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Gearboxes.

Robert Watson

Well Known and Active Website User
VOC Member
OK, I need to be educated on A gearboxes. I have just dismantled two of them, one from the A twin and one that came with the TTR. The twin one was, as I suspected it would be, quite a mess. Broken gear teeth, several case issues that may be able to be repaired, and mostly well worn out. The other one is also a standard BAP type, in fact identical in almost every way to the one from the Twin. I suspect it came from a Meteor that was canabalized for parts for various bikes back in the day.
I know the TTR should have a close ratio gear set, but as I expect it will not likely have its throttle twisted in anger I am fine with standard gears. I want to replace all the internals in the Twin box, so I need to know what other boxes have the same internals, if anyone knows. I also am lead to believe that the post war singles used the same gears as the prewar ones, is that true?
Does anyone have a spare gearbox they are willing to part with????
 

nkt267

Well Known and Active Website User
VOC Member
I'm not an expert on Burman boxes but over the years have canabalised other Matchless/AJS gearboxes for parts.You must make sure with Matchless/AJS gearboxes that you get the heavyweight 500cc ones as although the 350cc ones look right they are of different dimensions.on the 500 boxes the gear lever pivot and the kickstart pivot are both large diameter and I think on the the 350 the gear lever pivot is smaller than the kick start(thought I'd found a cheap gear lever till I checked it).
If you have Burman part numbers Draganfly Motorcycles of Bungay may be able to help(Ariel specialist).The BAP box fitted to Ariels is similar but the mainshaft is completely different.I have some Burman info somewhere If I find it I will post some better info. John
 

Robert Watson

Well Known and Active Website User
VOC Member
After several calls to UK suppliers (including the VOCS) I have educated myself on the Burman box and its internals, I have located a set of standard ratio dog type gears that will do the trick in the TTR. The only thing left at the moment is a mainshaft shifter fork. I have one good one and one that is useable but a new or better one here would be good. I am told they are not even being made, so maybe an opportunity for the VOCS as they dont look too complcated. Next, on to the case repairs!
 

nkt267

Well Known and Active Website User
VOC Member
The idea of producing selector forks was raised in MPH earlier this year by someone else looking for replacements.What about building a Comet from spares?:rolleyes: The selectors have numbers stamped on them,I suggest you post these numbers on the forum and we all search our boxes of odd bits to see if we have them.John:)
 

Robert Watson

Well Known and Active Website User
VOC Member
OK now I see where it went. It is a 42BA and fits the sliding double gear on the main shaft. All the "burman people" tell me they are not available, maybe we need to bribe that man in Holand to make a drawing!!
 

nkt267

Well Known and Active Website User
VOC Member
I have checked on the Draganfly site
http://www.draganfly.co.uk/main.html
they list a BA layshaft selector item 3214-31 @£22.05 +tax and shipping,but no mainshaft selector.
Download ariel list 14 and you will see their gearbox parts in section 19.
You can also download the price list as well.
I do have a pair of these selectors but as I look after 3 Comets they are the only spares I have at the moment.I will keep an eye out for 42BA/1(PR50-42BA) and 43BA/1(PR50-43BA) at shows for you and see what turns up.If you have found some by then, they will always come in handy for someone.John
See ebay item 300159510360 This gearbox is located in Estonia and is for a 500 single sunbeam.
 
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Robert Watson

Well Known and Active Website User
VOC Member
Hey John and John. Thanks for the replies.

The layshft selector of course is the one that doesn't wear out, that is why they have them! The main shaft one is the one that wears out and is not available new anywhere - Draganfly, VOCS and others I have tried. The three pieces in the gearbox that seem to take the most abuse are 14 BA, 15 BA, and the selector. None are available new at the moment but the good news is that 14 and 15 are, as they say. in progress. I have it looks like, a used selector fork in transit thanks to a very kind Club Member - what a Club, and I have also located a full dogged gear set. It's not a close ratio but it is in reasonable shape. This will go in the TTR and the gears that came with the box with the TTR will go in the twin. Now I have some serious case repairs to make, although I'm on the trail of a main box, I do have one kickstart cover (3BA M12 if anyone has one- and it is different from the post war Comet) that is a real mess, having blown out the snap ring groove that holds the main bearing plus some other cracks! In the meanwhile I have started rebushing the good bits I have. TT Industries in NZ list a full box for NZ$5700 but I suspect that nothing would be interchangeable - except the complete box.

This is just the gearbox, I can't wait 'till I tackle the engines!

