On my quest to fix my F3, I bought a stage 1 jet kit. In the kit are instructions on how to bypass the air solenoid so that the ram duct feeds the carbs at both low and high speeds. One of the possible issues with my bike (flat spot at about 4k-5k rpm) is that the solenoid isn't kicking in due to a malfunctioning speedo.

Now the instructions state this mod is for race purposes. While I have no intention to race this bike, I am considering doing it anyways. Any comments? Any possible downsides to doing this?

 

The only reason its considered a race only mod is due to noise restrictions. the only reason the flapper is there in the first place is to reduce noise at a certain rpm so the bike passes the noise emmisions standards. It will not harm performance or your bike. It may hurt performance once you install larger jets and adjust your carb to the specs.. I believe they raise the e-clip a position or two, which will make the main jet take over sooner than the stock jet. When this happens, you will be dumping in more fuel sooner, and with the flapper still closed, you may experience bogging.

as far as it being the reason for the flat spot, it could be, but I would lean more towards a restricted main jet. even a too lean pilot jet can cause this issue. As far as I know, the flapper is rpm controlled, not speed controlled, so the speedometer really shouldnt have anything to do with it. But Im not 100 percent sure on that.

I would bypass it.

 

I checked the wiring schematic in my manual. There's a relay between the solenoid and the speedo so I'm guessing they are connected and the solenoid hasn't been switching from low speed to high speed air.

I know the carbs are spotless, having cleaned them twice (the 2nd time overnight soaking in carb cleaner and air through everything). The pilot screws were way off and now corrected. I haven't been able to ride since putting in the jet kit but I already know she's running too lean (won't idle steadily without half choke). I'll correct the lean condition later this afternoon and balance the carbs.

Thing is the bike, prior to installing the jet kit, was running too rich even with a restricted fuel flow (clogged fuel filter & non-fucntioning fuel pump). Before bypassing the solenoid, I'll try her out with the new jets & pilot settings. If the flat spot is still there, I'll bypass the solenoid and go from there.

 

the bike idling steady is a sign of the carbs being out of sync. So if your doing that soon, it may clear up that problem.

Just out of curiosity, how many turns out did you end up going with your pilot jets?

 

Went according to the kit's instructions which is for 1/2 turn.

The primary problem was a massive flat spot starting about 5k rpm. It turns out it was the solenoid. Bike was suffocating because the solenoid wasn't switching to the high speed air flow. Following the kit's instructions to the letter (first time I put in jets meant for a completely stock bike) and I still had the flat spot. Just finished bypassing the solenoid and she snaps through the RPMs & gears like butter.

The carbs still need to be synced but I'll do that when I get the tool (prolly from JohnnyX)

 

So how did you bypass the air solenoid? I just cleaned my carbs and I'm having the same problem.

Is it just a matter of taking the solenoid/flapper out and connecting the hoses from the outer and inner vent to the hose going into the carbs?

Cheers

 

lol damn dead thread... i need to know how to bypass also same problem here...

 

Here:
https://cbrforum.com/forum/cbr-600f3...83/#post840830