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GS750es Carb problem???? I'm stumped!!

  • Thread starter Thread starter rvnkvn
  • Start date Start date
Ok... Last night i removed the carbs, made sure the o rings were in the intake boots, and bench sync'ed the carbs. I also checked and adjusted the floats to 23mm. I had the intent of shimming the needle, and replace the pilot , but everything i took home was the wrong part OR did not have the correct tool for the task.

Rode the bike in today, the cold start was perfect, the surge at cruise was gone and i could use 5th gear without bogging at 45 mph. BUT the idle hot was bad, and the bike would not restart till I held the throttle wide open.
I did notice that when i do have it running, i can apply the choke and slowly shut it off, and for a brief moment ,all cylinders are firing smooth and normally.

I have not vacumme sync'ed yet, and I know it needs it to be perfect, but it seems like the last float setting made matters worse....
 
Again, unscrew the pilots screws a few turns. Try 4.5 opposed to your current 3.
 
I think there may be a communication issue here. You can not tune the idle without vacuum synching the carbs.

You can't.

Let me say it again. You can't.

Now, you do what you gotta do and I for one will watch. And, I promise not to comment on this again.

Chris
 
So.. you have to use the vac reading to set the mixture screws to smooth out each individual cylinder, and then play with the needle and jet settings.. correct??
 
No.

I'm assuming your bike has some form of CV carbs. When you connect the manometer to the four vacuum ports on your intakes you adjust each using the screw adjusters between the carbs. If you bench synched these carbs you had to use the same adjusters to set the butterfly valves all at the same opening amount. Those are the adjusters you use. Don't mess with anything else at that time.

Once you have all four carbs with the same vacuum reading and the manometer disconnected (and the vacuum ports on the intakes closed back off) then you can look at adjusting the mixture screws.

You can look at your repair manual, search this site and the internet in general for how to vacuum synch motorcycle carbs to get all the details. The above is just a nutshell version.

Chris
 
If it wont idle right now, do I just use the idle adjustment now and set it around 17 to 1800 rpm to sync the cylinders with the butterfly adjustments, and worry about the mixture screws later?
 
You may need to turn the idle up some for now. But, keep it as low as possible and as you make sync adjustments the idle speed may increase. If it does then keep turning the idle speed down. Try and make adjustments when the idle speed is around 1100-1500. I would re-sync after you reset the mixture screws too.

One more question: Are you sure the low speed ports are clear? When you cleaned the carbs did you blow carb cleaner from where the mixture screw is through the low speed passages in the throat of the carbs? There are typically 2 or three low speed ports in the throat of the carbs that are fed off the pilot circuit. One is controlled by the mixture screw and the other two are under and just the other side of the butterfly valve and activate when the throttle is opened. If you take the mixture screw out you can put the spray nozzle tip from the carb cleaner in where the mixture screw goes and blast those passages. Some times carb dip doesn't get these cleared out. You may have already done this but if not then I would before you sync and try to make mixture adjustments.

ETA: Here is a link to a CV rebuild guide from Bikecliff's website. Did you follow this when you cleaned your carbs? http://www.mtsac.edu/~cliff/storage/gs/mc_maint/GS_CV_Carb_Cleaning_Series.pdf

Chris
 
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I didn't say to tune the idle, I just said to unscrew the pilot jets up top. My carbs are NOT sync'd, yet doing this gave me a steady idle I've been searching for for years. Sync will come soon though, that's for sure.
 
I Rode the bike in to work after all the work from the last post, and went to start home last night. Full choke, fired right up,on 3 1/2 cylinders, shut the choke off after warm,still had to blip the throttle to keep from dying. Now when you roll back on the throttle, it does not take gas, just a BOG. So I switched the petcock to prime, still a bog, but not as bad. Stalled in an intersection, FINALLY got it restarted on 2 maybe 3 cylinders. Finally I called my wife, to bring the truck and haul this problem home.

I hooked up a remote fuel tank directly into the carb's, could see gas going to the carb, but never got it to fire on all cylinders. Got Spark, should have fuel but don't have all of the float bowls full.

Time to take the carb's back off and check the fuel feed lines to all the carbs....I'm probably going to take this somewhere where they really clean things up better than me.
 
It would cost me too much with freight, and the cost of your service. I'll have it done locally. Thanks for offering though!
 
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Hrm.....with all the horror stories that have been posted here lately, I think I would shy away from taking them in somewhere. If you backed out the mixture screws and it started to bog on the way home you might have been loading the cylinders up on fuel. Did you pull your plugs and see if they were rich (black)? And, yes, what you were suggesting a few posts back about syncing at about 1800RPM would have been a good idea. Then like resjuditca said sync and THEN set the idle screws. Try backing down the idle to like 1500 after each carb is sync'ed.
 
Yup, all the plugs were black. have the float bowls off looking around, found a crushed screen with junk past it in the #3 cylinder. It also has a broken stand on the float pin. It's holding, but the top of it does not cover the small end of the pin that retains the float. I might have found some of the problems...
 
rvnkvn said:
Yup, all the plugs were black. have the float bowls off looking around, found a crushed screen with junk past it in the #3 cylinder. It also has a broken stand on the float pin. It's holding, but the top of it does not cover the small end of the pin that retains the float. I might have found some of the problems...
Click to expand...

Uhh....ya I think so :( Sounds like it was loading up on fuel. Thinking that's why mine is running so s#!tty right now. Replaced the carb boots and those were probably leaking so now that the intake leak is fixed, need to get a proper tune. Hopefully this weekend!!
 
I found a broken "tower " on the #3 carb. The pin still is retained, but is there a way to secure the small piece back on to make sure the pin stays put OR do I need to get a new carb body?
 
There was a post about how to repair the post on a broken carb body. Think it was a couple months ago. Do an advanced search for "broken post" for the last 6 months or last year and should find it.
 
rvnkvn said:
I found a broken "tower " on the #3 carb. The pin still is retained, but is there a way to secure the small piece back on to make sure the pin stays put OR do I need to get a new carb body?
Click to expand...
I have a complete set of carbs for that bike also, that I could ship out to you with the airbox if you want, I have a clean set and a set that needs to be gone through. dro. p me a PM if interested . Also sent you a PM on the air box with shipping. HJFisk
 
Does everyone go through this same trouble with pods on the bike? What a pain in the azz. SERIOUSLY considering selling my Uni-pods and going back to a all stock set up so I can enjoy the bike. Not easy to do right now when you are worried about stalling and calling the truck to pick me and the bike back home..... ARUGH!!!
 
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