Robert
 

Robert Watson

Well Known and Active Website User
VOC Member
Yes, Me again.
Contrary to what I have been lead to believe, I find that the actual gear case Post war vs Pre war is NOT the same. I know the K/S case and covers are different but so is the case. The external lugs are opposite and the adjuster location is quite different, and the prewar one is a Mark 3, the Post war one is a Mark 26. It still appears that most of the internals are the same. I have one good case from a single and two others, both from Twins (they are for all intenets and purposes the same as the singles), one of which has been welded in several places and one or which needs welding in three places, one to repair a small hole where it appears an errant gear tooth has been jammed between case and a gear and pushed through the case, and the other where two stud bosses have been drilled and tapped out oversize and one is very crooked and loose and the other is cracked and stripped. Welding here I am sure will cause some distortion problems. Meanwhile if anyone has a spare series A gearbox looking for a home??????

Robert
 

Don Morris

Active Website User
VOC Member
Robert

I have'nt been able to add any information on the Forks, but as you have the box to pieces and mentioned studs this reminded me of some of my problems with an A box.

A common mod is to fit the studs with 1/4 Whit, in the Alloy, and make the outer threads 1/4 BSF, for the nuts. This gives a better clamping force and less chance of the nut working loose. The standard is 1/4 Whit each end. Also make the studs as long as possible, in the alloy, tapping the holes if necessary. This makes the thread longer than normal and enables you to pick up on good threads.

I found it possible to increase to 5/16 two of the studs that hold the inner case of the gearchange/kickstart compartment to the gearcase proper. This helps to locate them together, and is not seen from the outside. Mine was originally rocking and fretting the mating surfaces. The best way of doing this is to put the shafts in the box, ensure they turn freely and then drill tapping size through both gearbox and inner cover. Separate and carefully enlarge the hole in the inner cover, to the stud size, this enables the new studs to act as dowels.

Another problem with mine was the kickstart return stop. This was replaced with an Socket Headed Capscrew with a special nut on the outside, special in the sense that the nut has to be reduced in diameter on its face to fit. The head of the capscrew has to be taken down a little to fit in and a short piece of hose over the head acts as a buffer.

Hope above helps and good luck, Don
 

Robert Watson

Well Known and Active Website User
VOC Member
Thanks Don

There were 3 stud holes in the main case that had been opened up to 5/16 tapped crooked and/or cracked through. One I retained as not too bad, and two I ground off completely and welded up, faced off in the mill and re tapped to 1/4 unc (apart from a few degrees as good as 1/4 bsw). I'll be making new studs to suit anyway. On the Twin K/S case all the 1/4 tapped holes were more or less stripped out, so I helicoiled 4 of them. The k/s stop has also had repairs so more work required there yet. Still chasing some bits but have another selector shaft on the way from the UK courtesy of a Club Member. One cover needed a clutch arm boss - it had a very loose bolt rocking around in it and that had cracked the case all around -- more welding. One had the cable boss on the k/s case missing -- more welding. I'll have a little flatening and straighteneing to do I'm sure, but in the end should have a couple of good gear boxes. The main shaft in the twin was bent .040" in the middle and worn down about .003 under the driving gear. It has been ground down and is off at the hard chromers for build up. Then I'll rebush the driving gear to suit. Lots of work. I'm making them all oiltight so I can run oil in them, so lots of holes to plug! Trouble is I have to get the whole of them put together before I know if I've done a good job!!

Cheers
 

Robert Watson

Well Known and Active Website User
VOC Member
Thanks for the offer. I've heard that Scots were slow to put their hand in their pocket:), but to be beaten out by a Yorkshireman!! I received one today from a very kind Member in W Yorks, so that is one more step to completion!
Robert
 

fgth130

Active Website User
VOC Member
The idea of making selector fork drawings came about after a letter in MPH earlier this year, and the drawings of the BAP selector forks have now been made. One of each fork (NOS) was put on a Mitutoyo measuring table, other examples were also measured, and the drawings were prepared.
They will be reviewed at the next Tech. Committee meeting in a few weeks time; when approved drawings are usually at the Spares Co. within 3 - 4 weeks.
 

Robert Watson

Well Known and Active Website User
VOC Member
Thanks Frank, I would have bought a new mainshaft fork, but my pleas have not fallen on deaf ears. I have enough now to assemble a good box for the twin plus one for the TTR that will be put together with all welded up cases and a couple of slightly loose gears, although that too will be overcome. We'll see when it is assembled if the welding has messed it up too much!

Robert
 

fgth130

Active Website User
VOC Member
Robert, the drawing of 15BA has been started, but has hit problems, because we're off to Australia for 10 weeks starting early Jan '08, the problems are retirement and time available . . . Glad to hear you located a selector fork, they're truly hen's teeth these days.
 

Robert Watson

Well Known and Active Website User
VOC Member
Now a new issue to question. Has anyone ever done or heard of being done, a double backlash on a Burman set of gears. I seem to recall that they can be awkward sometimes, usually downshifting into second and first?? Anyone?

Robert
 

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