Carburettors explained, how do they work?

[Kiwi Rider]

Here's some technical info for those members with a thirst for knowledge on carbies, often a mystery even to mechanics!
Most mechanics under the age of 35 will only have FI under their belts, carbies?? give them to the old vet mechanics lol.

http://www.mikuni.com/pdf/vmmanual.pdf

http://www.mikuni.com/pdf/hs40_manual.pdf

 

[Bumblebee]

Sure is nice to no longer deal with carbs except on the lawn equipment....

My neighbor bought a new lawn tractor and it has a Kawasaki fuel injected engine in it....

 

[WuzzaCBXRider]

I had twelve of them between two bikes but actually once they were synched and kept clean (used frequently) they worked perfectly well. They did drink gas though. I never got over 30 mpg and about 22 mpg when I was really honking them. Most CBX owners weren’t so much ‘riders’ as they were owners who brought them out every summer, with gummed up carbs, and then had to have them cleaned, adjusted and synched before they could ride them. One rally I attended, which I dubbed a parking lot rally, an owner trailered his from SF to Morro Bay on hiway 1, one of the best riding roads around. Some treated them like trophies instead of motorcycles.

 

[kim windsor]

My 37 Indian had one carb my 500 H-1 3 carbs almost all of my best after that had at least 4 carbs but ,time they are A. Changing

 

[ROADTOAD1340]

I had numerous sets of Mikuni RS series flatslides for my many GSXR11's over the years , and though they were great to work with setting up , I truly love my injected motorcycles .

 

[fallenarch]

So for you carb guys: Are carbs smoother than injection (assuming they are adjusted properly)?

 

[Bumblebee]

I've never found any smoother...

In the carb tuning days, there was no ECU to plug into so the AFR was always in question.

We had to really rely on the tuners to get the carbs close to where they needed to be...spark plug chopping was far more serious to getting the tune close.

Tuning 2 strokes was a thing of mystery...I had the fortune to serve with a guy who cut his teeth tuning 2 racing 2 strokes...he was more an "alchemist" than anything else.... by the time he was done tuning my 2 stroke, the plugs were a light tan color. He told me the stock oil injection system wasn't able to be tuned so he had me buy and aftermarket racing oil injector which was able to be tuned to get the mixture just right.

I remember my GSXR race bike spending lots of time on a dyno while the carbs were being fine tuned...if we raced on a track which had higher or lower elevation, there was no way to adjust the carbs in a hurry to get the bike spot on unlike what can be done today.

I spent a lot of time getting the tuning for the carbs on my Bandit almost perfect...when I sold it a big container of jets and needles went with it, and I sure don't miss them.

 

[bigoltool]

I don't miss screwing with float heights and those little clips and washers! Must have had the carbs on and off my GS1150 100 times over the years!

 

[pcs]

i swapped my FI suzuki ltr450 to carb. makes more hp but that is bc i has already bored the throttle as big as i can. i run a larger single hayabusa style down draft carb. definitely not a smooth as FI during partial throttle but that ltr is used for hill shooting drags so i don’t use part throttle much. clogged jets and dumping fuel every time you swap jets get annoying especially when you’re spending close to $10/gal for race fuels.

 

[Bumblebee]

One can certainly tell when a bike (or car) is out of tune..

On a ride today I fell in behind a couple Harleys and a metric cruiser and the fumes coming off those were enough to make my eyes water. I actually pulled off to let them get down the road...as there was little wind, they were out of sight yet I could still smell the fumes off their bikes..

I later got behind a "tuner" car and it smelled similar....

The AFRs on these vehicles must have been way off as probably all they did was throw on parts with no dyno time..

Reminded me of the carbureted days and them always being out of adjustment.

 

[Kiwi Rider]

It’s great to hear all your stories and experiences with carbs... sounds like general consensus is . . . “Good riddance to carbs!” Lol
My DRZ400E has a Mikuni flatslide pumper carb and I’m about to strip, inspect, clean, overhaul and tune it so I see it as a challenge in a positive light rather than a pain in the a$$.

