Ever wanted to set your Cub on fire?

[jimbob200521]

Originally Posted by yeeter

Not sure if they will reach, but maybe also swap plug wires if possible?

I don't believe they'll reach.

Bassblaster: When you said what plug you had, did you mean RC12YC? Either way I'd bet it's a bad ignition coil but first I'd double check wiring. Intermittent firing dependant on RPM's is odd for a bad coil but not for a bad connection.

[BassBlaster]

Yeah I probably did. I pulled the plug and looked at it, came in and posted. Didn't write it down so I probably got it backwards.

What wires am I checking? I took pics when I pulled the engine and took everything apart. Everything is hooked up the way it was before. As for the wires that go behind the blower housing, nothing is pinched and I can move them in and out of the housing.

[Sam Mac]

Originally Posted by BassBlaster

Im not partial to any plug brand. That's what was in it when I bought it so when I was replacing all the filters, fluids, etc. I bought the same plugs. Ill get the NGK's

I swapped the plugs from one side to the other and the problem stayed on the same side.

My bet is a dead mag, or you have a short in the kill wire. Last test. Pull both plugs stick them in the plug wires and crank it over and look to see if you have spark with the plugs laying against the engine, try to put the plugs on something like one of the bolts that hold the tin work on. Don't buy new plugs just yet. Just to confirm that the plugs are good after you do the test I just described swap the plugs and do it again.

[Sam Mac]

You can't swap the plug wires, each coil fires it's own cylinder.

[BassBlaster]

At my son's baseball game now. I'll try that when I get home and report back.

[yeeter]

Originally Posted by Sam Mac

You can't swap the plug wires, each coil fires it's own cylinder.

I meant complete swap Sam (in case a bad wire), not just one end. A long shot.

Kill wire would affect both sides wouldnt it?

[Sam Mac]

Originally Posted by yeeter

I meant complete swap Sam (in case a bad wire), not just one end. A long shot.

Kill wire would affect both sides wouldnt it?

Maybe, kind of depends on if it has a bad diode. Maybe what I do is over kill but when I know I have a problem with a mag or a kill wire considering what it takes to pull the engine and tins to get at the parts I just replace them all unless it's a low hour engine. The way I look at it is if we are talking about 20 plus or minus year old ignition components it's time for new. Maybe you can get a few more years or days out of it by doing 1/2 the deal, I have better things to do than pulling engines out of Cubs for a $50-$60 mag or a $15-$20 kill wire. If it's 20ish years old it's time. Just my 2 cents.

[Eslenk]

Recently, I started my 2084 with the recently installed 18hp. engine that had been running perfect, and it was idling on one cylinder. I pulled the plug, cleaned and re-gapped and re-installed and not firing. As it was I pulled the spark plug wire off and just as it got maybe 1/2" from being un-clipped the cylinder started to fire. Pushed the wire back on and stopped firing. I went back and forth between the plug wire being fully on, not firing, to pulling the plug wire off maybe 1/2" from being fully on and the plug would fire every time I pulled the wire slightly off. I did this at least 10 times because I couldn't believe what it was doing. Replaced the spark plug and haven't had a problem since.

Don't know if that's your problem but I never seen anything like that before.

[Sam Mac]

Well it's been fun today, the mother ship is here to beam us Galaxians up so talk to you kids tomorrow.

[BassBlaster]

Okay, pulled the plugs so I can watch the spark. Good spark on left, no spark on right. Switch plugs to opposite sides, good spark on left, no spark on right.

Next step to pull the engine back out to get at the coils?