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I have some misunderstanding on how to properly do a plug chop to check for jetting. I know you need to warm up your engine, and put in a fresh set of plugs, then run wide open for 1/2 mile and hit the kill switch. this is were I need info. When you hit the kill switch, do you keep the throttle to the bar, or let it go? do you coast to a stop, or lock up the brakes so the engine stops?

I have tried twice after installing Boyesen reeds, and an SLP trail can on my sled. both times I warmed it up good, ran full and hit the switch, but I let the throttle go, and coasted to a stop. when I checked the plugs, they were pretty much white on the PTO side, and more of a tan color on the mag side. I still have stock 440 jets in it, and the Boyesen instructions had said that I should be dropping down to 430/420, because they make an engine run rich. temps were -6 to -9 celcius both times. I am thinking that because I let the throttle go, and coasted to a stop, it makes the plugs look leaner......

Any help is appreciated
Sean
 

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-Warm sled up GOOD. You don't want a cold seize.

-Wide open for 1/2 - 1 mile

-While holding it wide open hit the kill switch.

-KEEP throttle to the bar and allow the sled to coast to a stop.

-Check plugs and repeat as necessary.

The reason that you want to hold it to the bar is to keep the engine from entering a lean condition when you cut the ignition at full throttle.

Chances are that is why you are seeing a "lean" condition on your PTO side.
 

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What Sledhead907 said!

You should also do the same check in the midrange to check the needle jet/jet needle... You can have mains that are spot on but still burn up the engine because of too lean a needle in the midrange.
 

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make sure you jet up before you test. you could easily be too lean and run it wot and seize look at the plugs and oh well it looks like i was too lean. especially in the mid range very easy to burn down if too lean in the mid range. always jet rich and decrese from there while testing.

and actually a plug "chop" is when you cut away the threaded portion of the plug and check the mixture ring that is at the base of the porcalin. this is the most accurate way to check your jetting but just checking the color of the insulator nose visually will do fine as long as your not looking for the last 1 HP.
 

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If you are seeing white, jet up before you run it again

I do it alittle different than some others but I'm sure they do the same thing.
run WFO (after what you sould always do...warm it up.) hit the kill and brakes at the same time, I don't hold the throttle WFO at this time

I'm sure it is 6 ways one way and half a dozen the other.

But you do sound lean, I would be jetting up NOW
 
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