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Does anybody still mess with carburetor tuning/jetting?


Eddo Rogue

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I do a lot of messing with carbs on bikes....wondering if anybody does that with vehicle carbs?

I think the last time I rebuilt an actual vehicle carb was maybe 20 years ago.

I mostly rebuild single cyl/small engine carbs.

did an inline 4 cyl set of carbs once....made a home made vacuum gauge to sync em...not sure how I pulled that off.

I am putting cleaning a Keihin FCR now. The air/fuel screw spring popped out and disappeared...and the o ring is stuck inside the carb body....so I decided to take a break and post this thread. I dont own any carbureted vehicles or bikes with more that 1 cylinder....yet I am sick of rebuilding carbs.
 


rusty ol ranger

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I do a lot of messing with carbs on bikes....wondering if anybody does that with vehicle carbs?

I think the last time I rebuilt an actual vehicle carb was maybe 20 years ago.

I mostly rebuild single cyl/small engine carbs.

did an inline 4 cyl set of carbs once....made a home made vacuum gauge to sync em...not sure how I pulled that off.

I am putting cleaning a Keihin FCR now. The air/fuel screw spring popped out and disappeared...and the o ring is stuck inside the carb body....so I decided to take a break and post this thread. I dont own any carbureted vehicles or bikes with more that 1 cylinder....yet I am sick of rebuilding carbs.
Race guya mostly anymore. Guys who drive carburated stuff will usually just buy a midsized holley or edelbrock and bolt on, half ass tune it, then bitch about how bad carbs suck.

I havent messed with anything but my beloved 2150 2bbls for 10 years or so. Even then i dont play with jets and things since they are on stock engines, just tune em and let them do their thing.

Small engines same deal. Rebuild them to stock and call it a day.

i do need to do something with my 48 cub last time i worked it hard it seemed like it was starving a bit.

Unfourtantly carbs are a dying thing...as much as it pains me to say. Even mowers have EFI now.

I was always a die hard carb guy, but ive slowly warmed up to EFI now in kinda indifferent. EFI is still a pain to fix IMO and from my standpoint i dont really see the advantage to it over a properly operating carb
 

Josh B

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I have a trash can mostly full of old carbs and glass fuel filters in a shed that I never did anything with
 

gw33gp

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The last time I played with jets on a carburetor was about 15 years ago when I went back to a stock Holley on my 428CJ powered 69 Fairlane Cobra. The previous owner had installed a Holley double pumper on it, and I did not like the way it performed. I also wanted the car to be as original as possible. I found out right away the stock jets were not working very well mostly due to the change in gasoline since 1969. It took a few tries to get it right with the help of some guys on the FE Forum. It has worked very well since then.

My race car uses SU carburetors, and the jets are not changed for tuning. The tapered needle that runs through them is typically changed for tuning. Then I discovered the needles can be adjusted up and down for tuning for elevation and air temperature once the correct ones are use. This is kind of a fussy thing to do but easier than changing jets or needles, once my crew chief modified a depth gage for measuring the extended length of the needles.

I am also rebuilding a carburetor on an old Craftsman 6 HP motor that powers a Sears shredder. The hard part was finding the correct parts for the rebuild. That motor is over 50 years old, and I don't have any manual for it. I was not sure I could even find a rebuild kit for that old carb. With an extended internet search, I have a kit on order and am hoping it is the right one. There are no jets to change on it. There are just two adjustment screws, one for idle and one for higher rpm that are used for tuning.
 

superj

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i love carbs. my last one was when i converted my jeep from the stroker 4.5 to the 302. originally the 4.5 had a weber two barrel on it but it wasn't working out for the previous owner. i bought an offenhauser intake and put a holley four barrel from a 65 or 66 mustang on it and it ran awesome, better mileage and power. than when i swapped to the 302, i swapped the carb over to the 302 since the stroker was going to another wrangler.

i also converted my 79 bmw 320i from mechanical fuel injection to a two barrel weber carb using an intake for a 60 something bmw 1600. sucker was awesome after that. i always regret selling that car.

i was going to puta holley or another brand on my 79 gmc heavy half stepside but once i rebuilt the stock carb and tuned it properly, i was getting 14mpg on the highway so i knew it was about as good as it was going to get. it also ran awesome so no point in swapping since most people want to run a carb which is way to large for their engine so its tough to find a smaller cfm carb that actually is what fits a stock 350 v8.

the one pain in the butt carb i have had was on a 79 honda accord cvcc. it was a three barrel and the floats had holes in them. no one had a rebuild kit and a replacement carb was more than i paid for the car. so car left my possession.
 

