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Author Topic: suzuki bandit gsf250p help  (Read 754 times)

Offline chamarang

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suzuki bandit gsf250p help
« on: May 29, 2017, 03:38:38 AM »
i need to synchronize my carburetor by feeler gauge any one know about the gauge ex;-(0.7mm,0.8mm) and i saw the manual carburetor service data instruction like this   (By-pass (B.P.)    #1:0.8 #2:0.7 #3:0.8 #4:0.8   <-)

Offline chamarang

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Re: suzuki bandit gsf250p help
« Reply #1 on: June 05, 2017, 01:11:34 PM »
anyone help me

Offline ventYl

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Re: suzuki bandit gsf250p help
« Reply #2 on: June 07, 2017, 02:10:06 PM »
Hi, it is not important (nor even possible) to sync carburretors to any specific vacuum value. Just remove your fuel tank, plug something into petcock vacuum line so you are not losing vacuum on 1st cylinder, attach your gauge of whatever type to respective places (I never was B250 so I don't know if synchro ports are on carb covers or as a part of rubber boot). Start the engine, let it warm up; ideally long enough that cooler fan will turn on, raise idle RPM a little bit (let it idle some 500-1000 RPM higher than standard).

Then do a synchronization of nearby carbs. First set up mating screw on throttle assembly between no. 1 and no. 2 so that vacuum reading on both these carbs is as close as possible. Then do the same for carb no. 3 and 4. This should give you two pairs of carbs (left / right) with same vacuum reading in the pair but potentially different between pairs. Now use the screw between carb no. 2 and no. 3 to equalize vacuum readings of both pairs.

After each touch of adjusting screw hit throttle bar a little bit to release all tension in throttle mechanism introduced by the adjustment attempt. Do it like 1/8 to 1/16 turn, give it a little bit of throttle, turn the screw again, give it a little bit of throttle and so on.

It is also possible that after you equalize left pair vacuum to right pair vacuum you will have to re-adjust some of pairs. I would treat this as absolutely normal. Sometimes the bike requires 2 to three iterations to make setting perfect.

Don't hurry it. Make yourself sure that the setting is as precise as possible. B250 is small-displacement bike so it is quite sensitive to any kind of imbalancement in it's setup. Tight synchronization of carbs will give you more crisp throttle response and more stable idle than poor synchro.

edit: Just to be clear: do not try to reach any specific pressure. It is not possible because intake manifold vacuum is depending on quite a few external factors like absolute air pressure, height above sea-level, overall engine condition, air filter age/condition and type of exhaust.

Generally you can expect something near 0,8 bar (of absolute pressure = 0,2 bar of vacuum) at idle. It will rise to almost 1 bar (=no vacuum) if you accelerate and will fall to 0,5 - 0,6 bar if you close throttle letting engine to decelerate. As RPM will fall vacuum will raise back to about 0,8 at idle.
« Last Edit: June 07, 2017, 02:14:14 PM by ventYl »
Bandit 400 1991 - stock except of swap from GK75B to GK75A

Offline chamarang

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Re: suzuki bandit gsf250p help
« Reply #3 on: June 13, 2017, 08:14:22 AM »
ok.thanks.can you explain the needle clip position and pilot screw returns.

Offline ventYl

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Re: suzuki bandit gsf250p help
« Reply #4 on: June 13, 2017, 08:30:05 AM »
pilot screw is a screw you will find on the bottom of carb body at the end nearer to the cylinder head (not to the airbox). these (one on each carb) are setting fuel mixture richness from fully closed up to about 1/4 - 1/2 opened throttle. if thi screw is fully screwed in no fuel will be able to pass through idle circuit, thus this screw has to be slightly turned out. usually this setting is like 1 + 1/4 to 2 + 3/4 turns out (fully closed and then given amount out) to get proper mixture on idle and in partial load.

needle clip position may be variable (depends on carb construction) or may be not. if it is variable then needle is held in slide typically by using circlips and needle contains several grooves where circlip can be placed. different position of circlip means that needle will be higher or lower when slide is on it's basic (lowest) position which in turn means that smaller or larger hole is opened by the needle. this governs amount of fuel from 1/2 to fully opened throttle.

I never saw 250s carbs thus I don't know if these have adjustable or fixed needles.
Bandit 400 1991 - stock except of swap from GK75B to GK75A

 

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