Shifting problem 1975 yamaha XS650B 28,462 miles

[jsbernaix]

I have a 1975 Yamaha SX650B motorcycle that will not shift when the engine is warm. I used to ride this bike as a kid (it was my dad's), it was stored in my fathers barn from 1985-2007 unriden. It worked fine when put in the bard 20 years ago. I have been restoring it, slowly. The shifting problem began immediately after we got it running last year and back on the road kind of if a 5 mile trip means it is on the road. I am new to this and it is a project for me and my oldest son when he is home in the summer from college.

I switched the engine to motor cycle synthetic oil; it had conventional oil when we began the project. I switched to synthetic oil when I experienced the problem. I was trying to increase slickness in the oil reservoir (shared for engine and transmission) thinking it may solve the problem.

It shifts great and runs wonderfully until I cover about 5-6 miles then the motor cycle will not shift any longer. The shifter will not allow up shifting or down shifting until the engine cools again, then it is fine for another 5-6 miles. I have gently removed the glaze from the clutch plates they had just a little rust from being stored so long unridden I guess.

I am putting a new thrust washer and needle bearing in this weekend to see if that helps. Ideas? My next area to address will be the shifter shaft assembly am I thinking correctly?

 

[pyrocentric]

All of my shifting problems have been clutch related. I'd say you're on the right track.

 

[gentlemanjim]

Yes do the proper clutch adjustment.
Slack cable at handlebar lever - fully
Snug actuator crew and back off 1/4 turn lock down
Reajust cable with 1/4" free play

 

[inxs]

- if that fails check the shift shaft for straightness...as the cases heat up the alu expands faster than the steel shaft, if the shaft is bent it can bind-especially in the left side cover hole

- if stripping the clutch again check the shift drum stopper spring, this may be on its last legs

- check the spring for lever #2 and the adjustment while you are at it

 

[jsbernaix]

Thanks, I appreciate your ideas and thoughts. I will let everyone know how it went after we complete the work this weekend.

 

[jsbernaix]

I have another question concerning this project. Last night we removed the pressure plate to get everything ready. We of course had to take out the clutch springs. I have an old Yamaha service manual for XS 650 models 1970-74; remember the one I am working on is a 1975.

The springs measured 34.8 mm, the book says they are ok if they 34.6 mm. I purchased a full set of six from a XS 650 parts store on line. The new springs measure 43.2 mm. Do I really want to install the new springs that are that much longer when I reassemble, will it cause any problems?

 

[wideload]

I removed the stock springs from my 1978 and measured the clutch springs at 34.6MM. Who knows how spring length relates to the strength of the spring? At any rate I replaced the stock springs with a set from MikesXS - they measured 43.3MM. No problems at all. I can't say the same for his throttle cable that I odered at the same time. It was a couple inches shorter than stock with a real puny cable.

 

[jsbernaix]

Yep my springs came from the same place. Our measurements are almost identical. So I will put in the new ones. Thanks. I have not run into the problem like your throttle cable yet, but I am new and I am sure it will happen. Thanks again!

 

[jsbernaix]

I am to the point of adjusting the lever and shift drum as posted above and had a quick question. The lever marked number 2 in the figure above interacts with pins directly below the five pointed drum. Are those pins supposed to be directly below each of the five points or is it ok if they are slightly off each individual center? Basically i guess im asking if when making the adjustment do i need to worry about the pins or simply the piece that is displayed on the right side of figure 1.12 above.

Also when I shift with it all apart it will shift about 50% of the time. The rest of the time it will get stuck between gears and i can get it to pop into the next gear by gently crancking the kick starter. This happens when i down shift and aslo when I up shift.

Also is there a trick to getting the lock nut loose? (also shown above)

 

[jsbernaix]

Partial solved. THe lock nut on the shifter arm adjustment was backed off with a crows foot wrench head 13 mm (barely fit). Boy what a tight area with very few options to get a tool in.

Shifting problem is still a 50% -50% problem sometimes shifts perfect other times hangs up between gears?

While My son and I were taking care of the cluch and shifting problem we attacked a started problem. Before we started the project the starter that would only engage about 20-25% of the time. The rest of the time the starer would turn but not engage. We read the forum about start bolts on this site and it helped. It gave us many ideas to try. We accessed the starter instead from the clutch side. Replaced bendix and the spring and the clip (oh the clip). The clip from mikes was was wat too big so we pressed it, streched it and grinded it until it fix (3-4 hours, my son is continued reshaping until it fit and moved in the guide in the block)) now the starter engages and starts every single time.

Now we need to keep working to figure the shifting problem!