Kawasaki FS481v backfiring and sputtering - help

[larryinalabama]

Originally Posted by BIGDOGMN73

So what's the plugs name like in a parts list. I searched for it and nothing. One other note that I just noticed today...it only does the backfiring at FULL throttle.

Heres the deal.
I had the same symptoms as your having.
I changed the spark pulgs because I figured after 800 hours it might need it anyway, made no difference. So I took the air cleaner housing off and saw the casting plug had had came out,,,

I dont know if the plug comes in a curaburator kit, but the curaburator is 180$ and Im cheap so I thought about how to fix it.

The main carburator jet goes through up to where the plug goes and it looked like there were passeges so some sort of plug was neccesary.

I wound up <DONT LAUGH> taking a small split lead fishing weight and breaking it in half filed on it till it could be tapped into the carburator, then took some 2 part epoxy and put it on top so the plug wont fall out. It has worke for about 6 weeks so Im sure its a permant repair.

[BIGDOGMN73]

Are intake gaskets a big deal? The thing runs strong.

[BIGDOGMN73]

I'll give that a try.

[BIGDOGMN73]

So I followed up with my local engine guy who did the following:
1) Checked the compression which was normal
2) adjusted the carb
3) adjusted the values

Engine is still backfiring.
After he was done he said it could the ignition coil is weak, but not showing on the test or maybe the value is sticking.
So I replaced BOTH ignition coils and it seems like the issue is WORSE. Before it would just back fire here and there if the engine wasn't at full load, but after replacing both it seems to backfire at full load all the time. Full load meaning throttle full, blades engaged and I'm on a sulky. Any other idea's outside getting into the values which doesn't sound like fun and doesn't sound cheap.