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by Mal Marsden - 06/16/22 7:00 pm
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Allan G, L.A.B., madsundaysurvivor
Total Likes: 7
Original Post (Thread Starter)
#870654 01/31/2022 7:45 PM
by madsundaysurvivor
First of all my apologies, it is not easy for me to understand your language and I hope you understand me. blush
I have a Bonnie 1965 runing several years with electronic sparx ignition, allways without problems, starts first or second kick.
Now I have opened the engine for a repair and I have had to disassemble the ignition
And this is my dout:
In my bike the full advanced ignition are 39 degree btdc
Have I align the white dot with the hole of the sparx plate stator in this position (39 degree)? Or have I to subtract the 13 degree of sparx advance curve and to line up the hole with the dot to 26 degree (39-13=26)?

Another question, for delay the ignition I have to turn the plate clockwise, right?

thank you so much for your attention
Liked Replies
#870866 Feb 2nd a 03:47 PM
by John Healy
John Healy
The engine configuration is mk1 CARBURETORS 190 main jet with original air filter, B8ES spark plug (I think it is similar to Champion N3C)

Triumph did extensive testing a Mira (Motor Industry Research Association - 850 acre testing grounds in the UK) on spark plugs. What they found out was that plug manufacturer's cross reference charts were not accurate.

For a stock bike you should tune to the manufacturers recommended grade of plug. This is part of toughening an engine to destuctive pre-ignition and detonation. Tuning to the wrong grade of plug makes you one step closer to problems. If you are having problems with a recommended plug, it isn't the plug! You need to address what is causing it to give you problems. Not doing so can be expensive.

The natural way Amal (and Mikuni) carburetors wear can make you want to put in a hotter spark plug. With mileage the needle jet gets larger from the constant rubbing of the up-and-down movement of the needle. The bike is then running rich from around quarter to half throttle. This is where most riding is done. This can make the proper plug look rich, or in worst case senarious, foul. The inclination is to put in a hotter plug. But the wear in the needle jet has less and less influence on the mixture as the slide is lifted above half throttle. You don't need that hotter plug and it can quickly become a glow plug and allow the engine to pre-ignite.

What you should do is correct why the proper grade of plug is fouling!!! It can be something as simple as a worn needle jet — as little as 0.0005" increase in the inside diameter can cause problems. Or as we always said at the dealership, "Its the needle jet stupid!"
2 members like this
#870655 Jan 31st a 07:53 PM
by L.A.B.
1 member likes this
#870745 Feb 1st a 02:57 PM
by madsundaysurvivor
thanks lab clarified
1 member likes this
#870751 Feb 1st a 03:34 PM
by L.A.B.
Originally Posted by madsundaysurvivor
I think that the problem with the breakdown was that the ignition was moved to a more advanced position.
On the highway at about 70 mph it started to make a pitted detonation noise, I don't know how to say this in English.

That's 'pinging' in US English or 'pinking' in UK English.
1 member likes this
#870864 Feb 2nd a 03:36 PM
by L.A.B.
Originally Posted by madsundaysurvivor
By the way, what pistons and rings of acceptable quality can I buy on the Internet in Europe? In Spanish stores this does not exist
1 member likes this
#870887 Feb 2nd a 07:22 PM
by Allan G
Allan G
Unless you have checked your needle jets with a pin gauge you have no idea of their condition. I’ve found new jets to be ok when out the packet but with some jet holders, they can crush the jet down 0.0005” - 0.001” when tightened up. New needle jet holders from Burlen (makers of Amal don’t seem to do this) but some of the older ones can and will.

As your looking at buying new pistons anyway I’d be interested to see what the piston skirts look like? There has been excessive heat in the chamber, it may have materialised its way through the piston and show up as 4 contact points running top to bottom of the piston skirt. (4 corner seizure) which can still be present even if you didn’t find the pistons lock up).

You can get some good pistons from MAP Cycle, they are in the US but their prices are really good for pistons and I have had parts arrive quicker than suppliers in my home country. MAP sell the rings separately, this gives you the option of a decent set of rings or a lesser quality.
1 member likes this
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