whos familiar with carbs here?
 

alright, so i have a 81 suzuki gs550 that i decided to turn into a cafe racer. problem is, after i rebuilt the carbs, one of the little legs taht holds the pin for the float on one side of carb #4 broke clean off. its jbwelded for now, and holding, but i figure since i need to rejet the bike for 4 pod filters and a full exhaust, i may as well get the carbs for the gs650, same carbs with different jets. heres my question. either jc whitney or jegs, not sure which one i saw it in, sells air fuel meter/sensor that consists of a sensor, and a module and gauge for $250-ish, and another for $350ish thats the same thing, but comes with a wide band sensor, module, etc. both include a sensor bung.

my question is this one. if i sync the carbs and get the iddle right by adjusting the idle screws, all that good stuff, after its synced up, you think its possible to run that wideband or other air/fuel system to see where im running for easyer tuning, as opposed to the trial and error jet fitting? like, see where it reads? also, i have to have it on the road to get the reading at certain rpms under load?

also, i hate to be "that guy" and ask everything there is to know about a certain thing, but how do carbs work in regards to air/fuel mixture at various rpm? if im getting a good ratio at 4k rpm, does that mean ill get a good one at 9k rpm, or even at redline?

last off, the bike ran fine after i did a full tear down and cleaning, but torwards the end of last riding season, i pulled off the air box cover, and it started completely flattening out at 5-7k rpm, like it wouldnt accelerate anymore. at all. in fact. at that point, at full throttle, it would slow down more then at it would at no throttle. to my understanding, at this point, i hit a very very lean condition, ran really hot, and was shooting fire balls out of my exhaust when i cut the throttle.

i know this is long and annyoing, and my posts are almost always long run-on sentances, and i apologize, but i finally can afford to get the subie AND slow suzie(the suzuki) up and running!!

Re: whos familiar with carbs here?
 

1. Why would you buy another set of carbs when you just need a body? You can always put different jets in yours (my guess is you'll need to replace 'em anyways unless the carbs your looking at were properly rebuilt.

2. The wideband might work though bikes are tricky with multy cylinders etc. You'd be much better off to spend that $250 at a good shop which can do the tuning right. Yes I love new tools too!:lol:

3. Bikes are tuned very tightly. Removing the airbox cover will definately screw with it. Heck I had to rejet when I put in an aftermarket foam filter in my NH.

Re: whos familiar with carbs here?
 

1st ya need to get the carbs synced, via vacuum gauge.
http://www.denniskirk.com/jsp/produc...d=41804&mmyId=
to make sure they're opening @ the same time.
no you can't just guess.
here's another A/F gauge that works well.
http://store.summitracing.com/partde...5&autoview=sku
the a/f gauges are nice for fine tuning. though EGT, exhaust gas temp, would be better. you can get some multimeters w/ thermocouple plugin and check each cylinders temp.
just goin up a couple jets probably won't solve your issues as the mains only come into play after 1/2 throttle. you probably need to richen your pilots, effect 1/4-1/2 throttle. change or raise your needles. so more fuel comes thru main earlier compared to stock. to get main size right ride along preferably in 5th and run wide open, the just slightly back off throttle. if bike slows down you're close or a lil rich. if bike picks up a lil then you're just a lil lean. come up 1 size jet @ a time.
with a a/f gauge just cruising along should be reading lean. cruising/no load engine runs fine @ 15:1
plug reading is still the best method, run good ngk stock heat range plugs.
these are cv carbs right? not flat/round slides. make sure vacuum diaphragm
is in good shape and slide ride smoothly up and down bore.
cv's are harder to tune than flatslides.
as for pulling airbox cover off, did you change jets then?
cuz it probably was running lean, as said earlier if you back off throttle and it picks up r's, you're lean. 80's bikes were notoriously lean, for emissions
if you're shooting fireballs might wanna check your timing too. i like the fireball via running wide open, hit kill switch for a sec then flip back on. :D

Re: whos familiar with carbs here?
 

thanks a bunch guys! update on that, the bike was dirtyer then imaginable (Well, maybe not quite that bad) and it was in the 70s outside, so i decided to work on the bike. started as a cleaning, and definately went alot farther than that. more on that in a second. back to carbs...

