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Discussion Starter · #1 · (Edited)
Here's a litte pictorial how-to on throttle body synchronization. Today was the first time I ever did this so I'd appreciate any comments from those in the know, especially on the last part that deals with the throttle lever gap.

Synchronizing the throttle bodies (TB) insures that the flow rate of air into each cylinder is identical. A number of undesirable symptoms occur if the TBs are not synchronized. These include a rough running motor with more vibration than normal, also power and gas mileage will be reduced.

Each TB has a small port at its base which allows measurement of the air pressure inside the TB. This pressure will be less than ambient due to the opening of the intake valves during the piston’s down stroke. On the SV1000 there is a single TB synchronization screw which simultaneously changes the position of butterfly valves in both TBs. When the air pressure is the same the TBs are synchronized. Static vacuum measuring devices such as a mercury manometer or air flow measuring devices like rotometers (ball in tapered tube) may be used.

The first step is locating the small ports at the base of the TBs. Both are visable when looking through the large triangle opening in the frame on the right side of the bike.

Note: This statement is incorrect and will be appropriately edited in the final version of the How-To.
 

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Discussion Starter · #2 ·
Because the ports are rather inaccessible (especially the front) I followed the advice of some forum members who installed permanent extensions. The diameter of the base of the ports is 4 mm. I purchased some 5/32 inch (3.97 mm) ID vacuum tubing from an auto parts store. I could not find a hose clamp small enough for this application locally so I ordered them online from http://fittingsandmore.com/. For the plugs I used 8-32 X ½ inch machine screws. I used a small amount of high temperature silicone sealer on the base of the ports and some vacuum grease on the screws.

I took the air box off when I installed the extensions. Its not necessary to do this but I wanted to have a good look around and it does make the job a bit easier by providing increased light and clearance. There’s a hose and a couple electrical connectors that need to be removed from the air box before it is removed from the TBs. Finally the air box is removed by loosening the two ring clamps that secure it to the top of the TBs.

Note: My bike has Chewy’s pair removal mod. If you still have the PAIR system on there will be additional items to remove from the air box before it can be removed from the bike.
 

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Discussion Starter · #3 · (Edited)
The SV manual states that the TBs should be synchronized with the air box removed. I’d rather synchronize them with the bike set up as close as possible to the way its ridden. So I made the vacuum measurements with the air box and air filter back on and the gas tank lowered.

First I warmed up the bike to normal operating temp then I took out the 8-32 screw plugs from the TB port extensions. Then I connected a multi-tube mercury manometer to the extensions using an accessory for carburetors that came with the manometer. I then started up the bike without touching the throttle. I was surprised to see how far off my bike was. I made the adjustments to the TB synchronization screw with the tank up then put it down to make the readings. The height of the mercury columns bounce around a bit (maybe about 3 % relative) so I mentally averaged the readings for about 15 secs. After a few tweeks to the balancing screw the Hg columns evened out. The idle speed changes when the TB synchronization screw is adjusted so after each tweek I reset the idle to 1200 rpms.
 

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Discussion Starter · #4 · (Edited)
After the adjustment was completed I removed the manometer and replaced the plugs in the extensions. Then I attached the extensions to the water hose that connects the radiator to the overflow tank with zip ties. After the below pic was taken I pushed the extensions down a bit so they stayed out of sight.

My apologies for the poor focus on the manometer pics. I didn’t download to the PC right after taking them. I thought they looked ok on the 2 “ LDC display on the digicam. By the time I saw their poor quality the job was done. Since the height of the Hg columns is clearly discernable in the pics I didn’t bother to retake them.
 

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Discussion Starter · #5 ·
Need help here

I need some help with this one. The SV manual gives a clearance spec for the throttle lever gap. It’s tough to measure due to tight clearances around the mechanism. I had to cut a small piece off the proper size feeler gauge and hold it with a 90 degree hemostat. They also caution not to adjust the position of a set screw which by inspection looks like the easiest way to adjust this clearance. It was not obvious to me how one makes this adjustment and the manual gives no clue.

So can anyone out there help me with this last part and explain how to adjust the throttle lever gap without use of the set screw shown in the pic?
 

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I'm guessing here, but it sounds like the warning not to adjust the screw is one of those warnings that attempt to dissuade folks from adjusting their whatever, due to the smog laws. I bet they adjust the screw at the factory! I dunno - maybe I'm full of it, but I bet that's it. I'm sure there's a Suziki guru here who will know.
 

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"..there is a single TB synchronization screw which simultaneously changes the position of butterfly valves in both TBs."
The sync adjust screw adjusts only 1 of the primary butterflys (butterflies?) relative to the other (the linkage normally moves both together). My understanding of TB sync is that the vacuum in a throttle body is an indication of the load on the cylinder - less vacuum means the cylinder is working harder then the other. When balanced, both cylinders are putting out the same power - giving the least vibration. On old airhead BMWs, throttle balance could be done by alternately shorting the cylinders spark plug to ground and noting the RPM the engine would drop to - and balancing the rpm drop. (You could also listen to the transmission gear rattle at idle in neutral and balance for minimum rattle).
I think the butterfly stop screw is not to be adjusted as it sets the fully closed position - the plate sticks in the body if it is closed too tight.
 

