8 vs 9 plugs - Snowmobile Forum: Your #1 Snowmobile Forum

sldnrockies · 04-03-2008, 04:55 PM

I have an 01 800 summit. I read that 8 vs 9 plugs may help a bogging prolbem but that they will burn hotter. Would they burn hot enough to burn down my motor?

**smallengineguy** · 04-03-2008, 08:03 PM

I'd leave the 9's in there and find out why it's bogging to begin with. Are the plugs a dry chocolate brown color? Or are they oily black?

BC_Dan · 04-03-2008, 09:09 PM

The misconception about heat range in plugs is that they "burn" hotter. That is not what happens. The heat range for the plug indicates the plug's ability to get rid of heat from the combustion process. For example, an NGK 9 will get rid of heat better than an NGK 8. Each engine is designed to use a certain heat range to prevent hot spots from forming in the cylinder that may cause piston/engine damage. If you are fouling plugs, going to a plug that is "hotter" just means the plug keeps the heat in better, and it indeed could get hot enough to do damage (not likely with a one-step increase). Like SEG said, it's better to figure out what is causing the problem and fix the problem instead of doing a band-aid fix by going to a different heat range plug.

sldnrockies · 04-03-2008, 10:16 PM

The plugs are oily black.

I also just recently cleaned my exahust valves which i had never done before. There was a little black carbon build up on the corners of the valves but not a lot. I haven't run it since cleaning them. Would that have been causing my problems?

BC_Dan · 04-03-2008, 11:12 PM

Usually, exhaust valves that are gummed up will cause the engine to be really flat on the top RPM range and you will lose power big time. If they are black and oily, the oil pump may be giving too much oil, causing the plugs to oil foul. Black without being oily is usually an indication of too rich a mixture and may require rejetting.

**smallengineguy** · 04-04-2008, 07:18 AM

Give it a rip across a lake or long field. Then shut it down while it's wide open. Look at the plugs. If they are still oily, then you can adjust the carbs slide needle, etc to dry them out a little.

sldnrockies · 04-04-2008, 03:44 PM

I will give it a try.

Thanks for the help it is very appreciated.