Josh B

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Looks like the floats could be patched?
 

Eddo Rogue

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skyjacker front leveling kit
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Crossed threads are tight threads.
i love carbs. my last one was when i converted my jeep from the stroker 4.5 to the 302. originally the 4.5 had a weber two barrel on it but it wasn't working out for the previous owner. i bought an offenhauser intake and put a holley four barrel from a 65 or 66 mustang on it and it ran awesome, better mileage and power. than when i swapped to the 302, i swapped the carb over to the 302 since the stroker was going to another wrangler.

i also converted my 79 bmw 320i from mechanical fuel injection to a two barrel weber carb using an intake for a 60 something bmw 1600. sucker was awesome after that. i always regret selling that car.

i was going to puta holley or another brand on my 79 gmc heavy half stepside but once i rebuilt the stock carb and tuned it properly, i was getting 14mpg on the highway so i knew it was about as good as it was going to get. it also ran awesome so no point in swapping since most people want to run a carb which is way to large for their engine so its tough to find a smaller cfm carb that actually is what fits a stock 350 v8.

the one pain in the butt carb i have had was on a 79 honda accord cvcc. it was a three barrel and the floats had holes in them. no one had a rebuild kit and a replacement carb was more than i paid for the car. so car left my possession.
I think you are talking about the infamous quadrajet. Great carb IMO. Rebuilt a many back in the days.
 

Eddo Rogue

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Location
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Ranger 4x4
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4.0 V6
Engine Size
OHV
Transmission
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2WD / 4WD
4WD
Total Lift
skyjacker front leveling kit
Tire Size
31-10.50R15
My credo
Crossed threads are tight threads.
The last time I played with jets on a carburetor was about 15 years ago when I went back to a stock Holley on my 428CJ powered 69 Fairlane Cobra. The previous owner had installed a Holley double pumper on it, and I did not like the way it performed. I also wanted the car to be as original as possible. I found out right away the stock jets were not working very well mostly due to the change in gasoline since 1969. It took a few tries to get it right with the help of some guys on the FE Forum. It has worked very well since then.

My race car uses SU carburetors, and the jets are not changed for tuning. The tapered needle that runs through them is typically changed for tuning. Then I discovered the needles can be adjusted up and down for tuning for elevation and air temperature once the correct ones are use. This is kind of a fussy thing to do but easier than changing jets or needles, once my crew chief modified a depth gage for measuring the extended length of the needles.

I am also rebuilding a carburetor on an old Craftsman 6 HP motor that powers a Sears shredder. The hard part was finding the correct parts for the rebuild. That motor is over 50 years old, and I don't have any manual for it. I was not sure I could even find a rebuild kit for that old carb. With an extended internet search, I have a kit on order and am hoping it is the right one. There are no jets to change on it. There are just two adjustment screws, one for idle and one for higher rpm that are used for tuning.
Same goes for most motorcycle carbs. They are tunable with the needle. The keihin FCR39 is a very common carb on race bikes, and retrofitted as an upgrade often. This thing has a library of various tapered needles with multiple clip position settings.

I have done my share of tuning with jets, but only recently dabbling with needle/float adjustments...mostly out of necessity.

I don't bother with small engine carbs....if they need anything beyond a half ass cleaning, I just order a new one off fleabay...They're like $20 bucks for a knock off and work fine, and have them for everything.

So far I've run knock off fleabay carbs on my pressure washer, weed whacker, chain saw, and log splitter...It works!
 

Eddo Rogue

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4WD
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skyjacker front leveling kit
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My credo
Crossed threads are tight threads.

gw33gp

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Same goes for most motorcycle carbs. They are tunable with the needle. The keihin FCR39 is a very common carb on race bikes, and retrofitted as an upgrade often. This thing has a library of various tapered needles with multiple clip position settings.

I have done my share of tuning with jets, but only recently dabbling with needle/float adjustments...mostly out of necessity.

I don't bother with small engine carbs....if they need anything beyond a half ass cleaning, I just order a new one off fleabay...They're like $20 bucks for a knock off and work fine, and have them for everything.

So far I've run knock off fleabay carbs on my pressure washer, weed whacker, chain saw, and log splitter...It works!
I looked at knock off carb for my Craftsman engine. None of them had the throttle choke control mine has. The throttle is not totally controlled by the throttle linkage. It is controlled by a governor. It can be throttled back, but there is a spring in the complex linage the allows the governor to override the throttle. I decided it would be better to rebuild. It is a diaphragm type carburetor with no float and the diaphragm and needle seat needed to be replaced. Of course, once I took it apart, the gaskets also needed to be replaced. That carburetor body is still in great condition.
 

