Help please, no gears

[Sye]

The saga continues. I have stripped, checked and rebuilt engine number two three times now. Each time, I can select all of the gears on the bench, the drum turns and there are no issues whatsoever. Once it's bolted up and in the frame it's a different matter.

I can't select any gears again and I'm thoroughly pissed off with it. I know something's wrong but for the life of me can't see what it is. I've checked the guide bolt and tried with it slack and no joy. It's intact, so there's nothing broken off it.

What else can I check without having to take the motor out again? What can I check by removing the clutch and stripping the right side of the engine, or the left side for that matter?

Other than copious amounts of alcohol, insulting the wife and hitting it with a big hammer, does anyone have any ideas please?

[davis]

Man, I feel for you Sye - I mean I know your pain! So, I'll throw something in, not being one who has had a successful engine build yet.

You said it worked on the bench before being bolted up. Did you bench test it with all engine bolts torqued? If not, then something may be pinching when bolted up. If that's the case at least you could solve the problem on the bench.

If it goes into the bike torqued up and working then I would just mount it without any other hook ups and try it. Then hook it up system by system. Clutch cable to check clutch disengagement. Does it go into neutral? Are the engine brackets correct and the frame straight so that the case is not abnormally stressed when clamped in? Basically, start over on the bench with successful gear changes then progress step-by-step to see where the problem starts. Don't know if this helps but good luck.

- Bob

[slawsonb]

I'll just add words of encouragement and concurrence with davis that slow isolation is the best way to figure this out.
...bert

[hardy]

Good advice! That's problem solving 101. Change one item, if no change noted, put it back and change the next.

Good luck, my theroy is its pinching together when closed up...

Ryan

[fiction]

This is what stopped my gears from selecting,I'm guessing it's part of the rotary disc gear.it was floating around in the crankcase gear selector side.but the bottom engine mount bolt (the pointed ones)had gone through into the gearbox .i would try without the bottom bolts in just to eliminate them .

[Sye]

I now have the right side engine casing off and am almost convinced that the problem is something to do with the drum shifter or maybe not, I'll try and explain my reasoning.

This engine was completely rebuilt, new crank bearings, seals, con rods, everything. It selected the gears easilly on the bench, the drum turned and the shift forks moved as they should. It was pristine clean, with nothing in the cases to cause a problem. All bolts tightened to the specific torque settings.

I have looked at it today and here is the problem.

When you move the gear selector nothing moves. The change arm teeth (No 1) move slightly on the shift drum teeth (No 35) but then stick tight. If I compress the two ratchet pawls by hand (No36), then the shift drum teeth move and there is a click as it engages the shift drum but then it locks instead of rotating the shift drum stopper plate (No 12) and engaging a gear. I have tried to move the shift drum using a pair of pliers on the end of the shaft (No 9) but it's stuck solid. I have loosened the shift drum guide bolt (No 10) and spring tensioner (No 15) but it's made no difference.

It looks as if it's going to be an engine out job for the fourth time but I just don't understand how the shift drum can rotate freely and engage every gear on the bench but stick tight when assembled and installed.

I'm not going to take the engine out just yet, I will see what I can do by taking the drum shifter mechanism apart and looking very carefully at the component parts to see if there is a worn item or assembly problem. That said, if the drum is tight and doesn't move, that's a waste of time and it's got to come out and be split again.

Any ideas welcome please.

[Sye]

And the winner is...................................Davis, hurrah. 

Didn't take the engine out, just slackened every casing jointing bolt by 1 flat and it truned, so slackened them all off a little more and then torqued the bolts up to the lower end of the spec and hey-presto, we have gears.

I'm a happy bunny again.

[slawsonb]

It would be interesting (but I'm sure you have no patience for more experimenting) to see which of the bolts causes the bind. Or more correctly what part of the case is deflecting enough to cause the bind.
...bert

[BRT-GTR]

 Sye (Happy Bunny),

         Very pleased that you've got it sorted.  Strange one!!  Just been looking at a bottom crankcase with just the shifter drum inserted. On the face of it there are no case bolts near the drum, just the two lower engine mounting bolts, so why the drum should have jammed is odd.  Are these the cases, you posted some time back, that had the cracks near the bearing knock pin bosses in the gear box, if so, could be something to do with that.
        Good luck with the rest of the rebuild, Brian.

[coxy]

Glad you got it sorted sometimes things can be very frustrating. Time to crack a beer