Recommend electronic ignition for 750

S

smlav

Senior member
Location
Shropshire UK
I’m looking at getting an electronic ignition for my SF1 engined GTL. Choice between Saches and DMC Witt. I believe former has a standard advance curve, where latter has multiple curves to choose from. This bike will be ridden gently, not thrashed and not tracked. I’m interested in ease of installation and reliability.

Advice appreciated.

One reason for this choice is that parts for points are difficult to source, and potentially impossible in future. Another reason is to avoid a repeat of picture below -
 

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smlav said:
I’m looking at getting an electronic ignition for my SF1 engined GTL. Choice between Saches and DMC Witt. I believe former has a standard advance curve, where latter has multiple curves to choose from. This bike will be ridden gently, not thrashed and not tracked. I’m interested in ease of installation and reliability.

Advice appreciated.

One reason for this choice is that parts for points are difficult to source, and potentially impossible in future. Another reason is to avoid a repeat of picture below -
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There is a great alternative to ignitions you listed. I have been using a “tri spark” ignition from a triumph twin- works great. You only need to make a plate to mount it.
 
That piston doesn't look like the result of the ignition system to me! You can also adapt systems that retain the mechanical advance - I ran a Suzuki GS backing, plate, trigger and little black box for years. Never missed a beat.
 
Sachse are plug and play. I also believe Redax has Ignitech as a ready to install unit. Take note of the comments regarding why that piston looks like it does. If that happened with gentle riding it wasn't the points at fault.
 
I would stick with points ( points didn’t cause your piston to hole) because you already have them, just plonk a new set on ( VW points with pin removed ) set them up with a strobe and your away. I have original 1969 points, new coils ( VW) and new condensers - starts instantly, runs fine- ideal. Holed piston could well be weak mixture ..
 
That holed piston was in 1980/1. Was standard GTL carbs, air filter, no air leaks, tappets all good, NGK B9ES, engine had about 18k miles on and had never had oil in longer than 1500 miles. Was riding up M1 late at night, throttle fairly wide open, will have been on main jet. My understanding is that holes usually caused by air leak, plug to hot, bad timing. I used to strobe the timing, but I’ve read that the advance mech requires lubing and I’m not sure I was on top of that. I like the idea of no maintenence electronic, and so many on here say it transforms the bike.
 
Piranha-bro2 set up a Suzuki GS backing, plate, trigger and little black box in my bike. I can attest it ran faultlessly for years without amiss but the mechanical advance unit was in good condition. Ohh and i didn't miss the wear (motor not so crisp), replacement and adjustment of points!
 
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"My understanding is that holes usually caused by air leak."

No,an air leak causes damages/seizures at the intake side
of the piston.
 

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Another way is restrictions in fuel flow, guess how I know. I had a Bonnie that did exactly that. Being young and dumb, I swapped a twin carb head to a single carb and used a carb jetted for the twin carb setup. Massivly lean jetting and then flogged the arse of it up a big hill chasing 2 much later faster bikes. I was wondering what that marbles-in-a-can sound was. It was fun till it became extremely expensive.
 
Ernesto said:
"My understanding is that holes usually caused by air leak."

No,an air leak causes damages/seizures at the intake side
of the piston.
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Air leak? Not necessarily - a piston will always cook on the inlet side and the cause can be a lean-out caused by low float height, insufficient fuel flow from the taps, lean jetting ... or an air leak.
 
smlav said:
Thanks, so ignition or plug? Plugs were same for 18k miles, whereas timing depended on DPO …. Me!
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If you were running 9s it won't have been the pliugs. 8s maybe ... but 7s - which Teddy on here is running in his brand new rebuilt SF2 will absolutely hole a piston. We're yet to hear back from him after several of us on here were flabbergasted to read that he was running those plugs. I hope you're not stranded out in BFN with a holed slug, Teddy!!
 
smlav said:
I had a habit of turning on just the one fuel tap (i was young, knew no better), bet that was the cause. I was religious about timing and oil back in those days.
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:eek::eek::eek::eek: I hate to ask - but you didn't think it would improve your fuel economy did you?! :ROFLMAO::ROFLMAO::ROFLMAO::ROFLMAO:

Brother Lee holed one at 140kph on his SF2 doubling with me from Adelaide back to Melbourne overnight (I'd ridden my SF1 off a small cliff in the Adelaide Hills when my drum brake failed to retard my progress sufficiently while chasing said brother and another).

Someone errantly told Lee to use a hotter plug for high speed riding - the shit some people talk!!! ... so he fitted a W240T2 Bosch in place of the W260T2. The rest is history. But 2am stranded between Kaniva and Nhill in mid-winter ain't fun!
 
piranha-bro2 said:
If you were running 9s it won't have been the pliugs. 8s maybe ... but 7s - which Teddy on here is running in his brand new rebuilt SF2 will absolutely hole a piston. We're yet to hear back from him after several of us on here were flabbergasted to read that he was running those plugs. I hope you're not stranded out in BFN with a holed slug, Teddy!!
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Thanks Pirhana,
I was using 7s when I initially got the bike which was running horribly due to malfunctioning carbs, etc, etc. Once I rebuilt the carbs and had the top end rebuilt w/ new pistons, I'm using 8s and keeping an eye on them as the motor is being broken in. So far the plugs are burning nice and clean and not too hot- I definitely don't want to hole them!
 
hooksey said:
Well if they are burning clean, best go to 9's (y)
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Have to agree completely with Mr Hook - cheap as chips insurance. Put 9s in it. If they don't foul you have zero reason to fit 8s, and in so doing take the possibility of plug heat causing a hole in one of those beautiful new pistons. You want to be able to ride the wheels off the thing and not have that risk always in the back of your mind. A no-brainer.
 
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