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carb tuning help needed.

  • Thread starter Thread starter motocycle shawn
  • Start date Start date
M

motocycle shawn

Guest
ok so i have a 81 gs1100e motor i pulled off a junk frame. motor runs great when it was on the other bike. now i have installed it on a new frame and added a 4-1 v&h pipe and K&n pods. swapped out the 115 main to a 122.5
cleaned & removed all jets and so on ( all of them) the butter fly's read 140 on them not sure of the meaning. but with everything but the butter fly's removed they have been dipped and every thing reinstalled. with my carb pro 2 resynchronized them all and set the air/mix to 2 turns out on all carbs.
the bike starts right up every time and idles better then ever. rev real good to but yet it pops and stumbles from 5000 rpm up. rev's good when parked runs like poo if your drive it. can't tell if i am running out of gas or over doing it on gas. I'm sure I'm over looking something here. better to ask for help now.
here are some photos of my the carbs scyn and the make of the carb and the bike I'm restoring for my wife.

have not yet tried to use my color tune set yet.

beforesync.jpg
aftersync.jpg


carb.jpg


wifesbike.jpg
 
I also run K&N pods and a V&H 4-1; I have 47.5 pilot jets and 140 main jets with my idle screws out 3 turns. A lot of people here are going to tell you you need a jet kit to run pods and a pipe, and they're probably right.
Though I have Factory Pro needles in my bike now, it ran pretty good for years with the stock needles raised up a bit. I don't remember how much exactly, but the previous owner either got smaller aftermarket spacers for the needles, or shaved the stock ones down.
 
well the pilot jet said 40 on it if i remember right. so you think i'm lean on fuel?
i'm just looking to gwt it to ride down the road for her with out popping and flat spots. going to pick up a dyna kit just not for some time .its a to and from work bike. lucky to brake 60mph with her on it.
 
45 pilots are stock, are the 40's mikuni jets? Who knows what someone did to "fix" the carbs in the last 31 years. Could be from junk rebuild kit.
 
carbs

carbs

think i will pull them back off and make a list of all the jets.
 
You're running very lean. The 122.5 main isn't near enough and you've made no changes to the pilot and jet needles?
Others here with the same model and similar mod's should help you with the jetting. Generally, you need to go up approximately 6 full sizes on the mains (30 increase) for your mod's, or more. Jet needles will need to be raised and the pilot jets increased. Many times you'll still have throttle response issues that can require drilling out the orifices to the diaphragm chambers. Lighter diaphragm assembly springs can help too. The air jets may need modification (see jet kits/general re-jetting info) for your type carbs. The CV carbs often require more than just new mains, jet needles and pilots. You'll also need to vacuum synch once all the work is done for better performance.
 
carb help

carb help

ok this is what i got.


Main Jet = #122.5 had 115 in it.
Main Air Jet = 160 i have some 170
Jet Needle = 5D58 only one c clip setting?
Needle Jet = X-3
Pilot Jet = #40 i have 4 45's and 2 47.5's ones

all the slides have a 1/8 hole in them now . stock ones hold a 3/32 bit good so i take it slides have been drilled all ready.

so who's got ideas? really need a hand here :confused:.
with them set like they are she starts and idles great revs fast to 5000rpm then shixy from there. will cruse down the rode but no passing power and it cuts up bad or bogs down.
 
Dude I am not trying to sound like a dick, but there are a million threads on jetting CV carbs for pods and a pipe and 90% of them end in "Buy a damn Dynojet Kit"...

The stock needles WILL NOT WORK with pods. They're way too fat and the taper is too slow. The jets themselves are only part of the issue. As a mater of fact the needles are the most important part because that's where you spend most of your time...even at 60 mph.

You can do serious damage to the engine running it lean on a regular basis. I strongly urge you to shell out the $120 or whatever it is and buy a Stage 3 kit, follow the directions and you'll be golden minus having to adjust the clip position maybe. For as much as you spent on your sync gauge, you could have solved your problem. You're just gonna keep chasing your tail if you don't.
The CV carbs cannot be jetted by hand with stock needles. Believe me, I spent and entire season trying. In the end, I bought the kit and within 20 minutes the bike was running better than it ever ever had, and even though I thought I had it pretty close, I was amazed at how much power I was leaving in the table. To get the mid circuits even useable, you have to have like a 132 or larger main with the stock needles and then it's soooo overly rich up top it's drowning.

Point is, no matter what you do, unless you use a kit, the bike will run like **** somewhere in the rev range if you use the stock needles....
 
carbs

carbs

well said. thats what i was hoping i could get around and i got the carb tune before i built the bike . but sure did help to have them.
one last ? did some one mess up the slides? i hate to get a dj kit to find out the slides have been drilled too big. for now i guess i will just put the RS36 carbs i have on it till i can get a kit. thanks for the info.
 
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