 

[Bumblebee]

It’s great to hear all your stories and experiences with carbs... sounds like general consensus is . . . “Good riddance to carbs!” Lol
My DRZ400E has a Mikuni flatslide pumper carb and I’m about to strip, inspect, clean, overhaul and tune it so I see it as a challenge in a positive light rather than a pain in the a$$.

I still have carbs, they are just on power equipment now..

Ever work on a carb off a string grass trimmer??? Now they are a PITA...?

One of my neighbors wondered why his snow blower wouldn't go last fall...of course he asked me to look at it...the carb was so gummed up it was easier to just go get a new one..(which we did).

I bought him a jug of fuel stabilizer for Christmas....

 

[pcs]

im still messing with carb too all the time. easy to fix especially if you break down in the middle if the desert. FI is just less maintenance for daily use, more time riding rather than tuning and setting. i got a decent sized lectron carb crammed in there and it need constant tuning.

 

[WuzzaCBXRider]

im still messing with carb too all the time. easy to fix especially if you break down in the middle if the desert. FI is just less maintenance for daily use, more time riding rather than tuning and setting. i got a decent sized lectron carb crammed in there and it need constant tuning.

View attachment 1638031

View attachment 1638032

How about a pic of the rooster tail under WOT?

 

[WuzzaCBXRider]

A couple guys I know who got tired of six carbs went turbo and used a big Harley carb, the black and red ones. Mine’s the bagger in the middle.

 

[Bumblebee]

A couple guys I know who got tired of six carbs went turbo and used a big Harley carb, the black and red ones. Mine’s the bagger in the middle.View attachment 1638033

That's a lot of power in those spaghetti frames....

I had a buddy who had the exact same bike as yours...

 

[c10]

So for you carb guys: Are carbs smoother than injection (assuming they are adjusted properly)?

They can be . A ZRX1200 set up by me will be using CVK 36mm oem units modified lightly , and using a DJ jet kit on a full exhaust system . Dustin Moody makes a FI kit for the ZRX I would like to ride one some day.
Of course I've been working on ZRX carburetors for 17 years now . this is my 22 year old son Joseph when he was about 7 or 8 years old .
The thing most people get wrong on a carb is EVERYTHING !
Flatslides are great for power but not rideability compared to a CVK

 

[Bumblebee]

They can be . A ZRX1200 set up by me will be using CVK 36mm oem units modified lightly , and using a DJ jet kit on a full exhaust system . Dustin Moody makes a FI kit for the ZRX I would like to ride one some day.
Of course I've been working on ZRX carburetors for 17 years now . this is my 22 year old son Joseph when he was about 7 or 8 years old .
The thing most people get wrong on a carb is EVERYTHING !
Flatslides are great for power but not rideability compared to a CVK View attachment 1638035View attachment 1638036View attachment 1638037

I remember being a wee lad and watching my dad work on carbs off engines around the farm at the kitchen table!

We had a big workshop but the kitchen in the house was closer to the coffee and snacks....

The old days before Ski-doo went to Mikuni they used Tillotson carbs...these old carbs had a rubber diaphragm that needed to be replaced quite often. It was nothing to see a couple snowmobile carbs sitting on the kitchen table at breakfast time.

Seemed I was always working on a carb myself although the Mikunis needed much less work. And I learned a valuable lesson from my dad when it came to Mikuni carbs, they have a drain screw for a reason. Once I discovered a bit of preventive maintenance against gumming up, I only needed to concentrate on tuning them after that.

 

[pcs]

How about a pic of the rooster tail under WOT?

haha, i actually don’t have many pics myself in action

 

[michael parris heuberger]

It’s great to hear all your stories and experiences with carbs... sounds like general consensus is . . . “Good riddance to carbs!” Lol
My DRZ400E has a Mikuni flatslide pumper carb and I’m about to strip, inspect, clean, overhaul and tune it so I see it as a challenge in a positive light rather than a pain in the a$$.

Hi. At the track the main jets were to small. We did not have bigger ones ,so out comes the drill bits. The second try we spot on bike went the fastest it ever did.