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Timing a Petter. Carbon plug

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Timing a Petter. Carbon plug Empty Timing a Petter. Carbon plug

Post by Pettercutter Sun Aug 18, 2013 3:27 am

I have got my Petter AS 3BHP running few days ago but had trouble starting it today. On removing the plug I found it heavily fouled with carbon. I suspect the timing so reread the Petter Instruction book and confirmed that the impulse starter should click just before the piston reaches TDC. This seems about right but the manual goes on to say that you can check the timing with the impulse trip out of action by turning the engine in the wrong direction and then with a thin piece of paper (Rizla...) between the points the exact instant of the breaker opening can be determined and at this point the magneto is in the position where the spark is delivered to the cylinder.

When I do this I get a completely different story and the paper comes loose with the flywheel miles away from the arrow marking 20 degrees before TDC.

Any idea why this might be so and would this cause the carbon buildup?

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Post by Appletop Sun Aug 18, 2013 3:34 am

Sounds like the timing is way out then, about all you can do is time it up "backwards" with the rizla and see how you get on from there. Am I right in saying your AS has the gear driven mag? I know the AHM is chain driven and if the chain is loose this could affect the timing when turned backwards.

And just make sure you are using BLUE Rizla papers, green ones are too thick.....Wink 
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Post by Pettercutter Sun Aug 18, 2013 4:00 am

OK I gave it another go and think I see what I did wrong...I read that you turn the engine backwards and kept going backwards till the gap opened up but now see that yo go backwards to put the impulse trip out of action then go forwards to get the points to open up.Doing this I can get the firing point to about 15 degrees before TDC...but I have run out of movement on the magneto as it is turned as far as it can go clockwise. Having lost the original magneto coupling (OK I may as well admit it, burnt..) the new one we made might be slightly off so that would explain why I can't get to the exact 20 degree before TDC point. It runs at present although I am sure it should run smoother than it does.

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Post by Pettercutter Sun Aug 18, 2013 4:04 am

And yes the Rizlas are blue!Very Happy 

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Post by Appletop Sun Aug 18, 2013 4:04 am

http://www.ebay.co.uk/itm/GENUINE-LISTER-PETTER-TD113-MAGNETO-COUPLING-327041-/261252906835?pt=UK_BOI_FarmingEquipment_RL&hash=item3cd3e2ff53

Bloody good price though!!
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Post by michael3 Sun Aug 18, 2013 7:57 am

If the AS is anything like the A1, ie gear driven mag, you may need to move the mag on or back one tooth to give yourself the timing range you want.

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Post by Pettercutter Sun Aug 18, 2013 7:50 pm

OK will have a look into it but not for a while now as I have to go away for a few weeks...will try again in the autumn. Thanks to everyone for chipping in! cheers James

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