Carb Needles

[headcoats]

We have all been using JJH spec needles in our PWK 28 carbs as this was the one to get as they were the same spec as the standard KR needles

I have had loads of trouble setting mine up especially low and midrange
It has always screamed off in the powerband but light throttle was always compromised by something.

Just got this off the RD site

QUOTE
hello,

tobster,

JJH and N68X are the same I believe

Here are the specs for JJH and N68A which is fitted to the KR1

JJH
J = 3' 00' Taper Degrees
J = 25.40 L1
H = 2.435 Dia

N68A
A = 1' 35' Taper Degrees
H = 24.25 L1
R = 2.75 Dia

Seems to be a fair bit of difference


Now does anyone have the low down on what is the equivalent of a replacement needle ?

I ended up running (YPVS 350 engine)

#152 main (premix)
JJH needle clip 5 (richest) (will not run on anything less)
#45 pilot jets
airscrew 2 turns out (i know)
Ramair filters.
Allspeeds with detachable end cans
Mick Abbey Tune
V force 3 reeds

I went to #160 mains in the summer and lost 4.5 BHP and it wouldn't rev over 9 grand,so went back to 152's

Anything less than #45 pilots i get a horrible jerking on light throttle and only going up on the pilots seemed to cure it

But i guess the thing i need to know is about these fabled JJH needles

[dave32]

Sounds like you need a richer needle,why not profile your own?And you'r right,the kr needle is leaner than the other suggested alternative.
File a flat on one side(it doesnt need to be round) at the thickest part(top),this will richen the bottom end up just off closed throtlle.
The standard profile aint designed for a tuned/barrel inducted 350,so it aint gonna be right.
You can see how much your taking off,dont go too mad,just try a bit and see how it responds.
Why you running the airscrew so far out?
Could be why you need large pilots.
HTH
Dave

[headcoats]

There is a raging debate on the RD Forum now about these needles but the question is what are folks on here using when their standard needles have worn out as you can no longer but them from the dealer ?

[dave32]

So are you'r needle's worn out?
If so it will make the mixture richer,and your's sound too lean so a stock needle aint no good anyway,i cant see why anybody would think the stock needle is gonna be right for a 350 yam tuned or otherwise.
Personally i wouldnt worry about the stock needles as they obviously dont suit you'r setup,as long as you get it to run as it should it does'nt matter what profile you end up with.
Dave

[dave32]

The original N685A needles were superseded by N99,im guessing these are stock kr1s needles?
Am using these in my b2 and they work fine.
HTH

[martin]

you are not completly right there, the 99 needles were fitted to the last batch of kr1s [c3] as those carbs have a 4.0 cutaway on the throttle slide.
and the 68 needles are fitted to carbs with a 3.5 cutaway

[dave32]

The point was,you cant get the 68's but you can get the N99's.