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Discussion Starter · #1 ·
I recently purchased some Boyesen power reeds to replace my stock reeds on my 00 mxz 700, they are worn. I did not buy the new reed cages or anything, just reed petals. Reading through the info provided they claim their jets tend to make sleds run rich. Anyone have any experience with these reeds. I really do not want to deviate from stock jetting if I don't have to. Any help would be greatly appreciated.
 

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I've run them lots.

Motocross and sleds

They run a little lean on bottom and rich on top.

Amounts to about 3/4 to 1-1/4 turn in on the air screw. If your within 1/2 turns out - go up 1 size pilot.

on top you can drop 1 or 2 jet sizes.


Jetting on top is pretty easy, check your piston wash and egt.

Pilots can be more troublesome. From closed throttle, give small chop shots to engagement, ride around and "feel" if throttle responce is OK. If your RPM is hanging up or you get hesitation, your still too lean.

If you blip the throttle and you tend to bog, you've gone too rich.

Good luck!
 

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I run 260's.I have no other carb changes other than jetting.
 

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Wait a second, im not a jetting "expert", actually im not really that good at it, but. I put on an SLP pipe, and they said to go up 2 sizes on the mains, actually I stuck w/ the stock ones, because it was running rich as hell last year, I thought it would clean it up, havent really had a change to test it out yet. but anyways, I heard that the main jets only affect your mid and top end jetting. how do I setup my low end and idle jetting?? I cant seem to find that air screw you guys are talking about on the TM-40 carbs. any help is appreciated. thanks.
 

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To answere your question sledcrazy, here is a picture of a ski-doo Mikuni TM-38. It's similar to your 40mm's

The pilot air screw is item 73 on the schematic.
 

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Discussion Starter · #6 ·
Should I just ride it before I do anything and see how it is. I dont want to be one of these guys rejetting every two seconds out on the trail, Especially with an airbox. I want to be able to jet it once and ride it, that's it.
 

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Actually the best way to set the pilots is while running Steimy.

When you set your pilots you need to make sure the engine is a normal running temperature.

The best thing to do is get a 2 feet long piece of drill rod, and grind the tip to make a standard (flat) tip screwdriver . Make sure the edges are nice. A piece about 3/16 dia should work fine.

At the other end, just wrap hockey tape until its large enough to get a good grip with you ridding mitts or gloves.

This tool will let you adjust the pilots from far enough that your hands don't get caught in the engine compartment. This area can be pretty crammed on some sleds with hoses, electronics, airbox, etc.

You will only have to ride around the house a few times until you get the pilot stage set for best throttle responce.

Cost of tool is about $2.00. Time save is huge!


For the wide open throttle, use the kill switch method.
 

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heres a question about checking your WOT jetting. you are supposed to hold it to the pin for a while then hit the kill switch and keep holding it to the pin, right????????

i did this, and after about 30 secs after shutoff it does a huge backfire, this cant be good for it. are you sure that is the right way?
 

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Dusteater,

Your method is correct, however your sled had one of two problems

1. Your clutch could have been improperly set-up.

The reason you had a backfire could be because your clutch had partial engagement. The engine was being driven from the belt while coasting to a stop.

When this happens, sometimes you pump a heavy fuel/air mixture through the pipe. An accumulation of gasses combusted after the expansion chamber due to the excessive pipe temperature.

Don't be afaid to try it again but be sure your clutch disengages. If anything, try to increase your belt deflection for this test. It may bog a bit out of the hole, but top end is the only thing your really interested in.

2. The other possibility is that you were running so lean that your expansion chamber may have been on the edge of pre-ignition temp.

this way, maybe a few strokes of unburnt gasses while engine RPM decreases may have been sufficient to combust.

Either way,a full throttle run with engine shut-off it is critical to leave throttle wide open, This way you still ensure some lubrication during the RPM decrease.When running an engine at full RPM even running out of gas can destroy your engine.
 
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