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Discussion Starter · #1 ·
Hi guys,

I've gone through my carbs and set them up as per the manual, but I have some questions.

Please confirm I've done this right:

- To sync the two carbs, I used an exact 1.7mm drill bit as spacer to set the PTO slides from the engine side of the carbs.

- Then I adjusted the mag side with the adjust nut to get the same.

- At this point the two slides are 1.7mm gapped on the engine side and no throttle cable is attached.

- The manual says to now connect the cable and adjust the throttle such that when at full throttle, the gap to the upper hard stop is 0.5mm-1.0mm. So I did this.

- Now the slides are equal, but at rest are much higher than the 1.7mm gap when I sync'd them without the throttle cable on.

- Should the slides return to the lowest sync'd position when the throttle is at rest? And I ignore the upper limit to the hard stop? Or is the upper limit key and the 1.7mm was just to set them up relative to one another? Note that there are different specs for different models on the base gap (mine is 1.7mm other sleds are 1.5, 1.8, 2.2)

For the choke setup

- The manual says to adjust the cable so the gap to the upper hard stop is 0-0.5mm. If I do that, the plungers don't retract all the way to their seated position.

- If I do the other way so that they are fully seated, they don't even come close to the hard stop at the top of the stroke.

- Is it more important that the little plungers are closed when the choke is off or that they open all the way and don't seat to the bottom position when choke is off? I suspect I need to make sure they are fully seated when choke is off and ignore the gap to the stop.

Sorry if the questions are basic, but it's the first time I've set up dual carbs like this.

Thanks in advance!
 

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Answers to your questions.
1. More critical that they are same when closed limit is made. Be sure that the carbs open all the way and both move at same time.
2. Choke. Best have them SHUT OFF COMPLETELY when not on. Open is open. Not closed is open. Besides, you'll have issues.

For exact synchro, you would need a flow bench or more expensive certified calibration equipment. Not needed.
 

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Discussion Starter · #3 ·
Thanks!

1. They both move at the same time and open all the way until the cam hits the hard stop. But at rest the engine side carb slide gap (with the cable adjusted and attached) is around 3/16" or 4.76mm. Spec at rest without the cable was 1.7mm. Thoughts? Should rest be 1.7mm and ignore the upper limit or set to upper limit (i.e. the hard stop) and let the slides zero throttle position be the 4.7mm? The manual says to adjust idle speed to +/-1/2 turn on the idle screw from the setting I have it at.

2. I'll set so they are closed when choke is off. I agree - not closed is open :)

Thanks for the insight.
 

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Discussion Starter · #4 ·
Update:

I set the choke so that off = plungers all the way down. This means on full choke, the plungers don't stroke all the way, but as Mac-Daddy said above, closed when off is a must.

For the throttle, I adjusted the cable now so that the zero throttle position of the slides is the 1.7mm measurement on the engine side. There is only a hint of slack in the cable at zero throttle. Now that I've done that, the slides do not go all the way up at full throttle.

So the question still is - is the 1.7mm spec zero position key to maintain, or is the wide open throttle with the slides clearing the opening proper way to set it? My gut still says it should be the 1.7mm, otherwise why have such a tight spec and different ones for various sleds? If I do this, the slides do not open all the way and the cam doesn't hit the hard stop as per the other part of the spec.

I've looked through a LOT of posts and can't find a clear answer on how to properly set the throttle cable. There is no difference in cables between the 600/700/800's (I didn't suspect there would be, but I checked just to be sure - mine is a 600 chassis, 800 engine).

Would really appreciate insight from those who have gone through this :)

Thanks!
 

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Is this a new mod for the sled, or are you just dialing in? The carb synchronization is one thing I do on a bench. The cable adjustments I do on the sled.

Something is missing here.
 

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Discussion Starter · #6 ·
Just dialing it in. New reeds, cleaned carbs, resetting to spec.

I set up the slides with carbs out. 1.7mm gap on the slides on the engine side. No throttle cable attached. As per manual.

Then I put in sled and go to set the throttle cable. How do you set your throttle cable is the question? If I set to open all the way to the hard stop, the zero throttle position has the slides higher than what I set on the bench at 1.7mm.
 

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Discussion Starter · #7 ·
So, here's what I've done so far to baseline the sled and hopefully solve the wet mag plug

- Pulled and cleaned carbs

- New petals on the vforce reeds (the ones on the mag side were cooked on the tips)

- New plugs (ones in the sled were probably double the spec gap)

- Sync'd slides using drill bit. This is now the zero throttle position.

- Oil pump lever moves ever so slightly before throttle cam does.

- Reset air screws. Fully in and back 1.5 turns.

- Choke is set so that zero choke has the plungers fully retracted.

So, now that all is done and back together (along with my fuel buddy) there isn't a stitch of snow in sight to even attempt to test it. I may drag it out on the weekend to get fuel back in the system, check/tweak the idle and check the plugs to see if they are more even than before.

Thanks for the help Mac-Daddy.
 

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Synch your carbs so they are equal when they are wide open. The needles are mounted in the slides, and the engine isn't fully on the main until the last 1/8 of throttle. When the engine is making 133 bangs a second, the needle height is very important. Idle is t a real big deal, the slide cutaway provides enough air to draw the fuel from the opening. Make sure you have correct free play after the idle speed is set. This will affect the oil pump cable, so check that as soon as its synced and idling correctly with the right free play. Adjust the starter jets so they are bottomed and you can raise the cable in the ferrule about .040".You'll see a bit of movement in the linkage that lifts the plunger. Important that they are bottomed. It will start just fine with that amount of free play
 

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Discussion Starter · #9 ·
Thanks. I suspect the idle will be a bit low being set as I have it. If I adjust the idle screw, I'll watch the throttle cable slack and adjust it when I have the idle set. I'll be excited if it starts and idles without issues.....
 

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Discussion Starter · #10 ·
Fired up from empty on about 6 pulls. Idled perfect and purred like a kitten. Well, a noisy one with an aftermarket can on it, but still, very nice.

Without being able to run it, it is hard to tell, but I let it warm up and pulled the plugs and the mag side still looked a bit wet. I need snow otherwise it'll have to wait until next year to really put it through its paces.
 
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