Fish's 1992 750C Engine Rebuild and Other Goodies

[Freddy]

I got good pressure with my old master cylinder, but the new one just would not build pressure. So I have ordered a new master cylinder with the correct bore, and hopefully that will solve the issue.

My thoughts for what its worth, the size of the master cylinder bore shouldn't really stop you being able to "build up pressure". Theoretically the size should only affect the amount of lever travel (the smaller the bore the greater the travel) and system pressure (smaller bore the greater the pressure, I think??). If you can't pump up a decent pressure,after getting the majority of air out the calipers then to me it indicates air still trapped behind the master cylinder.

Assuming the replacement master cylinder was correctly engineered, first check when released you have some freeplay between the level and master cylinder piston. If so, to get air out of most motorcycle master cylinders, fill the reservoir, then looking down into the reservoir (if you have a remote one obviously this can't be done) just ever so slightly depress the brake lever and watch bubbles that will rise up out of one of the holes in the bottom. Keep working the piston slowly back and forth across the point where the bubbles escape (which is just in the very first part of movement) till they are no more. It can take several minutes, as additional air rises up out of the lines. You should then have good pressure to re bleed the calipers.

Lots of people seem to struggle bleeding motorcycle front brakes, trying all exotic methods and tools to do the task. However my experience is they are VERY easy to do with the method described.

[Fishrider]

So, after spending $75 on a set of controls with a 5/8 bore master cylinder that didn't even fit my control area, I bought another master cylinder exactly like my old one for $40. I could have got it cheaper, but one day service from Amazon is sometimes hard to pass up. Guess what? It worked.

Freddy, thanks for the advice. I did try your bleed system on the old master cylinder to no avail. However, it made bleeding the new one a snap.

I am waiting on a new needle bearing for my clutch rod. Maybe another week or so. I don't think that is the issue with my clutch problem, but I thought I would replace it just to be sure. I going to put the clutch back together like it would be on a standard 750 output shaft. Meaning no bushing.

I was wondering if my clutch cable may be a tad short. It is not stock. To index the arm correctly on the clutch shaft I do have to turn the shaft clockwise a bit to get the arm to match up properly with the dash and dot. Should the arm index easily and then take up the slack with the adjuster at the cover and the control, or should it be a little difficult to get on the shaft? Right now both adjusters are fully lengthened. Which means all I can do is adjust the cable shorter. Should I be looking at this as a possible issue? If this is not clear, I can make a quick video showing what I am talking about.

If I can get the clutch to work, I can road test this thing.

Thanks, Mike

[Fishrider]

So I started it up today after putting everything back together the way I though it was supposed to go. After letting the engine warm up, I pulled the clutch. I heard a distinct scraping sound. I pulled the clutch just a few times to make sure. Every time the same sound. So I drained the oil and pulled the cover again. The shaft is definitely somehow pulling on the rod incorrectly. You can see the damage being caused to the shaft. I made a short video with what I think is happening. My motion is exaggerated but it shows what I think is happening as the gouge on the shaft perfectly matches the outer ring on the clutch rod. Eventually the rod gets worn down then it slips off the clutch rod eventually putting enough pressure on the clutch rod from an odd angle that the rod gets bent and then breaks. I am at a loss how to fix this.

Edit: Is it possible the rod is being pulled out of the shaft too far and has a slight angle to it when the shaft puts pressure on the rod? Could making the end of the clutch rod that sits inside the shaft longer solve the issue? Or it this something to do with where the clutch shaft is sitting?

[youtube]https://www.youtube.com/shorts/R1YOkzExcFw[/youtube] I wasn't sure if this was going to work, so i posted the url below.

https://www.youtube.com/shorts/R1YOkzExcFw

[Fishrider]

I think I am getting some deflection as I surmised in my edit as you can see in the video. With the rod being pushed out a bit further when the shaft is actuated I think the deflection is even further. I had, originally, thought that I may need to somehow lengthen the part of the clutch rod that sits in the shaft either by having a new piece made or mating another piece to the clutch rod by a threaded piece. Although, currently this is all theory.

