Jumps from closed throttle

I have been trying to diagnose a problem with my 97 501FE. I've only had the bike for about 6 months and I'm slowly sorting through various small stuff before I take it out for some remote area woods riding.

In short, it is very difficult to control off of closed throttle. It feels like the carb. slide is sticking and then when I apply enough force to raise the slide the bike lurches so hard it really upsets the suspension and makes the bike very freaky to ride at slow speeds.

I have checked the throttle cable routing, the throttle grip sleeve and housing, the cable itself. I have cleaned the carb. jets, checked the needle and jet for wear, checked the slide for wear, all look clean and in good condition. It has a PHM40 with a 272 needle jet, needle is at 3 from the bottom, 195 main, and 45 pilot, 1-3/4 turns on air fuel mixture.

Is this characteristic of the carb./engine? I've read about people removing a 1mm slice off the leading edge of the slide but I'm not entirely confident with that nor do I want to soften the hit all the time.

I've raced and driven many different machines but precession throttle control has always of optimum importance. I'll admit I'm using the Husaberg on the street right now where this problem is probably much more noticable.
I've also noticed the front end wants to rise when this lurch occurs. I'm not sure about the sag and or preload settings so this could also be adding to the problem.

If it's typical I may just stop using it much on concrete which would be too bad because the bike is a real kick to ride otherwise.

Any help would be appreciated.


97 501FE Husaberg, 95 Ducati SS/SP, 67 Triumph 650TT, 77 Husqvarna CR250, 02 Suzuki 650DR, 01 Kawasaki Concours, 99 Honda Cr250.

There is a 40 stamped in the bottom of the slide. I have measured the slide bore and the slide and it has .005" per side clearance. The slide does wobble when it is closer to the bottom but considering it is largely unsupported by the slide bore anymore I figure that may be expected.

The PHM on my bike is a round slide and has no plastic pieces, and the air filters are clean and oiled.

If I understand I would remove 1mm (.019") off the angled surface of the air filter side of the slide. I gotta tell you I think Taffy and Burt Munro (Worlds Fastest Indian) are the only people that can remove .019" accurately with a file.

I don't mean to be sacrilegious but my 77 Husky came with a Bing carb and I replaced it quickly with a Mikuni. My 67 Triumph had Amals and I replaced them with Mikuni's. My Ducati 900SS which everyone knows is Italian came with Mikuni's. So do people put Mikuni's on Husabergs?

Before anyone busts me for thinking 1mm is .019" I just had brain fade. I guess I got tangled up with the concept that if you are only removing 1mm total off the mouth of the slide you would have to remove .5mm on a side.
In other words if you are removing 1mm from the plane that is defined by the angled surface, then you might be removing 2mm total where that surface meets the adjacent bottom plane, and creates the mouth.

I still think I will do it in a mill or a surface grinder rather with a file.

I have modified the slide and the results are good. It now pops alot on deceleration, but that is probably the pilot jet. I adjusted the air/fuel mixture and that improved things some.


My carb. has a 45 pilot jet but the doc info. says I should be using a 33 with a PHM40 round slide. I'm already way over that so it seems wrong to have to go even larger now. I ride primarily at 600ft to 1000ft above sea level.

I will try the throttle cam (mx/enduro) if my bike infact has this feature.

The bike still jumps enough to be distracting in the middle of a turn on concrete. I am working with some suspension adjustments also.

I know all of you have answered these types of questions in the past and the doc information is helpful but it seems most information applies to newer bikes than my 97 so that's why I ask.

Thanks for your patience and suggestions.