alright, so i dont understand the whole needle adjustment which im imagining controls which/how many little holes are exposed on the main jet? problem is, the needle on my mikuni carbs is not adjustable, and is vacum operated. ive heard words tossed around regarding "shimming" the needle, but im not understanding how or what this would do, or where "shims" of some sort would go. and yes, it is a CV carb. i plan on doing all the work myself

1. pulled off the intake snorkel and airbox, as im planning on replacing that with the pod filters.
2. pulled off the battery tray, which is also where the regulator/rectefier was mounted to. anyone know if this will be a problem, or can i mount that anywhere that is within reach of the wiring?

3. started cleaning frame. couldnt get far..

4. eventually ended up pulling entire wiring harness out completely, as the turn signals didnt work before when i went out, and the headlight worked... sometimes, and am planning on a dyna s ignition sys. was WAY easyer than i though, as the wires have only one place they can connect, and harnesses only have one connection.

5. removed stock coils with boots hard attached, as one boot is torn, and #1 cyl only gets spark when the boot is held a certain way, or out of sheer luck. its electrical taped together. Will be doing a Dyna s replacement on the ignition sys., and dyna coils to replace the stock coils. have to source out a mechanical advancer for ignition for dyna coil to work, from any 1980 or older suzuki gs.

6. Removing stock 4-2 exhaust, replacing with full mac 4-1 exhaust, but pulling the stock can off, and replacing with a M4 gp shorty style can.

7. and some body stuff, mostly to make it more "cafe racer" and less "universal japanese bike". stock 03 gsx-r 750 rearesets comeing soon.

nice thing is, none of this really cost any extensive amount! except for the exhaust:(

Re: whos familiar with carbs here?
 

First of all, you can build a very effective vacuum guage with some aquarium tubing, t-fittings, and colored water, for just a few bucks. A Google search should turn up plans and directions on use.

Second, you can get some good information on your air fuel mixture from your spark plugs. Google "plug chop" for more info on that one.

Shimming the needle normally involves using some very small washers to adjust the needle's position relative to the jet orifice for any given position of the vacuum diaphram. Or maybe it changes the position of the slide... I can't remember right now.

Finally, make sure you clean every little passageway in the carb bodies with some good carb cleaner and a very fine brass or copper wire, and refresh all of the rubber o-rings throughout the carb. A tiny leak or blockage somewhere can have dramatic effects on the performance of the carb. Also check the condition of the float needles to make sure the "cone" is not worn or pitted.

When you pulled the float bowls was there any rust or gunk in the bowls?

Check out the message board at gstwins.com. It is focused on the GS500, but there is a ton of information there that should be useful to you as well.

Hope this helps.

Re: whos familiar with carbs here?
 

cone on float needles? refering tot he tip of the needles, right?

i found a stage 3 dynojet jet kit for my carbs for 90-110 dollars depending on the source! that made me really happy! i also found a brand new condition jardine full exhaust for my bike that was discontinued long long ago on ebay:( that made me quite sad, as its a bit over 300 dollars!! just cant afford it at the moment! im looking into plug chops later tonight when i get all my daily stuff done, i have the day off, im just on a temporary break at the moment. im going to work on that vacuum gauge cause i dont want to spend 100 dollars on one!

id like to spend the money on the subie more, but at the moment, id rather be out riding, and its cheaper to fix the bike then the svx, and i dont have a running vehicle... bike is a better idea.

Re: whos familiar with carbs here?
 

Yes, I am refering to the tips of the float needles, make sure they are creating a nice seal.

I would not get the Dynojet kit. Just buy the jets themselves, and shim the needles as needed...way cheaper. You can try a variety of sizes of jets for less than you'll pay for the kit- shop around, I think the jets for that bike should be less than $5 each.
Also, Dynojet tends to use needles with a different taper than stock, which makes it hard to compare your setup to the stock settings and to what other people are running on the same bike.

This site looks like it has some pretty good info and a pretty active forum:

http://www.thegsresources.com/

I wasn't thinking about the fact that you have four carbs to synch, so the water trick wont work as easily as it does with just two.

This seems like a pretty good design though:

http://www.xs11.com/xs11-info/tech-t...chronizer.html