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Twin gearbox troubles

Upstreeter

Well Known and Active Website User
VOC Member
Help! I had what I thought were failings on my part to select gears properly with a bit of jumping out of third gear. This became more frequent culminating in coasting to a halt with no gears being able to be selected at all. Removal of the outer casing (Gearchange side) and all looked ok. However, by sticking the indicator lever back on and trying to move it in either direction whilst rocking the back wheel to and fro I can get one gear (in roughly the neutral position) and another neutral beyond that. Other than this all is solid no matter how much I try and persuade the lever (albeit carefully). Am I looking at a problem with the vertical (bevel) mechanism or the camplate, or both? Worse, will the crankcases require parting? Any advice would be the most welcome thing in the world at the moment...short of an end to the war in the Congo, credit crunch, global warming etc.
 

petermb998

Well Known and Active Website User
VOC Member
One quick check is to check the cam plate spindle under the dynamo.
If this has come out this is possible your problem. (Broken Boss). I hope not.
I had this happen on a newly rebuilt engine which had not been run in, and all I had was top gear and a false neutral and I had to return home from work at Dagenham in Essex at 6.00am along the A12 to the Dartford tunnel when there was only one tunnel in the 1960s and on A2 to Rainham in Kent. 30 miles with only top gear going through the Medway towns.

If this is the case it will mean a complete strip down of the engine. sorry.
This happened to me 32 years ago on my 1st Vincent and I am sad to say although repaired I never got the chance to reassemble and run this Vincent.
I hope you have better luck.
best regards Peter
 

john998

Well Known and Active Website User
VOC Member
Twin gearbox

Hello, unless the bevel that is moved by the shaft with the indicator is damaged, or the casting that holds the cam plate bevel spindle has failed, you should not have to split the cases. It sounds like the gearbox is going to have to see the light of day, not as difficult as you might think. Remove the clutch and primary drive then the 10 1/4 screws on the round hatch. Also remove the kick start ratchet on the gear change side. In a panic I once did this and reassembled the thing between races at Cadwell.
A light clout with a soft faced hammer on the clutch shaft, on the gear change side will move the hatch. You will then be able to see the problem.
I do not remove the cam plate spindle, it is best left undisturbed. John.
 

pifinch

Well Known and Active Website User
VOC Member
Before you start pulling your engine to bits, please check your gearchange adjustment (Paul Richardson) It takes an hour or so & costs no money, if you have already verified this then I apologise for talking rubbish, but the easy option is the free option.
Steve
 

Upstreeter

Well Known and Active Website User
VOC Member
Thank you all so much for your trouble. It seems there are several options for visual diagnosis prior to major surgery! We've checked as per Richardson but nonetheless it is a valuable suggestion. Again, I appreciate you all sharing your hard-won knowledge.
 

Len Matthews

Well Known and Active Website User
VOC Member
Could possibly be a melted mainshaft Selector Fork. It's happened before mainly due the double gear's engagement dogs being worn or the oil level being too low. If so, no need to split the crankcase.
 

methamon

Well Known and Active Website User
Non-VOC Member
Caution

Prior to removal of the primary chainase screws, do remember to de-tension the primary chain. I seem to remember reading this in KTB or Richardson over the weekend and failure to do so can result in damage?
 

timetraveller

Well Known and Active Website User
VOC Member
There is but it takes a very brave person to do it. You can cut off the original and weld in a piece of aluminium the shape of the later crankcase bosses. I have had it done to at least two crankcases which had the original boss broken off and the later design is much stronger than the original. It is often forgotten that the engines were being developed throughout the whole production run. Although financial trouble caused troubles with some aspects of quality to-wards the end the 'D's were developed after consultation with many riders and there are several aspects of the later engine and suspension which are better than the early ones. Note that I have no axe to grind here as I have 'B', 'C' and 'D' engines. I seem to remember that his 'ighness the 'iggins gave an improved design for the pivot in MPH some time ago :).
 

Upstreeter

Well Known and Active Website User
VOC Member
And the winner of the gearbox problem diagnosis prize is....wait for it.... Len Matthews!. Thanks Len, and a big sigh of relief all round with no crankcases to split. The main shaft selector fork is totally b..g...d and has filled its corresponding channel between the dogs with brass. The curious thing is that there are no signs of wear and there was plenty of oil in the gearbox - no blueing of teeth, nothing. This has wiped the smile off my face.
 

John Appleton

Well Known and Active Website User
VOC Member
The main shaft selector fork is totally b..g...d and has filled its corresponding channel between the dogs with brass.
Hi Upstreeter, my Rapide used to do this on a regular basis! Found the cause to be excess end float in the clutch mainshaft, which I rectified by fitting a 40 thou. spacer ,in addition to E76, behind the bearing in the gearbox manhole cover. You should also check that the G30 spindle is not bent as a result of the siezure.It is also worth mentioning that ,since renewing the gearbox bearings in a recent rebuild, the extra spacer is no longer necessary although there is no obvious wear in the original bearings
John
 
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