Mixture screws on jetted 1998 CBR600 F3
 

Hello all,

A previous owner of my 1998 CBR600 F3 put on a jet kit (142-144-144-142), K&N and aftermarket exhaust.

I don't know any more details than that, because I only found this out when I stripped the carbs.

The pilot screws seem a long way out (2.5 turns), given the factory setting is 1.5 turns.

I've had a look online at the instructions for dynojet's stage 1 (I have no idea what was actually fitted) and they have the pilot screws only backed out 0.5 turns i.e. the opposite way to what mine are.

My feeling is the bike is running rich. The condition of the plugs back that up.

I have a Gunson colortune, and I can screw the pilots all the way in and it still runs, and doesn't even look lean. It is definitely running rich at higher revs (4-6000rpm) using the colortune.

Has anyone run a similar setup and knows what their pilot screws were at?

I'll keep working with trial and error, but it would be good to have a better starting point. Moving from 2.5 turns to 0.5 turns is a fairly drastic change in the lean direction!

Cheers

Are you going back to stock, or was the settings for a different exhaust, could be the jet needle is on a lower clip making it richer, see here

Thanks for the reply (again!).
I'm not going back to stock as I can't justify the expense on replacement jets etc right now. I just feel the mixture is right out of whack at the lower to lower-mid range.
Needles are on 2nd clip, but it feels right in the mid range so I'll be leaving them be.
I'm just confused as to why the pilot screws have been adjusted in the opposite direction to what I would imagine they need i.e. after jetting they have been opened more, not closed.

Just wondering, did PO return the can back to stock and keep the can that was set-up for the rejetting , as you know an upgraded can will lean out the jetting, would check out again the pilot screw adjustment think it should be closer to 3 turns out to lean the mixture, jets are bigger than what they should be for stock,
Edit re-read the first post see you have the upgraded can on, and if the engine is still running with the screws turned in you will need smaller pilot jets

Have a look at this on e-bay , I ordered 4x#40 for a cbr400rr got them in 3 weeks ,worked well and cheap:)
https://www.ebay.co.uk/sch/sis.html?...72.m2749.l2658

Thanks once again for the reply.
I've done some playing around today and 1.75 turns seems to be the sweet spot, although I won't know until I've pulled the plugs after riding it for a bit.
Thanks for the link too - ideally, I want to put the bike back to stock and if I can get all the jets at that sort of money it shouldn't break the bank
Just for my confirmation... when you say "3 turns out to lean the mixture", doesn't turning the pilot screws out enrich (not lean) the mixture?

Correct matey, what I meant to say was 3 turns out for stock can, as the upgrade can already leans it out, and those jets work a treat (they have even got the Kehin stamp on them)

Brilliant, that makes sense. Thank you