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Model 30 valve and ignition timing - Part 2

Submitted by simon_amos on Mon, 18/02/2013
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To all those that offered advice on my first post, I would just like to say thank you. I did finally get to the bottom of the starting difficulties with my '56 Model 30 International. In exasperation after managing to only start the bike on three occasions in 3 months' worth of fiddling about, I eventually gave in and replaced the TT carb with a brand new Concentric mk1 'premier' from the Amal division of Burlen Fuel Systems. The carb turned up already jetted for the bike and whilst it does not look quite in keeping with the rest of the motor it looks a quality piece of kit. I mounted it on 2.5 inch stainless studs with a John Tickle 1" Manifold spacer, a 10mm tufnol insulating spacer and some reduced hexagon stainless BSF nuts to attach the carb. I made my own cables using PFTE lined mountain bike gear shift cables with new barrel nipples soldered on. Nice and smooth.

With this set-up, the bike started second kick. It did need choke for the first 30 seconds but then settled down to a nice idle. It now starts easily hot or cold. I eventually settled on timing at 38 degrees BTDC full advance after consultation with George Cohen (thanks George).

The real proof will be how it goes on the road. I can now look forward to that.

I will try to post some pics. The bike looks a little strange at the moment as I have rigged it up with a fuel tank from a 1930's Atco lawnmower just so that I can tinker without damaging the beautiful Manx ally replica tank.

Does anyone know about chronometric rev counters? - mine seems to be reading too slow. I think I have a 2:1 rev counter drive off the magneto drive pinion. Should it be 1:1?

Submitted by gordon_johnston on Mon, 18/02/2013

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If you have a 2:1 drive, you should have a 4:1 rev counter. If you have a 2:1 rev counter, you need a 1:1 drive. Norton seemed to favour 2:1 rev counters, so you probably need a 1:1 drive. Last time I checked, Speedograph Richfield had them in stock at £90.

Submitted by simon_amos on Tue, 19/02/2013

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Thanks Gordon. I would rather change the tacho if possible. My tacho take-off is one of the nice bronze-bodied types and just looks right for the bike. I have already had to lose the beautiful TT carb to make way for the concentric.

Submitted by andy_marks on Tue, 19/02/2013

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What a few people I know have done, and what I plan to do when I get my inter back together, is to use a concentric carb for running in and getting the rest of the bike set up properly. Then put the TT carb back on and use that. This way you know any problems that surface are carb related and you can focus your efforts on setting that

Submitted by simon_amos on Thu, 21/02/2013

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Thanks Andy & Graham for your carb tips. I am really struggling to work out what is wrong with my TT carb. It looks to be in very good condition. What I did notice on the few occasions that I managed to get the bike to run with it fitted was that the engine would die on small throttle openings - say less than 1/8 open. That suggests to me that the pilot circuit is not delivering any fuel but whenI stripped the carb everything seemed in order. It may also explain why it was so difficult to start! I have also checked things like fuel height in the float chamber. The carb drips fuel out of the pilot air bleed just like it is supposed to. I have been setting the pilot screw at 1.5 turns out and also every other setting under the sun - but no joy. I think I will stick to the concentric for the time being whilst I sort out all the other 'little' issues.

 


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