1981 XJ750RH Seca Rebuild

Start off with a quick story about my bike.

So I bought my 81 Seca 750 back in June of 2007 while I was still in college. Paid $200 for it from my old boss who let it set outside for 4 years under a tarp. After bringing it home and a months of tear down and cleaning the bike, I had it road worthy. In a year and half put 4000 miles on it. Loved every minutes of it. Then on my return from a scenic trip along M-22 in Northern Lower Pennisula Labor day weekend '08, it started to skip out of 2nd gear under load. I rode it for another couple months then put it up for the winter. Since I finally graduated from college and saved some money I bought a nicer bike the following spring and parked the Seca in the barn for two years. After two years of sitting (periodically running it) I decided I want to finally put the time and effort into really making the bike look and run good.

So here I begin. Last fall I pulled everything off of the frame, and repainted the frame and rebuilt the front forks. It then got cold out so it then sat all winter.

Finally when it started to warm up a month ago I decided it was time to start working on the motor. I have left the top end intacked and don't plan on rebuilding, other than checking shims and replacing the valve cover gasket, and rubber bolt boots.

As for the bottom end. I have spit the case and removed input and output shafts. When removing the output shaft, I removed the cover in the gear box housing and noticed the bearing cover was all jacked up. Picture below.

Next I have attached the 2nd and 5th output shaft gears. Too me they look fine with some slight wear. The 3rd gear looks kinda jacked, but never had issues.

I would like opinions on my Shift forks. I don't if the shift forks have anything to do with this or not, but when I first got the bike I replaced my neutral switch because it wasn't working and noticed the tip was rounded off. I replaced it and it worked for a little while then stopped working. When I pulled it out today it looked perfectly fine. So wondering if the forks are worn not allowing the shift selector tube to fully depress the neutral switch.

Anyway, while I have the motor split, I'm going to replace the starter chain guide, the start clutch springs and pins. The Rollers still look good to me with not grooves. What other items should I look at while I'm in. Like I said before I don't want to pull the top end apart.

Please let me know what you all think. I can post more pictures if you want.

 

Looks like either you've got everyone stumped, or the right audience just hasn't seen your post yet.

I know pretty much nothing about transmissions, so I'm afraid I can't help. I was a bit tempted, though, to just say something, since I know there are some pretty knowledgeable guys on here that would quickly jump in to argue ;-)

 

I know...I'm kinda shocked as well. Unless those aren't even the gears that typically have issues. i guess I should just replace the middle fork along with the gears that typically have the issues.

 

I'll summarize my questions here:

1. Does it matter if the output shaft bearing has it's outer cover? The manual shows the bearing with not cover.
2. Since I have the case split should I just split the case even though the gears don't look too bad? Or does anyone know of a place in Michigan or somewhere else that I can have the undercut and hardened cheaply?
3. Should I replace the shift forks. I have no idea if they are worn or not. They don't look bent. I can send better pictures if needed.
4. While I have the case split what items should I replace?

Everything looks like its in pretty decent shape. No weird wear marks from what I can see.

List of Items I plan to replace:
1. Starter clutch springs
2. Starter clutch pins (rollers don't have any wear to them)
3. Starter Chain Guide?

Then fix the transmission so it doesn't jump out of 2nd while under load.

I'm open to all suggestions and opinions

 

Any Input from anyone??

 

Yes, it does. The bearing is supposed to be lubricated by the oil system however some bearing manufacturers have the correct size bearings that are covered to hold in the expected life-time of grease. This seems to me that the incorrect bearing was installed.

Don't know, don't live there. Someone from that neck of the woods should chime in sooner or later.

The facory manual should spec the thickness of the contact pads on the fork. replace any that don't measure up.

The starter clutch chain guide and all seals. Your list is good, run with it.

 

Not and expert on trannies, but from what i can see in the pics.
That bad seal on the bearing would be an instant replace signal. Not worth taking the chance of it going bad, and trashing the trans.

If that is a burn spot (not just oil) on the 3rd shift fork then you have an alignment issue. Possibly from the bearing.

While inside the case. Double check all bearings for wear/excess play. Make sure that the bolts on the starter clutch are properly torqued with loctite.

Not sure what your asking about on the undercut and hardening.

Hope this helps
Ghost

 

Ok, the bearing only had a cover on one side of the bearing. The part that faces the inside of the case didn't have the cover, but the outside did.