Still can't get the Youtube frame to work.
https://www.youtube.com/shorts/XvHJSUmrJIc

[Richard]

I just wonder, should the clutch rod still rotate when engaged? It seems to be rotating looking at the damage...
I would need to see for myself (my own engine I mean), it''s too long ago since I've been working on my clutch

[Fishrider]

I just wonder, should the clutch rod still rotate when engaged? It seems to be rotating looking at the damage...
I would need to see for myself (my own engine I mean), it''s too long ago since I've been working on my clutch

I wondered about that as well. You would think that the clutch plate would spin around the clutch rod when engaged. At, least, that is what I thought the needle bearings purpose is. Its possible, that with the deflection, the clutch rod is getting pinned against the clutch plate and thus spinning. Which is partly causing the damage. In other words, since the clutch rod is not sitting fully flat against the needle bearing when the shaft puts pressure on it, the rod spins with the plate. Or, at least, spins enough to cause an issue.

One of the problems here is that I am not sure anyone else has made this particular modification work. The other bikes this modification has been done on used a push control for the clutch instead of the pull configuration. This deflection theory is the only thing I got right now.

I dropped off the clutch pin to a guy who is going to shop it to a couple machinists he knows in the area. Not sure how long that might take. I have a new needle bearing on order, but I really think that isn't the issue.

[Richard]

I think the rod is somehow spinning even whith the bearing, that's obviously not good. So what could cause this behaviour I wonder...
Is the rod maybe pulled sideways somehow so friction is causing the spinning?

It's a lot of work but I would try the same test but this time make sure the rod is very well lubricated with grease (not oil) just to see if you still hear that sound...?

[Fishrider]

I think the rod is somehow spinning even whith the bearing, that's obviously not good. So what could cause this behaviour I wonder...
Is the rod maybe pulled sideways somehow so friction is causing the spinning?

It's a lot of work but I would try the same test but this time make sure the rod is very well lubricated with grease (not oil) just to see if you still hear that sound...?

This is exactly what I was saying. I put grease on the rod before running it last time. Although, I only oiled the bearing. I think the rod is being pulled sideways. That is what I meant by deflection. I am researching a couple options.

1) Machine a new clutch rod with a 6mm longer shaft. I would think this would effectively keep the rod from being pushed at an angle.
2) Machine a custom nut. 12mm total with threading 6mm on one side and 10mm opening for the clutch rod. This would effectively add back the 6mm lost from the 550 output shaft.

I am going to cut a hole in my clutch cover that already has a hole in it from the damage so I can see if the rod is being pushed during actuation. Of course, I can't run it this way, but it might give me insight into the issue. If I can physically see the rod being pushed at angle rather than pulled straight out, then maybe I would be one step closer to this diagnosis.

[Richard]

I am going to cut a hole in my clutch cover that already has a hole in it from the damage so I can see if the rod is being pushed during actuation. Of course, I can't run it this way, but it might give me insight into the issue. If I can physically see the rod being pushed at angle rather than pulled straight out, then maybe I would be one step closer to this diagnosis.

I think this WILL reveal the issue and I'm very curiuous about the result. You're great in video recording and I can't wait to see it

[Fishrider]

I cut the hole. What I determined is that I believe that the shaft was incorrectly installed by myself and the mechanics that put the bike back together. I give kudos to Scirocco on Kzrider for diagnosing the problem correctly here: https://kzrider.com/forum/2-engine/6074 ... =36#866822

That being said, I am still going to affect a fix for the movement of the clutch rod. I should have an update this weekend.

This first video shows actuation when the shaft is installed correctly. I can't see any issue with the actuation. Interestingly, my clutch cable is almost too long now with the rod in the correct position. My cable went from being adjusted all the way out to all the way in at both adjusters.
https://www.youtube.com/shorts/zDMkkxXCWVM

The second video shows how much movement I am getting from the clutch rod which I still think needs to be remedied.
https://www.youtube.com/watch?v=UU9isH7TcoQ

The third video shows the problem when the shaft is installed incorrectly. The gouge in the shaft is what happens as the rod spins against it. My guess is that when the shaft is out of place the clutch rod is not actuated correctly and still spins causing the damage. You can see that if the rod is spinning against the shaft how quickly damage can occur.
https://www.youtube.com/watch?v=LA2hgCOJp8Y