I'm pulling my hair out trying to figure out this fueling issue; carbs are ABSOLUTELY FLOODING the goddamn engine when you go wide open throttle; works extremely well and pulls like a champ at part or half throttle though.

Confirmed this on several dyno runs, the engineer just scratched his head and told me to buy new carbs (Which i wont do because im on a severe budget to keep this champ running).

Checked the main jets (136/138+38 pilots, so stock everything for EU bike) and cleaned everything out, and it still runs like ****.

Anyway, got a new set of stage 2 jets in the mail, 140+42's since im running K&N+Full yoshi header+silencer system.

Is this the goddamn ram air solenoid that has failed on me? is it something else?

Gallery at imgur with specs and datasheet from the runs:

https://imgur.com/a/MunMKFY

 

Any luck? I have something very similar. Fine at cruise and mid, but give it any throttle and its pig rich. 10:1 on AFR gauge. I am using 126 dynojet jets which are equivalent of stock keihin sizes and its still terrible.

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You say you're going up a few jet sizes - I think you'll just make it worse. You wanna come down if anything. Don't think it's your air solenoid - I took mine off completely to see if that was the issue but it makes no difference. Doesn't seem to affect the fueling at low throttle either.

 

Have you checked the air flow is adequate? restrictive flow air filters will make the mixture rich by reducing the air component on high flow rates (ie higher RPM). Sometimes it is the simplest things.

Have you also checked the carb diaphrams for any holes / tears? This can lead to similar issues although typically more at mid range RPM.

 

I have got to the bottom of this. After months of head scratching by process of elimination I tracked it down to float needles. The tips of them were fine and so I'd over looked this but the spring loaded plungers had gotten soft over time and I assume because these bikes use a fuel pump, it's enough pressure to overcome the weak springs and let fuel past. Anyway 4 new float needles has my air fuel ratio in the 12s and 13s rather than 10s!

I used these from wemoto https://www.wemoto.com/bikes/honda/cbr_600_fv/97/picture/carburettor_float_needle. Perhaps not the cheapest but seem good quality.

Worth trying for the cost of 4 float needles.

Regards

Dan

 

Oh for the love of god is it this simple?! Ive been trying to solve this for the past 7 months after getting it on a dyno to find out why its bogging down, mind you usually the lambda probe only goes as low as 10:1, the tech was guessing 7:1 based on the exhaust smell and soot.

Gonna head out to the shed and pull off the carbs (AGAIN) and change the bloody float needles (and seats).

 

Let us know if your issue was the same.

 

Definitely worth a try. The quick test is to turn the carbs upside down on a bench and measure the float heights with them like that. This contradicts the manual as they tell you to measure them with the float tab just resting on the plunger. Anyway, at this point mine were about 11mm because the plungers were weak enough to be being compressed by the weight of the floats, which leaves you with a very high fuel level. After putting the new float needles in, when turned upside down, the springs were strong enough to hold them at the 13.8mm or whatever it says in the manual - I can't remember the exact height from memory. If that makes any sense.

Let us know how you get on. Oh FYI - I settled at 132 mains on all 4 cylinders (dynojet sizes), giving me ~13:1 - ~13.3~1 under full throttle- that's with standard header, aftermarket can, K+N panel filter. No other mods. Just to give you a baseline.

Thanks

Dan

 

Well found i'm sure a lot of folks with the older bikes will find that very useful

 

@Nobby_trussin That really is a good way to check the condition of the float needle. I had never really given it much thought. Given that they float height is not adjustable on the F3's that is really you're own recourse.

 

Great. Gonna get some time to do this saturday, gonna measure as best i can. dont really know where to measure but ill find a way. its the comparative measurement thats important.

Im going with 140 mains and 42 pilots (yoshi full system + K&N) gonna get it back on the dyno and see what results i get come springtime.