I Give Up

[HobieSun]

Ok, I bypassed the petcock, not a difference at all. Put back together, readjusted the float level on the fatter side, didn't make a damn bit of difference. Thought that I may have some air leaks between the airbox and the carbs so I sealed it up tight with a few different things, not a damn bit of difference. I can hold my hand over the airbox hole a certain way and get it to rev hard all the way to 10k, if I take my hand off of it, it will bogg, if I put the airfilter box in it will bogg. I have good spark, new plugs, timing matches, getting plenty of fuel through numerous ways, no air leaks, everything has been looked over and/or adjusted. Complete charging system is new, battery, regulator, stator. I am done. Trading the POS in. I have never had anything give me so much S^&! and run so badly.

P.S. Anyone want a 1980GS750L in perfect running condition, that just happens to run ****ty? I have $800 in it.

[Scud]

I have not seen your previous posts so I am not up on all that you have done......sooooooooo........You know that these bikes will run like a raped one when all is in order, sounds to me like you are missing something.

Sorry for asking questions that you have already answered...but..

Did you take the carbs off and clean and dip them thoroughly? Are all the jets the same in all carbs? Did you sync your carbs after what you have done so far?

Check all parts of the carbs to make sure that they are all the same. I am no expert but the boys on this site have turned me into a GS mechanic albeit to the tune of around $1000.00 dollars to get my 1980 GS 750E running like a champ again.

Tell you what, keep the bike, wait until winter time when you can spend more time (and probably more money) on the bike.

Don't let this get to you, I have been exactly where you are now, there are many of these older bikes that have been brought back from the dead, you will not regret it and just think of the gratification you will get when it eventually runs great....not to mention all the stories..heh,heh,heh.

Address the issues one step at a time, but for Christs sake...do not give up.

Scud

[speedzter2000]

HobieSun...Oooooh...do I know how you feel....
also try the air mixture screws, and idle adjustment screw...
On my bike, it was bogging down, and there were a couple of things wrong...mixture screws out way too far, and idle screw turned all the way in...
I know it's the little sh!t that's going to p!ss you off...trust me...
Why give up now?? I know you probably want to ride, so do I....BUT...when you Do get it right, you'll be smiling all the way to the bank knowing you dont have a bigger insurance payment, and a bike payment...
Good Luck!!
BTW...if all else fails...there is a web-site that will go through your carbs for about $150. They have a pretty good reputation. I THINK the web-site is : motorcyclecarbs.com...or search for it here...someone else listed it...

[HobieSun]

Hey guys,
I completely went through the carbs and everything looked really good. I blew out every jet, took the slides out and looked at everything. As far as the mixture screws, on the 80 they have aluminum plugs in the way of adjustment, I think that I would have to possibly drill them to get them out. I figured that since they were there, someone didn't have the chance to mess them up. The idle screw is fine as well, (its adjustable and seems to work well). Everything on the carbs seemed to match. I did not bench sync them however, I wasn't entirely sure how to do that, all of the slides seemed to be right about the same height as the rest. I do have a vacuum sync tool but that is for fine tune.

Before I took the carbs off I had an extreme rich condition, black smoke everywhere. From idle to 7 to 8k. The bike never would get over 7 to 8K under load since I bought it, but from idle to that it would run like madness. When I took the bowls off, the floats where way off, it looked like as if someone bought new floats and stuck them in. I adjusted that (twice) the first time I set them at 23mm, the book calls for 21.4 to 23.4, then I thought that maybe I went a little fat for that so I bent the tabs about half of what they were to begin with. Also, I was a little confused when I first got the bike, the rubber plugs had melted into the bowls. I had never seen such a thing and asked on the forum what the heck they were and they said not to worry, you don't need them. So I cleaned them out and left it without pilot plugs. When I took the carbs off I replaced the plugs. Once I got done with that it wouldn't rev over 6k in neutral. That is basically where I am now.

[sandspur]

Pop the plugs to the mixture screws & take the mixture screws out , The small o'rings that seat them may be bad & need replaced. Make sure the small holes by throttle plates are not plugged & clean, Do a bench sync, I had my carbs off many times because I didn't do this to start with. Hope this saves you a few steps

[Jethro]

You took the slides out with the jet needle, but did you remove and clean the needle jet? That's the long, brass tube the needle actually resides in. It has ports in it that need to be free.

