1980 gs 550 spittin and sputterin at at about 40mph

[wkraner]

I build a bobber bike using a 1980 gs550 motor. the exhaust is cut up and is straight pipe for each cylinder. the intake on the carbs is just a small cone air filter for each carb. i have it idleing ok and it will rev up in neutral just fine. i took it on the road the other day and when i got to higher RPMs to try to get up to speed it seemed like in 4th gear is just wasnt getting enought fuel or too much and wouldnt get up to speed. i dont know much about carbs but the guy i bought the motor and carbs from said the carbs where rebuilt. they look clean on the outside but no telling what all was "rebuilt". any thoughts before i start taking the carb apart.

[cowboyup3371]

Howdy and Basscliff will be along shortly to give you his official welcome. You'll find lots of good information on the website he gives you so please do read up on it.

Where are you at since it is possible someone on here might be able to give you a hand?

[DanTheMan]

Straight pipes and cone filters=too much airflow. It' way too lean. You'll have to re-jet and reset needles to get it run right with that setup. These engines are made to run right with the sealed up airbox and backpressure. Gas engines, unlike diesel engines require backpressure for proper running.

[wkraner]

I live in northwest Arkansas. Thanks for the response Dan. if i do rejet the carbs, how do i know what jets to get? is it just a trial and error sort of thing? do i just go to my suzuki dealer and order from there or is there a good online site that sells? i appreciate the help.

[BassCliff]

Greetings and Salutations!!

Hi Mr. wkraner,

You may be in for some trial and error. With pod filters and straight pipes I would suspect you'll need to go up three of four sizes on your main jets, up one or two sizes on the pilot jets, and shim the needles. You can order parts from your local dealer or from online OEM vendors. The "plug chop" procedure will probably be necessary to dial it in. I don't know if Dynojet makes a stage 3 kit for your bike but you might have a look at their website. Otherwise, your "mega-welcome" has carb part vendors and my little website has a few tips and tricks. Let me share the love.

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", the Carb Rebuild Series, and the Stator Papers. 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

[wkraner]

Thanks for the info and for the great welcome basscliff. i am pumped a found this site. i had been searchin all over the net while i was building this thing for info on the bike. i will def take you up on all the great info and links and let you know how it goes.

[wkraner]

I just got in my larger jets and am working on cleaning my carbs, new O rings, and shimming the needles. this is my first carb rebuild so the step by step picture go-by on this site is great. its making it a much easier process than i thought it would be. one question i have is that the new main jets i got in (from jetsRus.com) that the head of the jet is smaller diameter. the main jets that were in the carb are 92.5 and i ordered 100 and 105s just for some trial and error. i made sure i ordered the correct jet for these carbs from the site. the pilot jets i got match up perfectly other than being a 45 instead of the stock 40s. the new main jets are the same length and thread in fine but i just wanted to make sure the smaller head of the jet is ok or if i ordered the wrong one. any help is greatly appreciated.

thanks,
will

[tkent02]

You probably did order the wrong ones, but if they are Mikunis they will be numbered correctly, if they thread in OK you should be good to go. The head diameter won't have any effect on fuel flow.

[wkraner]

thanks tkent. i just checked the website and i ordered the correct ones for my mikuni BS series carbs and they are new mikuni jets. i didnt think the head size mattered just the hole size for the fuel flow. thanks for veifying.

[wkraner]

well i put the new jets in (went up 4 sizes on the main and 2 on the pilot and shimmed the needles). rode it to work this morning for the first time and it ran great. thanks to all who suggested what to do. the carb rebuilt went smooth. i also dont have any leaking gas like i did before the new o-ring kit. i could do some trial and error and mess w/ the sizes of the jets a little more to fine tune it but the way its running now i really dont want to mess w/ it. i didnt build this bike to race anyway, just to cruise around in. i owe the success to the helpful replys and to all the information and resourses this site has so thanks . i did notice though that after i got the bike back together and ran it a few times that this morning when i went to start it up that it took some cranking to get it started. even w/ the choke on it didnt want to fire over. after multiple tries it finnally started up and ran great from then on. on lunch when i took it out it fired right up. would the larger jets be the reason of the cold start up this morning? is there anything i can do to make it fire up quicker? thanks again for all the help.

Will

[BassCliff]

Hi,

Have you checked the valve clearances yet?



Thank you for your indulgence,

BassCliff

[Dave8338]

That would be my suggestion as well, Cliff!

[wkraner]

i have not. i will search other post and the other resources on your site to see what all is involved w/ that. could it be that i need a hotter spark plug since im putting more gas thru?