Rb Sprocket set up

[sydduckett]

Have run in my Rb20 and 4th gear really isnt happening, pulling like a train in all the others but no matter how much you give it in 3rd 4th just falls away immeadatley. Not sure if this is the sprockets or the pipe so am going to swap the Nk for a JL2 then see how she goes.
Think i will have to change the sprockets as well, can any one let me know what sprocket set up i should use. Im current running like this:

L1150 box
Nk Mid pipe
30m delly
46x16 sprockets

Someone sggested i try 47x18?

Ta
Sef

[carlos fandango]

You have a final ratio 4.9 at the moment so a change to 18/47 would give you 4.4 which would make it worse.
I have a rb20 with a gp150 box and 18/47 sprockets giving 4.8 and i like it. it does have the big gap between 3rd and 4th but i blast it everywhere anyway so dont notice it much. i do have to change down on long hills but i sacrifice this for faster on the flat
I have also tried the li150 box with 16/46 sprockets but didnt like it .
What carb are you using?
Russ

[bazman]

You have a final ratio 4.9 at the moment so a change to 18/47 would give you 4.4 which would make it worse.
I have a rb20 with a gp150 box and 18/47 sprockets giving 4.8 and i like it. it does have the big gap between 3rd and 4th but i blast it everywhere anyway so dont notice it much. i do have to change down on long hills but i sacrifice this for faster on the flat
I have also tried the li150 box with 16/46 sprockets but didnt like it .
What carb are you using?
Russ

I'm using af close ratio with 19/46 giving 4.8 and to be honest struggles in 4th on a roads if slight headwind, so going to try 18/46 with one of the german chain guides which pushes the chain down, so no need to change the chain. Gives 5.1 ratio maybe too much of a change but will see.
What did you not like with the li 150 box?

[ABC]

my mates rb 20 runs fine with the li150 box 16/46 sprockets nk race and a 34mm vhsb and it pulls like a train in all the gears. . not that much slower than my rb22 with the same set up. i would try the 34mm on it as they have more power than a ts1 .then just ride it like you stole it!

[Muttley McLadd]

Are you sure it's gearing that's the problem? You're running the same as my iron 185, and that's fine. I'm about 13 stone, so it's pulling a fair weight too.

[Diablo]

Its probably the pipe causing the problem. Try 16/47 with an 81link chain. This gives final gear ratio of about 5. I'd be surprised if it doesn't pull this nicely and still rev on to a good top speed.

[sydduckett]

I presume that its the gearing as there really is nothing there when you hit 4th just dies. Have had a couple of other people have a go and they have said the same as wanted to check it wasnt me being a tad nervous when giving it the beans. We have a 34m delly and a JL2 pipe which we are going to try combinations of first before mucking about with the sprockets.

Doing my head in but hoping to get somewhere with it today

syd

[Train Driver]

Sorry something wrong there i am running a classic rapido 24mm mikuni through an ancillotti and mine pulls Li150 and 18/46 and my delicate 224lb frame even 4th. max revs are 6500 in all gears.

[sydduckett]

6L, i know what you mean but i dont think you can do comparisons with diffrents kits when talking about sproket set up. Really need somone who has got rb 20 with 30m carb and nk exhaust, then i have a direct comparison...at least i think thats the best way. all trial and error i guess

syd

[sydduckett]

Have tried the 34 delly today and wasnt an improvement so i guess its either the sprocket se up or the box, 4th is still not there,even worse with the 34 so back on with the 30. People seem divided on the best sprocket set up so im a bit stuck for what to try next. Have a spare JL2 pipe im going to give a go to see if that makes any difference but i cant really keep trying pipes, so does anyone have any suggestions. Got an li150 box would a Li125 be any better as a mate has a spare i coulds try that?
Have now done the 600 miles so will drop it down top 3% but dont think that is going to change things much. also i feel theres no point in getting it jetted/dynoed yet as it feels like a gearing issue?

Any suugestion in order of lowest cost first appreciated..

As you were

syd