Jetting

Question:

Love the hints and tips you guys always have. Been reading up on some jetting info and thought, “hey i could ask these guys!!”

I recently bought an 04 800 HO Ski Doo motor and put it in my 06 440 chassis. I have a dynoport pipe and SLP can, along with a cudney billet head, cudney clutch kit, new cudney pistons and rings, v-force 3’s and an Ataac system.

The coldest I will be running is -30 degrees celcius. Altitude 0-2700 With all this aftermarket stuff no-one even ventures a guess at what i should start my jetting at.

I am curious on your thoughts. Pipe (dynoport says IF in CANADA up 2 on the mains) v-force 3’s (seems a few guys have been lean after adding them – so up 1 for them) I have installed 450 mains, 22 pilots, and the skidoo 600ho 3 clip needle on the richest setting. The sled was bogging with 470 mains the other night and just sluggish… but definately safe.. will be doing a couple plug chops with this jetting to see..

I should add that I leaned it out 3 weeks ago (-27 outside) was running all stock jetting (400 mains, 17.5 pilots and stock needles) and had put on 200+ miles varying throttle and temps so thought it was safe… was really snappy and felt awesome! (maybe cause it was lean!)

Thanks for any input.. going on a 250-300km trip this sunday so any input you could give me would be greatly appreciated!

Sheldon

Response:

Thanks for your question.

Honestly, there’s only ONE answer to your question. Start way fat on the main and do WOT checks until you get the right color plugs for the temp. Then, you’ll have a base line and can move either way depending on temp using a Mikuni jetting wheel.

Make sure – with the compression you have gone to that you are always using good premium fuel or the whole deal goes out the window. Now, if this were a race mill for sno-X this wouldn’t be a concern but it will be because it sounds like you are trail riding this engine. Yikes!

For most engines modified to this degree they would be used in the mountains – lots of WOT, little mid-range – or sno-X all WOT and zero mid-range. You have the unenviable task of sorting out the mid-range. This will be problematic and requires a very steady hand.

If I were you and going on a long ride with lots of mid-range throttle application I’d get use to blipping a lot! I’ve seen this kind of thing before and the mid-range is what will squeak your mill – not WOT. Be careful and get the help of an experienced tuner for mid-range stuff.

Even seasoned race mechanics aren’t that good at the mid-stuff simply because they never have to tune for it. Know what I mean?

Good luck,

Motorhead Mark

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