1981 gs850 off idle wanting to stall

[snowmobilejon5000]

It runs perfect after about half throttle and will cruise perfectly down the hyway but off idle when I give it gas it burbles and sputters until I build up some rpms. It also idles perfectly. Just that first quarter to half throttle is messed up. I have tried every direction with the fuel screw and it isn't helping. There are no air leaks in any of the boots, has oem air filter and is a snug fit and the exhaust is oem. Compression is 150-148-149-152. The carbs have been gone through and I used an air compressor and carb cleaner in every orifice then finished the cleaning with running fuel though every orifice to make sure it is flowing. The float bowls were leveled within specs. The petcock is working perfectly and there are all new fuel and air lines on the bike. Valves have been checked and are within specs and the timing is correct and is advancing properly. Should I tear it down again and check the float bowls again or what? I am stumped. I have a haynes manual and the only thing it doesn't say is for the fuel scew it just says fixed well what is the fixed value because the person that had it before me didn't leave it alone and they are all way different.

[BassCliff]

Greetings and Salutations!!

Hi Mr. snowmobilejon5000,

My first thought is that the carbs have not been completely disassembled, dipped in parts cleaner, cleaned properly, and a complete new set of O-rings installed during reassembly. Most first attempts involve only a partial dis-assembly and a squirt or two of carb cleaner. This is not sufficient. (And aftermarket "carb kits" are junk.) The complete and proper procedure is in the links below. This includes removing the idle mixture screws (what you called "fuel screws") so that the passage can be cleaned and the O-ring replaced there too. (To set them use the "highest idle method".) For a list of what NOT to do, read this: Top 10 Newbie Mistakes. For what TO do, read the links below.

Anyway, let me dump a TON if information on you and share some GS lovin'.

I just stopped by to welcome you to the forum in my own, special way.

If there's anything you'd like to know about the Suzuki GS model bikes, and most others actually, you've come to the right place. There's a lot of knowledge and experience here in the community. Come on in and let me say "HOoooowwwDY!"....

Here is your very own magical, mystical, mythical, mind-expanding "mega-welcome". Please take notice of the "Top 10 Common Issues", "Top 15 Tips For GS Happiness", the Carb Cleanup Series, and the Stator Papers. All of these tasks must be addressed in order to have a safe, reliable machine. Now let me roll out the welcome mat for you...



Please click here for your mega-welcome, chock full of tips, suggestions, links to vendors, and other information. Then feel free to visit my little BikeCliff website where I've been collecting the wisdom of this generous community. Don't forget, we like pictures! Not you, your bike!

Thanks for joining us. Keep us informed.

Thank you for your indulgence,

BassCliff

[snowmobilejon5000]

They were completely dissembled and dipped for a day in my trusty bucket then I ran compressed air through every orifice and put all new seals gaskets and the o rings on the intake boots on the intake of the engine. How many turns out is the idle mixture screw supposed to be. I have it at 3 on all of them but it stutters off idle. After half throttle it comes to life rips all the way up to redline.

[Nessism]

The 850's are sensitive to airbox leaks. How are the end cap seals and the seal on the airfilter looking? Common weatherstrip foam can be used to replace the OE foam if deteriorated.

One other thought is vacuum sync. Have you done this?

3 turns open on the pilot screws is in the ballpark. You can always try 2.5 or 3.5 and see what happens.

[snowmobilejon5000]

The air box is sealed tightly I used a windshield wiper blade around the filter and it is a snug fit. Going between 2.5 -3.5 doesn't make a difference. It still hesitates and sputters off idle then once the rpms build it takes off like a rocket. I cannot get at the center lock nut for the vacuum sync or I would do it now. I made a homemade vacuum sync with bottles and hose from auto zone like the one in this forum. I have tried every tool in our garage to get at it.

[Nessism]

One way or another you have to do that vacuum sync. Motion Pro sells a nifty tool that gets at those adjusters that's well worth the $20 it costs.

[snowmobilejon5000]

Could you give me a link to the tool, I want to get one. thanks

[850 Combat]

http://www.motionpro.com/motorcycle/partno/08-0022/

Here is the tool. I have synched my carbs a number of times without it, but I'll probably buy one. I don't understand why you are having a problem though.

As to your lean condition off idle, regardless of what you have done, those the suggestions above are correct. You have air leaks in the airbox, carbs, or intakes, and/or you have pilot circuits not properly functioning.

[Steve]

One other thought is vacuum sync. Have you done this?.

Very good point.

I cannot get at the center lock nut for the vacuum sync or I would do it now. I made a homemade vacuum sync with bottles and hose from auto zone like the one in this forum.

This part scares me.

Motion Pro sells a nifty tool that gets at those adjusters that's well worth the $20 it costs.

I have not seen one yet that will get at the center adjuster.

The only way to get any kind of tool on the center adjuster is to remove the throttle and/or "choke" linkage from the top of the carbs.

I will usually leave the adjuster locknuts on the loose side after the bench sync. (You said you had the carbs off and cleaned, didn't you do a bench sync?)
Makes it much easier to loosen it just a little rather than having to break it free when it's tight.

.

[snowmobilejon5000]

Yes I bench sunk them. I used allens of the same size between the butterfly's and the wall to get them to the same opening distance. I am truly puzzled why it runs so good except for off idle, right now I have the carbs off again and I am checking the float height to ensure I measured correctly but everything looks normal.

[Steve]

It sounds like you did everything pretty much right, but have not mentioned where you have the mixture screws set.

If they are too far in (as in 'close to stock'), you can turn them about a full turn in either direction without noticing any change.

If your float levels are set correctly, start with the screws about three full turns out from lightly seated.

.

[snowmobilejon5000]

Carbs synced and she running like a beast. Chalk another one up for GS resources, I'm going for a ride to work on my beast of a 1981 gs850 with 21000 miles on it. Found the problem, the new petcock that I put on had a broken copper tab on the one end, I bought a new 50 cent part and synced the carbs with my homemade rig and it runs like a champ with the fuel screws at 2.5 turns on each cylender. I can run all the way up to 9 grand without even a pop. After work tonight I will take pics and a video tomorrow morning and post it on youtube and put the link on here. I cannot thank everyone enough. I just rebuilt a 400 dollar garage find and now it is going to be my daily driver. Everyone on here rocks. Jon V officially out to ride.

[BassCliff]

Hi,

Outstanding! I congratulate you on your fine work.

After all is said and done and the world has gone "Mad Max", I think the GS850 will be the last motorcycle left running.

Now let's see those pictures, please.


Thank you for your indulgence,

BassCliff

[snowmobilejon5000]

Two pictures until morning when I get a video uploaded. Too dark now, something about it is midnight, I guess that means it is dark out.

http://s1212.photobucket.com/albums/cc448/snowmobilejon5000/?action=view&current=pic2.jpg#!oZZ1QQcurrentZZhttp%3A%2F%2Fs1212.photobucket.com%2Falbums%2Fcc448%2Fsnowmobilejon5000%2F%3Faction%3Dview%26current%3Dpic2.jpg

http://s1212.photobucket.com/albums/cc448/snowmobilejon5000/?action=view&current=pic2.jpg#!oZZ2QQcurrentZZhttp%3A%2F%2Fs1212.photobucket.com%2Falbums%2Fcc448%2Fsnowmobilejon5000%2F%3Faction%3Dview%26current%3Dpic1.jpg

[BassCliff]

Here ya go...







Thank you for your indulgence,

BassCliff