Sundial Moto Sports

Red spark at plugs
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Author:  Hush [ Sat Jul 25, 2020 3:16 am ]
Post subject:  Red spark at plugs

I'm used to seeing a fat blue spark on bikes, my 74 GT550 shows a rather insignificant small red spark? I have just fitted some aftermarket coils, new plugs and caps. Bike is not yet ready to be started but this is the point I am up to right now. Should I be expecting a blue spark and if yes, where could my problem lie?

Author:  GTandcbr [ Sat Jul 25, 2020 4:23 am ]
Post subject:  Re: Red spark at plugs

If you are still on points my guess would be condensors need replaced. Other thing is the battery charged and in good condition. Put a multimeter across the battery and also check the positive feed to coils. Sometimes there can be a significant current drop between the battery and the coils through an old wiring loom and connectors

Author:  Hush [ Tue Jul 28, 2020 8:39 pm ]
Post subject:  Re: Red spark at plugs

Yes think you are right, new points and condensers ordered.

Author:  Hush [ Tue Aug 11, 2020 5:37 pm ]
Post subject:  Re: Red spark at plugs

New condensers fitted and new coils as well but still only a weak red/orange spark? I had to add some extra wiring to get the new coils to right mounting point, would this matter? I also used push-on connectors to the coils, should I have just directly soldered onto the coil pick-ups? New points turned out to be Chinese and of faulty manufacture so I cleaned and dressed the old Suzuki points.

Author:  Alan H [ Wed Aug 12, 2020 1:20 am ]
Post subject:  Re: Red spark at plugs

Unfortunately, if you've filed the points, you've removed the protective coating on the faces. New points are the only way to go.
What voltage do you get at the points when they are open? Much below 12v will give a poor spark.
You'll have to start tracing (and testing) to find loose/bad connections from battery through the fuse to ignition switch (then kill switch if there is one) coils and points.
The earth is very important too from battery to frame and battery to engine.
Is the battery in good condition and 'filled' with acid, charged to 12.8 ish volts? How long does it take to go flat?

Author:  GTandcbr [ Wed Aug 12, 2020 3:38 am ]
Post subject:  Re: Red spark at plugs

Why did you have to add wiring for new coils? Are they OEM or afternarket?

Author:  Hush [ Wed Aug 12, 2020 7:46 pm ]
Post subject:  Re: Red spark at plugs

Coils are aftermarket, Suzuki no longer makes them and one of my old "oatmeal" set tested bad, Battery is new and shows 12,8 volts but at the coils I get only 9.5 so I am thinking either bad ignition switch or kill switch. I was wondering if I can direct wire the coils to a hot wire just to test this out. I know of two other 550 owners who are using these same coils without issue so it is probably something to do with my bike. Yes dressing points will ruin them but I only want the bike to start as I am looking at electronic ignition for it and they won't be my red/orange spark issue. :)

Author:  jabcb [ Wed Aug 12, 2020 8:30 pm ]
Post subject:  Re: Red spark at plugs

You can use the relay mod. Then that 9.5V is only used to turn the relay on & off. The relay hot is connected directly to the battery via a new wire with a fuse.

Also, whatever is causing that big voltage drop might also be screwing with your alternator output. Easy to deal with -- you can use the relay to directly power the coils & alternator.

Author:  GTandcbr [ Wed Aug 12, 2020 11:33 pm ]
Post subject:  Re: Red spark at plugs

I have done the relay mod to my 550. It is definately worth it and not difficult to do it sits under the tank. 12v at my coils.

Author:  jabcb [ Thu Aug 13, 2020 6:35 am ]
Post subject:  Re: Red spark at plugs

Did the relay mod on the GT550 cafe build & upgraded to a modern voltage regulator. Both fit where the old regulator was.
See my build topic for a pic.

Its a popular mod for the Suzuki GS-series bikes because they have a more complicated wiring setup that can cause big voltage drops.

Author:  Hush [ Fri Aug 14, 2020 8:25 pm ]
Post subject:  Re: Red spark at plugs

So I removed all the extra wiring I had used and just flipped the coils around to make up for the shorter wires, also removed the wire connectors that I had used to connect to the coils and hard wired direct. This gave me much improved blue spark, still not starting but I'm getting closer. The rebuilt engine has an amazing amount of compression and now I have the spark cured I am looking at the fuel I used to attempt to get it going, my partner runs a petrol station and tells me petrol has a shelf life of only 6 weeks and I'm pretty sure I bought this petrol for my mower back about then so maybe the octane rating has dropped so much I'm using water. I do know not to use Ether as it is too dry on new engines. I shall try fuelling up on new gas and see if that works the magic.

Author:  GTandcbr [ Fri Aug 14, 2020 11:31 pm ]
Post subject:  Re: Red spark at plugs

Just remember to drain all the old fuel out the tank AND carbs. New gas on top of old gas still wont inprove the fuel. :wth:

Author:  Alan H [ Sat Aug 15, 2020 12:47 am ]
Post subject:  Re: Red spark at plugs

Easy start is your friend for a first start - or in the case of your neck of thee woods - start y'bastard.

Author:  Hush [ Sat Aug 15, 2020 4:54 pm ]
Post subject:  Re: Red spark at plugs

Actually I have some of that canned Ether but was told not to use it as it gives no lubrication to the cylinders and as the engine has been rebuilt and everything is new and tight I think I will just change out the petrol from the carb float bowls (tank not yet ready to use) and see if she will fire on that. :)

Author:  GTandcbr [ Sat Aug 15, 2020 11:55 pm ]
Post subject:  Re: Red spark at plugs

Fine to use that starter fluid. The oil pump will provide oil to the cylinders every time the engine turns. If you are concerned a sqirt of 2T oil down spark plug hole first but there is no need

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