I recently bought a used 1996 Honda CBR F3 bike but the speedometer/odometer doesn’t work. I’m not sure if the gauges or speed sensor is the problem.....but anyway... the bike runs well in 1st gear, as soon as I get it into 2nd gear around 4k RPM is begins to bog down heavily making it unridable as if it's not getting enough gas and/or air.

I have been reading that the high speed air vent doesn’t open until 12mph....but if the speedometer doesn’t work then maybe the bike doesn’t know to open the high speed air vent to allow more air into the carbs therefore causing the bike to bog down in gears greater then 2nd due to air starvation??? I have heard of people w/o gauges and their bikes run fine (maybe they grounded the pink wire from gauge cluster to keep vent open all the time??)

Does this sound like a plausible explanation? Or does the air vent that opens up after 12mph not really have any thing to do with the speedometer or the poor performance?? Does anyone know exactley how the bike knows to open the high speed vent? Maybe it opens the vent based off the Tachometer and I might just have gummed up jets from old gas sitting in the bike during storage(which the owner told me happened but I'm not sure to trust him)? Or maybe a combination of both??

Please help...Thanks

 

nobody?

 

Got me...

Is the harness plugged into the back of the cluster?

 

Sounds like the carbs need cleaning . I have seen bikes run fine without the speedometer connected .

 

It's a possibility. According to the schematic the PAIR valve relay is connected directly to the speedo.

This is what I'd do - I'm not sure if the PAIR valve is normally open or closed (#7 or #4). Let's assume that the normal position is the -12mph intake (#7 hose). You could try jumping the solenoid so that it switches the direction of air flow to the +12mph (#4 hose). Or you could disconnect the #6 hose from the PAIR valve and connect it straight to the #4 hose via the air filter then test ride the bike and see what difference that makes. It's not going to run perfectly but if it doesn't bog down then the speedo/PAIR might be your problem.

On my track bike I removed the PAIR valvealtogether. The number 6 hose is routed to the small air filter then directly to the high intake (#4 hose). The bike was then rejetted to accomodate this change.