rich/lean carbs on off on off ahghhh

[Mark M]

could this be in the needles???? or should I just stay with the main jets as the issue??? thanks.

Sort things in the order I posted. Do not go jumping around or you will never get it unless you are lucky.

1) Pilots
2) Needle
3) Mains

So, leave the 120's in and get the lower circuits working first. It sounds like you are reasonably close on the pilots because it starts, idles and rides away OK at low throttle settings. Where are the air screws set? If you are less than 1.0 turn out or over 3.0 turns out, you need to step to the next appropriate size of pilot.

Mark your throttle as I described. Then go road test it and see where you are when the bog hits. It sounds like your needles are set very rich, but the only way to know is test it carefully. If it is the needle circuit, then you need to pull the carbs and lower the needles a full notch and then re-test. Repeat as necessary until it will pull through on to the mains cleanly.

Edit - I forgot to mention that the size of mains you have in has almost no effect on the needle. You can run it with no main jet in at all and it will run on the pilot and onto the needle, then bog as it tries to get onto the mains. So, do not fart with your main jets until you sort the rest out.

Finally, test the mains with the choke. When you think you are good, do some plug chops to confirm.

Mark

[shack426]

Hey thanks a lot!!! my air screws??? Mine are sealed, they have not been drilled out. What do I do about that?? also please explain plug chops?? is this where you reve up the throttle to a point then just turn t he engine off??? and then check the spark plugs?? and testing mains with choke?? I believe you said to get a constant speed and pull in some choke and if rpm increase then its lean and if it bogs badly its rich, boging some is close. am I correct? thanks Mark for the info.

[Mark M]

Hey thanks a lot!!! my air screws??? Mine are sealed, they have not been drilled out. What do I do about that?? also please explain plug chops?? is this where you reve up the throttle to a point then just turn t he engine off??? and then check the spark plugs?? and testing mains with choke?? I believe you said to get a constant speed and pull in some choke and if rpm increase then its lean and if it bogs badly its rich, boging some is close. am I correct? thanks Mark for the info.

1) Air Screws - they should just have a cap glued over them. Drill a small pilot hole in the cap (carefully, don't break through by much or you hit the screw head underneath). Thread in a big self tapping screw and use the screw to pull/pry the cap off.

EDIT - You NEED to get the screws set before you touch your pilots again. You may have had the right pilot all teh time, but simply lacked the fine adjustment needed to make it work perfectly.

2) Plug chop - Put clean or new plugs in. Warm up and ride onto the highway. Try to stay on the mains for a decent distance, a mile or two at least. Before you roll off, hit the kill switch and then coast over to the side of the road. Let it cool for a few minutes, then pull a plug or two (oh yeah, you need a spark plug wrench/socket and ratchet with you) and see what color they are. Be careful not to roll off after the main jet run, or the lower circuits will put deposits over the main jet ones and alter the readings.

3) Testing with the choke - you are correct. This one can be tricky because you are on it pretty hard and then you have to reach over and pull the lever a bit while hanging on at the same time.

I must confess I have not done a true plug chop on my 1100E, I simply got it close with the choke and left the mains a touch on the rich side for safety. It affects nothing in driveability or mileage and I know I will not burn a piston on a cool day in spring or fall. I have buttery smooth bottom end and midrange response and power and it pulls HARD well past the 9500rpm redline. I spent way more effort getting the pilots and needle correct because they affect the part throttle response and mileage which are way more important to me on a street bike.

Mark

[chef1366]

55 pilots are way too big. Look into valves or idle mixture screws.
Didn't read all the posts but did you clean these carbs?

[bwringer]

I'm a little concerned because you have one cylinder that's running rich or wet with gas.

That sounds like you have a bad petcock that is leaking gas through the vacuum diaphragm.

You've cagily kept this information a secret so far, but I bet the rich cylinder is #2 -- IIRC, that's the carb where the vacuum line for the petcock is attached. (The GSR Hive Mind needs DETAILS, dammit!)

This is potentially very VERY VERY damaging, so please get a new petcock -- a new petcock from Suzuki is only about $50, it needs replacing anyway, and will last another 20 years or so.

Please do not screw around with a petcock rebuild kit, hillbilly retro-engineering, or spend unholy amounts of money on a Pingel that won't fit right and you still have to remember to shut off every single ride. Just replace the thing so you can worry about other stuff for a few decades.

[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

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.

[chef1366]

Get a Dynojet stage 3 kit.

[shack426]

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