Please Help ..300ex losing power + shift problem

[taterm6]

Heres the deal. I just bought a 98 300ex. It appears to have many performance mods done to it, but i have no information as to what. I know the exhaust is aftermarket, but i dont know what brand, and I also know it has the k&N air filter.

The motor was supposably "just rebuilt". I agree with this because it is very clean, doesn't leak a drop of anything, doesn't smoke and I can visually tell that it has all new gaskets and seals.

Here is my problem. The motor fires right up, idles, and appears to run fine. I can put it in first and let it idle around in the street or hit the gas and fly through the gears, everything is fine. Its when i go up a hill in first that it will start to cut out. I have to stop and "baby" the throttle before it will rev out. If i stop, it will idle fine, but hitting the gas only wants to cut the engine out. It usually takes a good 20 seconds of working the throttle for it to act normal again.

Any ideas to what may cause this as it makes it very difficult to ride

Another problem that i have is that after I start it in neutral and drop it into gear it tends to jerk forward for a moment. When I want to get it back to neutral i have to rev it up and shift to neutral, or just shut it off. It doesn't shift as smooth as i would expect, it just kinda "drops" into gearwhen upshifting and downshifting. I figured this could be a simple clutch adjustment or possibly running a different oil. (i have no clue what is in there now)

I have no clue if the motor has been bored, or if there is a performance cam in it, but it kinda sounds like it may have a cam. I guess there is no way of finding out without taking the motor apart.

Thanks for the help.

[bwamos]

On the jumping thing in neutral. That is normal on the 300ex's from what I've seen. