VH Primary Drive

[andrew.chapman]

Having successfully repaired the crank shock-absorber, I thought I would replace the worn primary chain while it was apart. The new chain appears to be the correct one and has the same number of links as the old one.

However, I can't move the gearbox forward far enough to get the right tension on the chain without twisting the gearbox on its mounts slightly. The reason appears to be that the outer casing fouls the bolt that goes into the timing chest to hold the magneto mounting bracket.

Is this a known problem? If so, is there an easy solution without taking the gearbox out?

[brenton.roy]

Hi Andy,
I don't know how the swing arm VH's are set up, but this sounds a long way forward to me.
How much shorter is the new chain (stretched length)?
You should be able to put in a half link if you just need a little more length.
Brenton

[john.nash]

Mine doesn't do that ?
I have a 54 VH and I put a new chain in it?

What sprockets are on there ?
I think I have a 23T engine and a standard clutch wheel.

[andrew.chapman]

Me too. Engine sprocket is 23T and the clutch sprocket is 44T ( I think). The new chain is 1/2" pitch and 74 links.

The old chain was apparently the same but slightly shorter, of course. It always was a bit close between the gearbox and the engine but now there is a bit less that no space at all.

I wondered whether the gearbox may not be mounted quite right. Could somebody have fitted the wrong plates from another model, I wonder?

[Simon.Gardiner]

My s/arm VH has the gearbox pretty close to that timing cover bolt, with a new chain, there's only just enough clearance.
Two possibly daft points - the cover hasn't been re-tapped to fit a larger stud/nut has it? And are the primary sprockets in line?

[brenton.roy]

Hi Andy, I doubt it has wrong plates. The primaries and the timing chest determine where everything sits. As long as the main bits are square to them you're Ok.
The main question is how much adjustment you have backwards, to take up chain wear. The actual length of chain doesn't matter.
Does the adjuster nut locate and have plenty of thread?
Brenton

[andrew.chapman]

Now that's interesting. I don't have an adjusting screw. On mine, you just loosen the clamp bolt and rotate the gearbox by hand. On closer inspection, I also noticed that a PO has fitted 2 washers under the offending bolt head. It isn't at all clear why he did that. It's a tiny thing but it seems to be enough to cause the fouling.

To save myself a load of unnecessary hastle, I plan to fit a half link. It's a bit of a cheat, I know but I am exraordinarily short of time, not to mention lazy.

[john.nash]

You don't have one of these :

http://www.draganfly.co.uk/shop/pd-1871 ... goryId=146

I think you have to move out/ake off the gearbox/engine plates to get it in.

Without it, then isn't there a risk of your gearbox moving under load? Mind you it's probably been like that forever

[brenton.roy]

Hi Andy,
Not having the adjuster might explain why the gearbox is so far forward - to jam the box in place.
if you don't fit the adjuster screw I'm pretty sure you'll spend a lot of time adjusting chains.
There should be a steel pin on the top of your box for the eye of the pictured screw. If it is there (not broken), and the tab is there for the adjusting nut (on the engine plate), it's pretty straight forward to hook this up. You could make the screw with a nut and a bolt welded together.
I reckon the box will come back a long way.
regards, Brenton

[nevhunter]

I usually end up with a 1/2 link in the primary. I don't like them as they are considerably weaker than a plain link. The adjuster is almost a must as the back chain will have much more tension in it than the front, especially in first gear. Always end up with it trying to push the box forward for this reason. Nev