4mil cheeta cub stock carbs jetting

[hykrymez]

wuz up guys i have a 2006 banshee with a 4mil and a cheeta cub the bike had 34mm carbs and ran good but now it has stock ones.. the jetting on the carbs now is 340 and when i try and take off the hole it shuts off ( only when i take it out hard like when racing.. im thinking its way to rich..? should i go like 300 or 290 jetts? and in the future when i start working again i want to get bigger ones what size does anyone think i should put? thank

[SonOfSand]

We need to know what elevation you ride at, and what the average temp is. What is the needle set at? Do you have pods or the stock air box? These are all part of the equation. I feel confident in saying you should not go any leaner though.

[RadarRacing]

I'm not gonna bust your balls and since this is your first post don't take this as anything other than me trying to help but you need to look at your sparkplugs to tell what you have. Plug chops and all that stuff is on this site very easy to find. Learn to read a sparkplug as your first step to learning what jetting you need.

[J-Madd]

You won't find a lot of info about where to start jetting stock carbs on a cub. There was a long thread a few years ago about how a guy had to go with relatively small jets due to the fact the that the Cub creates more intake velocity than stock cylinders and draws more fuel through the jets. Good luck. And yeah, as mentioned, check your plugs to see where your jetting is at.

[camatv]

if its falling on its face is stupid LEAN!!

 

last cub i did had a clean up port by me cpi's and case porting with stock carbs ended up with about a 410 main in it. ran bad ass.. stick a 400 in it and see what happens.

 

cubs like FUEL!

[wacko2000]

Welcome to the HQ first off

And i really cant help ya with the jetting on a cub

But as far as stock carbs go, I was running 380-420 in a 4mil, aggressive trail port and all the other shit

32.5 pilot as-well

What pilot do you have in right now?

If i had to guess, without knowing elevation or anything, i would say that you are way lean.

I would listen to the above ^^^^ and jet up some, learn to read the plugs and than slowing come down on the jets if need be

Good luck

[J-Madd]

Requiring bigger jets is not always an indicator that one motor needs or likes more fuel than the other. I run 0.116" mains in 16 mil Cheetah and 0.124" in the 4 mil Cub. The 610 cc Cheetah no doubt requires more fuel than the 421 cc Cub.

[sleeper06]

If any one knows about effeciant porting its wacko

[camatv]

are the slow jets the same size on those 2 motors same power jet style?

 

i have noticed that the bigger cheetas DO use a smaller dump, main ( with gas converted carbs) i FEEL <--( OPINION) that the cheetas are much more efficent than the cubs. the larger motor makes more power easier and with less fuel demand BUT a carber ator also reacts to the pull across the jets and the size of the air supply to the bowl. rember the carbs actually drawing a vacume in the bowl and the outside pressure is whats pussing the fuel into the carb..

 

i know on my 535 i can almost run the pj's off on my 44mm packards. and it will run really strong. most cubs i just cannot seem to get enough fuel to run them very far as they really demand a lot of fuel.

[J-Madd]

I actually had the Dave Moore powerjets on the cub, so I was getting more fuel than it should be able to use. I just took it to the dyno Saturday (since my above post) and ran some 0.118" dumps and mains, and clippard powerjets on the carbs and it would make the same power, rich or lean. The Cubs do handle fuel in a strange way. I had never thought about it as "fuel efficiency."

 

Had my Cheetah on the Dyno, and when it got just a little fat, the HP would fall of a ton. I'm talking - 20 hp with a turn of the powerjet.

[camatv]

the wording for it is volumetric effeciency i believe? ( been a while since i dealt with it) its the ability of an engine to fully fill its cc size without any type of adders like NOS or turbo, super charger most motors are in the 90-98% range and its kinda hard to get an engine to overfill itself UNLESS you use a concept of internally pulling a vacume on a motor or use a higher velocity intake/ port design to add weight to the air coming into the motor and after the piston stops use that higher velocity to help overfill the engine.

 

i used V.E. calculators in the automotive field sometimes to figure the condition of an engine and/or test certain componets like emmisions parts and intake MAF sensors and stuff.

 

those dave moore pj's are pretty sensitive i like them they dont waste as much fuel i feel as other pj's. the clippards work good too.

 

also rember the less fuel is in the bowl the less pressure?? is able to push the fuel inot your cylinder. what i mean is if your bowls have less fuel in them its also harder for the motor to pull the fuel into the engine. also one of the reasons i dont run alky carbs pig rich on the slow's/ needles, lower speed's. puts more fuel in the bowl for the run instead of blowing it all out the pipe.