Mixture screws on jetted 1998 CBR600 F3
#1
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
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
Last edited by hk3; 02-26-2018 at 04:04 PM.
#3
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.
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.
#4
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
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
Last edited by CaBaRet; 02-27-2018 at 03:44 AM.
#5
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
https://www.ebay.co.uk/sch/sis.html?...72.m2749.l2658
#6
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
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
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?
#7
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)
#8
#9
That seems a little much. We have pretty much the same setup and my dynojet kit called for I pretty sure was 140s on outside and 138s on inside. I could have that backwards but my bike was already jetted all it’s missing is the 140s cause the person before me didn’t have K&N filter on it so as I put one on I rejetted. It also called for the e clip on the needle 4 spots down. The pilot screws I back out 1.5 as .5 is not enough. But I pretty much have a whole kit for a 95 F3 minus the 140 plus two more 138s. If you want it I’ll sell it to ya for 50 bucks plus shipping if you think that is fair or shoot me a offer. Hope this helps
Last edited by HAndHEldJEsuS; 03-07-2018 at 07:12 AM. Reason: Messed up and out a quote from different post in the replay
#10
That seems a little much. We have pretty much the same setup and my dynojet kit called for I pretty sure was 140s on outside and 138s on inside. I could have that backwards but my bike was already jetted all it’s missing is the 140s cause the person before me didn’t have K&N filter on it so as I put one on I rejetted. It also called for the e clip on the needle 4 spots down. The pilot screws I back out 1.5 as .5 is not enough. But I pretty much have a whole kit for a 95 F3 minus the 140 plus two more 138s. If you want it I’ll sell it to ya for 50 bucks plus shipping if you think that is fair or shoot me a offer. Hope this helps