Author Topic: Looking for help setting up timing on A10  (Read 1383 times)

Offline Pecon

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Looking for help setting up timing on A10
« on: 05.10. 2012 15:47 »
I have just received my rebuilt engine from the engineering works and am hoping for some help setting up both the valve and ignition timing. Reading the manuals the valve timing seems straight forward, just get the slot on the valve gear and the dot on the crankshaft to line up with the idler gear. However when I do this and turn the engine over I cannot get the marks to line up again, no matter how often I turn the crank over. They are at best one tooth out. Is this normal or should the marks line up at least once every couple of revolutions as I suspect?.

The second thing I am looking for help with is setting the ignition timing. I do have access to a degree wheel but have never used on before. There does not seem to be a mark on the mag gear so I assume that this does not line up with anything on the cam gear?. While I have in the past worked on bikes with coil ignition magnetos are a mystery to me. Any help gratefully received.

Thanks,

Peter

Offline Goldy

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Re: Looking for help setting up timing on A10
« Reply #1 on: 05.10. 2012 16:30 »
Peter you are correct about the valve timing, as long as they line up to start with I am sure that there is someone on the forum who will be able to tell you how many times you need to rotate the crank to get back to the original marks, but not anything to bother about. Some people use discs for ignition timing and if you do a search on the forum you will find the info. I stick with the traditional method which uses a piece of welding rod or thick wire and a piece of thin paper such as tissue paper. Wedge open the auto advance and open the points and insert the paper so that it is trapped between the points. Rotate the back wheel in top gear in the usual direction until the inlet valve opens and closes. Insert a piece of rod down the spark plug hole to rest on top of the piston. When the piston gets to the top put a mark against the rocker cover with a marker pen. Measure the timing distance on the piece of welding rod ie 3/8" and turn the back wheel in the opposite direction. Then turn the back wheel in the correct direction slowly until the marks are in line. Turn the points until the paper will pull out with only light pressure, then lock up and then re check.
All the best Goldy
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Offline Pecon

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Re: Looking for help setting up timing on A10
« Reply #2 on: 05.10. 2012 18:53 »
Thanks Goldy, it's a relief to know that I might have done something right  *smile* . I had an idea that when the valves and pistons avoided each other that things were reasonably OK. Thanks also for the info on setting up the ign. timing, I will have another look at it over the weekend.

Peter

Online chaterlea25

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Re: Looking for help setting up timing on A10
« Reply #3 on: 05.10. 2012 19:58 »
Hi Peter,
Feel free to give me a call if you need help
Hope to see you next weekend at Leopardstown show??
Regards
John O R
1961 Super Rocket
1963 RGS (ongoing)

Offline morris

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Re: Looking for help setting up timing on A10
« Reply #4 on: 05.10. 2012 20:32 »
Hi Peter,

Indeed, gear trains are strange things.
I have never made the calculations, but it may well be a couple of thousand revolutions before the marks line up again.
If all the gears would have the same diameter and the same number of teeth, then the marks would line up at every revolution.
But, let's say you have a 20 teeth gear meshing with a 100 teeth gear, the same teeth would line up every 5 revs.
If you change this to a 21/100 the same teeth would only line up after 100 revs, and to make matters more complicated, there are 3 gears in the the timing game, all of different diameter and number of teeth.
What counts is the number of turns the camshaft makes according to the crankshaft, and it's position to the crankshaft.
The gear markings are just there to get you started.

Have fun!   
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Online bsa-bill

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Re: Looking for help setting up timing on A10
« Reply #5 on: 05.10. 2012 21:34 »
Quote
I have never made the calculations, but it may well be a couple of thousand revolutions before the marks line up again

Well not that many, can't recall exactly but around 70 ish or maybe 80 ish before the marks line up.
camshaft goes around once to the cranks twice ( I presume this is where the crank pinion gets called the halftime gear). the camshaft pinion has twice the teeth of the crank pinion
The number of teeth on the  intermediate gear does not matter as it just conveys continues movement a tooth at a time  from one pinion to the other, the only consideration is that the same teeth do not mesh at every revolution so as to even out wear
no marks required on the magneto pinion as it is held onto the magneto shaft by a taper.

AS Goldy says as long as you get the marks lined up then the valve gear is set and safe as long as have all three pinions in place ( it is not unknown to remove the intermediate pinion for some reason and turn the engine with it off, this can bring piston up while valves are down - ouch)

all the best with it
All the best - Bill
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Offline Pecon

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Re: Looking for help setting up timing on A10
« Reply #6 on: 05.10. 2012 22:00 »
     Thanks guys, now I know why maths was my least favourite subject. John I will indeed give you a call if I run into trouble, many thanks for the offer. I will indeed see you at the show on the 13th. I will tell you the sad story of my experiences with the engine then.

Peter

Offline RichardL

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Re: Looking for help setting up timing on A10
« Reply #7 on: 05.10. 2012 22:18 »
I'm so glad this has come up again. It reminds me of how this forum has grown and thrived over several years. Back in '08 we were discussing this and I played with numbers to come up with 98 revs of the crank for timing marks to realign. Here is the post from back in the dark ages when we had about 60 members versus today's 541. http://www.a7a10.net/forum/index.php/topic,789.msg5039.html#msg5039

Richard L.
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Online groily

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Re: Looking for help setting up timing on A10
« Reply #8 on: 06.10. 2012 07:30 »
Your memory is encyclopaedic Richard!
Now, 60:541 is another tricky one, especially with no intermediate timing marks!
Cheers, Bill
Bill