Sunday, July 31, 2011

backfiring on acceleration possible cause

The last few days, my KMD 150 GY6 would start dying at intersections and give an every-now-and-then backfire.
I replaced the fuel and vacuum lines and fuel filter thinking there might be a vacuum leak because the hoses on the intake were almost ready to fall off!! :o
That didn't fix it.

Yesterday on the way home from work, it ALMOST left me stranded with the horrendous popping and backfiring.....would hardly climb hills......under load and acceleration as well as stalling at lights.
What made me think it was fuel was it would idle and rev great and part throttle was okay but once you put it under load....WOW! Fuel problem, right? EEEE! Wrong. Read on.....

So first thing this morning I tore into it thinking for sure I had ingested crud into the carburetor (blocked fuel circuit) or a tore diaphram (no part throttle enrichment) or.......
Nope.
No crud, diaphram is perfect and carburetor is spotless inside.

I beat my head against the wall for a good 4 hours this morning chasing what I thought was a fuel problem.

The problem was the two small coil wires!!
If you have these symptoms, by all means....check the two small wires at the coil!
One of mine was so loose it basically fell off in my hand!
I have NO idea how it made it over 600 miles!
It's been shorting/arcing since new, I bet.
There was black stain inside the connector boot and on the terminal from arcing/shorting.
The other terminal was a POOR fit.
I squeezed down on them with pliers to tighten their "grab", cleaned the terminals and connectors and they fit 100% better.

No kidding.....my scoot has NEVER run this good!!!.

I only hope I can save someone else the 4 hours of tinkering I went through diagnosing the problem......I beat my head against the wall chasing what I thought was a fuel problem for it to turn out to be ignition related.

Now she's running TIP TOP.

Keep scootin'!




credit to mogy6 at scootdawgforums

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