rich/lean carbs on off on off ahghhh

[Steve]

OK, I'll take a stab at this. 8-[

First, you were tossing jet numbers out there and mentioning what changes were made. You finally told us (after being prompted) what bike we are talking about. My question all along has been, "What was the starting point?"

Let's get down to basics. I looked in the carb sticky at the top of this forum and found this information in post #61:

GS 750
1980- 81
LT/LX/EX Model

Carb: BS32SS (4 separate carbs)
bore size: 32mm (1.26)
id no: 45400
idle r/min: 1050 +/- 100 r/min
fuel level: 5mm +/- 0.5 (0.20 +/- 0.02)
float height: 22.4mm +/- 1.0 (0.88 +/- 0.04)
Main jet: 112.5
Main Air jet: 1.7
jet needle: 5C28
Needle Jet: Y-4
Pilot Jet: 42.5
By-pass: 0.8, 0.8, 0.8
Pilot Outlet: 0.7
Valve seat: 2.0
Starter jet: 50
Pilot Screw: Preset
Pilot air jet: 170
throttle cable play: 0.5-1.0 (0.02-0.04)


Here is the list again, with some of your changes highlighted:
Carb: BS32SS (4 separate carbs)
bore size: 32mm (1.26)
id no: 45400
idle r/min: 1050 +/- 100 r/min
fuel level: 5mm +/- 0.5 (0.20 +/- 0.02)
float height: 22.4mm +/- 1.0 (0.88 +/- 0.04) You said .095", hopefully you meant 0.95".
Main jet: 112.5 122.5 / 120 / 112.5
Main Air jet: 1.7
jet needle: 5C28
Needle Jet: Y-4
Pilot Jet: 42.5 42.5 / 55 / 60
By-pass: 0.8, 0.8, 0.8
Pilot Outlet: 0.7
Valve seat: 2.0
Starter jet: 50
Pilot Screw: Preset still preset :shock:
Pilot air jet: 170
throttle cable play: 0.5-1.0 (0.02-0.04)


You have pods and a pipe installed, so there will be changes necessary.

Stock main jets are 112.5, so the 122.5 mains would be a good starting point.

Stock pilots are 42.5. I am not sure if you would need to go beyond a 45, so the 55 and 60 would be way too much.

Your mixture screws are still sealed? Shame on you. That would be the first thing to change, but it won't be enough to compensate for your pods and pipe.

Your pods do not appear to be K&N, but I can't agree with the concept of not oiling them. It is the oil that catches the dirt, not the paper. The paper just keeps the oil in place. Start fresh. Clean all four pods, let them dry. Spray a very light film of oil on the filter, let it wick into place. Spray a little more oil if necessary, but do NOT over-oil. The concept is to moisten the filter, not to saturate and squeeze out the excess.

You said your floats were set to .095". Hopefully you meant 0.95". The 0.95" setting is leaner than the spec of 0.88 +/- .04". Get your float level closer to 0.88" before changing anything else. Having the float level too low will really mess up the rest of the jetting. Make sure that the levels are as close as possible for all four carbs.

Suggestions:
1. Adjust your valves. This is the best starting point, and it probably needs to be done, anyway.
2. Clean and lightly oil the pods.
3. 122.5 mains, 42.5 or 45 pilots.
4. Float level set to 0.88".
5. Set mixture screws to 2 full turns out from lightly seated.
6. Fresh spark plugs
7. Warm it up and do your plug chops.
8. Let us know how it's running.

.

 

[shack426]

Hi thanks for the reply. the cyl. that was wet was number 4 (the one all way or right when sitting on bike) but now it will fire and run and get the pipe hot as the rest. It has a slightly brown ish color to it as the others now have a very clean new look. as for the petcock, yes it is malfunctionion but stuck in the open position. The vacume line to it is pluged off and there is a manual valve installed after the petcock to the carbs. (yeah i know i have to remember to shut it off all the time) but I know its flowing fuel to the carbs though. Thanks. still trying to work through it ahhgghahh.

 

[shack426]

Hi Steve thanks for the imput. Sorry about the bike description (originally in my first few posts) the float level...............ahhhh my cheap manual haynes says 0.95 in. so i need to go to 0.88, thanks for that piece of info. I'll go ahead and pop out the plugs on the air/screws and adjust to your specs. (air screw, mixture screw the same??) the pilots being to big, yeah I see what you mean, it will start but only if I get it to start the first firing or it takes playing with the choke to get it to fire up. Once its fired up though it will start up with no problem. sitting in the garage and reveing it up in the 1/8 to 1/4 throttle range it sounds grreat and has great response. At the mid throttle range is where it stumbles on its face. Do you think I need to do any adjustments to the needles??? since the stumbling seems to be in the needle circute or so I have been told??? but I'll do as you suggested and see where its at. be back soon to update. Thanks for all the help.

 

[shack426]

still banging my head ..update 81 gs750

still banging my head ..update 81 gs750

Help!!!! this is an update of my progress on the 81 gs 750 stumbling on its face syndrome. my other posts tell what I have done to this point. As of today I have cleaned carbs per specs here and put 45 pilots in the bike, it now starts and runs great. It will rev up to 4k sounding beautiful. It has 120 mains in it now but have not been able to get up to throttle region where the mains come into play so not sure if there correct. I have raised the needle one shim from a stock shim of one. Is this enough???? they seem so small and thin I'm not sure if one is enough. I now have a total of 2 shim washers on the needles. When I take it out onto the street it stumbles at 4k, just can't get anything out of it at that point. Whats going on here????? due to the throttle position, I'm around a 1/4 to 1/2 throttle when it acts up and this should be in the needle circut, am I correct????

I raised the needle hight because it was stumbling in the same place prior to the current mods and was advised that it was in the needle circut needing more fuel, is this correct???

some recape: the bike has pods and a VH 4/1. plugs look lean right now. all are firing.

The bike has gone from not starting and running when I first got it (had 112.5 mains and 42.5 pilots), to being to rich and fouling the plugs with(122.5 mains and 60 pilots) to 55 pilots and still hard to start, to whats in her now. 120 mains and 45 pilots with needles having 2 shims.

can a bad petcock be causing some of this?? fuel seems to be flowing just fine.

Its just falling flat on its face at around the 4k mark. 1/4 -- 1/2 throttle area. Thanks for any and all imput.

 

[Guest]

Get a Dynojet stage 3 kit.

 

[shack426]

Yeah your right, I'll get one coming asap.