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Discussion Starter #1
I just checked out my jetting last night, (it was about 40 degrees outside), and I noticed that the chaincase side cylinder was jetted perfectly, then i took out the plug from the clutch side clyinder, and noticed that it had no color on it, looked brand new, like it had never been used, so that mean its running too lean. They both have the same size main jets and needles. I dont know what is going on. I just took the carbs apart again to look at everything, it seems fine. I also kept the 490 mains in the chaincase side (the side that is fine) and put 540 mains in the clutch side (side that was too lean) and nothing changed, still the same color! Does anyone know what could be happening??
 

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If it is a new plug, it might not be black yet. If you can, look down into the plug hole to the top of the piston. See if there any clean spots around the outside of the piston, then you are getting enough fuel.

If it is black all the way across, it is lean.
 

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Discussion Starter #3
there is black specks all over the piston. i fired it up again, same plug color. so what does black specs around mean??
 

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Sledcrazy,

You should only see brown/dark brown over the entire piston except the transfer ports, these areas should be washed away (for me 3/8 to 1/2 away is safe, others feel less, others more)

Just a question, I have been jetting combustion very presicely for years, It's part of my job, I get paid to do this. But i fail to see how you can test it without a load on the motor. The sled needs to be run on snow so that you have actual conditions on the motor. Also, relative air density, motor temp, ambient temp, airbox temp need to be measured to set your baseline jetting. And in my opinion this cannot be done in the shop.

How are you testing your sled? I can help if I know your procedure.

Let me know what method you are using and I can help.
 

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Discussion Starter #5
Well how do you get a "baseline" for jetting?? I think im gonna wait till the first day i start riding to jet it. But once I find the temp, airbox temp, motor temp, and relative air density, what do i do w/ that info to get a baseline??
 

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Once you have your ridding conditions met. Jet for the conditions of the day, ie. jet it perfectly at that days temp, air pressure, etc.

Once you find a jetting that you are happy with, use THAT as your baseline.

From here, use the "Hotlzman correction factor chart" to determine the proper jetting for all temps and pressures.

Like I said, It doesn't matter what temp it is as long as your ridding it, You can set it up on the grass for +50 if you want and then use the chart to re-jet it for +70 if your ridding conditions are the same. (but stay on the grass, you will need to find a new baseline if your running on snow)

For your sled I suggest you wait for snow, then you can establish your baseline using several tests. (WOT for 1/4 mile, 1/2 throttle for 1/4 mile etc.)

For your pilots, you should really wait until its cold enough in my opinion.

Just my 2 cents
 

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Discussion Starter #7
how do you adjust your pilot jets?? are those the ones right next to the main jet?
 

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Your pilot jet is the brass jet that is removable with a screwdriver in the float bowl area - the outlet is a small diagonal hole at the exit of your carb.

It has it's own a/f adjustment on the carb side (small brass screw)

the pilot stage controls 100% of the throttle operation from 0-1/4 slide opening, from there it decreases in importance to 10-5% of total operation (at WOT)

there are 2 methods of setting it. "Ride and feel" or " increase in RPM"

Ride and feel is easy but less precise:

Run the sled, blip the throttle. Adjust air screw

If your lean:
1. The RPM will "Hang up" and not decend properly to idle
2. At 1/4 throttle your sled will serge and not run smooth it will be starving
3. When you gun it, it will hesitate

If your rich:
1. You will bog when you gun it
2. You will puff black smoke when you gun it

Turn the air screw out for leaner, in for richer.

The Increase in RPM is the best method but tougher to do.

The Idle should be stable, then turn the air screw leaner until the RPM rises at its highest point (about 2-300 RPM higher than idle)

You should set it 1/4 turn back from the highest RPM.

You need to be able to find the right setting within 1/2-3 turns on the pilot air screw.

If you are lower than 1/2, go 1 size smaller on the jet
If you are higher than 3 turns, go 1 size larger on the jet.


Just my own experince, If you haven't added aftermarket reed on your machine, the stock setting should be fine. If you add Boyesen or Carbon tech, you will need to re-set them.

Also, you cannot properly set your midrange or main jetting before you set the pilot stage because there is 10-5% of this flow that will be part of those stages.

Good luck! Let me know how it turns out
 
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