I'm trying to jet my bike using Viper Bikers manual, which is very good btw

Just opened up the carbs on my NC24 and found 115 in the front and 110 in the back.
The manual says it should be 112 - 110.
Could this be causing the bike to run rich and backfire occasionally??
When the bike is cold it doesn't really pull at all at high rpm, and when warmed up I think it pulls ok but i don't know any different as its the only bike i've ever owned.
Would the best course of action be to lower the front jets to the standard?? Or raise the rear jets to 112?

The only mod on my bike is a scorpion end can.

Any advice appreciated :)

Hi I'm no expert but I would try the std jetting and also check your air screws as I just found mine miss adjusted . Mine may have been set up with restrictors at one time as it had a set of 110 main jets ( NC30 ).

castrol101 wrote: When the bike is cold it doesn't really pull at all at high rpm

Probably not a good idea to be revving it high when it's cold.

Probably not a good idea to be revving it high when it's cold.

I don't make a habit of it coz i know its bad, but was just to check the jetting.

you need to buy new needles then to go down a jet size?

not new needles just new main jets..

okay, so the needles are the pilot petrol squirters and the main jets are the big petrol squirters? hehe

that is my understanding... You can change pilot jets in the same way you can change main jets though without changing the needle itself. You can also adjust needle height to play with the mixture i.e. rich/lean

castrol101 wrote:

Probably not a good idea to be revving it high when it's cold.

I don't make a habit of it coz i know its bad, but was just to check the jetting.

I doubt you can check the jetting on a cold bike revving in neutral and not pulling any load.

Take it for straight line tests somewhere where you can give it the berries ina couple of gears after each fettling.

Get an idea of where you stand with rich/lean and whereabouts in the revs this is so you know where to start changing your carbs.

It is a ballache...but worth it. This is why we pay dyno operators to do it in 2 hours for you...

Lope wrote:okay, so the needles are the pilot petrol squirters and the main jets are the big petrol squirters? hehe

Have a look at some carb diagrams and it makes sense..