The BSA A7-A10 Forum

Technical => A7 & A10 Engine => Topic started by: Steverat on 10.01. 2019 19:07

Title: Idler endfloat
Post by: Steverat on 10.01. 2019 19:07
Still assembling the timing chest on Josef's '51 A10.
Everything is on straight except, it seems to me, the idler which has massive endfloat.
Does this matter,. or do I need to get some shims for it?
Title: Re: Idler endfloat
Post by: muskrat on 10.01. 2019 19:28
G'day Steve.
The idler pinion should be a tight fit on the shaft and when the inner cover is on and the dynamo drive sprocket is fitted there should be only minimal end float.
Cheers
Title: Re: Idler endfloat
Post by: beezermacc on 10.01. 2019 22:10
Don't forget to fit the cork washer behind the dynamo drive gear, that's what takes up the endfloat.
Title: Re: Idler endfloat
Post by: Swarfcut on 10.01. 2019 22:26
Steve...Crude but effective as detailed by Beezermac, the cork washer under the large dynamo sprocket will control any endfloat. Often looked on as an ineffective oilseal, it does the job simply and is self adjusting. Don't forget to put grease in the dynamo cavity.

 Swarfy
Title: Re: Idler endfloat
Post by: Klaus on 11.01. 2019 08:17
Don't forget to fit the cork washer behind the dynamo drive gear, that's what takes up the endfloat.

Its only for the camshaft, and the cork had to be grind to correkt size. There should be a visble endfloat when all is fit and tightened.
I convert to a spring, like the Goldys, with no corkwasher.

At one enginge I shimmed the idler to turn free with no endfloat. It was a flop, as the enginge running hot, there was this strange noise, let me know theres something wrong. *eek*

cheers Klaus
Title: Re: Idler endfloat
Post by: Swarfcut on 11.01. 2019 09:11
Steve... The cork washer you need is 67 708, listed as "Idler Pinion Spindle Oilseal." It is only about  3-4mm thick, ID fits the spindle, OD extends slightly larger than the raised spindle bush location on the inner cover. Fits between the inner cover and the underside of the dynamo drive sprocket.
 
 The amount of initial float depends on the gap between the supporting bushes and the idler gear. No wonder you thought you had a problem. With the dynamo drive sprocket in place the cork washer is compressed between the cover and the sprocket, which draws the idler gear outboard and effectively locates it gently against the inner cover bush, eliminating the float. Give the underside of the cork washer a dab of grease to stop friction charring on first start up.

 Swarfy.
Title: Re: Idler endfloat
Post by: Steverat on 12.01. 2019 21:13
Steve... The cork washer you need is 67 708, listed as "Idler Pinion Spindle Oilseal." It is only about  3-4mm thick, ID fits the spindle, OD extends slightly larger than the raised spindle bush location on the inner cover. Fits between the inner cover and the underside of the dynamo drive sprocket.
 
 The amount of initial float depends on the gap between the supporting bushes and the idler gear. No wonder you thought you had a problem. With the dynamo drive sprocket in place the cork washer is compressed between the cover and the sprocket, which draws the idler gear outboard and effectively locates it gently against the inner cover bush, eliminating the float. Give the underside of the cork washer a dab of grease to stop friction charring on first start up.

 Swarfy.

Excellent explanation thank you very much.
I found the cork washer in amongst the gasket set and fitted it, seems just fine.
Title: Re: Idler endfloat
Post by: Brian on 16.01. 2019 01:34
I fit oil seals to mine, done quite a few now.
Title: Re: Idler endfloat
Post by: Steverat on 16.01. 2019 04:26
Very good looking solution how do you machine the counterbore? I suppose concentricity doesn’t have to be so exact with a flexible seal, but still...

Swing the whole thing on a mandrel in the lathe? Or do you have (green envy) a vertical mill?
Title: Re: Idler endfloat
Post by: Brian on 16.01. 2019 07:11
I do have a mill but what I do is turn up a piece of metal to fit nicely in the bush and then bolt the casting to a face plate in my lathe, then clock off the  piece of metal and then machine out the housing.

Title: Re: Idler endfloat
Post by: RDfella on 16.01. 2019 19:12
Brian - nice piece of engineering, but is this not, as someone posted a few days ago, a case of overthinking non-existant problems? I note the bronze bush has been shortened by a fair bit in order to accomodate the seal, which is a downside. Also, the cork seal not only seals the shaft, preventing leakage into the dynamo chain area, but counteracts endfloat as well. With your seal modification I presume the cork is left out, thereby allowing endfloat? In my view, creating two problems to solve one that didn't exist.
Title: Re: Idler endfloat
Post by: Brian on 16.01. 2019 20:30
What I do is measure the end float before I remove the casting. Depending on how much end float you can either just machine out the bush/housing or remove it and place a shim washer under the lip of the bush or in this case make a new bush with the correct thickness. I give them .002" end float.

The cork washer does work to a degree but it is a crude way of controlling end float and sealing the oil. The part of the bush you remove has the scroll in it so you actually remove very little of the surface area of the bush. The seal I use removes 1/4" of the bush.

My method gives fixed end float and total sealing so no possibility of oil getting into the generator drive, in my case a belt. I agree this is not an essential modification but once done it is a "set and forget", you dont have to think about sealing or end float ever again.
Title: Re: Idler endfloat
Post by: RDfella on 17.01. 2019 09:56
Brian - thanks for the clarification. With endfloat catered for, a lip seal probably is the best insurance for a belt drive.
Title: Re: Idler endfloat
Post by: Brian on 18.01. 2019 21:53
RDfella what you say about overthinking a non existant problem is a valid point.

I have done quite a few modifications to my bikes and none of them are absolutely necessary. A stock standard A10 will work perfectly well as it came from the factory. None of my mods make any significant improvement on their own but all put together they do make for a more refined bike and overall improve the enjoyment of owning and riding one.

I might also add I do quite a bit of light engineering work for myself and others so probably look for things to do just for the hell of it.

Just some of the things I have done to my bike are,

12 volt with belt drive
oil seal on idler pinion
oil seal behind clutch
modified clutch lift to needle roller lift
oil filter in return line

And others that dont come to mind at the moment. All my mods are internal or hidden so the bike still looks as it should.

The main thing is to have a bike you enjoy regardless of what has been done, its all about riding them.
Title: Re: Idler endfloat
Post by: Peter in Aus on 19.01. 2019 01:51

The main thing is to have a bike you enjoy regardless of what has been done, its all about riding them.

My thoughts exactly *smile*
Peter
Title: Re: Idler endfloat
Post by: rocker21 on 21.01. 2019 13:08
converted mine to a needle roller bearing with built in seal, chopped of the bit of the bronze bearing with the thrust face on it and used that,, or if loads of end float make a thicker one,  have to grind the shaft a little , seems to work just fine, no cork washer and the srm belt drive modded to fit an alton , got good lights and no oil leaks so far,
the oil seal is only at one end of the needle bearing and seems to get enough oil, no machining  of case to get bearing in, there is one thats a nice press fit  and crankcase side used one without the seal and used old bearing to make thrust face as needle roller is slightly shorter so cut it on lathe and put a slight taper on it and pressed it in.