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Plug heat range

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Discussion Starter #1
I was talking to some friends and we got on the subject of spark plug heat ranges. A few people I know have found that the heat range there Sled OR Quad came with may not have been the best choice. So of these ended up going Hotter and some Went colder.

This started me thinking......has any one tryed changeing there heat range with any luck. I'm sure 1 heat range plug dosn't fit EVERY rideing style and diffrent trail condetion's. I also found out that engine RPM and load WILL have affects on a given spark plug....per NGK web page. They suggust fine tuneing a heat range to a given app. they also instruct that engine RPM and engine load should also be considered when selecting a plug.

Any one have a thought on this ?
 

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It's safer not to mess with your heat range, especially if you already are running fairly clean. But I'd say there are exceptions. One of my good friends is a very experienced mechanic with a local skidoo dealer and he gave me the advice that with most 2 strokes, for maximum engine life 50:1 isn't enough oil and you should be shooting for more like a 40:1 oil ratio, if not 32:1. If you do this you *might* experience early oil fouling (I never have), but in my opinion you definitely do not want to rejet to compensate for extra oil.

That's where raising the spark plug heat range comes in. On the Vmax and the EXT (fully stock engines) I run BR8ES instead of BR9ES (one step hotter) because the theory is it helps burn off some of the excess oil. My buddy runs BR8ES in his 2000 RMK 600HO. I've gone a full year (spring to spring) on one set of plugs on that old Vmax, about 50 riding days and a full summer of non-use in the middle, and only after that year did I need to change them, and even then they did not look oil-fouled.

On the Piped RMK and the SKS EFI I run the stock BR9ES because the plugs look very dry and clean all the time even though they are running at about 40:1 oil. I would say with either pipes or EFI in general you should be very very careful about making any changes. So definitely make your choice based on how the engine is running with stock plugs. Be sure you are tuned the way you want it first. I think changing heat ranges should be pretty much the very last step in the tuning process. And I'm not sure why you would ever want to go colder than stock...maybe someone else can address that.

Note that we also run premium fuel at all times. It's possible that with cheap gas a hotter heat range could cause preignition and really mess up your engine, so don't think there's no risk. I'm told that NGK heat ranges are narrow, meaning it is a small increment between the different plug types. I don't know if that's true or not. Only do this if you feel it's necessary and then be careful.
 

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If the fuels you burn vary in quality or grade, then going outside a heat range is probably not a great thing to do. Also judging the oil burnoff on the plugs may not be done easily due to fuel deposits which vary, again with the quality of the fuel.

I run standard plugs in warm and very cold weather. I (usually) change them once a year though it is rarely called or. (The extra oil-mixed tank I usually start with in the fall sometimes leaves an oil deposit.) I run my oil at 50:1, sometimes just a bit thinner. I know the crank can use all I throw that way, but the pistons don't need more than that and the rings really benefit when there is no oil residue in the grooves. We tend to have a single fuel source most of the time so dealing with those issues is simple. I have seen no benefit to messing with plug heat range.
 

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On my '04 Legend 600SDI, BRP originally called for BR9ECS plugs. After a couple of seasons dealing w/ the plug fouling issues, BRP told the dealers to run BR8ECS plugs.
 
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