Gearbox Mainshaft Bush on C15

[Spaceman]

Within measurement error, they seem to correspond with what I measured? If the length is not close to 19.1 mm then the bush is completely unsuitable.

[Barnsey]

Interesting stuff!  Converting to mm I make that about 20.27 mm.  I also note the disclaimer that some machining may be needed. Now if only I had a lathe?!   NO!  If I had a lathe I could just make the thing from scratch!.   <Humph!>  Put a lathe on my wish list. 

[Spaceman]

Just done a few more measurements and mine more or less agree with those provided by CMS if you assume their length does not include the flange.

The actual hole in the timing cover is 19.70 mm in diameter and is therefore the order of 0.14 mm smaller than the diameter of my bush giving an interference of just over 5 thou which is probably about right.

With these types of bushes, they ideally need to line reamed to give the correct clearance for the main shaft. If you need to take the engine to a machine shop to get this done, they would also be able machine the bush down to the correct size and to fit it.

[Barnsey]

Hey check this out:

https://draganfly.co.uk/shop/64637/mainshaft-bush-58x-79x58-1959-only/#40-0223

They have both versions on here, the short one and the long one. 

[chaz]

bear in mind, 19.05 is the decimal equivalent to 3/4" which would have been the original size and SI / BS tolerances may be different.
Ive recently fitted a cam bush on the B40 which being  a few thou thicker on the flange tightened up the crank rotation. took a while to fathom what the problem was (on the forum) but I got there with the help of some engineers blue.

regarding lathes, I picked my small Clarke (Chinese made) one locally for £500 with the milling/drilling head and done many custom parts with it. results just as good as the £2000 Colchester lathe I had but not tried changing gears and screw cutting as I use ring dies.

[Barnsey]

OK, No 3 bush has now arrived and looks to be the right item. I am going to set up my engineers vice in my cabin to press it in with.  This is a job which has been waiting around since I moved house two years ago.My only critisism is that the bush isn't quite as snug on the shaft as I might like but I am going to go with it. 
  Iv'e also ordered a new spring and plunger to go under the kickstart pawl. \the old spring gripped the sides of the hole and wouldn't push the plunger out far enough.  I wonder if this might have been the root of the problem. 
If the engine kicked back and the pawl didn't disengage that might cause some damage both to the engine and to your foot.    I note that the vendor was nursing an injured foot at the time, which was why he was selling his bikes (so he said) .

[Spaceman]

You ideally need to heat up the timing cover first before pressing the bush in - it should drift in easily using the right size socket and a mallet. After it has been inserted, it will be a snugger fit on the main shaft and, if you're lucky, it won't need to be reamed out afterwards.

[Barnsey]

Thanks for the info.

  What is the best way to heat the cover?  Oven or blow torch?  Any idea what tempterature?

   Ian 

[Spaceman]

It just needs a bit of heating from a blow torch around the hole in the timing cover. With a bit of luck you'll be able to see when the bush is about to be able to slide in. I normally support the cover on a couple of 3 x 2 wooden off cuts so that it is stable when you try to drift the bush in.