Burman BA Advice Needed

[Dave.Barkshire]

The 37NH gear changes have been getting a bit crunchy over the past year and the time has come to have a look. The main shaft can be pulled in and out by grabbing the clutch center and the end play is about 2mm. So I have removed the gearbox end cover and suspect that the tube which the kickstart gearwheel rotates has worn. It is 0.91" long and I wonder if it would have been 1" originally? I can feel a bit of burring on the end. In my mind, if it was 1" long then the end play would be gone.

So the quetsion to the panel is whether my thinking is correct? If so I will have to find out if this part is available. A photo below should show the tube.

Also, the clutch innner is a bit worn where the clutch plate tongues have touched it. I think that this part should slide off the shaft but mine seems to want to stay where it is. Any tips?

[david.anderson]

Dave
I have a BA apart at the moment. The kick start ratchet pinion bush in mine measures 0.810” long? So maybe you have measured wrong by .1 (or I have a bigger problem than you do). Or is your box a CP being an NH.
The clutch inner hub can be tight on some shafts. A pair of bent tyre levers with just a little pressure exerted against the outer hub to rock it (remember it is only pressed metal) will generally do the trick. If not a puller with thin (or ground down) feet will do the job.
If the inner hub is excessively worn by the clutch plates you will always have a crunchy change as the plates will not loosen and slide on the hub to disengage. I built up my hubs on one side of the slot with weld and then ground the slots back to size and individually fitted each one to a new clutch plate. A milling machine would have been nice but some gentle work with an angle grinder and finish sizing with a file did the job. I am back to crunch free gear changes.
David

[brenton.roy]

Hi Dave(s), I can help with the gearbox, as long you don't ask me to know what I'm doing!
I have a CP on a '37NG that needs to come apart, and should be the same gearbox as yours Dave.
It might take me a day or so to get to it - I'm off with the grandson, but I can measure the bush when I get back.

re the basket inner, there isn't a great thickness of splines. David's methods sound good. If they don't work, and if you don't have a rubber seal on the mainshaft, a butane torch would do the job. It should pull off by hand.
Another possiblitity for a worn inner is to mill new slots next to the worn ones. I think Drags do this by exchange, but you might be able to find someone local to do the machining. If the chatter marks aren't too bad, you might be able to file (dremel?) them a bit.
Also, the tabs on the plates wear as they rattle, so as David suggests, new plates are worthwhile.
regards to you both, Brenton

[Dave.Barkshire]

Thanks David/Brenton

I have sent an email to Lester to see if he has one on the shelf. I have been thinking about this part and it takes a pounding every time the clutch is used so its no wonder that it would wear.

[Dave.Barkshire]

I just had an email from Lester to say that the only 'Kick start ratchet bush' which he has is just under 0.9" long. I will have to go through my box of old fasteners to see if I can find a washer or something to take up the gap. Otherwise I will be Ariel-less this summer.

[brenton.roy]

Dave, sorry, i haven't been good at getting back to you. I got as far as taking the cover off last night. I will measure the bush tonight.
Before disassembly, there is no measurable backwards forwards play in the mainshaft.
Brenton

[dave.owen]

Dave, was it just a clunky gear change or were other symtoms present.ie did it jump out of gear, any gear hard to engage.There may be other issues

Dave

[nevhunter]

IF you can't get a new clutch centre, you can make a spacer from an old steel clutch plate and place it on first and all the plates will then be displaced onto the unworn parts of the cast iron centre and they won't stick. Ensure the last one won't fall off the centre when the clutch is pulled in. This won't happen if the corks are not too thick. Your gearbox could have a bearing that is a bit narrower than original on the LH side. Spacing it with a washer should work OK. Nev

[brenton.roy]

Hi Dave, I think Nev is right. When you get it apart, you'll notice that neither the clutch inner basket or the bush has anything to do with mainshaft end play. With both the basket off and the kickstart mechanism out, I still have no end play.

The CP bush I have is 22.5mm.

Behind the kickstart mechanism is a circlip and a washer. I don't know enough about gearboxes to say whether this could be thicker and not affect functioning, but you certainly could shim out the free play at this point. Otherwise, it's mainshaft out and shimming the other end (hopefully the former, which would be much easier...).
You'll need to wait for a gearbox person to reply for accurate info about this.

regards, Brenton

[Dave.Barkshire]

Dave, was it just a clunky gear change or were other symtoms present.ie did it jump out of gear, any gear hard to engage.There may be other issues

Dave

The box has been working just fine. I have never had it slip out of gear so far as I can remember. I felt that it was getting a bit crunchy going into first and recently the other changes have been getting a bit physical. Because the clutch pushrod travel has to absorb the endplay I think that this means that it is not able to push the plates far enough apart.