Bugger - fires on starter button but dies as soon as starter button disengaged...HELP

[guyfawkes]

This feels *exactly* like there is a ignition circuit solenoid (a la bmw) that has stopped working but is bypassed by pressing the starter button.

Had a quick look at the wring diagram (1980 SG imported from US to UK) and can't see anything like this anywhere....

This also feels very much like the "next stage" of the occassional high rpm misfire problem I mentioned earlier that everyone said was prolly the pick up wires in the left hand outer case... I'll be honest and admit that since this was an intermittent rare problem I didn't pull the case and check... intuition would tell me that this latest development would indicate that it isn't the pick up wire thing, but what the hell do I know, could be 100% wrong.

Anyone come accross this before got any advice or tips before I start pulling it to pieces?

cheers in advance.

[ratbyk]

Starts but won't run.

Go straight to the ballast resistor. It is located under the fuel tank, left front just behind the horn. Pull both wires off of it and then connect them together. In effect bypassing the resistor itself.
When you are in the "start" mode this unit is bypassed. Once the engine starts and you release the start button then the resistor comes into play.
It is tin coloured, about 2" long and about 3/4" across. A wire connects to each end. What it does is reduce battery voltage to about 9 volts while the bike is running but allows full battery voltage to the coils while in start mode. You could likely run the engine for short periods of time with it bypassed but if you try and run the engine for long periods of time you could overheat the coils.
Ken/Sooke
78E Ratbyk
82 FT500 "lilRat"

[John]

Ballast Resistor

Check the ballsat resistor. It is located on the left frame rail under the fuel tank . It is silver and it's long and skinny. According to my manual the wires are either orange, or brown. The resistor is used to decrease voltage to the coils when the bike is running Approx 8-9 volts, but when cranking, the coils need a full 12 volts to make sure the coils fire a good hot spark. Just like an old Ford. Disconnect the resistor, and bypass around it, and try starting it again. You could use an ohmeter to check for exessive resistance, or an open circuit. I ride an 80 SG also, and I'm kinda familiar with these circuits. Good luck mate.

[Snow]

Ok you ballast experts, here's a question

I've got Accel Coils now, so can I just get rid of the ballast resistor?

[John]

resistor

I wouldn't, unless the coils can handle a full 12-13 volts all the time. If it ain't broke, don't f&^k with it

[John]

Re: Starts but won't run.

Originally posted by ratbyk
Go straight to the ballast resistor. It is located under the fuel tank, left front just behind the horn. Pull both wires off of it and then connect them together. In effect bypassing the resistor itself.
When you are in the "start" mode this unit is bypassed. Once the engine starts and you release the start button then the resistor comes into play.
It is tin coloured, about 2" long and about 3/4" across. A wire connects to each end. What it does is reduce battery voltage to about 9 volts while the bike is running but allows full battery voltage to the coils while in start mode. You could likely run the engine for short periods of time with it bypassed but if you try and run the engine for long periods of time you could overheat the coils.
Ken/Sooke
78E Ratbyk
82 FT500 "lilRat"

Great minds think alike

[guyfawkes]

Ok, assuming it is the ballast resistor, which sounds likely given the wiring system you guys describe, two questions.

1/ any recommended replacement item?

2/ if I do short it out do you reckon 10 / 15 miles on a shorted resistor is excessive re damaging the coils?

many thanks to all in advance.

[ratbyk]

Ballast resistor

You should have no problem running 10/15 miles with the resistor bypassed. If you cannot find another XS 11 resistor you could very likely run virtually any automotive ballast resistor in it's place. They all do the same thing. Cut battery voltage back to about 9 volts.
Go to any automotive parts supply store and enquirer about the availability of their stock of ballast resistors. Pick one from their assortment that will fit into the space available with similar wire connecting terminals.
Ken/Sooke
78E Ratbyk
82 FT500 "lilRat"

[Hobbit]

resister

I wouldn't run it any longer than I had to. Not only is the voltage higher, but so is the amperage.

During cranking the starter draws so much amperage that the sytem voltage also drops. The resister is by passed so that the coils get all of the voltage that is available (not necessarly 12 volt) at that time.

[pgg]

Removing the resistor on the original 'weak' coils may POSSIBLY shorten their lifespan but for dynacoils a resistor is just excess baggage. Even the fitting instructions advise to REMOVE any ballast resistor from the circuit. I'd assume accel coils would be very similar to dyna.

[wildbill]

The bike I own has Accel coils on it when I got it.Did not have a resister anywhere that I could see.Sounds to me like a bad ground,could be in handlebar switch,would check that first.The simplest things can be the hardest to track down. Good luck

[Snow]

After reading through some older posts about ballasts, ohms, and coils, I've come to the conclusion that I need to remove my ballast , so that is what I will be doing this afternoon

[strom]

Check your engine - frame ground wire... Engine is on rubber mounts, so is the exhaust (if original...type...). If the resistor thing doesn't work.

LP