I'm a little confused so hopefully somebody can set me straight. I've got a 1997 600 XC with an XLT motor in it. Last year I had the carbs cleaned by my local shop and they did general maintenance including new spark plugs. The shop set the carbs to run a little more lean and afterwards discovered that the engine's lower seals needed to be replaced (which as I understand will make my sled run even more lean). I didn't have the seals done because of cost but my sled ran well all winter.
Just the other week, I went to a Polaris dealer and got some new plugs for the 2008 season. They gave me some NGK BR9ES plugs. I then realized that last year my machine was running BR8ES plugs. I know that the 8 versus 9 has to do with the heat rating. What I don't know is:
Will going up to a 9 or down to a 7 heat rating help my lean condition? Will using one of them hurt my sled?
(I've never had a manual for my sled/motor, and the 1997 Polaris shop manual shows different versions of the XLT motor using either the BR8ES or the BR9ES plug. How do I find out which XLT motor that I have? SKS/RMK/LTD/LTD SP)
stock should be BR9ES, the 8's are a range hotter. 7's would be too hot and could do damage. Heat range does not lean or enrichen the fuel/air mix. The heat range bascially describes the ability of the plug to dissipate heat generated by the combustion process. Sometimes people will go to a range hotter to help prevent fouling, but that is a band-aid approach. To prevent fouling, figure out what is fouling the plugs and adjust/fix the problem. The seals are definitely something to keep an eye on, if you go too lean, you will generate enough heat to melt holes in the pistons...
2007 RMK 700, 2008 RMK 600, 1995 AC Prowler 2-up, 1980? AC Cheetah
So if I'm hearing your correctly, since my problem is the opposite of fouling (lean carbs and bad seals), I want the sled to dissipate more heat so that it doesn't get as hot in the combustion chamber. Therefore I want a colder plug which would be the 9. If I kept running my sled with the "8" rating plug (or especially 7), it could melt my engine because it's already running lean/hot and running a hotter plug would make the problem worse.
If that's the case then I feel like I finally understand it. Thanks! I'll keep an eye on those plugs too to see how they look after a good run.
Good to know - 612er and I had this conversation last night.
I just put new 9ES's in my sled, but I have had some problems with fouling. I'm 2 sizes leaner on the mains but don't want to go further since I sometimes ride in -20 degrees F. Is an 8ES a bad idea for me? Anyone use 8s in their carbureted 600 HOs (or other Liberty's)?
Current Sled - 2006 600 HO
Old sleds - 1999 XC500, 2002 Classic 550 (wife's)