sync yer carbs!

[1KPerDay]

Took me 22K to talk myself into doing it on the GPz... but check out how off they were.

My setup: ran a hose from a gas can to the fuel line; worked loverly.


First reading before adjustment. Check out #1 cylinder.  


After synchronizing #1 and #2...



After synchronizing 1&2 with 3&4...

Crap, that one didn't turn out at all. You'll just have to trust me.

whole process took less than a minute. AFTER hooking up all the hoses and crap. Which took like an hour.

[bizarro]

So where are Beeker and Bunson Honeydew?

[1KPerDay]

 

[MK96xj]

Nice noticeable difference after adjusting?

[Andrew]

 

[chornbe]

Curious to see how much smoother it is at 3-4K RPM. A lot of times, the idle sync is a good reference point, then further fine tuning at various throttle positions and RPMs is icing on the cake. But that far out... the difference has to be immediately noticeable, huh?

[Thor]

I sync my carbs at least once a year, sometimes more.  Once an engine builder told me that an out of sync engine greatly reduces engine life, I've made sure to do it religiously.

127,000 miles on a CB900 with no engine rebuild, but carb sync at least once a year.  I sold the bike and it is still going as far as I know.

My understanding is that an out of sync carb bank creates additional stress on the crank and valve train.  I don't really know, but the improved performance and reduced vibrations is worth it to me.

[1KPerDay]

Curious to see how much smoother it is at 3-4K RPM. A lot of times, the idle sync is a good reference point, then further fine tuning at various throttle positions and RPMs is icing on the cake. But that far out... the difference has to be immediately noticeable, huh?

Dunno... the GPz is always very smooth. I've only put on about 160 commuting miles since but I guess it's smoother, it sounds good, but I also got all the shims at the loose end of spec and replaced the plugs, and put in fresh synth oil and filter. Now for the fork rebuild.

[MadMax96]

I have that same sync tool and it works great - no need to spend any more unless you really want to.

The first time I sync'd the carbs on my Bandit it was a huge difference.  Right as I made the final adjustment to the two pairs, you could HEAR it suddenly smooth out - I was shocked.  I've done the adjustment at least 2 or 3 more times since I've had the bike and it's never been as out of whack as it initially was.

The valves are about due for adjustment - so I'll probably do the sync then since I'll already have the tank off.

[rgbeard]

I just used that same sync tool on the Trophy.  (borrowed the tool from a friend).  It was outta sync, not as much as yours, but still significant.  

I have noticed a little smoother running.  My prior bike was a Thunderbird, and it was outta wack much like yours on it's first re-sync.

[MK96xj]

How about a link for the sync tool?

I will need to do this soon as well.

[MadMax96]

That one is the Motion Pro Economy Carb tuner I'm pretty sure...

This is the first link I found with it - you might be able to do better on the price if you search around:

http://www.onlineparts.com/Motion+Pro+Economy+Carb+Tuner+%5BP520%5D.html

[Yankee Dog]

How about a shot of the carb tuner (manometer).  I think that is a DIY waiting to happen.  

Yankee Dog

[1KPerDay]

Yep it's the motion pro one. Get it quick... pretty soon quicksilver will be bannnnnnnnnned and your home declared a disaster area by the EPA.

[Frantik1]

Yep it's the motion pro one. Get it quick... pretty soon quicksilver will be bannnnnnnnnned and your home declared a disaster area by the EPA.

It may already be hard to find one with merc in it, and even harder to get it shipped. I bought a Motion Pro about a month or so ago that is filled with what looks to be Scope mouthwash.

[Tyrroneous]

I bought the same carb synch tool a few years ago.  It worked really well for the first while.  I kept in the box it came in and left the mercury in the little reservoir at the bottom of the gauge.  I guess, overtime, the mercury reacted with the plastic because when I got the tool out to use it a couple of months ago, the reservoir broke at the slightest bump and spilled my precious heavy metal all over the garage.    So I did what any self respecting grease monkey would do...I swept it out of my garage and down to the gutter so that the neighborhood dogs could lick it up.  

I think I'll try and fab up my own using the Motion Pro frame and some substance other than mercury.  Anybody have any ideas what to use?  




Oh yeah, back to 1K's original post...on my Seca, its amazing how much smoother the bike idles once the carbs are synched.  I can actually get 'em pretty close just going by the sound.  

[chornbe]

I bought the same carb synch tool a few years ago.  It worked really well for the first while.  I kept in the box it came in and left the mercury in the little reservoir at the bottom of the gauge.  I guess, overtime, the mercury reacted with the plastic because when I got the tool out to use it a couple of months ago, the reservoir broke at the slightest bump and spilled my precious heavy metal all over the garage.    So I did what any self respecting grease monkey would do...I swept it out of my garage and down to the gutter so that the neighborhood dogs could lick it up.  

