Best electronic ignition 750 Combat

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There are 4 things which affect combustion temperatures and knocking - the anti-knock rating of the fuel, the compression ratio, the fuel/air ratio and the ignition timing. The optimum is a balance of those 4 things. Usually your comp. ratio is fixed, and you don't change your fuel - so you end up balancing two things - your mixture and the amount of ignition advance you use to fire it. If you advance your ignition point, it usually has the same effect as leaning-off your mixture. Even if your advance is a few degrees wrong for the fuel you are using, you usually correct by adjusting the mixture. As far as power goes, there is nothing in it. HOWEVER - the needle and needle jet are critical if you are seeking high performance. If you have a range of needles with different tapers and a programmable ignition system and don't change the fuel you use, you might get a bit more out of petrol. You would probably find you would be playing a lot with those two factors at every race meeting. I get around the problem by using methanol fuel. It has unlimited anti-knock and hides-up the tuning errors. I never race using petrol, even in two-strokes methanol is better.
 
Normal practice when setting main jets, is to do plug chops using the next range hotter plugs than you use for racing. That way the combustion temperatures stay sensible. But setting the needle jets is much more critical. It is normal to run slightly rich on the main jets.
Elf racing fuel has an antiknock rating of 102. - You can go leaner or have more ignition advance without burning things or getting detonation..
The British race old bikes using petrol. They also play cricket.
 
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Fast Eddie said:
+1. Coil breaking down is def suspect #1 for heat related spark woes...

So the coil swap over should be your next test AFTER NEW SPARK PLUGS...

Seriously... we’re 3 pages and nearly 60 posts into this thing... and we’re talking about new ign systems and coils... and you ain’t told us whether or not you’ve tried new plugs yet...!
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Sorry Nigel - I will indeed try new plugs - certainly a simple thing to do to eliminate them as a possible cause but the inductive timing light showed intermittant loss of juice through the left HT lead to plug.
 
Fast Eddie said:
Please do not accuse me of having any understanding of ignition... :oops:

Ref the tuneable system, I put an earlier version on a very highly tuned 988cc BSA/Triumph triple some time ago. I went forwards and backwards with the curve like a mad thing, in search of ‘secret’ potential. It made very little noticeable difference, basically not possible plot within the normal variance seen between runs. Perhaps a better dyno and / or dyno operator may have found something, but I believe it would have been small.

What I did learn was that a big, fat, powerful spark does yield big dividends. I replaced an aged Boyer and 4v coils with a tuneable Tri Spark, with a dedicated spark, and 3 very high output 12v Dyna coils. That change yielded almost a 5bhp increase.
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I have 2 quite different maps in my Seeley and switching between them on the dyno, there was zero difference in power anywhere, and I have noticed that EL ignitions seem to produce very weak sparks, I guess this is because it is such a quick short spark. I think a coil works better and give a much fatter spark when the saturated primary is cut and the resultant collapse of the magnetic field gets to work on the secondary rather that the other way round.

I could see this as an advantage when the throttle is opened as weak mixtures don't seem to like quick short sparks. I think the number of sparks required by our low revving twins can be more than adequately supplied by points and coils when everything is in good condition, just needs a bit more maintenance.

I also think advance curves and ultra accurate timing aren't as important as we like to think, after all, it was common to weld up the ATU for racing and Steve Maney recommends only 26deg for his 920 engines, so like you say in your earlier post +/- 2 deg might be more than close enough, although I think I would err on the minus.
 
Have swapped plugs side to side with same result - missing on left cylinder. New plugs in both sides same result - missing on left cylinder.
Pretty safe bet that it is not the plugs . When it cools down I will swap out the coils / HT leads and see what result that presents.
 
Well, that’s progress.

“Once you eliminate the impossible, whatever remains, no matter how improbable, must be the truth”...
 
storm42 said:
I have 2 quite different maps in my Seeley and switching between them on the dyno, there was zero difference in power anywhere, and I have noticed that EL ignitions seem to produce very weak sparks, I guess this is because it is such a quick short spark. I think a coil works better and give a much fatter spark when the saturated primary is cut and the resultant collapse of the magnetic field gets to work on the secondary rather that the other way round.

I could see this as an advantage when the throttle is opened as weak mixtures don't seem to like quick short sparks. I think the number of sparks required by our low revving twins can be more than adequately supplied by points and coils when everything is in good condition, just needs a bit more maintenance.

