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Norton 16h valve timing

Submitted by steven_woods1 on Sun, 19/07/2020
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Submitted by steven_woods1 on Sun, 19/07/2020

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Hi All,

Hope you can help, during the lock down I have been working on my 16h restoration. The problem I have is I have confused myself over the valve timing. I have set it so many times I am now back to square one!. Any help work be great?

Thanks all

Steve

Submitted by richard_cornish on Sun, 19/07/2020

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Hi Steve,

   You don't say what year your engine is as the valve gear changed several times over the years. From 1934 to 1947 the gears run as a train, so the exhaust cam runs backwards and the inlet forwards. On the 1948 to '54 engine both cams run backwards. The valve opening period on the later engines is the same for both cams, but on the earlier engines it is less on the inlet cam.

   For both engines it is best to have the barrel fitted but the head removed. Turn the engine to top dead centre, if you have the mag timed up make sure you are on the stroke with the points closed. Turn the engine forward so the piston moves down a 1/4 inch and fit the exhaust cam so it has just closed, checking the rotation as above. Next, turn the engine back over TDC so the piston is coming up 1/4 inch from the top and set the inlet cam so it is just about to open, again checking the correct cam rotation.

   You might not be able to get the positions dead accurate but you should be fairly close with a fraction more measurement rather than less. The early engines have a 3 key-way half-time pinion with the slots in different attitudes to the teeth and this allows finer setting. Get back if I haven't explained this very well.

Hello Richard,

Sorry i am late getting back to you.  Work has been a nightmare!, Anyhow thanks for your reply. I will try the timing again at the weekend. One quick question is the 3 way pinion it needs a puller to get it off so i try and set the timing and see how close i can get without the need to remove. Am i right in thinking i may not need to remove the 3 way pinion?. Sorry if i have misunderstood but i have been going round in circles with this. 

Submitted by richard_cornish on Tue, 21/07/2020

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Hi Steve,

   Yes, if you haven't taken off the half-time pinion, try the timing with it in that position and see how close it is to the 1/4" setting as I guess the bike was running previously. As I said earlier, a little more than a 1/4" will be O.K. but if it's much less the performance will suffer. If you do have to take it off you will need a decent 2 leg puller as they can be fairly tight. Setting with the pinion off is easier as you can just tap it on enough to check so you can get it off easier if you have to. Don't forget, if you need to strip it in the future, make sure you mark the cam-wheels to save you the hassle next time.

Hi Richard,

I have had a go at the timing last night and i don't think i got it right. I did manage to get the valves rocking at TDC. My only issue is the the cams i think should be at 4 0'Clock not 10;0 Clock. Sorry if i have missed something.  I did speak to someone last week who had worked for a Norton dealer and he explained how to set the timing up and he just said the same as yourself, the funny thing was he told me when you get it its easy!!!

Thanks again Richard 

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Submitted by richard_cornish on Fri, 24/07/2020

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Hi Steve,

   This all looks O.K. to me. The cams are running in the right direction so if you have got the exhaust just closed at 1/4" after TDC and the inlet just starting to lift at 1/4" before TDC you should be good to go. I see you have a tight wire advance on your mag, so make sure the lever is pulled tight when you set the ignition timing, and while the head is off for best accuracy. Let us know when you try the start-up and how it runs.

 


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