The BSA A7-A10 Forum

Technical (topic titles must be descriptive) => A7 & A10 Engine => Topic started by: Atoll on 24.09. 2018 15:50

Title: Fram to crankcase lug cut off.
Post by: Atoll on 24.09. 2018 15:50
My A7SS frame is a 1960 model with a1954 engine. However, it looks like in order to fit the engine the rear mounting lug has been cut off. All observstions etc welcome.here is a close up pic.
Title: Re: Fram to crankcase lug cut off.
Post by: RichardL on 24.09. 2018 20:26
I think something, maybe the frame, is bent. I don't know if it's even possible to mount the engine plates wrong, so that the engine is 1/4"-1/2" too far left.

Richard L.
Title: Re: Fram to crankcase lug cut off.
Post by: KiwiGF on 24.09. 2018 21:47
My A7SS frame is a 1960 model with a1954 engine. However, it looks like in order to fit the engine the rear mounting lug has been cut off. All observstions etc welcome.here is a close up pic.

I assume this is swing arm motor in swing arm frame?

If swing arm motor, Is the spacer between primary case and engine at the front of the case fitted?

If everything else is ok (frame not bent) I’d be tempted to weld on a new frame bracket and make up a front spacer thicker than standard to overcome the problem.

Sometimes it’s nice to know the cause of a problem but better to just get things to fit!

Edit: spacer is 42-7518
Title: Re: Fram to crankcase lug cut off.
Post by: RichardL on 24.09. 2018 22:29
If the engine is shifted too far left, then it seems there is a good chance the engine sprocket is not aligned properly with the clutch basket sprocket. If they are both shifted over, then it seems a good chance the gearbox drive sprocket is misaligned with the final sprocket at the rear wheel. I wonder, really not sure, if adding spacer thickness between crankcase and inner primary won't cause inner primary to interfere with the clutch basket (the inner primary may already be unusually close to the clutch basket). I guess I'm saying that a dose of diagnostics would inform the decision on the cure.

Richard L.
Title: Re: Fram to crankcase lug cut off.
Post by: muskrat on 25.09. 2018 11:50
G'day Atoll.
I'm not aware of any crankcase dimension change 54 to 62. Normally the lug on the inner primary lives inboard of the frame lug. Some meet up but others may take one or two washers (between the lug and frame) to meet. In your photo it appears the IP lug is in line with where the frame plate was, meaning the IP lug needs to be about 4mm inwards. See if you can loosen the engine and plate mounts and twist the motor to bring the PI lug into position. Now the fun bit. Make sure your wheels are in line and check the sprocket (gearbox and wheel) alignment then check primary alignment. Once it's all good with shims if need be, weld a lug on the frame.
That'll keep you outa the pub tonight ;)
Cheers
Title: Re: Fram to crankcase lug cut off.
Post by: Atoll on 25.09. 2018 11:56
Thanks for all the advice guys much appreciated.
Title: Re: Fram to crankcase lug cut off.
Post by: duTch on 25.09. 2018 12:55
 
Quote
...... In your photo it appears the IP lug is....... twist the motor to bring the PI lug into position......

 I'm just having trouble keeping up with Internet Protocols & Ancient Geometry; 'IP' & 'PI'    *countdown*
Title: Re: Fram to crankcase lug cut off.
Post by: JulianS on 25.09. 2018 13:36
Should be OK without the frame lug fixing. I have not used the rear fixing in over 40 years of use and innumerable miles with no problems.
Title: Re: Fram to crankcase lug cut off.
Post by: bikerbob on 25.09. 2018 15:37
I found that the problem with that rear fixing is it is very awkward to get a nut and bolt in, I overcame this by drilling and tapping the rear whole in the rear primary case and enlarging the whole in the frame lug to suit it is now a simple job to fit.
Title: Re: Fram to crankcase lug cut off.
Post by: berger on 25.09. 2018 17:57
the trick is to leave the two bolts in the primary inside case loose  and then things should line up, I found this out years ago when I noticed the sliding plate was interfering with the clutch center that fits on the gear box mainshaft taper