Need carb jetting advice for my GS550

foebux

New Member
So guys,

I plan on installing K&N Pod filters with 4 to 1 mac exhaust and i need your help on jetting.
My main jets are 80 and pilot is 50. so according to a guide i found i should replace it with 87.5 and 52.5.

here is the link to the carbs: http://www.bikebandit.com/1978-suzuki-gs550e/o/m21517#sch258406

and would any mikuni jets fit with the carbs? where is a good place to buy jets from? Also, if you have any other jetting advice i would appreciate it (i.e. changing jet sizes, etc.).


Thanks guys!!
 

cxman

Active Member
DTT SUPPORTER
try this

http://www.jetsrus.com/a_jet_kit_street/suzuki_550_GS550_1977-1979.htm
 

SeanGSUK

Strength is measured in tolerance, not mass
I have pods and a Motad 4 into 1, my carbs are running #97.5 mains, runs well, my garage says it is still a bit lean though and needs #100s. These are VM22s. Don;t know if that is any help?
 

cxman

Active Member
DTT SUPPORTER
are you sure you dont mean VN22SS vm22 is a mikuni tiny carb for pit bikes?
 

foebux

New Member
I believe mine are vm22ss. The link I've provided above is the carbs that I currently have. I'm just wondering because I read people that have around 100 size main jets. Mine is 80 stock and was recommended to change them to 87.5 with pods and the new exhaust
 

cxman

Active Member
DTT SUPPORTER
ok i think we are talking the same thing as i understand they are vn22ss no matter

once you establish that you have no vacuum leaks and that the carbs are clean and working properly

and that you have the correct heat range spark plugs go by the plugs and chop tests

and jet till its right so if it looks lean go up a size or 2 till you get it right

if you are close now you could raise the main needle up 20-30 thou in the slide and see if that does it
 

foebux

New Member
Re: Re: Need carb jetting advice for my GS550

cxman said:
ok i think we are talking the same thing as i understand they are vn22ss no matter

once you establish that you have no vacuum leaks and that the carbs are clean and working properly

and that you have the correct heat range spark plugs go by the plugs and chop tests

and jet till its right so if it looks lean go up a size or 2 till you get it right

if you are close now you could raise the main needle up 20-30 thou in the slide and see if that does it
Thanks for the advice, what does it mean to be "in the correct heat range" and "chop tests"?
Also how do I determine if I'm in the correct heat range?
 

cxman

Active Member
DTT SUPPORTER
heat range is one of the numbers in the spark plug part number

so make sure you have plugs in your bike that are original part number

do not try to jet your bike with iridium plugs in it

a chop test is when you drive the bike at what ever speed you are trying to test it for say 65 mph

then you quickly pull the clutch and kill the engine and look at the color of the plug

that will tell you how the engine is burning the fuel

if you just drove home and pulled the plugs they would get stained and give you false information as you would have a

different throttle setting
 

teazer

Active Member
DTT BOTM WINNER
cxman said:
.........
do not try to jet your bike with iridium plugs in it
................
Why do you say that? In the same heat range, it should be the same process - apart from reading the electrode which could be misleading.
 

cxman

Active Member
DTT SUPPORTER
that is the reason the tip temp is much hotter and they self clean and throw a plug chop out
 

teazer

Active Member
DTT BOTM WINNER
Mixture is read down where the insulator meets the shell and that should not be any different than a regular plug. If the OP is trying to read ignition advance or heat range off the center electrode, that would be a challenge, but he can still read the side electrode for that.

We use Iridium plugs on a few bikes that need a fine wire to minimize misfires and don't have much trouble reading the plugs after a chop.
 

cxman

Active Member
DTT SUPPORTER
your eyes must be newer than mine lol

i have a tough time with them so use the older type oh well
 
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