Carb bore, slide size relitive to needle and jetting.

[krazyinski]

I like many others read a lot of threads on jetting and mods. I have noticed a lot of threads regarding RB carb mods and jetting and tunning. there at times recommendations made on needle size or type. I have played with many needles on my bike B, C, D needles. how ever and have settled on the C needles. D needles are to rich to use in a stock carb bored out to 36mm with 5 slide . most of the best detailed info has com from you that have a RB carb with leaner slide. This took a while for me to figure out. does not seem as if there is that many on this forum running Fredette mods.

[m0rie]

Do you happen to have a log of the needles (and jetting) you have a tried, clip positions and what the results were?

[krazyinski]

yes I have.
bike info 220 nikasil cylinder, ported, milled head,carb bored to 36mm
fmf woods pipe, power core 2 can.

temps 90-99 humidity 40% 700 ft ^sea
fuel 40:1
pilot , needle , main , air screw , results
45 - 1173-3 - 160 - 3 - rich at 1/8 to 1/4 with a big hit

45 - DEM-3 - 155 - 3 - good 0-1/8 flat spot 1/4-1/2, less top end

42 - Dem-2 - 155 - 2-2 1/2 - rich at 1/4 - 1/2 may be to fast of taper lean 3/4 to wot plug chp shows lean.

42 - cek-3 - 155 - 2+-1/2 - rich at 1/4 ok on the rest still to rich get the drips big time feels flat on wot

42 - del-3&2 - 155 - 2 - feels same as dem to rich

42 - cel-2 - 155 - 2 - does not want to idle at working temps, throttle response good, still drips

42 - cem-3 - 155 - 2+-1/2 - pulls hard a gear to high
after a lot of on off 0-1/4 throttle it has a 1/4-1/2 rich stumble.

42 - cem-2 - 158 - 2+-1/2 - crisp off idle response, will pull corners in third with good solid power,(no stuble,studders or bogging) top end feels unlimitted or faster than I want to go. plug read is moca brown. still get the drips a little, not bad.

42 - cgm - 158 --2-- this is the perfect summer setup the bike runs perfect top to bottom in 90 degree 40% humidity weather.

[m0rie]

This is with Fredette porting and a Fredette bored PWK correct? 36mm with no divider plate or slide modifications?

[krazyinski]

This is with Fredette porting and a Fredette bored PWK correct? 36mm with no divider plate or slide modifications?

yes

[santod]

42 - cgm - 158 --2-- this is the perfect summer setup the bike runs perfect top to bottom in 90 degree 40% humidity weather.


We ride in similar condition and I have had the same experiences with all the commonly recommended needles. For the most part they are too rich down low and sometime create idling issues.

I recently moved to a CEN needle and have had great success. A strong bottom end, good idle and great pull through the powerband. If you have not tried this needle I would give it a shot.

Bike Info

1997 kdx200
38 pilot
155 main
CEN needle
1.75 on air screw
Rad Valve
No porting
Stock 35 mm carb

[krazyinski]

I will give it a shot, it seems as if the porting is a big player in my jetting. for the past few months I have raised the needle to compensate for the cooler temps.

[fuzzy]

Keep us posted. 'Commonly recommended' will more than likely not apply to your ported cyl, but the near-infinitely tunable carb will get there eventually!