1919 AJS 750cc V Twin Restoration

**olderdan** · Aug 23, 2021, 05:38 AM

The Engine

After making new bushes and shafts for the crankshaft and rods I was pleasantly surprised when the gudgeon pins slid though both conrod eyes when fitted to the big end.
The whole crankshaft assy however is real problem to get running true, the tapers in the flywheels are clapped out and not seating properly due I think to the engine being run with loose seatings (everything is of bolt up construction). Best I can achieve so far is a .005” TIR error on both main shafts which is no good and not helped by a 3.5" stroke. My only option is to skim the tapers in the flywheels to reclaim them, fortunately they will just fit on my home made faceplate. I cannot afford to remake the shafts again as I no longer have access to tool room equipment i.e hardening and grinding. In a last ditch attempt to save this potentially scrap engine I decided to grind the inner flywheel conrod faces with a milling spindle and a diamond speed pin, this was successful as the fly wheels are truly spaced when assembled on the crankpin. This has brought the run out down to .0004" tir which is the best I can do and for all I know is as good as the original. This has taken around forty hours so far and it is pure stubbornness that has kept me going. Next the main bearings and case assembly.

**tonyfoale** · Aug 25, 2021, 02:43 AM

Alan,

That old design of taper and nut fitting was never good, particularly when applied to the bigend also. The width of the nut takes away potential engagement length of the pin in the wheels. Velocette eliminated the nut on the bigend.

As you have ground the tapers, the pins must seat in a bit further, has that resulted in having to shim the gear/s on the timing side to restore their lateral position?

The more modern approach of pressed in parallel pins in relatively wide wheels results in a more robust crank. Of course when you are restoring an old engine you have to work with what you have. Good luck with it.
BTW 0.0004" runout will be better than the original spec.

**olderdan** · Aug 25, 2021, 01:00 PM

Thanks Tony
I totally agree this is a bad design.
You are correct in that the main shafts have protruded into the flywheels a little further (it is a 16 degree inc taper), I had to shorten the small taper end and the threads to compensate. I actually ground the nut clamping faces and faced the nuts from a tight fitting screw cut mandrel to avoid any bias to the crankpin. This is an old chuffer of an engine and only rated at 4HP which is why it survived the abuse. I havent got to the timing gears yet and the cases have had a fair bit if welding so more trouble ahead.

**tonyfoale** · Aug 25, 2021, 03:27 PM

I could never get interested in restoring anything like. The temptation to "improve" the design would be just too great to ignore and I'd end up with a modern look-alike and not the real thing. It would have 40 hp not 4. I greatly admire those who can remain faithful to the original but it just ain't me.

**Frank S** · Aug 25, 2021, 04:35 PM

Originally Posted by tonyfoale

I could never get interested in restoring anything like. The temptation to "improve" the design would be just too great to ignore and I'd end up with a modern look-alike and not the real thing. It would have 40 hp not 4. I greatly admire those who can remain faithful to the original but it just ain't me.

I'm a lot that way myself. maybe not 40 hp when completed but significantly more that it was designed for.
A friend gave me a 1923 Ner-a-car chassis that was more rust than motorcycle. but eventually I had more motorcycle than rust just no engine for it or rims I even wound up with a set of drawings for most of the engine components. Someone in England had built one back in the day with a 4 cylinder inline which got me to thinking about going that route but things transpired and the whole project was abandoned and left in Kuwait. I sometimes think about building a Frankin-style trike based on the ner-a-car concept hub steer and all but with somewhere in the neighborhood of a 1 ltr 3 cyl GEO metro engine if those things could get 58 MPG in 89 in the car I think I could squeeze 120+MPG in a trike weighing 1/3 of what the cars did

**tonyfoale** · Aug 25, 2021, 05:21 PM

Originally Posted by Frank S

A friend gave me a 1923 Ner-a-car chassis that was more rust than motorcycle. but eventually I had more motorcycle than rust just no engine for it or rims I even wound up with a set of drawings for most of the engine components. Someone in England had built one back in the day with a 4 cylinder inline which got me to thinking about going that route but things transpired and the whole project was abandoned and left in Kuwait.

The Ner-a-car was unusual because it was made in England and the US. There were some technical differences but I do not recall just what.
Here is a pic of my good friend the late Vic Willoughby.

1919 AJS 750cc V Twin Restoration-neracar.jpg

**NortonDommi** · Aug 25, 2021, 05:25 PM

I've always wanted a Ner-A-Car. A proper gentleman's bike. Started on a Diesel powered trike using the O.E.M. parallelogram steering which I thought would work well if set up to offset the front wheel to the outside of the turn when turning for weight balance then the gummit changed the 'law' so that I would have to pay 2-Ton road user charges so I dropped it.
Tony. You once mentioned that you had worked on the O.E.M. steering but found it NG for motorcycles at speed. Any thoughts on the application for a trike with front wheel steering? Yes I am aware that 1 wheel at the front is not good and the reverse of logic.

**tonyfoale** · Aug 25, 2021, 05:56 PM

Originally Posted by NortonDommi

Tony. You once mentioned that you had worked on the O.E.M. steering but found it NG for motorcycles at speed.

I have never worked on the OEC. (OEM??) I have analysed its geometry and concluded that it was unstable under braking and in its day it probably got away with it only because of the abysmal brakes of the period. None of the virtual steering axis designs that I have seen have impressed me.