1966 250 scrambler transmission issues

[dariddle]

I just finished rebuilding my 250 narrowcase scrambler and only seem to have 4 gears. With the rear wheel elevated and the shifter box off and using pliers to turn the shift drum I can only engage 4 gears. I assume that eliminates a shifter box problem but I'm confused as to what is happening in the gear cluster. I fear that I might have to split the cases and start over Any ideas about what might be wrong. Thanks for any help.

[Duccout]

Hi,

Sorry to hear of your woes. Have you had the bottom-end apart? Is there a point where the selector drum turns but does not select a gear? And, sorry to ask a stupid question, but are you sure that it is a five-speed engine?


Cheers,

Colin

[dariddle]

Yes I completely disassembled the engine and checked all the gears and bearings I didn't attempt to shim the transmission,I just put it back together. The shift drum rotates easily and the gears engage just fine but I can only feel 4 gears. It's a late 1965 or early '66 so I'm pretty sure it's a 5 speed plus when I had it apart it had the gears of a 5speed as far as the comparison to the repair manual indicated. It's either first gear not engaging or 5th gear not engaging..

[Bevel bob]

I read that the 5 speed drum selector tracks were not well formed and a bit of drum slop was better than a tightly shimmed one.

[ranton_rambler]

The advice I was given was to assemble the gearbox without the crankshaft in place and then you can see/feel what’s going on inside.
Obviously it means splitting the cases but I think you have to accept putting them together and opening them up again numerous times to get everything right.
Ian

[dariddle]

I'm afraid your right about having to split the cases.. I'm going to fiddle with the shifter box one more time e to see if that helps. The frustrating part is not knowing exactly what is happening in the transmission. It all went together well during assembly and seem to function correctly but I have to admit that the transmission is not my strong suite. I put back together the way it came apart but since it was a non running motorcycle I don't know if there was a pre-existing problem.

[Bevel bob]

You can change the gears without the selector box being in place .should pinpoint the problem area.

[dariddle]

I put a different shifter box on yesterday that has a stronger return spring and that didn't help. The fact that I can only find three gears when I rotate the shift drum without the shifter box in place leads me to believe I have somehow assembled the transmission incorrectly,. I hope when I open the cases up I will recognize the problem. I have limited transmission experience. Anybody near Indianapolis, Indiana.

[Duccout]

I wish that we could be of more help. I cannot imagine what the problem is - possibly the selector forks assembled incorrectly - but you will have to strip the engine, remove the crank, leaving the transmission in place, and reassemble the cases. Then you can shine a torch into the transmission and rotate the shifter drum and see what is happening.

Good luck,

Colin

[LaceyDucati]

If you remove the selector box you should be able to rotate the selector drum tang with a small shifter. If you can't select the gears via the tang while turning the engine then the problem is internal.

The drum should rotate over 180 degrees a little in both directions (for a 5 speed), neutral is found with the tang vertical. First is back from vertical, then back in the other direction past neutral, through the gears until 4th is reached which is 180 degrees from from neutral. 5th is further round with the tang past the vertical position. Have you checked you have installed the selector box in the correct orientation as there are two times the tand is vertical, one correct the other will find you at the top of the box with only a few gears.

Regards Nigel