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excellent demonstration man, so how far off were u?
non-sync TB will contribute poor gas milage? I wonder if I have to have mine set.
 

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"...explain how to adjust the throttle lever gap without use of the set screw shown in the pic?"
I don't think it is an adjustment - the sync adjustment changes the front throttle valve position relative to the rear - but the rear should be at that position during the adjustment (set by idle setting?). The procedure says: "Make sure that the throttle lever should have a gap A (between the throttle lever and throttle lever stopper screw) during synchronization." (italics addded by me). If the gap is off by a lot, possibly some other fault is present causing one cylinder to be far off from the other? (leaking intake, plugged injector...)

(Disclaimer: Don't base anything on something I post - it's just my opinion!)
 

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Found the reference I mentioned early regarding the throttle stop screws - from a BMW R1100 TB sync procedure:
"Resist all temptation to adjust the throttle stop screws on the bottom side of the throttle bodies. If one were to mess with these and accidentally back them out too far, the throttle butterfly will close too much, and when the whole works cools down, the butterfly will jam in the throttle body......in other words, JUST DON'T DO IT!"
 

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Discussion Starter · #13 ·
sniderj said:
"..there is a single TB synchronization screw which simultaneously changes the position of butterfly valves in both TBs."
The sync adjust screw adjusts only 1 of the primary butterflys (butterflies?) relative to the other (the linkage normally moves both together). My understanding of TB sync is that the vacuum in a throttle body is an indication of the load on the cylinder - less vacuum means the cylinder is working harder then the other. When balanced, both cylinders are putting out the same power - giving the least vibration. On old airhead BMWs, throttle balance could be done by alternately shorting the cylinders spark plug to ground and noting the RPM the engine would drop to - and balancing the rpm drop. (You could also listen to the transmission gear rattle at idle in neutral and balance for minimum rattle).
I think the butterfly stop screw is not to be adjusted as it sets the fully closed position - the plate sticks in the body if it is closed too tight.
This is interesting, I assumed the sync screw changed both butterfly valves because when I turned the screw one Hg column got bigger while the other got smaller.
 

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It is amazing how much less vibration that I had when I did this. I did mine at 3000 miles and should have did it at 500 miles, that is how big the difference is. If you have not done this, you are missing out. I do have a tool (homemade) if any of the Des Moines area guys want to use it.

TIP: DO NOT adjust it when the cooling fan is on(unless your bike always runs hot). Let the fan kick off and then adjust it(my fan rarely kick on when riding). If you adjust it for normal temps(190-200) it will be off slightly at higher temps(210-220). And vise versa.
 

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"This is interesting, I assumed the sync screw changed both butterfly valves because when I turned the screw one Hg column got bigger while the other got smaller."

AFAIK, the idle adjustment screw on the left side sets the front primary butterfly valve position, the rod on the right side connects the front to the rear butterfly, and the sync adjust screw adjusts the rear cylinder's idle position (and thus balance). If the sync adjust is turned so the rear cylinder increases it's throttle opening (it's vacuum goes down), the RPM will increase slightly, and now the front cylinder is turning faster with the same previous throttle opening - so it's vacuum reading will go up (less load). The opposite will occur if the rear butterfly is closed relative to the front. I think....
 

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Excellent job Mark!:supsmiley: No doubt this will help many people to do this themselves. I know it would have helped me when I did my first one. This will make an EXCELLENT addition to the SuzukiSV1000 site.
 

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Discussion Starter · #18 ·
gunluvS14 said:
excellent demonstration man, so how far off were u?
non-sync TB will contribute poor gas milage? I wonder if I have to have mine set.
You can see how far off my TBs were in the pics of the mecury manometer. The pic with the two different height colums of mercury shows the imbalance.
 

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Bayouboy said:
This is interesting, I assumed the sync screw changed both butterfly valves because when I turned the screw one Hg column got bigger while the other got smaller.
One cylinder is the base, the throttle cables lead to that one and the tickover screw adjusts it's rest opening position, the balance screw adjusts the position of the other butterfly relative to that, the vacuum changes on both gauges as you adjust the balance screw because as either cylinder's butterfly opens or closes it does more or less work which alters the load on the other cylinder too.
I always adjust the balance with the tickover turned up a bit, say about 1600-1700 rpm, this evens out the vacuum pulses a bit and seems to allow slightly more accurate balancing.

If you're going to set the TPS do it before balancing the TBs, I can't see why but it does sometimes alter balance a bit.
 
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