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PostPosted: Sat May 09, 2020 10:35 am 
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Still in the Driveway

Joined: Mon Apr 18, 2011 4:52 pm
Posts: 8
1973 GT750. I replaced my points with a Boyers Bransden electronica ignition several years ago and I’ve struggled every since to get with consistent spark. After I chased my tail with timing and carburetion I realized I was a weak spark because it was running poorly at idle and high rpm when the bike was hot but operated just fine when it was cold. It would also stall out at idle when hot by switching on the headlight. I swapped out the coils for another set of used coils it made no difference. I hotwired the coils directly with a toggle switch to give them a little more juice and did help, but still lost power the longer I drove. Fast forward and I have completely rewired the bike with new wire looms I purchased on eBay, and replaced the coils with aftermarket (admittedly I went cheap on these but the specs were as good or better than OEM). The bike starts first kick and performs beautifully for the first 20 to 30 minutes of riding BUT if I get stuck in traffic in the South Texas heat (I live in San Antonio) or ride at high rpm for an extended length of time my old ghosts come back. It loses power and is a bear to keep alive at stops. Not overheating, and it coughs like there’s I burned fuel heading out the pipes.

Here’s my theory: the Boyers Bransden electronic ignition fires all three spark plugs together, basically resulting in three times the firing rate they were made for. I spent much of the last few years eliminating loss of voltage from old wires but at this point I think the coils themselves are fatiguing due to to the firing rate. Has anyone else seen this? Does anyone make an aftermarket electronic ignition that doesn’t fire all three plugs together? What about race ignition, possibly better quality components will illuminate the fatigue? Any other tests I could run to help solve the problem? I think I’ll order cooler plugs to see if that makes a difference. New battery, new adjustable voltage regulator set slightly “hot” at 14.5V.


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PostPosted: Sat May 09, 2020 4:40 pm 
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Moto GP
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Joined: Mon Dec 13, 2010 4:32 pm
Posts: 3535
Location: southwestern Pennsylvania
Country: USA
Suzuki 2-Strokes: 69 T350 thru 75 GT750
I have Newtronics ignition on both GT750s & it works fine. There were some complaints about the early kits, but some years ago Autocar acquired Newtronic & improved the kits. It’s an optical setup that uses a disc that provides dwell similar to the stock points.
http://autocar-electrical.co.uk/products/newtronic-ignitions/suzuki-mc/ckt-su6a

The Accent kit is popular & has a good reputation. It’s also the easiest to install because it doesn’t use an external control box.
I installed it on a GT550 cafe build that I’m slowly working on. Its has 3 circuits & 3 pickups — one set for each coil.
Imagecafe-GT550-1233 by jabcb, on Flickr

The Accent website is in German. You send an email to place an order. He understands English & is easy to work with.
http://www.accent-electronic.com/ELZ2Coil.html

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BAS (Bike Acquisition Syndrome) - too many bikes but have room for more

Suzuki:
GT750 2x75
GT550 72 project & 75
GT380 72
T500 73 project
T350 69, 71 & 72 project
T250 72
Honda 85 CB650SC & 86 CB700SC
09 Triumph Bonneville SE


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PostPosted: Sun May 10, 2020 1:34 am 
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World Superbike
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Joined: Thu Feb 16, 2012 11:50 am
Posts: 2340
Location: The Republic of South Yorkshire
Country: England
Suzuki 2-Strokes: 2 x GT550s GT750, T200, TC200
Can't understand why people go electronic.
All my Suzukis run fine on points. I check 'em once a year if I remember at season start, and just ride. The Hippo averages at least couple of thousand a year and we tour 2 up on that, so does the 550 and that gets spanked - the 200s less.
I'd be replacing the electronic back to standard and see if there's other underlying problems like bad connections and low voltage to coils/sensors or even battery not charging properly when the engine is warm. Sounds like a voltage issue to me. What is the battery voltage when the pribkems start? 14.5 volts will boil a lead acid battery, is it going dry when you get back after a long run? Same voltage will kill a glass mat battery too.

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