Weird Valve Timing - Norton 19S

Greetings,

Have you checked the crankshaft pinion? Some have X 3 key ways to enable such an offset......

Good luck

Rgds Steve

Could be that your mag internal timing is not the best , if you retard to what would normally be a good starting position and you don't get a worthwhile spark ,so you then advance to a good sparking position and its too far advanced. try closing down the points gap . Could be a wrong points base or a missing /worn key.

It's not sparking on the wrong stroke, is it?

Maybeit it is time to give Mike Pemberton a call. His contact details are conveniently on the back of the Apirl Roadholder.

Mike is often on the Norton Singles face book page, you could post this query there.

dan

Hi Pete, I've not come across anything like this but here's a thought: Could there be something astray with the exhaust tappet on the engine in the bike? It is the only thing I can think of that might be different between the 2 engines. The Maintenance Manual & Instruction Book for '57/'58 states that "inlet & exhaust tappets should not be interchanged" (Page 14, Para 23).

I think Mike Pem has mentioned that the keyways in the camshafts are not always machined correctly, which would throw the timing out but would expect that to have the same effect on both engines.

Have you tried to start the engine once you have made the 3 tooth offset?

Cheers, Ian McD

With the valve timing 25/30 before and after and the spark around TDC it should not be kicking back unless you are being a bit of a wuss with the kickstart! My Ulster had a terrifying kick untill I found the right method. If it has good compression then carefull use of the lifter is needed.

Hi Pete,

It sounds like you have 2 inlet marked cam wheels on both inlet and exhaust. This is quite possible as the gearwheels can easily be pushed off the camshafts and swapped. I have had teeth strip on these gears in the past so anything could have been changed by previous owners. I don't know if this is the reason, but worth checking. I think after all this time the timing marksshould only be a guide and you should check with a degree disc just to make sure.

Regards, Richard.

I have thought a bit more about the tappet idea and (before someone else says) it is probably rubbish! Although the advice on not interchanging is given in the book the inlet and exhaust tappets have the same part number so really not possible to affect valve timing. Richard's suggestion of a swapped cam seems feasible but still doesn't explain why the timing marks are correct in one engine but not the other. It might be worth comparing the 2 half-time pinions. I am now thinking that the dots on those wheels may be in different places with respect to the keyway. If the engine runs OK with the 3 tooth offset probably best to add another mark to the gear and keep a record of which is the correct one for your engine.

Ian McD

If what I have suggested regarding the dot position wrt keyway is correct then I think the inlet timing should be affected as well. From memory the keyway for the half-time pinion is at either tdc or bdc so it should be possible to check the dot position without removing the pinions.

Ian McD

Have you tried using a degree wheel to check your cam timing? I installed a set of Mike Pemberton's racing cams in my own model 19S and used the degree wheel to dial them in while ignoring the little punch marks on the gear wheels.

Hi Peter did you find an answer to the valve timing issue ? I have the same thing on a 19 engine I purchased and suspect it is the position change on the half time pinion that will be the answer as the exhaust is closing slightly to early , but the inlet is spot on .

Eric .