broken burman gearbox

[iamthest1g]

hi lads

ive just reassembled a burman box on a 1950 ariel 500 single ,a type 4b i think!,
but its grinding going into first and i cant figure it out .i found there to be play in the
main shaft which i thought could be something to do with it.

[33d6]

Crunching/grinding going into first is more likely to be a clutch issue with the clutch not freeing completely before you oick the the gear lever up with your number 9 boot.

There can be several reasons for this ranging from a very simple lack of rider technique to clutch wear to mainshaft end clearance.
Proper technique is to kick the bike over with the clutch lever pulled in thus freeing off sticky plates before every cold start. Simple but often overlooked by many.
Secondly general wear and tear on the clutch or the clutch lifting mechanism. If it doesn't free properly it will always crunch. this is just a matter of checking everything over and getting it spot on. A little bit of wear in every separate part adds up and causes problems. Near enough isn't good enough.
Thirdly, and the sneaky one, is the mainshaft end clearance. If there is excessive clearance then instead of the clutch freeing properly when you pull in the clutch lever the whole mainshaft complete with clutch moves outwards so the clutch doesn't completely free up.

As the vast majority of English gearboxes are built on the same principles it doesn't matter what make or model of gearbox you are working on the same things happen in all of them. These are standard gearbox maintenance issues. Learn on one and you understand the basics of them all.
Best of luck, I think Ariels are one of the British industries better efforts and quite underrated.

[iamthest1g]

i should have mentioned that when i took it apart ther was heavily worn pieces of a heinz beans tin made into crude spacers .they were on the main shaft outside tge bearing .is there ment to be a spacer on the end of the main shaft??

[33d6]

Lord knows what bodges a previous owner has got up to but washers made from Heinz bean tins are not a good sign. Burman did say a temporary repair could be made using a hardened shim on the end of the gear change camshaft to maintain correct endfloat  but thats about it for shims in your type of Burman box.
I think you probably have a very tired gearbox that needs some loving care.
Obviously I have no idea on what you have to hand to do a full gearbox overhaul but Ariels did make it easy as they used only the CP and BA Burman box between 1936-51 so information is plentiful and good spares can still be found.
For full information I would get myself a copy of 'Ariel Motorcycles' written by C W Waller and published by C Arthur Pearson Limited in their Motor Cycle Maintenance and Repair Series. It  fully covers your gearbox. The old weekly magazine "Motor Cycling" also printed a useful article on servicing your type of Burman gear box in their February 13th, 1941 issue and the VMCC Library will cheerfully supply a copy of that.
It might interest you to know that in the early years of WWII, "Motor Cycling" ran an ongoing series of articles covering the maintenance and repair of most WD motorcycles. The Burman gearbox article is but one of a couple of dozen in the same series.
Just remember a good overhaul of the gearbox will outlast several engines so do it properly now and you'll be an old man before you need to do it again.
Best of luck, 
 

[iamthest1g]

cheer for that bud

whats the more perminant solution to this trouble???

[33d6]

Well, the obvious and permanent solution is a full gearbox overhaul and how you go about that depends on you. If they are worn, this can include replacement of the plain bearings and reaming to size afterwards as well as routine replacement of ball races. If your workshop doesn't run to the necessary tools then its a matter of finding one that does and I suppose for an Ariel owner the obvious candidate is Draganfly Motorcycles.
As this thread started with you only being concerned about a grinding noise when putting the bike in first gear and the sad story about Heinz bean tins only came out later it would seem sensible to check out the clutch at the same time. 
This all sounds as if it could cost a bit but as I said earlier, once done you will never have to worry again and as any 1950 Ariel is a keeper and is capable of any ride you will ever want to do then it is cheap in the long run. I did a lot of foreign touring on on a VB Ariel that also pulled a chair at times. I have good Ariel memories.
Cheers,

[davebarkshire]

I have a 1937 Ariel which has developed the same problem and am about to go into the shed to throw some spanners around. Having asked a few experts it seems that these boxes often develop too much end float on the mainshaft so that the clutch pushrod spends half its travel taking up the slack from the end float, therefore creating clutch drag. I've also been told that this is often due to the nut coming loose (kickstart end) or maybe some wear in the bearing (also kickstart end).

The remedy to the first cause is usually straight forward so long as the thread has not bee chewed up in which case it might be recoverable with a thread file (I did this one on a CP box which is mostly the same as the BA box).

The remedy to the second cause means taking the box apart. Some people then use shims and this is where your remnants of coffee tin have probably come from.