Backfire on 1988 Marathon...

[steve_empire@yahoo.com]

I did the HEI ignition mod on my 88 Marathon and it runs great now, however there is a backfire sometimes when I let off the throttle. I don't want to blow out my exhaust system, which I just re-did.

Any suggestions? Is it timing? How do I check the timing on the 244cc Robin engine?

Thanks,
Steve

[my1423]

Usually is is from your throttle butterfly not closing all the way allowing gas into the engine when the ignition is off and the second you give just a little throttle the spark makes it backfire.
Also can be caused by needing a little adjustment on the micro switch to keep the ignition on a longer to clear the fuel.

I actually added a small cap to my solenoid to keep the ignition on longer.
It would run the spark 5-8 seconds after i let off the pedal.

Sorry but i dont remember the size. 24v electrolytic cap found in the parts bin about the size of a d battery.

[steve_empire@yahoo.com]

.

How did you wire up the cap?

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[my1423]

Cap is labeled + -. Some just have a black line for neg -
Just connected it between the 2 field terminals on the solenoid.
Use a meter to determine + -
I think + lead to the micro switch but i am not sure if all are wired that way.
It just provides a few seconds of power to keep the solenoid on and is charged when the switch is activated.

Warning too big a cap can fry your micro switch by pulling too many amps at once.
This will also keep the solenoid on for a long time as it slowly discharges.
If you want you can add a small resistor in line on one cap terminal. This will slow charging and discharging. Play with different resistors to get it as slow as possible.

Cap i used, Wish i could remember the size. I sold my cart or i would go look.
Thinking back i think it was a little smaller about the size of a c battery.

[steve_empire@yahoo.com]

Does anybody know how many microfarads the electrolytic capacitor needs to be?