"Blind Syncing" Carbs? - Snowmobile Forum: Your #1 Snowmobile Forum

meburdick · 11-22-2012, 09:42 PM

Hi, all.

I'm used to syncing the carbs while they're in the sled, and I'm wondering if anyone has some tips for syncing them while they're nowhere NEAR the machine they go in.

I've pulled the carbs apart and cleaned them thoroughly (very dirty) for a friend, and I'd like to give them back with adjustments that are at least sort of close to where they need to be. I have the complete setup (he pulled the carbs, the throttle cables, and the choke cables) to work with out of the sled and I need some tips on syncing the throttle slides AND the choke plungers.

Thanks!

**RJ Gleason** · 11-22-2012, 10:04 PM

The chokes you can do as long as the lever is there too, but the throttle also needs the lever so that you can set the free play properly.

meburdick · 11-22-2012, 10:09 PM

Thanks, RJ... Good point on the lever, and he did pull that whole thing. Any suggestions as to how to know that I have the chokes adjusted right?

I was thinking that I would try and 'eyeball' it with the plunger unscrewed to gauge how far into the body it would be able to go and leave just a touch more than that as slack.

**smallengineguy** · 11-23-2012, 05:40 AM

There should be about 1/8" of free play in the choke cable before it starts to lift the plungers. Not sure if you can duplicate that out of the sled or not.

meburdick · 11-23-2012, 05:52 AM

Ok. I would think that I could use my vernier calipers to measure the depth of the carb body opening where the plunger inserts, add 1/8" to that measurement, then use it as a guide to set the jamb nuts on the cable before installing into the body.

ridegreen · 11-23-2012, 10:01 AM

This is how I was told to adjust the choke and It's always worked and never had a problem. Use a micrometter, run it down the to the base of the choke and measure from base to the very top of the choke, then keep that measurement and then measure the choke plunger from the very top of the threads to the bottom of the plunger and it should be the same measurements in length and make any adjustment that needs to be made, that way you know the plunger will sit flat inside. This is how I make my adjustment and it works.

meburdick · 11-23-2012, 07:13 PM

Quote:

Originally Posted by ridegreen

This is how I was told to adjust the choke and It's always worked and never had a problem. Use a micrometter, run it down the to the base of the choke and measure from base to the very top of the choke, then keep that measurement and then measure the choke plunger from the very top of the threads to the bottom of the plunger and it should be the same measurements in length and make any adjustment that needs to be made, that way you know the plunger will sit flat inside. This is how I make my adjustment and it works.

That is essentially what I was thinking... I would measure the depth of the opening, add 1/8", and adjust the cables so that the measurement from the bottom of the plunger to the top of the threads was that measurement.

ridegreen · 11-24-2012, 10:00 AM

Quote:

Originally Posted by meburdick

That is essentially what I was thinking... I would measure the depth of the opening, add 1/8", and adjust the cables so that the measurement from the bottom of the plunger to the top of the threads was that measurement.

Yup, that's it. I was doing one time and didn't have anything the measure with so I used a tooth pick, worked just as good.

steepndeep · 11-25-2012, 12:22 AM

On the round slide carbs there is a small hole on the right hand side as you look down into the top of the carb. My dealer always took a small wire that he had pointed and put a 90 degree bend it. He would insert wire into hole and you can feel the plunger lift as you lift the choke lever. Once it lifts enough the wire slides under the plunger and that is enough for the choke to function properly and it should be much quicker than doing a bunch of measuring.

meburdick · 11-25-2012, 07:15 AM

Quote:

Originally Posted by steepndeep

On the round slide carbs there is a small hole on the right hand side as you look down into the top of the carb. My dealer always took a small wire that he had pointed and put a 90 degree bend it. He would insert wire into hole and you can feel the plunger lift as you lift the choke lever. Once it lifts enough the wire slides under the plunger and that is enough for the choke to function properly and it should be much quicker than doing a bunch of measuring.

What you're describing is a way to ensure that the slides go all the way to the bottom and doesn't ensure that they all move up at the same time or move up the same amount. Verifying this makes sense because a plunger that doesn't completely close will cause it to run way too rich and not idle correctly.

The measuring takes about a minute and there is no substitute for it that I can find.

mrholmquist · 11-25-2012, 09:59 AM

you cant sync chokes or throttle slides without the respective cables being connected.

That is essentially what you are syncing for .....the length of the cables. the cables are not the same length and they do stretch over time so periodic syncing is necessary to compensate for this.

Syncing is not a matter of getting both barrels screwed into the carb to the same height it is a matter of equalizing cable free play on multi carb systems which use more than one cable to operate them.

Once you have done that you can equalize the closed throttle slide height using the idle stop screws which is independent of the cables but only if the cable free play has been adjusted correctly
first.

The same goes for choke plungers ....see post 21 in this thread :

http://www.snowmobileforum.com/polar...oils-have.html

meburdick · 11-25-2012, 10:11 AM

Did you read my first post in its entirety? All cables present and accounted for.

mrholmquist · 11-25-2012, 10:16 AM

my mistake

in that case you can use the drill bit method to sync the slides and the method I described in the link for the chokes

meburdick · 11-25-2012, 10:21 AM

The procedure you linked to is a good one... Just wanted to be sure that I wasn't still missing something.