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Dommi timing

Submitted by john_brookes on Thu, 26/07/2018
Forums
Heavy Twins

I'm doing magneto stuff to my 1957 88. i ACTUALLY HAVE A LEAK FREE CHAINCASE AT THE MOMENT! Not wishing to disturb it I stuck a Helix protractor on the crank end (picture herewith) with Blue tack. To help read it I coated the back of it with white water paint. It is quite easy to center up. Clean the crank end with cell. thinners first and it sticks well. I checked it had'nt moved several times. But it stayed put OK. When I remove it I shall double check for Blue tack up the crank end.

If anyone wants to know it is a Helix Heliglas LO9 protractor.

Attachments Helix.JPG

Submitted by john_brookes on Thu, 26/07/2018

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Previously howard_robinson wrote:

Hi John - So where's the picture (picture herewith)............?? Regards, Howard

Howard I will try again. Only thing I can think of is it is too many pixels or whatever. I'm not too up with all this tech. stuff.

Submitted by john_brookes on Thu, 26/07/2018

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Howard,

I think I might have cracked it. Click on the attachment bit and then it will download for you to open..................Hopefully!!

There may be more than one image as I tried several times?

John.

Submitted by paul_standeven on Thu, 26/07/2018

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A former Norton employee who I know has a large steel timing disc on a turned fitting which clamps to the timing side mainshaft.

Paul

Submitted by Xanna_jeannett… on Fri, 27/07/2018

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well its sods law the timing should be done from the left hand side as this is the first cylinder to fire and you need to remove all rocker covers too see if all valves on the left are closed to get a accurate timing of 30 degrees before top dead center fully advanced

Submitted by paul_standeven on Fri, 27/07/2018

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I don't think the engine will mind which side you put a timing disc on. Just as long as the timing is accurate.

Timing a magneto on a parallel twin, I have never worried which of the two sparks is on which cylinder. If it's sparking on valve overlap, swap the HT leads over. Now someone will tell me there is a magical quality to having the spark from front HT pickup to left cylinder. Or is it the other way round?

Paul

Submitted by john_brookes on Fri, 27/07/2018

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I knew that the left is the one to time it on so no problem there. What threw me for a short while was of course having the disc on the right side means your standard diagram (rotating anti clockwise) is wrong. You have to think about it in a clockwise sense. It just did'nt seem right after 60 years of looking at it the other way!!

I had the rockers exposed anyway to check the valve overlap.

Has anybody managed to open the picture I downloaded?

John.

Submitted by howard_robinson on Fri, 27/07/2018

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Previously john_brookes wrote:

Howard,

I think I might have cracked it. Click on the attachment bit and then it will download for you to open..................Hopefully!!

There may be more than one image as I tried several times?

John.

John - that image is fine and the rig you have should operate well. Don't be temped to turn over the engine using the camshaft nut. It will be better to engage a high gear and turn the back wheel to move the engine position. Be extra careful that all the blue-tac is removed from the crankshaft hole........Cheers, Howard

 


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