I also think advance curves and ultra accurate timing aren't as important as we like to think, after all, it was common to weld up the ATU for racing and Steve Maney recommends only 26deg for his 920 engines, so like you say in your earlier post +/- 2 deg might be more than close enough, although I think I would err on the minus.
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There are plenty of people who fit race cams into motors without fitting the type of exhaust system the cams were developed with. If you don't try to optimise your settings, you probably lose a bit. There used to be an old idea that if you fitted the best motor into the best frame, you ended up with the best bike. However the best Triton is never as good as a good Manx.
With 650cc Triumph engines, if you use E3134 race cams with the specified timings and the same type of exhaust system as used by the 1953 T100 kit, they actually work perfectly. But if you fit mufflers, you are playing a different game. A 2 into 1 exhaust system is very different.
The ignition advance I use with methanol is based upon years of experience. It is 4 degrees ahead of where it would be with petrol, but I am using it with low compression. At 12 to 1 comp. , it is normal to use the petrol advance, with methanol..
If you were using Elf racing fuel, you would probably benefit by running a couple of degrees more advance. Whatever advance you use, you jet to suit it anyway.
 
The spark plugs give the indication that combustion conditions are correct. So maximum power is achieved with maximum fuel consumption. If the revs are higher, you use more fuel. If the jets are bigger and you are using more fuel without raising the upper limit of the rev range, you are probably getting more power. That is usually what happens when you raise the compression ratio and change the jetting to suit, or change the ignition advance and jetting.
 
Swapped coils and their respective HT leads and missing has disappeared but something is not right as it is running just a little ragged when it was so smooth before. I need to take it for a longer ride to see if trouble resurfaces - frustrating ...
 
If it’s a bad coil, swapping it to the other side doesn’t make it good.

You sure this isn’t connector related...?
 
Fast Eddie said:
If it’s a bad coil, swapping it to the other side doesn’t make it good.

You sure this isn’t connector related...?
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Thanks Nigel -
Not certain and that is why I think I need to start to dig deeper. There are plenty of stories out there about soft failures like this - I am jammed up with real life responsibilities for a few days but I want to run it a little longer than I had time for today . If it starts cutting out on right side then it would seem to be the coil / HT lead .
Frustrating because I worked a long time on this one and it was running beautifully - and I know it will again - but truth be told I would rather be riding it than wrenching on it . Boo hoo Don’t you feel sorry for me ?
Seriously I appreciate all the help you and the others have given.
Cheers - Richard
 
If it was running smooth but missing on one side and now not missing on that side but rough, it does sound connector related to me too.

Clean and tighten the spade connectors.

Pull back the boots and check the HT connections and tighten around the wire and plug/coil interface. Clean those too.
 
Worry not. You'll get to the bottom of it...... 3 more months and I can begin the search for my woes, so you're not alone as you stroll down heartache alley.
 
All working beautifully again - idle a steady slow tick over , running well throughout rpm range , starting on first kick again . This may sound like good news but the fact remains that the problem may not be gone, just hiding . Perhaps it may have been the connections at the left coil but I don’t think so as the spade connects were removed and reconnected several times during this process and were and still are tight fitting. The problem went away after swapping coils side to side. I will be removing fuel tank this afternoon as it is no longer centered and coming dangerously close to the headstock on the right side . While off I will go over all wiring. I have ordered a Trispark and two coils to keep on standby but not quite ready to give up on the standard ignition yet .
Thanks again to all for the opinions and help.
RT
 
Sounds like it was a connection issue that got 'fixed' when you unmade/remade the connections for the swap. ;)
 
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Looks like this thread got off the rails a bit.

Early Boyer left me miles from home on a cold dark night in pre-mobile phone days due to its low voltage issues locking up the sprag on my MKIII.

Pazon Altair has been flawless, easy starts, no stumble off idle, so I'm a fan. Stock coils; also fitted 3 phase alternator to keep battery fully charged. If I'd had the 3 phase first I'd probably still have the Boyer but wouldn't have the better advance curve of the Altair.
 
Richard Tool said:
All working beautifully again - idle a steady slow tick over , running well throughout rpm range , starting on first kick again . This may sound like good news but the fact remains that the problem may not be gone, just hiding . Perhaps it may have been the connections at the left coil but I don’t think so as the spade connects were removed and reconnected several times during this process and were and still are tight fitting. The problem went away after swapping coils side to side. I will be removing fuel tank this afternoon as it is no longer centered and coming dangerously close to the headstock on the right side . While off I will go over all wiring. I have ordered a Trispark and two coils to keep on standby but not quite ready to give up on the standard ignition yet .
Thanks again to all for the opinions and help.
RT
Click to expand...
I removed the "Lucar" blade connections and put hoops on instead. One less potential loose connection point.

Cheers,

cliffa.
 
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