Using This Tool To Sync Carbs? - Snowmobile Forum: Your #1 Snowmobile Forum

ENR_Kyle20 · 11-18-2007, 07:00 PM

My local showmobile shop wants $100 to sync my carbs. But for less than half the price I can buy a tool that I think will work fine.

What do you think?

eBay Motors: Weber Carbs, Carburetors Synchrometer STE SK (item 150182534982 end time Nov-19-07 23:56:23 PST)

RedRider_AK · 11-18-2007, 07:22 PM

I don't even know what it means to "sync" carbs...

ac bigbore · 11-18-2007, 07:30 PM

Seriously, though, I just pull em out and eyeball them.
Like to see the slides start up the same time.
Get that much right and usually they will be pretty even
all the way up. There. Sunk. Or pretty darned close.

ENR_Kyle20 · 11-18-2007, 08:55 PM

synchronize the carbs, make them both open at the same time so the both do the same ammout of work. This device measures airflow. you put it on the carb and adjust the adjuster on the throttle cable on each carb to they both suck the same ammount of air at the same rpm.

I just noticed that you put a line and an explination. I thought that way your sig.. lol..

you just eyeball them.. like watch when one starts lifting that they both lift about the same time.

lowbudget · 11-18-2007, 09:09 PM

I didn't go to the link posted for the syncronizer but my motion pro measures the vacuum of each carb. Here is a how to article. It is a 4 cyl bike but the process is the same.
http://www.cartestsoftware.com/fz1/c...onization.html

http://www.angelfire.com/ia/z/FZ1carbsync.htm

puteman1 · 11-18-2007, 09:10 PM

I was having carb issues when i first came into this forum and did what i was told on how to remove and clean. What I did knowing they had to be open the same distance was used a set of feeler gauges under each slide assembly making sure the gap was the same in both carbs. I didn't even know their was a tool that did that seeing i am learning sleds myself. I am sure feeler gauges are cheaper tho.

**smallengineguy** · 11-18-2007, 10:06 PM

I use the Edelbrock carb sync tool. Used it for year, it's the BEST one I can find.

IRONDOG · 11-18-2007, 11:03 PM

Quote:

Originally Posted by smallengineguy

I use the Edelbrock carb sync tool. Used it for year, it's the BEST one I can find.

I'm with you, SEG- the Uni-Sync works great for me. Hard to use on some sleds though when the airbox can't be removed. Here's a link to one on eBay right now- eBay Motors: Uni-Syn Uni Syn Carb Carburetor Synchronizer MG Triumph (item 150184918568 end time Nov-25-07 13:45:59 PST)

ENR_Kyle20 · 11-18-2007, 11:08 PM

I dont have time for bidding, but I bought this a few hours ago

eBay Motors: PORSCHE 356 912 911 weber carb uni-syn balancer (item 160180541619 end time Nov-24-07 12:21:40 PST)

looks the same as all of them, so im sure it will work?

I noticed the vac ports on the carbs..but the must produce almost no vac.. The only guages that I have are for evacuating AC systems.. I dont think that guage will work.. either way. I got the airflow meter for like $20..

IRONDOG · 11-18-2007, 11:12 PM

Yep, that's the one.
Jerry
IRONDOG'S Snowmobile Swapmeet Free Ads

ENR_Kyle20 · 11-19-2007, 01:06 AM

so the one I bought will work..

does anyone have any instructions for this?.. Thanks

lowbudget · 11-19-2007, 03:38 AM

I've never seen that type. Ive always used the old mercury vacuum type how does it hook up?

**smallengineguy** · 11-19-2007, 06:53 AM

You put it over the intake and look at the plastic ball in the glass tube. You adjust idle screw until it's in the same place on all carbs.

ac bigbore · 11-19-2007, 09:35 AM

In a 2 stroke with tuned pipes, especially if separate pipes,
I would find it very unlikely that the flow would be uniform
throughout the throttle range. So many variables. Different
cylinder temps, different pipe temps giving different pipe
signals, possible different reed responsiveness, different
plug conditions. I would think that in the real world, setting
2 stroke carbs by slide position would be quite adequate.

If those of you with the vacuum gauges have actually verified
on a loaded condition (on a dyno) that the vacuum stays
equal through out load range and rpms, and changes in operating
conditions, then tell me I'm full of cxxx.

ENR_Kyle20 · 11-19-2007, 10:13 AM

I am sure you are right. but for $15 I feel like its worth it. the closer you can get them, the closer they will stay even with all those variables. If its nutz off at idle then you know its going to be all over the place at all speeds, atlease if you can sync them at idle and low rpm you know that your good part of the time. I would not have paid $100 for this service, but $15 I will do.

IndianRvrShiver · 11-19-2007, 10:27 AM

Quote:

Originally Posted by ENR_Kyle20

......I noticed the vac ports on the carbs..but the must produce almost no vac..

Vac ports on the carbs!!??

Those are prolly primer ports/nipples. If they're not being used, plug/cap them!!

ENR_Kyle20 · 11-19-2007, 12:40 PM

the nipple I was talkin about is and always has been capped, i am not posartive what they are for but after seeing that link about how to do it on a bike I just assumed that is what it was for, but there is also a small tube on each carb that goes into the air box. Maybe its not vac, but im sure a measurable ammount of vac can be found there?.. What exactly are those lines for? and I assume they should be hooked up to the air box not caped?

ac bigbore · 11-19-2007, 01:08 PM

OK- you synch the carbs at some point in the throttle
range, hopefully with the engine and pipes at operating
temp. Doesn't matter how you did it.

Now what if I tell you that even if the slides are in exactly
the same position at 1/4 throttle, they may be off at full
throttle? It happens, especially if the carbs are run off
cable with a splitter, rather than on a rack system. The 2 cables
coming off the splitter are on a t-bar that runs up and down a track. Does this cheap plastic t-bar stay perfectly even throughout the pull range? Do the 2 cables have the same
clearance in the housings? Something gives in this system
because I have had 2 carbs start out at exactly the same time
on the throttle pull, but end up about 1/8 off at the top.
So where do you synch it? At the top or bottom? If you are
off by 1/8 at the bottom, thats a lot. Considering the bleed
circuits, its probably a 75% difference if one slide is at
1/8 throttle and the other is at idle screw stop.
At full throttle 1/8 is about 12 % difference. Not enough to
worry about unless you are drag racing and inches over the
course of the run mean winning or losing.

Thats why I said in my initial response in this thread that
synch them so they start out together, and you are going to
be as good as you probably need, and maybe about as good
as you are going to get.

oldie yungin · 11-20-2007, 02:22 AM

i actually own a sync tool but have never even taken it out of the box. i find that the simplest method is the best and that for me is a good clean finger on the slides and my eyeball. set the clips the same and just go from there fine tuning until you have equal lift,drop, slack(about 1/8 inch)and idle adj.

ENR_Kyle20 · 11-25-2007, 10:19 PM

yea, it was kinda a waste of money, but I got someone to agree to go halfs with me.. so its only $10.. and I can make sure the idle screw is set the same on both carbs.. not a bad deal!