B52 Gearbox exploded drawings

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pallijen
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Joined: Tue Mar 29, 2016 6:48 pm
Location: Chesterfield UK

B52 Gearbox exploded drawings

Post by pallijen »

Hi all, I have a Burman gearbox which will not go fully into 1st, gear pedal has to be forced down to get it back down to neutral and grinds when I try to put it into 2nd. I have taken off the outer cover and there was a small amount of metal particles on the bottom of the casing. I have now taken off the inner cover to expose the internals and everything looks fine as far as I can see. I would like to have an exploded drawing of the internals before I go any further and take anything out. Other gears will select ok, just problem with 1st initially but now 2nd is starting to misbehave. I have put the clutch back to standard, this seems to work okay, the push rod disengages the clutch and you can see the plates separate but the clutch wheel still revolves. Is this correct? Would it make a difference with the chaincase on and oil in? Any advice as always appreciated. Thanks, Paul J
SPRIDDLER
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Re: B52 Gearbox exploded drawings

Post by SPRIDDLER »

pallijen wrote:the push rod disengages the clutch and you can see the plates separate but the clutch wheel still revolves. Is this correct?
By 'clutch wheel' do you mean the outer clutch basket (with a sprocket attached) within which the plates are stacked?

Have you refitted the primary chain? If 'no' then the basket is only being dragged around by the minimal friction in the separated plates. This will not happen if the chain is in place as the sprocket on the basket (your 'clutch wheel') is locked to the engine drive sprocket via the primary chain, in this case the basket will then turn only when the engine rotates.

When the clutch is 'free' (i.e. when the 'bar lever is pulled in) and the primary chain is in place the plates will be separated and turn when the kickstart is operated, but the basket won't turn.
When the 'bar lever is released the basket and the plates will all turn as one, and the engine will rotate when the kickstart is operated.
Would it make a difference with the chaincase on and oil in? Any advice as always appreciated. Thanks, Paul J
No. It will make no difference.
'There is a tide in the affairs of men
Which taken at the flood............'
pallijen
Posts: 32
Joined: Tue Mar 29, 2016 6:48 pm
Location: Chesterfield UK

Re: B52 Gearbox exploded drawings

Post by pallijen »

Thanks Rob, these are better than the one I downloaded. To answer Spriddlers questions, 1st, yes, chainwheel. Yes, primary chain was fitted. I think is all in order reading your bottom paragraph. Putting the correct clutch in meant that I had to change clutch centre for a deeper one to accommodate the correct amount of plain plates, change the four spring pressure plate for a five spring pressure plate which meant that I had to buy a new spring which is now being used alongside the old ones. Could this have any effect on operation? Thanks, Paul J
SPRIDDLER
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Re: B52 Gearbox exploded drawings

Post by SPRIDDLER »

pallijen wrote: I had to buy a new spring which is now being used alongside the old ones. Could this have any effect on operation? Thanks, Paul J
Only that perhaps being less fatigued than the others it may not need to be screwed in as far. You should adjust the springs so that when you hold the clutch 'bar lever in and operate the kickstart all the plates should be lifting equally and in the same plane.
The springs need only to be screwed in far enough to avoid clutch slip when kickstarting and when accelerating uphill in a high gear. You achieve nothing by over-tightening them except a heavy 'bar lever action.
If you're careful (and tuck your trousers into your socks) it's a good idea to take the bike out for a trial run before the rigmarole of refitting the outer chaincase. The lack of chaincase oil won't matter for a run of a mile or two provided that there's already a drop of oil on the chain.
Good luck.
'There is a tide in the affairs of men
Which taken at the flood............'
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Rob Harknett
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Re: B52 Gearbox exploded drawings

Post by Rob Harknett »

If you have gone from 4 to 5 plate clutch surely you would need all longer springs and cups. You would also need a longer clutch trust rod.
pallijen
Posts: 32
Joined: Tue Mar 29, 2016 6:48 pm
Location: Chesterfield UK

Re: B52 Gearbox exploded drawings

Post by pallijen »

No Rob, just needed longer clutch centre bolts to suit the deeper clutch centre. Thanks for the links. I've stripped the gearbox out and everything seems fine, dogs on the cogs are slightly worn but hardly noticeable. The small amount of metal that I found was only in the front part of the gearbox when I took the cover off. Just going to check with the exploded drawings that all gears are correct way round by the exploded drawings. Probably going to fit new springs to complement the one new one that I just fitted
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