally fine?

 

2nd gear is the one that gets the abuse on take off.

If the new shift mech isn't pushing the shift barrel far enough then the shift fork isn't pushing the dogs in as far as they can go also. So it could be some issue there, maybe.

Shift forks get worn or bent also. Bits of the primary chain guide have been known to restrict the gear change also.

Easy to see when split... Boroscope maybe somehow into that spot might illuminate your issue also.

 

I don’t have a borescope, but I could potentially get one. I don’t even know where I would snake it in to inspect the primary chain though. Don’t suppose you can go in through the cam chain hole?

I’m also not sure how I could have reassembled the shifter incorrectly such that it isn’t rotating the drum enough. I took a bunch of pictures before I disassembled anything so that I’d be sure I put it back together the correct way. To be honest though, it seemed like there was really only one way it could go back together and have the lever still move.

 

Try this.
When you put it in second gear, keep hard pressure on the gear lever while powering off.
If you feel the lever push your foot down then you can blame the shift fork/drive dog in the transmission.
If not then maybe the shift mech is the issue, not locking into position.

if I'm lazy on a gear change I've had it pop back into neutral also. Not lately mind you, because it's embarrassing.

 

Fantastic idea. I tried this on my way home from lunch today, and I felt no resistance whatsoever against my foot, and I held it in 2nd over 4000 rpm. It does make me suspect the shifter mechanism. Until I have spare time to drain the oil and take that side cover off again, I guess I need to shift with a lot more authority into 2nd.