1990RangerinSK

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I do a lot of messing with carbs on bikes....wondering if anybody does that with vehicle carbs?

I think the last time I rebuilt an actual vehicle carb was maybe 20 years ago.

I mostly rebuild single cyl/small engine carbs.

did an inline 4 cyl set of carbs once....made a home made vacuum gauge to sync em...not sure how I pulled that off.

I am putting cleaning a Keihin FCR now. The air/fuel screw spring popped out and disappeared...and the o ring is stuck inside the carb body....so I decided to take a break and post this thread. I dont own any carbureted vehicles or bikes with more that 1 cylinder....yet I am sick of rebuilding carbs.
Carbs are the devil.
 

1990RangerinSK

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Race guya mostly anymore. Guys who drive carburated stuff will usually just buy a midsized holley or edelbrock and bolt on, half ass tune it, then bitch about how bad carbs suck.

I havent messed with anything but my beloved 2150 2bbls for 10 years or so. Even then i dont play with jets and things since they are on stock engines, just tune em and let them do their thing.

Small engines same deal. Rebuild them to stock and call it a day.

i do need to do something with my 48 cub last time i worked it hard it seemed like it was starving a bit.

Unfourtantly carbs are a dying thing...as much as it pains me to say. Even mowers have EFI now.

I was always a die hard carb guy, but ive slowly warmed up to EFI now in kinda indifferent. EFI is still a pain to fix IMO and from my standpoint i dont really see the advantage to it over a properly operating carb
I've said it before, I'll say it again. Carburetors are the devil incarnate.
 

1990RangerinSK

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i love carbs. my last one was when i converted my jeep from the stroker 4.5 to the 302. originally the 4.5 had a weber two barrel on it but it wasn't working out for the previous owner. i bought an offenhauser intake and put a holley four barrel from a 65 or 66 mustang on it and it ran awesome, better mileage and power. than when i swapped to the 302, i swapped the carb over to the 302 since the stroker was going to another wrangler.

i also converted my 79 bmw 320i from mechanical fuel injection to a two barrel weber carb using an intake for a 60 something bmw 1600. sucker was awesome after that. i always regret selling that car.

i was going to puta holley or another brand on my 79 gmc heavy half stepside but once i rebuilt the stock carb and tuned it properly, i was getting 14mpg on the highway so i knew it was about as good as it was going to get. it also ran awesome so no point in swapping since most people want to run a carb which is way to large for their engine so its tough to find a smaller cfm carb that actually is what fits a stock 350 v8.

the one pain in the butt carb i have had was on a 79 honda accord cvcc. it was a three barrel and the floats had holes in them. no one had a rebuild kit and a replacement carb was more than i paid for the car. so car left my possession.
One more time for those in the back: Carburetors are Satan himself.
 

rusty ol ranger

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bilbo

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I did a lot of tuning trying to get my Ranger to run right after I swapped in a Holley 5200. It still isn't perfect, but it's serviceable and I got tired of running in circles messing with it. I could never really get rid of the tip-in stumble and kind of arrived at the conclusion that there's an issue with when/how the PCV valve opens and the carb not expecting it. If I tuned the carb properly it would get great mileage but be almost undriveable in town where there are lots of stop/starts. I could richen things up to get rid of 75% of the stumble at best, but mileage really suffered. When I moved to FL, my commute is 5 minutes across town so I have it adjusted more on the richer side. It sacrifices economy but I only put on 5-10 miles per day.

There have been countless small engine carbs I've messed with. I built up a trike a few years back and used a Predator engine for it. After an upgraded air cleaner and freer flowing exhaust I had to drill out the jets to bring it back in tune. Also I've messed with quite a few snowmobiles. Most of the ones I played with used Mikuni VM or TM carbs, and had the needle adjustments as described above. They had charts showing what effects the adjustments had for different throttle positions. Sleds seemed more finicky about tuning than anything else I worked on.

I once had an old Deere sled with a Walbro carb. It ran, but very poorly, so I decided to rebuild the carb and bought a kit. The carb was made up of plates with gaskets in between. Each plate had an array of passages, check valves, balls, springs, etc. ready to fly across the room at any time. It was imperative to get the right spring in the right spot on the right plate as they weren't all the same. It took me most of a day to reassemble it, what a nightmare. I never could get the sled to run again and sold it.
 

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