Gear Selection Problem

[NClark]

While I'm generally very pleased with my recently acquired 1961 B40, I've found an intermittent problem with gear selection. Starting off in first and going up through the gears is fine, but sometimes when coming down through the ratios, first and second will not engage.

When this happens the gear lever is almost locked solid, with very little movement. Changing up and down between third and fourth is unaffected, perfectly normal, but second and first are unavailable. This problem seems worse when engine and 'box are cold.

Stopping (without turning off the engine) often allows the lower gears to be selected after a few prods of the gear lever. Once warmed up, the lower gears will select on the move, though the slower the speed, the easier the third down to second change becomes. Once down into second, changing down to first isn't a problem.

Please can I ask if anyone has experienced similar symptoms, or what the cause could be? I'm wondering if there's an issue with the detent plungers engagement with the cam plate?? But I'm hoping not to need to dive that deep into the gearbox!

Nigel

[Kev D]

While I'm generally very pleased with my recently acquired 1961 B40, I've found an intermittent problem with gear selection. Starting off in first and going up through the gears is fine, but sometimes when coming down through the ratios, first and second will not engage.

When this happens the gear lever is almost locked solid, with very little movement. Changing up and down between third and fourth is unaffected, perfectly normal, but second and first are unavailable. This problem seems worse when engine and 'box are cold.

Stopping (without turning off the engine) often allows the lower gears to be selected after a few prods of the gear lever. Once warmed up, the lower gears will select on the move, though the slower the speed, the easier the third down to second change becomes. Once down into second, changing down to first isn't a problem.

Please can I ask if anyone has experienced similar symptoms, or what the cause could be? I'm wondering if there's an issue with the detent plungers engagement with the cam plate?? But I'm hoping not to need to dive that deep into the gearbox!

Nigel

You might be doing this already, but when l dip the clutch lever l aways give  a little blip on the throttle as l change down. The gears seem to mesh with less resistance .
   As l said ,you might be already doing this  though.

[NClark]

Thank you Kev. I do usually blip the throttle changing down, but on my B40 it doesn't make any difference selecting first or second. I've never had a bike with this particular gear change problem before.

Nigel

[V500]

I had similar issues with an Empire Star I had some years ago. Turned out the PO had used too viscous oil in the gearbox, and until it was really warmed up the pinions were reluctant to slide into engagement as far as they were designed to.
Cheap enough to try, anyway.

[NClark]

I had similar issues with an Empire Star I had some years ago. Turned out the PO had used too viscous oil in the gearbox, and until it was really warmed up the pinions were reluctant to slide into engagement as far as they were designed to.
Cheap enough to try, anyway.

Thank you,that makes sense, and would explain why the problem isn't so bad when warmed up. I'll try an oil change. Different oil types are quoted by the Haynes manual and other sources. Can anyone here say what oil spec would be best for a 1961 B40? I normally use EP90 GL-4 in my Triumphs from this era.

Nigel

[rhyatt]

The correct gbox oil is sae40 straight monograde and the correct primary oil is sae 20.
Do check the clutch pushrod freely after screwing in the clutch cable adjusting screw.
Screw pushrod adjuster in until it stops and then back out 1/2 turn
Start from there

[NClark]

The correct gbox oil is sae40 straight monograde and the correct primary oil is sae 20.
Do check the clutch pushrod freely after screwing in the clutch cable adjusting screw.
Screw pushrod adjuster in until it stops and then back out 1/2 turn
Start from there

Thank you, much appreciated.

Nigel

[Andy Kay]

My best friend owns 3 WD B40's, one he acquired was a rolling chassis with the engine out.
He had a similar problem. He checked everything before putting the engine in and on the bench, from neutral he could select 1st and go up the box to 4th, but when coming back down the box it would not go below 2nd gear.
He had to remove the gearbox cover and clusters and refit everything back in the neutral position, but the same thing occurred when trying the gears.
After much head scratching and research, it was discovered that the gear quadrant was fouling the casing and everything was cured with a file.
It also appears that the quadrants in different year models were slightly different and not interchangeable. Not to mention the problems with poor quality pattern parts.
I hope changing the oil cures your problem and you don't have to resort to stripping the gearbox.

[NClark]

Thank you Andy. Your friend's gearbox troubles sound like a real test of patience, but good to know. I sincerely hope my bike isn't so challenging!

Nigel