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Discussion Starter · #1 ·
Hi all, just got finishing some carb work on meez 96 750. Replaced the needle valves and seats. Noticed the needle valve were a little bit longer than stock. Adjustted as close to stock settings. Bike seems to run but kinda boggish and doesn't respond as quick (ie, on highway at 7000 rpm and twist the wrist. it accelerates but just not as fast as before). Dyno jet kit stage 1, Yoshi RS3 slip on. The tip of exhaust is sooty. I have the 132's and 130 mains as Dyno jet says, but should I go to 128 and 130 instead?? or reset my float height? Does float height play more of a role with a rich mixture here?

Thanks

RZR
 

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If you're asking about float height, it's probably a Factory kit.

I actually prefer the Factory kit, but the reason for the distinction is the Dynojet kits use Dynojet main jets which are a little different in their numbering system.

The float height affects the low end of the rpm range more than the top end.

The float height should be set every time the carbs come apart. Especially if you changed the needle, seat, or float. It's a little tricky the first time because motorcycle needles have 2 positions. The first contact and bottomed. The float height is defined at the point of first contact. The pointy end of a digital or dial caliper makes a pretty good float gauge after it's set to the float height and locked down. The point of first contact is found with the float bowl gasket surface at 45 degrees from the bench. The service manual is useful for defining the conventions, but really isn't intended to be a primer for guys on their first time through this.

To put a fine point on it, attach a piece of clear tubing to each bowl drain and run it up past the carb entrance with the airbox off. Start the motor with the tank up and open the drains. The level of the fuel in the tubing is the net effect of the float height and needle condition. This check isn't done very often, but if you have something that just won't idle it can tell you why.

After you're reasonably sure the fuel level is correct, the real off idle adjustment is on the mixture screw. Less than 1 turn, use a smaller pilot jet. More than 3 turns, use a larger pilot jet. Sometimes you wind up in between, and then the off idle response should be the referee of which way to go. I use a cheapie CO meter ($160) to set the mixture screws (2-3% CO).

I've had best results with the 130/128 mains, but at 7000 rpm you're still on the needle. Did you use the thick nylon stock spacer on the new needles?

I use the same cheapie CO meter for the first guess on the needle height. Run the motor up to half of redline in neutral and check the mixture. You're looking for 4-7% CO. One clip positon will be ~4%, and the little washers about half that.

I get the mixture and needle clip close, and use the dyno to determine the main jet. Then the needle height and finally the mixture screw/pilot jet. I set the needle clip by throttle response, not the dyno output.

A CV carb divides up the carb circuits by rpm, airflow actually. A flatslide divides the carb circuits up by throttle position. Most of the tuning guides you see are for flatslides. Any dirt bike experience you may have is with flatslide type carbs. For a 750 SRAD, figure up to 4000 rpm is the mixture screw / pilot jet, up to 8000 rpm is the clip positon, and 8000 rpm up is the main jet.

Good luck. After you get it right you won't tolerate anything else for throttle response. The fourth time you have the carbs apart you'll understand why FI and Power Commanders are so popular.
 

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Discussion Starter · #3 ·
Thanks, i'll try some of your suggestions. Let's you know in a couple days. I think I will switch to the 130/128's and readjust float height. Thanks again for all your help.

Rzr
 
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