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

[rvnkvn]

Thanks Chris... I'm getting really good at pulling carb's off the bike. I'll work on that tonight after work. I'l also double check the remaining intake o rings.

[resjudicata]

You should vacuum synch the carbs on the bike while it is running. Bench synch'ing is what you do with the carbs off the bike to try and get them close enough so the bike will run well enough to do a proper synch with either vacuum gauges or a manometer.

Chris

[Curly]

My trick is clamping one and two on just a little bit then levering on three and four into the boots. Taking them off is the easy part. Only good thing about pods.

The screws I'm talking about are the ones on top between the carb body and cylinder. They're hard to adjust, but a small glasses screwdriver works ok. Just lift the back of the tank. I use a flashlight to check orientation of the slot in the screw, turn it a bit, and check again to make sure I'm turning them all evenly. That's good enough until I sync the carbs.

Just start it again after every adjustment, see if it idles. Like others have said, no point in adjusting for highest idle until after you've synced the carbs.

[dueller]

My trick is clamping one and two on just a little bit then levering on three and four into the boots. Taking them off is the easy part. Only good thing about pods.

The screws I'm talking about are the ones on top between the carb body and cylinder. They're hard to adjust, but a small glasses screwdriver works ok. Just lift the back of the tank. I use a flashlight to check orientation of the slot in the screw, turn it a bit, and check again to make sure I'm turning them all evenly. That's good enough until I sync the carbs.

Just start it again after every adjustment, see if it idles. Like others have said, no point in adjusting for highest idle until after you've synced the carbs.

I adjusted mine with the middle sized flathead screwdriver on my Leatherman. Just the right size!

[rvnkvn]

So, I'll pull the carb's ,bench sync the throttle blades, and set the pilot air screws to 3 turns out, install back on the bike and fine tune the screws per cylinder to get the best vacumme signal.... After I get this sorted out, shim the needle ,possibll change the main and pilot jets. GOT IT!

Thanks everyone!!

[rvnkvn]

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....

[Curly]

Again, unscrew the pilots screws a few turns. Try 4.5 opposed to your current 3.

[resjudicata]

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

[rvnkvn]

I'll try that before i go home tonight...Thanks again..K

[rvnkvn]

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??

[resjudicata]

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

[rvnkvn]

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?

[resjudicata]

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/%7Ecliff/storag...ing_Series.pdf

Chris

[Curly]

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.

[rvnkvn]

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.