[DaveA]

Hi there,

I have a 99' fx650 which I purchased to refurb and modify. I do not know how it ran before it was dismantled. It was only started.
I have now rebuilt after refurb and I'm having trouble with engine hesitation with throttle open.

I have put a larger main jet (175) as it has a custom end can, with pod style air filter. I have also adjusted pilot screw out to increase fuel ratio.
I have inspected insulator between engine and carb.

Today I removed the air filter to see if the slide is moving up freely when throttle is opened. With the engine off the slide moves up. With engine running it pulses up and down. Is this correct?

Any help would be appreciated.
Thanks.

 

[ian6760]

Yep mine shoots up and down too without the filter. I do know though that it also runs badly and chokes it self up at full throttle with just a pod filter on, that I tried to cure with more fueling and that was wrong. Adding a small kink by using the original sleeve running into the airbox and 4-5 inch radiator pipe fixed it with a pod filter. From my limited understanding a CV carb needs the constant air pressure on the inlet side (or air restrictions) that the air box provides. Hence the carb is called a cv which stands for constant velocity. A pod filter does not provide this and I have experienced the engine leaning out at high revs and the engine bogs down. The kink and pipe extension has fixed this on my bike but I do still have the airbox in place but with the side off.
Hope that make sense and helps.

Ian.

 

[DaveA]

Thanks Ian, I'll give it a go once I get the diaphragm back it the carb.....

 

[DaveA]

Thanks again Ian.
I cut down the original hose and attached a ram air filter to it. I also returned pilot screw to stock and runs well now with 1.75 main jet.

 

[ian6760]

Happy days. :thumbup: