Carb sync... tool?

[Clumzi]

So now that the bike is running I need to sync the carbs. I've searched other threads and basscliff's site for how to do it and I think I get it... match #2 to #3 and set #1 and #4 a little richer. All fine and dandy... but how do you get at the mixture screws with everything hooked back together? Do I need a right angle flat head screw driver? There isn't much room in there! I can't figure it out. -nick

 

[dirtyfingers]

Motion Pro has them. This one is an expensive model, but variations can be found cheaper. Small screwdrivers can be made out of ground down hex keys and manipulated with your fingers tips, if you have the dexterity.

 

[SqDancerLynn1]

You need to do it with the tank off !! Either prop the tank up & use a longer hose or a small aux tank

 

[schlyme]

syncing carbs you shouldn't be messing with the mixture. for syncing the carbs you adjust the idle speed. #2 is usually the master, so you sync #3 or 1, then the other(#1 or 3). finally #4. at least that the way i just did my 81 gs1100. worked great.oh and i just used a regular screw driver for adjusting idle speeds. for adjusting idle mix i used i lil screw driver.

 

[Nessism]

On CV equiped bikes you adjust 2-3 first and get them the same. After that, you adjust 1/4 (doesn't matter which order) to match.

On bikes that have a cross-over pipe, 1-4 are supposed to be adjusted higher than 2-3 by a smig. Check the manual for more details.

All this assumes you have a sync tool. And none of this should be confused with adjusting the mixture screws. To do that, set them to 3 - 3.5 turns on the 550 and then tweak them for the highest idle speed.

Hope this helps and good luck.

 

[Clumzi]

Ness is always on point with my dumbass . Yes, I was talking about mixture screws. I set them to 3.5 turns out and need to fine tune from there. So the mixture screws, how to I get at them? -nick

 

[Steve]

You need to raise the gas tank high enough to be able to see the screws. I use a driver with a blade that is 8" long, making it easy to stick it down from above the frame on the inner two cylinders.

Don't forget that you will need to sync your carbs, too. That takes another set of tools.

.

 

[shadowfist]

Don't forget that you will need to sync your carbs, too. That takes another set of tools.

.

speaking of carb syncing tools... has anyone made a great DIY carb sync tool? for a 4 cylander bike? i have read up a bunch on how to make diy carb synch tool, but they all seem to think that "motorcycle= 2 cylander"... so, anyone made a diy carb sync tool for a '4 banger'?

 

[Riding Again]

See these threads:

http://www.thegsresources.com/_forum/showthread.php?t=130478

http://www.thegsresources.com/_forum/showthread.php?t=131862

http://www.thegsresources.com/_forum/showthread.php?t=133072

http://www.thegsresources.com/_forum/showthread.php?t=132173

They give you info on building and sync'ing.

 

[Steve]

speaking of carb syncing tools... has anyone made a great DIY carb sync tool? for a 4 cylander bike? ...

See these threads:

http://www.thegsresources.com/_forum/showthread.php?t=130478

http://www.thegsresources.com/_forum/showthread.php?t=131862

http://www.thegsresources.com/_forum/showthread.php?t=133072

http://www.thegsresources.com/_forum/showthread.php?t=132173

They give you info on building and sync'ing.

There have actually been several other attempts reported in this forum, with varying levels of success. I saw one personally where the person had used a single gauge and a 4-way manifold to select the cylinder. He was happy with his results. I checked his results with my mercury gauge and found them close enough to not worry about changing. He admitted that he did not change very much, so his bench sync must have been incredibly close. After watching me do another bike that was not nearly so close, he admitted that his manifold and single gauge method might not work so well in that case.

Basically, for all the time and effort you are going to put into researching materials and parts, then multiple trips to supply stores (or shipping charges if you order from that Interweb thingy), you may as well just get one that works. General concensus is that the Morgan Carbtune Pro is the best. The US Dollar has gotten a bit stronger against the British Pound, so the 65 Pound cost of the gauge, case and shipping is now $95.57. If that is just a little too much money, the MotionPro is $84.37 from Z1 Enterprises. Shipping to my house (yours may be different) is $7.78 for UPS Ground or $6.16 for USPS, making the total $90.53 or $92.15. Personally the three or four dollar difference makes it a no-brainer, go for the Morgan, get something that won't leak if you turn it upside down. They are both accurate and easy enough to use, so go for the convenience.

.

 

[Guest]

For what it's worth, I own both the Motion-Pro & Morgan Carbtune Pro units; as Steve indicated, the Morgan Carbtune Pro is the better choice.

