Help with split case, '81CB750C

[mrtwowheel]

Here's where I'm at right now. I split the case, no problems. I cleaned the gasketed mating surfaces and the Honda Bond surfaces. Nothing was removed from the shifting linkage or the gears. I'm doing this because I yanked out the seal at the output shaft thinking it was a regular seal.

I am trial fitting the lower case to the upper case. Shift forks line up to their grooves and the cases close together no problem with some slight taps that I suspect are caused by the dowel/locating pins being slightly tight or out of round. After the cases are settled together I cannot shift through the gears, not even one gear. I should be able to shift through the gears at this point right?

I do not suspect any bad parts here. Something is not lined up right in the shift linkage or the gears when I put the cases together.

I have Clymer and Honda manuals, not helping. I have searched for a week and am not able to find the missing info that I need.

 

[brettp]

I would think if the crankshaft is disengaged from the transmission you should be able to shift gears.

 

[mrtwowheel]

I could shift gears before the case was split. Most things Honda I can understand how they work and the purpose for every part, but not this gearbox and shift mechanism. Also the manuals suggest to shift through the gears before final assembly.

 

[mrtwowheel]

I took the lower case outside for better light. I'm starting to understand the shift mechanism in the lower case. I discovered the electrical contact for the neutral light. Now I can tell when the mechanism is in the first gear position. Also the spring loaded pawl that moves the grooved and holey shaft was out of it's position behind the star shaped thingy. I think I'm closer to the right path now. I'll trial fit the cases together again after the football game tonight. Grandson is on the homecoming court.

So, shifting forks unbound, shifting mechanism in first gear position, that pawl in the right place, fit the cases together. Maybe 3 or 4 successful trial fits and I sure hope that Bob is my uncle.

 

[mrtwowheel]

One of the manuals says to be sure that none of the other gears are engaged. ???????????? That's way above my head right now.

 

[brettp]

I have never had a crankcase apart, nor transmission. Curious to hear how this goes. And it sounds like you're on the right track!

 

[mrtwowheel]

I'll try to remember to take some pics. Hopefully I'll be ready to put the engine back in the frame by Monday.

 

[mrtwowheel]

Still trying to trial fit the cases together and get the trans to shift. Latest, it will shift to 2-1/2, it will not shift to 3rd gear. Shift forks are in the right positions.

 

[mrtwowheel]

Maybe I'm getting there. I threaded the front sprocket bolt into the output shaft and easily moved the output shaft a little bit, trans fell into 2nd gear. Shifted to 3rd, it would not engage, turned the output shaft again and it fully shifted to 3rd as if I had been in a "false neutral", trans continued to shift to 5th gear. I may be ready to reclean mating surfaces, install the output shaft seal and the O ring between the crank and primary, then the Hondabond.

Up and down, top and bottom, gets pretty confusing when the engine is upside down.

Scott

 

[mrtwowheel]

Sort of trying again with the trial fit, because I separated the cases this time with the shifting mechanism and the gears both in 5th gear. Fitting the cases together seems to be easier with both in the 1st gear positions.

Scott