G: Gearbox (Single - Burman) Burman clutch pushrod rod length

everiman

Active Forum User
VOC Member
Stevens in "know thy beast" says the burman clutch push rod is 11 3/8" long, and there should be a 5/16" ball between clutch push rod and the clevis fork. The one I took out of my 1954 Comet box (manufactured in late 53) is 11 5/16 long and the ball is 1/4". If I put a 5/16" ball in the overall length is too long for the adjuster thingy to sit flush with the cover. The clutch and plates look normal, but this is my first experience with Vincents, Comets and Burman gear boxes other than their Commando descendants, so what do I know? I have trying to find a clutch adjustment to stop it crunching shifting into first gear when stopped, moving shifts are fine, the clutch does not drag, the pressure plate rises level, there is no perceptible drag with the clutch pulled in and the kickstart depressed, so my last desperate attempt to cure this was to make sure that the lifting lever was at the correct angle for maximum pressure plate lift.
So my question is, were there differences in Burman boxes over the years regarding push rod, ball bearings etc.? If Stevens is right (is he right?) the longer push rod and ball will be way too long for my gear box.
 

ClassicBiker

Well Known and Active Forum User
VOC Member
I've been helping a fellow member with his pre-war Meteor's Burman gearbox. The pushrod that came with it was supposedly of the correct length. It wasn't. He resolved the issue by buying a longer version which I cut down a small amount to achieve a suitable amount of lift of the clutch pressure plate and allow some adjustment. Point being is I don't place to much faith what Burman supposedly fitted based on Burman documentation. The incorrect length of the pushrod was the lesser of all issues we dealt with based on what was supposedly correct. They may have altered the drawings but I think they used parts until stock was exhausted. So when things were supposed to change and actually did are very different dates. On top of suppliers not getting the word.
Now I haven't had cause to have my '50 Comet apart yet, it ran pretty well when I bought it 15 years ago, but it crunches a little going into first at a stop. Until the driven plates/clutch hbu and thus the mainshaft stop moving I think you'll get a little bit of that.
Steven
 

vibrac

Well Known and Active Forum User
VOC Member
It doesn't have to be a ball I have used a 1/4" roller before now
Incidentally the worst thing about burman clutches is that the rollers that the drum rotates on are not 1/4" long they are special shorter ones why burman did that rather than the thickness of the rotating part is one of life's mysteries perhaps they thought they would make a killing on selling sets of special rollers ( just one 1/4" mismatched roller can upset the system)
 

davidd

Well Known and Active Forum User
VOC Member
Evriman,

I assume you are talking about this:

Burman 11& three eighths inch Rod.GIF

The 330X clutch operating plunger and the 28X push rod are square ended? If so I would think a 1/4" ball would not hurt. I suspect you are doing the right thing if you keep what you have as I don't think you will diminish the crunching by changing that particular length.

You could also use a segmented 28X by making one yourself with some oil hardening drill rod. You can cut it into two segments and measure the two rods with whatever roller or ball you use to separate them to be the correct distance, that is 11 5/16" total in your case. You can heat the ends of the rods and dip them in oil, which will harden them. This is popular if the push rod continues to turn with the clutch and tries to wear out important items, but that is why the ball is specified in the drawing.

David
 
Top