Still having trouble with #1 plug fouling

[mcgovern61]

I checked my compression with the engine cold. Things do change after the engine's at operating temperature- the oil's thinner, things expand, etc. I'm going to do the compression test again twice- when cold, then right after a ride.

I'm just shooting straws here, check the compression hot, all plugs out, wide open throttle and see what your readings are. Carbon is unburned gas, so either too much gas and not enough air, or a condition that will cause the gas not to burn correctly such as a reduction in compression during the compression stroke. (maybe I'm thinking too much like a diesel, but that is where my experience is) Possible bad compression ring?

Joe, I'm with you on the electrical side too, but he did swap the good running stuff over without a change?

 

[kirkwilson]

Joe- I hear what you're saying but I just can't buy into it. If the problem was ignition then the problem would have moved to a different cylinder with what I've done.

The stock setup isn't complicated- you've got the sensor pickups- 2 of them- if one of the pickups was bad I'd have two bad cylinders. You've got the HEI modules- I switched them and the problem stayed with the bad cylinder. You've got the coils- and the wires going to them- again, I switched them and the problem stayed with #1- before I switched them that coil fired #1- fouling & 2- no fouling. After I switched the coils what was #3 is now #1- before no fouling- now #1 fouls- not the coil. All new plug wires and caps.

There are a lot of things in this stock setup that are common to more than one cylinder, and if one of those things was bad, I'd have more than one bad cylinder. You've got the things that are common to just two cylinders- if you swap them the problem should move to another cylinder, but it hasn't. There isn't anything else. When you've swapped every electrical part and the problem stays with the cylinder it's got to be something else.

Bro, I know you're doing your best to help and I appreciate it. Really. But everything electrical works on the other cylinders but no matter how you switch them around nothing fixes #1.

For now I'm just going to ride her - keep trying to figure out what's going on- and if I've got to put a new plug in I'll do it when she starts running on 3- until then I'm just going to ride-

 

[joedrum]

yea ithink thats the best thing to do for awhile kirk you might find that just running it might be the best medicine for it ....it might just fix itself :headscratch: :mrgreen:

 

[snowlover]

For what it is worth, in the 2-cycle world of snowmobiles, excessive heat in the exhaust is RICH. Un-burnt fuel going into the pipe, then burning. EGT temps on each pipe would show you the cylinder that was RICH due to high pipe heat.

 

[kirkwilson]

Snowlover- that makes a lot more sense- Since I put a different rebuilt carb on #1 it has run a lot better and isn't fouling- I still have the same plug in. Thanks for the info!