Britbike forum Forums British motorcycles in general British motorcycles in general Sparx ignition question

First of all my apologies, it is not easy for me to understand your language and I hope you understand me.
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

Thanks LAB
So... if I understood correctly I should align the white dot with the hole in the stator plate, when the crankshaft is at 39 degrees btdc, correct?

I have to repair the engine for a meeting this weekend and I don't have a stroboscopic gun to fine tune the ignition, retard or advance I have a doubt: If after aligning the white dot with the hole I want to retard the ignition somewhat, should I turn the stator plate clockwise?

Yes.


Yes.

thanks lab clarified

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.

Result was:
-white/green gradient spark plug electrode
-piston head marked at the ignition point
-cylinder liner and piston seized

The engine configuration is mk1 CARBURETORS 190 main jet with original air filter, B8ES spark plug (I think it is similar to Champion N3C) and 95 octane unleaded gasoline
I think I'll have to reset the ignition to 39 btdc and change the main jet to 200
Please can you tell me any more suggestions?

That's 'pinging' in US English or 'pinking' in UK English.

Is it possible to upload photos directly from the PC? I can't find the info to do it

You need to be a Premium or higher member to do that.
https://www.britbike.com/forums/ubbthreads.php?ubb=subscription&id=6

Ok thanks
engine pics

It requires a sign-in and I did that but the link doesn't go to the pictures:

"404
This is not the page you’re looking for.
It appears the album you seek doesn’t exist."

Try it now pleaset120 engine pics

Yes, I can see them now.

When I had a Sparx ignition I always found that it was a bit advanced once I put a strobe to it. But, that was on a BSA (counter-clockwise rotation.) Maybe it's better on a Triumph?

I don't know but maybe in triumph it can be the opposite in my case it was well set with strobe at the beginning, and then it changed, one piston is more degraded than the other.
when I repair it I will check that both coils jump the spark at the same time btdc 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

http://www.tioc.org/britbike/SBgeneralsparkplugs.pdf

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!"

thanks for your advice John.

In my years of experience as a racing driver in 2 strokes lightweight and 4T four of the 80s and 90s, I know the problems of wear and behavior of carburetors, especially dellorto, at altitude and weather. the needle jet and needle are good condition,

In my case the mix was shorter than long I think for some reason the ignition was too advanced and started pinging

I had tested the B9ES on the highway between 100 and 150km/h and the engine runs fine, but they make too much carbon in the city. Now I will try with the N3C. I think what I need is that when I repair the engine, make sure that the spark jumps at the correct moment from the manufacturer Btdc, then I will check the carburation and check the differences between B8Es and N3C

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.

hello allan

I agree with you about the needle jets, I can't measure it, just say that about two years ago I bought a kit of needles, jets, sliders and main jet in burlen/AMAL to update the carbs.

About the pistons, they are JC with good quality Japanese rings. Indeed, the problem has been an overheating of the combustion chamber, you can see it in the photos, caused by one of these three reasons:
fotos piston gripado
1 ignition too advanced (was pinging)
2 spark plug too hot
3 lean mixture
I'll have to find out what caused it.

Too late now, of course; whenever I am about to disassemble an engine that was previously running right, I first set the piston to a fixed point - either TDC using a tool, or align the alternator rotor mark with the pointer.

Next, I take a "Sharpie" FINE POINT pen and mark the electronic ignition stator plate with a single small mark touching both the stator and the engine case.

Then, I remove the stator and make a tiny mark as exactly in the center of one rotor end (with the magnet), aligned with one more mark on the engine case as well-aligned as I can possibly get it.

I never thought the white ink blobs that the manufacturers put on the rotors, are quite as accurate as I'd want them to be!

"next time..."

hello paul
Yes, I made those marks after the last strobe check (3 or 4 years ago). Now the stator was slightly offset but towards the retarding side, only a few degrees perhaps 2 or 3.
The problem is that I have little experience with Sparx and I don't know if they usually fail, on my other classic bikes I use electrexworld and on the racing bikes sellektra from italkit (similar to pvl)
Maybe it was wrong setting from the beginning . On the day of the ride, the weather tended to impoverish the mixture, about 2 degrees Celsius and a highway along the coast at a few meters of altitude.
Although I restored the bike more than 6 or 7 years ago, I had only done a few thousand kilometers on mountain roads, never long distances on the highway.