Although both units do the job, the MCP offers a few advantages:

- Uses solid rods in lieu of fluid (mercury substitute), so it doesn't leak or need refilling.

- Doesn't inadvertently suck fluid into the engine (when the bench sync is WAY off...)

- Doesn't require calibration every time it's used, it comes calibrated.

- Easier to see the background "lines" (graduations) when comparing the vac levels for all carbs.
​

I'm not affiliated with Morgan, nor receive any benefit from them - just giving you my .02 as a member that's used both.

Also, a well sync'ed set of carbs will really make your bike "sing" !!

Good luck,

Mike

 

[Clumzi]

Crap. I have to do it again. Big old n00b question time...

What is the difference between syncing the carbs and adjusting the mixture screws? I thought they were essentially the same thing.

I've seen the carb sync tool, the mercury kind with the four hoses, but I'd gotten the impression that that just did a better, more fine tuned job of what adjusting the mixture screws by ear does. So when you adjust the carbs via a sync job, what is being adjusted? Luckily, I think I have free to cheap access to a carb syncing tool but I didn't realize what it was all about. The friend of mine who has one just took a look at my bike and after a cursory look didn't see how or where to hook up the sync tool. So that is another question... where are the (what do you call them...) vacuum inlets(?) for the carb syncing tool? -nick

 

[Guest]

What is the difference between syncing the carbs and adjusting the mixture screws? I thought they were essentially the same thing.

Sync'ing the carbs equalizes the amount of vacuum each carb pulls. The result is the amount of "atomized fuel" pulled into each carb body is the same, & the slides will all operate at the same rate together...

Adjusting the mixture screws alters the air/fuel ratio (which is being pulled by vacuum into the each carb body).

The friend of mine who has one just took a look at my bike and after a cursory look didn't see how or where to hook up the sync tool. So that is another question... where are the (what do you call them...) vacuum inlets(?) for the carb syncing tool? -nick

Under each of the 4 intake boots, there's a screw & washer (don't lose the washer!). Remove the screw & thread in an adapter tube - this will allow you to connect the rubber hose to each carb.

Carbs 1,2 & 4 all have a butterfy adjustment screw (these are the same screws you did a bench sync with). You essentially adjust them all to be equal with #3. Actually, 2 & 3 should be the same and slightly less then 1 & 4.

Search the site for carb sync info - I believe there's lots of info with pics.

Good luck,

mike

 

[Steve]

Just to say what hikermikem said, but in a different way:

You have four carburetors in a row, but the linkage between them is not straight through. They need to be synchronized so they all open the same amount at the same time. Each cylinder is basically drawing the same amount of air past the restriction that the throttle blades impose. If the throttle for that carb is open just a bit more, there won't be as much vacuum. Actually measuring the throttle opening is rather difficult, but it is relatively easy to simply measure the amount of vacuum and use the adjusters between the carbs to acheive relatively equal amounts.

Now that you have equal amounts of air going to each cylinder, the engine will be powered somewhat equally by all the cylinders, making it run much smoother. Now you can tweak your mixture screws to adjust the amount of gas that gets in there at idle and very low throttle openings. Since you are varying the amount of gas that is mixing with the air, you are playing with the air/fuel ratio. At some point in the adjustment, you will get it real close to a mixture that it really likes and it will run just a bit better, meaning faster. If it runs too much faster, you will have to re-adjust the master idle control and continue. When you are done, you will think you have a new machine.

The sync adjustment should only have to be done after the carbs have been apart, but it does not hurt anything to check them every tune-up. The mixture, likewise, should only have to be set when things have been apart, but some things wear, other things move around, so it's good to check that, too. Personally, I like to check the sync, then, while the gauges are still attached, check the mixture. Then I check the gauges to make sure any mixture changes didn't affect the sync, then take the gauges off.

.

 

[Tazman001]

Morgan Carbtune

Morgan Carbtune

General concensus is that the Morgan Carbtune Pro is the best. The US Dollar has gotten a bit stronger against the British Pound, so the 65 Pound cost of the gauge, case and shipping is now $95.57. If that is just a little too much money, the MotionPro is $84.37 from Z1 Enterprises. Shipping to my house (yours may be different) is $7.78 for UPS Ground or $6.16 for USPS, making the total $90.53 or $92.15.

Just ordered mine, ?58 at today's exchange rate came to $85.43. Didn't buy the tool pouch. Can't wait to see them. I'll be sync'n my 750 & 1150 w/'em.