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What is my carb set up for?

  • Thread starter Thread starter Dodik
  • Start date Start date
D

Dodik

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So i finally got time to do carbs properly on my 1982 GS750EZ, when i got the bike it came with pretty old supertrapp 4-1, and no airbox, i found a front box but no rear and just used a cone filter on the end of the front airbox during summer and it ran a little lean i believe. i figured that somewhere down the line PO had to install some kinda jet kit but this is the first time i really dug into them to find out the actual numbers. the carbs are BS32SS

Currently installed________________Stock
Main Jet# 120 __________________112.5
Pilot Jet # 42.5__________________42.5
Air Jet # 150____________________170
Needle Jet 318 Y-5_______________ Y-4
Fuel Needle 5c32 ________________5c28

Comparing the numbers it looks to me that i have 1980 750 L carbs with main jet from dynojet kit stage one, does that look right or is this a 82 EZ carbs with some other kit? And lastly what should i do for the air as the cone filter on the airbox is not a permanent solution. What kind of air cleaner assembly should i look for with this setup i really dont want to spend 100 bucks on stage three if i can make it run right with this setup. Not really looking for power more into making it last long and run correctly.
thank to all in advance.
 
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Ok let me rephrase the question to run a stock airbox with high flowing filter and 4-1 pipe, do i just use two small spacers on top of the needle instead of the nylon washer, or do i also need to go to 45 pilot jets?
During this season bike ran pretty well from about 3.5k all the way to the redline so im sure i have adequate mains but low end had a few flat spots.
 
You need a jet kit with an adjustable needle.
Check out Dynojet or Factory Pro
 
i'll take a pic tonight of my needles but i think they are not stock there were 5 grooves on them w/ clip in the middle (3rd) groove. and they are straight were only the tip is tapered
 
finally ditched the flu and and can tackle at this again

the needle says 5c32 and also realized the slide is already drilled well here is a pic

IMG_1531.jpg


IMG_1529.jpg
 
Dodik said:
Does anyone know if that is a stock needle pictured above????
Click to expand...

I am going to take a stab at this and say no and yes. As your first post mentions, the "stock" needle is 5c28 and you say this is 5c32. So it is in fact, not stock at least for USA. However, from what little I remember and what I can glean from this web site, a 5cXX is essentially the same as 5cYY.

http://www.motorcyclecarbs.com/Mikuni_Jet_Needle_Dimension_Ch_W121C37.cfm#Series 6

Thus I would say that it will work like stock. Heck, for Canada, it may have been stock.

In your case without an airbox of any sort and a 4 into 1, I would guess, and I mean guess that you are probably lean on this needle. Best way to know is to do some spark plug chops at various throttle positions and compare how they look.
 
Resurrecting my old thread
I rebuild the carbs with all new o-rings dipped them, bench synced and raised the needle the clip now is on the lowest notch, also i have k&n pods and supertrapp 4-into-1, on it.
the bike started right up and i think it is running rich as it will only rev up to about 8k, the smoke is a bit whitish. But it ran smooth and consistent with occasional popping.
i have a diy manometer and waiting on my colortune. the question i have is if my carbs stick doesnt work and carbs will only be bench synced how bad or what are the negatives of setting fuel mixture per a given cylinder without them being absolutely synced?
 
Hey all im having a few issues with getting the bike to run well above 3k rpms here is what i've done so far

dipped carbs with new o-rings, synced them, raised the needle max clip is on the bottom slot. k&n pods. I have a colortune but had yellow or white lite i didnt really see any blue when trying to adjust it. bike really does not want to start when cold once it fires up it runs pretty smooth. it will rev through the entire rpm range with no load on it. However when i try to ride it it wont go past 3.5 -4k rpms i didnt do a throttle position chart on it yet so my guess is it wont go past 1/4-1/2 throttle. it starts to bog down doesnt die no poping if i hold t long enough it will eventually get thru the bogging and will accelerate.

main jets are 120 which is plus 3 from stock 112.5, pilots are stock 42.5 and air jet is 150 instead of stock 170.

Should i try to lower the needle a bit to second from the bottom clip? And should i go up to 45 pilots?
 
is that a dynojet 130 or mikuni 130? from what i remember 120 mikuni is 130 dynojet please correct me if im wrong. i have a mikuni 120 btw
 
Dodik said:
is that a dynojet 130 or mikuni 130? from what i remember 120 mikuni is 130 dynojet please correct me if im wrong. i have a mikuni 120 btw
Click to expand...
Mikuni 130
you're lean on the main with those 122.5s.
You want a main jet that will take you to redline and then you can tweak the needle and pilot.
 
thanks so much i'll try that this is for 750 right cause stage 3 dynojet kit only goes up to 130 in their numbering, im just trying to make sure that i dont waste time and money.
 
ok found the reasoning for 130's just placed an order on z1 for 130 mains and 45 pilots just in case i need them will let everyone know how it turns out
 
I've got a very similar set up to yours and fought almost the EXACT issue you're having. I kept the DynoJet main (125 I believe) and bumped up a pilot size to 45 (Mikuni) and the difference is night and day. Runs 10x better at higher RPM and pop's waaayy less on decel.
 
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well 130 mains and 45 pilots are in, it runs much better but still lacks a bit in 5th gear and is very hesitant to start, it will spin for a while until it actually catches on. should i go higher on the mains 132.5 or 135?
 
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