Has anyone had this problem (idler gear bush)

[townsends20]

This rgs came to me in bits, the guy that had it before had completely stripped it with the intention to re-build it, he must have got as far as renewing all the bushes in the crank case and the inner timing case and then went and died, 35 years later it came to me. On assembling the inner timing case would not fit flush with the crank case, I found that the idler gear was hitting the shoulder on the inner timing case bush. After making sure all was in line, I came to the conclusion that the  shoulder of the bush was to thick and it was a faulty part so I reduced the shoulder  by half and it fitted OK. I had been running the bike for about a year (about a 1000 miles) no problem except the oil was getting into the the dynamo chamber and out the back of the dynamo. Now as the weather was turning I decided to strip it down and get to the bottom of it, (so to you guys at the forum I go) found that the wrong bush had been fitted and instead of channelling the oil away from the dynamo housing it was pushing it through. I  rang Brian at lighting spares and he told me that the part no. in the BSA parts list was wrong, he sent me the right parts ( got them the next day) went to fit it yes! same problem and I had to reduce the  shoulder on this one to get the case to fit flush.
The bike is going great and no more oil leak but this con-not be right.
  Steve

[bsa-bill]

Hi steve - been there done that got the .............

Look here http://www.a7a10.net/forum/index.php/topic,2984.0.html

the good thing that came out of it was that it proved SRMs dynamo belt drive works in a chamber full of oil

[townsends20]

thanks for that bill , I have a srm belt dynamo drive and it works well in oil but I need to find out why the bush needed to be altered.
  steve

[Stephen Foster]

Could the timing covers have been milled to flatten them , this might tighten things up ?

[bsa-bill]

Steve, I missed out some of my reply ( had to go back and bit of the text disappeared, didn't  notice until I read your reply)
I meant to suggest that you check the pinion on it's shaft, it's key'd but just pressed on, is it possible it just needs knocked further onto the shaft

[KiwiGF]

Or maybe the case is "bent". I suspect the inner case is bent on my bike, from a PO failing to align the breather dowel...you never know what has happened in the past, and made a standard part not fit. In my case the easiest thing to do was make up a extra long dowel on the pinion, and use an extra thick cork gasket.

Having said that, in my experience it's a fair assumption to "suspect the part" 

If you got dimensions of the dodgy parts, that might help get to the bottom of the problem.

[townsends20]

 Steve  posted 24/10/12

Thanks for all your input I did check that the gear was on the pinion shaft in the right position and that it sits level with  the timing gears, the bush must be right as this is the second time I have had to do this, and there are no signs of the case being re-faced. Now with all your input  the only thing I can think has happened is  that it has been forced off by a Muller man at some point as there are some deep marks behind the dynamo sprocket,  without trying to press it back to shape (and that?s a no no!!)there is not much I can do, and it won't be easy or cheap to get a replacement with a rev. drive. I will have to live with it now as the bike is back up and running.
  What would you do???????????? 
  Thanks Steve

[chaterlea25]

Hi Steve,
I have come across the same problem when parts from different engines were mixed ??
I recently got an "As New" rev drive inner timing case, when I offered it up to a current engine project it would not sit home,
The lip on the bush was vilibly thicker than the original,
I must offer up another couple of standard cases and compare!!

HTH
John

[wardleybob]

I was unable to find a iner timeing case with taco drive so I alterd one

[bsa-bill]

I find it quite surprising just how much these cases flex, I know mine are slightly banana shape when offered up (touching in the middle and gaps at each end ) but pull in just fine, then again if BSA didn't know about metals who would (don't answer that one)