Also, with a good carb cleaning, you should pull the covers off the screws (drill them out- easy, not too far- then thread a wood screw into it and grip with pliers and pull) pull the screw out, and make sure that port isn't gummed up.

Did you pull the choke plungers and make sure they are not stuck and the o-rings are soft and pliable?

Is the bike entirely stock? Would the PO have changed the jetting at all? Is the pipe OEM? If you can get it to rev by putting your hand over the intake, it sounds like you now have a real lean condition.

Let me tell you, I've had the carbs off my bike in excess of 30 times. The one thing I have learned is to never take any shortcuts. If the bike has been jetted, it can be a nightmare to figure out what was done (drilled slides, heavy slide springs, some people even drill jets out themselves). Verify everything, and if it is questionalble- replace it. I have casued as much trouble as I have solved by just thinking I can compensate for something else by changing another thing.

Anyway, it takes time, but it can pay off. My bike runs like a swiss watch now, get's 43mpg, and goes like stink. Evaluate how much it's worth it to you, becasue the time is an investment.

[flyingace]

I can hold my hand over the airbox hole a certain way and get it to rev hard all the way to 10k, if I take my hand off of it, it will bogg, if I put the airfilter box in it will bogg.

Make a plastic cast of your hand and glue it to the airbox!

Seriously, this speaks of some kind of vacuum problem. With your hand in place restricting airflow, the vacuum increases and the (I assume) CV carbs open up. I know you've checked everything, but the evidence still points to it. Is everything absolutely box stock in the intake? The fuel intake system on these bikes is designed to work with the exact system as delivered - right down to the density of the foam filter. I've even heard of guys artificially restricting the air inlet just to solve the problem you describe.

[HobieSun]

Fly, that was simply funny as hell. That I believe is the first time that I have laughed while trying to figure this out. Thanks. And Sandspur, I lived in Florida for 9 years, those things absolutely suck.

Ok, back to the questions. When I cleaned it, I took the plungers(slides)out, I took the needle and seat out, I took every jet out and cleaned, I blew through every hole I could find. I didn't do anything with the choke. It doesn't seem to make a difference whether or not I pull the choke, just when I try to meter the air intake with my hand. Damn that plastic hand thing was funny.

Ok, so I guess I will check out the mixture screws. I guess I will double check the plugs and make sure that they were not pushed in too far. I went from extremely rich to not running above 6k.

I probably missed a few questions I will go back and repost.

OK, everything to my knowledge is stock. I had someone tell me that the jets were correct, and one person question it. I am not sure what the pilot jets were, I couldn't find a number on them. The air jets were all 170, the main was 112. When I took the carbs apart I may have missed something but it wasn't a shortcut by anymeans, if so I either wasn't brave enough or didn't think about it.

[HobieSun]

Pop the plugs to the mixture screws & take the mixture screws out , The small o'rings that seat them may be bad & need replaced. Make sure the small holes by throttle plates are not plugged & clean, Do a bench sync, I had my carbs off many times because I didn't do this to start with. Hope this saves you a few steps

Can someone explain how to do a bench sync?

[Jethro]

On an 80 1100, I don;t think those are stock. Unless the L's had bigger jetting. My 81 is a 108 stock and the 83 is a 112.5. Pilots for both should be 45's.

A bench synch basically is setting the butterfly plates (not the slides) to exactly the same clearance. Since the butterflys are all on individual springs, you need to take a small piece of wire or something between the plate and the bottom of the carb throat and adjust the throttle body screw so all of them match as close as possible.

[flyingace]

Think about it. If your carbs work well simply by restricting airflow at the intake, then they are working OK.

I guess there's a possibility the vacuum diaphrams inside the carbs are old and stiff. Also, make sure the upper chamber gaskets are OK and the screws are good and tight. Anyway, I think one of two things are wrong:
1. The vacuum levels are too low.
2. The carbs themselves are not responding to proper vacuum leves.

Best of luck.

[HobieSun]

ok, also its an 80GS750L. I am getting mixed signals on the jetting, so if anyone knows please let me know.