I think I'll try and fab up my own using the Motion Pro frame and some substance other than mercury.  Anybody have any ideas what to use?  

Add a few more feet of tubing and use ATF fluid.

[tomek]

I don`t know man,that cylinder# 1 looks awful ( before pic),you sure the idle was smooth before adjustment ?

How is valve clearance,how many miles from last check up? Valves out of wack will screw your vacum readings.

[HipGnosis]

I use to have a KZ650(SR) that eventually had a GPz750 engine in it.

I use to sync the carbs w/ 2 allen wrenches.

Take off the air filters (K&N individuals)
Lay the smaller allen wrench in the bottom of the carb and screw in the idle adjuster until the allen wrench would just slide under the carb slide.
Adjust other carbs so small allen wrench would slide in, and next size allen wrench wouldn't.
Return idle.
Return air filters.

So easy I did ea time I cleaned the filters.

She'd start w/ just a stab of the starter button...

[chornbe]

That's sync'ing throttle plates. That is not sync'ing air flow (which is far, far more important).

[denydog]

Lay the smaller allen wrench in the bottom of the carb and screw in the idle adjuster until the allen wrench would just slide under the carb slide.
Adjust other carbs so small allen wrench would slide in, and next size allen wrench wouldn't.

Using a small diameter wire or other spacer to even up the throttle plates is often called bench sync'ing, since it's often done on the bench after carb disassembly/reassembly.  It gets you to a starting point, and will allow the engine to run, but is no substitute for proper air flow synchronization.  All sync'ing methods consist of adjusting the throttle plates, but measuring airflow is the accurate way, because there are other factors involved besides the throttle plates, plus the idle screw adjustments are very small, and at least on my bike, are interelated due to the linkage arrangement.  I.E., carb #2 and #4 are sync'ed to #3 and #1 is sync'ed to #2.  

[Fudge]

I just sync'd my FJ over the weekend also.  It's handy having my recently purchased throttle meister so I can lock the throttle at a steady RPM (3K for me) and balance the carbs.

[chornbe]

Sync'ing them on a Dyno with the engine in top gear, under load, running at cruising speed is the top-notch way to do it. Do the idle sync to get you in the ballpark, then cruising-speed sync to smooth it further.

[stk0308]

I keep meaning to buy carb sticks and do my Triumph.  I'd need to fab up some fuel line extensions though.  Darn FI bikes anyway    I have done it once myself and it did seem to make some difference in smoothness.

[Fudge]

Sync'ing them on a Dyno with the engine in top gear, under load, running at cruising speed is the top-notch way to do it. Do the idle sync to get you in the ballpark, then cruising-speed sync to smooth it further.

Note to self, buy dyno....

[chornbe]

Note to self, buy dyno....

Hey, sue me. I didn't say it was a PERFECT plan

[Walker]

I bought the same carb synch tool a few years ago.  It worked really well for the first while.  I kept in the box it came in and left the mercury in the little reservoir at the bottom of the gauge.  I guess, overtime, the mercury reacted with the plastic because when I got the tool out to use it a couple of months ago, the reservoir broke at the slightest bump and spilled my precious heavy metal all over the garage.    So I did what any self respecting grease monkey would do...I swept it out of my garage and down to the gutter so that the neighborhood dogs could lick it up.  

I think I'll try and fab up my own using the Motion Pro frame and some substance other than mercury.  Anybody have any ideas what to use?  

Oh yeah, back to 1K's original post...on my Seca, its amazing how much smoother the bike idles once the carbs are synched.  I can actually get 'em pretty close just going by the sound.  

The mercury contracted and expanded with temperature changes.  Add in the density, and the vapor pressure, and it cracked the plastic.  I had the same thing happen to mine, except I was able to extract the mercury before it spilled.  I used it and some parrafin wax to fill some custom hollowpoints for home defense (No lead poisoning for people trying to break into my house, I don't screw around!)

Anyway, anyone who wants to make a really cheap synch tool:  Get a yard stick, some zip ties, a wire coat hanger, and about 12 feet of clear plastic tubing.  Carefully staple the tubing to the face of the yard stick, running down one length of the stick and up the other length with a gentle U bend at the bottom (or use zip ties, whatever works and you have at hand).  Fill the tubing with ATF so you have about a 2 foot tall column of ATF on each side, use the wire hanger to create a hook, and 'viola!  You've now made yourself a very inexpensive and durable manometer.  Just hook up the tubes to the carbs you want to balance (1&2, 3&4, 1&4 OR 2&3), hang the manometer next to your bike, and levalize the oil column heights with it running.  Mine cost me nothing, I already had the tubing, yardstick, zipties, and ATF in my garage.  The only challenging part was getting the ATF into the tube.  The way I finally did it was to stick one end into the bottle of ATF and carefully suck on the other end.