Scooterotica

it does look rather rich but also sounds rather overgeared, rb`s are rev monsters arent they?

Does look a bit rich but was this you just running it then checking the plug or did you do an actual plug chop and what setting was this actually at throttle wise?

From Rayspeed site instructions for RB20 fitting settings.
30mm delly
slide 35
x7 needle 2nd clip from top
AV266 needle jet
main jet 140
pilot 55 to 60
float 300
choke 80
mis 2.5 to 3.5 turns out.
your plug is very rich.These settings would be on the safe side,a starting point.

Ok, I've stripped the carb to see what's in it and found it nowhere near jetted for the RB20. It was fitted with a K21 needle rather than a U16. The main jet a 130 rather than a 170. The Pilot was a 30 rather than 55 and the choke jet a 60 not 50. The atomiser and slide were the only things that were ok. Now here comes the silly question. Would all these incorrect parts cause the symptoms I discribed in my original post? I've managed to find a website that has all the correct bits I need. I supposed the obvious answer is buy them and see? Any comments very welcome as I really want this to work. I keep hearing how good the RB20 is and I'm missing out on it. Thanks in advance Pete.

Ifound the best set up was 18 47 on an indian gp200 box. Re the rally pipethat may be oneof the reasons you down on power. I found that the only nk pipes that produced a power band were the mid and the race. The rally didnt, so i flogged it.

Good luck

...

Short gearing and a pipe that likes to rev, so suiting the porting of the RB kits. If you strangle the revs (cut short because the pipe becomes a rev limiter) or don't reach the revs because the gearing is too long you will stop the kit from working as intended.

Re: U16 vs K21 - Unless the K needle has been cut short, which some some dealers have done over the years, the U needle range is shorter than the K range, meaning that you cannot consider them as like for like with regard to taper length and tip diameter. The longer K needles will be far lower into the atomiser than the U needle with the same profile.

A mate of mine had the same issue on his RB20 with 34mm flatslide & using midrange NK

He had LI-150 box wi 16x46
Changed it to 15x46 & loads better

I built the motor 2 years ago and I'm pretty sure I used a 17/47 sprocket combo. I know I was aiming for AF's recommended final drive of 4.8. To be totally honest I'm doubting myself now. I think I'll whip the side casing off today and check exactly what's in there. If I jet the carb exactly to AF's recommendation and ensure the gearing is correct and useable the only thing left will be the pipe. Cheers guys I'll report back later.

Too rich.
At what point did you remove the plug; after idle; after sustained high revving; or after parking up ?
The colour isn't truly telling you the mixture at different openings of the carb.


Sorry missed all the other posts.