Jetting on pe 28mm carb Please help

[dadofethan47]

I had a 24 mm pwk carb on my girls apex and the one with the hose and power jet. It had 110 main and 42 pilot jet in it and was sputtery in the midrange. I was running tt 111 race fuel. Max rpm ported cylinder and hetrick gen 2 pipe. it has 165#s of compression.

I bought a pe 28mm roundslide. It has 42 pilot and 135 main. it starts to idle high 1.75 turns out on air screw. But when you hit the gas fast it falls flat on its face and bogs horrable. if you don't let off for a second it will die. Does anyone have any ideas on what needs to be done? I have moved the clip up down and maybe even sideways lol. I am at a loss on what to do. Please help
thanks

[bloodswet&gears]

When you had the bowl off to see what jets were in it, did you check the float level?

[dadofethan47]

It's supposed to be sittlng level right? Thats the way it is on mikuni carbs so just assumed these are the same way.

[Logan #34's Dad]

those jets should be pretty close BUT if your 24 only needed a 110 then your probably too fat.
The infamous "bog" is usually caused by either too much air or too much fuel. This is always a tricky one - trying to "fix" someone elses jetting issues not knowing whats been done so the engine or ALL the other components.
There is not that much difference between a 24mm and a 28mm. Throw like a 115 in that 28 and see how she sounds. I think that is way way lean though.
My advice: Go with good ole VP C12 - Once you start messing with crazy fuels OR have to much/little octane or Oxygen it gets REAL hard to keep up with jetting. I know we all want the fuel that "makes the most power" but most of the time we hurt the performance. And truth be told - engine power is NOT the main factor in a win or loss unless its drag racing....
Logan got outrode last year by a few riders even after he'd pull a holeshot.......It is what it is....
My .03 cents.....

[dadofethan47]

If you give it just a little throttle before you pin it it only has a small bog. about 1/4 throttle or so. If you just smash it to the bars when just idling it will die if you don't let off it. Stupid 90s starting to get fed up with them already and are first race is sunday and I am already getting tired of them. Ug going to be a long season.


Originally posted by Logan #34's Dad
those jets should be pretty close BUT if your 24 only needed a 110 then your probably too fat.
The infamous "bog" is usually caused by either too much air or too much fuel. This is always a tricky one - trying to "fix" someone elses jetting issues not knowing whats been done so the engine or ALL the other components.
There is not that much difference between a 24mm and a 28mm. Throw like a 115 in that 28 and see how she sounds. I think that is way way lean though.
My advice: Go with good ole VP C12 - Once you start messing with crazy fuels OR have to much/little octane or Oxygen it gets REAL hard to keep up with jetting. I know we all want the fuel that "makes the most power" but most of the time we hurt the performance. And truth be told - engine power is NOT the main factor in a win or loss unless its drag racing....
Logan got outrode last year by a few riders even after he'd pull a holeshot.......It is what it is....
My .03 cents.....

[Logan #34's Dad]

Yep, either its gulping to much air for the amount of fuel being delivered OR to much fuel for the amount of air.
If it ran good with the 24mm - go back to it. On the 24 i think your too lean on the main. If there is a mid-range issue then that is more than likely the needle clip position - compounded by a jet that does not allow enough fuel in. Just for fun, put like a 125 in the 24 then try it. With the rear wheels off the ground and the engine warm, hold the throttle at half throttle. Move the clip up or down on the needle until the revs stay somewhat consistant at half throttle. If the engine cuts out your rich if it revs on its own your lean.......adjust needle accordingly.

[dadofethan47]

Ok i will try that. The 24 has that stupid powerjet in it. But I will try what you said. I have the wonderful wife picking up a barrel of C12 on thurs. Thanks for the info.


Originally posted by Logan #34's Dad
Yep, either its gulping to much air for the amount of fuel being delivered OR to much fuel for the amount of air.
If it ran good with the 24mm - go back to it. On the 24 i think your too lean on the main. If there is a mid-range issue then that is more than likely the needle clip position - compounded by a jet that does not allow enough fuel in. Just for fun, put like a 125 in the 24 then try it. With the rear wheels off the ground and the engine warm, hold the throttle at half throttle. Move the clip up or down on the needle until the revs stay somewhat consistant at half throttle. If the engine cuts out your rich if it revs on its own your lean.......adjust needle accordingly.

[Ryko racing]

that carb should run decent with a 130 main 42 pilot and clip 1 or 2. we ran 135 42 clip 2 on all our cobras an its almost the same on the hondas. if you run oxygen go to 142 main.

[bloodswet&gears]

Originally posted by dadofethan47
It's supposed to be sittlng level right? Thats the way it is on mikuni carbs so just assumed these are the same way.
It should be 14mm from the bottom of the float to the gasket surface.
You will have to hold it at an angle, not upside down. You don't want the float to push down all the way on the needle. It has a spring loaded valve pin in the needle and you want it barely resting against it when you measure it.

[dadofethan47]

I tried everything with the 28mm Did float main, pilot, needle. And still had the bog on bottom, I went back to the 24 like logans dad said. Ended up with 118 main and 40 pilot needle in #2 position. I could probley go down 1 more on the pilot as the air screw is at 3 turns out before it revs up at idle. My daughter said it rips now. I can't judge as I am too fat to ride it. But it sounds better. But now my clutching is off again Dam it. I can't get a break

[redonkulousruntsracing]

I had the same problem with my 28mm on my boys RT 70. Was trying to tune with a 40 and 42 pilot jet and it didnt matter where the clip was on the needle it would bog when you just whack the throttle. Ended up going all the way up to a 50 pilot and the clip all the way down to get it right, Now when you whack it, it blows the tires right off of it, instant throttle. If you hit yours and hold it there and it dies, its wants more gas. Try a bigger pilot 45-50. If you have too big a pilot it wont act the same, it will blubber and stumble, but not fall flat on its face. Good luck. And by the way, mine runs best with a 135 - 138 main depending on weather.