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I got around to pulling my carbs off today to see what jetting was in the bike. It's a 1992 usdm oil cooled 750. Has a vance hines muffler, I'm actually not sure if it has a full exhaust or not as I don't know what the difference might be. It's black and has some rust showing. I'd guess stock? There is no baffling in the muffler that I can tell, and it was setup to run the k&n pod filters straight off the carb, no airbox.

The guy said it didnt like to idle that good, and the old filters were beyond useable. Too damn hard to get back on.

I have since picked up some new k&n filters for the bike, and figured, It was time to pull the carbs, and check out the jets.

This is what I am looking at.


The main on the right carb has a 122 main, and a 32.5 pilot.

Now the pilot jet has a mikuni marking, but I didnt see anything on the main.

If any carb guru here can recommend the proper jetting for my setup. I would greatly appreciate it.
 

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I got around to pulling my carbs off today to see what jetting was in the bike. It's a 1992 usdm oil cooled 750. Has a vance hines muffler, I'm actually not sure if it has a full exhaust or not as I don't know what the difference might be. It's black and has some rust showing. I'd guess stock? There is no baffling in the muffler that I can tell, and it was setup to run the k&n pod filters straight off the carb, no airbox.

The guy said it didnt like to idle that good, and the old filters were beyond useable. Too damn hard to get back on.

I have since picked up some new k&n filters for the bike, and figured, It was time to pull the carbs, and check out the jets.

This is what I am looking at.


The main on the right carb has a 122 main, and a 32.5 pilot.

Now the pilot jet has a mikuni marking, but I didnt see anything on the main.

If any carb guru here can recommend the proper jetting for my setup. I would greatly appreciate it.
it will vary greatly depending on engine health, elevation, ambient temperature, etc. you're going to be pulling the carbs multiple times trying to get them dialed in correctly. its all trail-and-error, running a temporary AFR gauge would greatly help otherwise you'll also be spending time on the dyno and doing spark plug readings for WOT runs. read over the "understanding carbs" sticky and look at your factory settings and go from there. you need to get a baseline to see how you are currently running across the rev range then go from there. If you have perfect compression across all 4 cylinders and the only mods are a slip-on and pod filters, then from STOCK jetting richen your main circuit by 2 or 3 sizes, raise your jet needles another clip position, and find the right mixture screw settings for best throttle response and idle, typically you'd want to back them out another turn
 

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Discussion Starter #4
it will vary greatly depending on engine health, elevation, ambient temperature, etc. you're going to be pulling the carbs multiple times trying to get them dialed in correctly. its all trail-and-error, running a temporary AFR gauge would greatly help otherwise you'll also be spending time on the dyno and doing spark plug readings for WOT runs. read over the "understanding carbs" sticky and look at your factory settings and go from there. you need to get a baseline to see how you are currently running across the rev range then go from there. If you have perfect compression across all 4 cylinders and the only mods are a slip-on and pod filters, then from STOCK jetting richen your main circuit by 2 or 3 sizes, raise your jet needles another clip position, and find the right mixture screw settings for best throttle response and idle, typically you'd want to back them out another turn
Thanks, I took a look at the guide, and it's a bit confusing. According to that I am using uk carb jetting, stock pilots, and 2 sizes up on the mains. I havent checked the needle position yet. I just got my new filters in today. I'll toss it all back on and play with the mixture screws first I suppose.
 

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Well, I got around to fiddling with the carburetors today. Putting the filters back on it started up good, but was high idling and would slowly rev down.

I decided maybe it was a synching issue, so I pulled the tank off and got setup for synching. During the process I decided to tighten the carb clamps a tad more. I then noticed after startup my idle was super high. It ended up being the clamp screw was pushing on the throttle return. I moved the clamps a bit, and all of a sudden my bike actually idles lol. I set it to about 1100, then started synching. They were definitely off a bit. both 1 and 2 and 3 and 4, but 2 and 3 were actually pretty close. I got them pretty much dead nuts. The bike idles pretty damn good now. I used the motion pro liquid one, just synched 2 at a time.

My pilot screws were out 5 flats. I ended up resetting them to about 3 1/8 flats out. I think I can fiddle with them a tad more, but it doesnt seem too bad. Here is a video if I can post a link, it does seem to hang for a real quick second around 1400 then drops, so I maybe I need a tad more fuel.

add a w as I am still under post count.
ww.facebook.com/shaun.stafford.54/videos/10218530624638285/
 
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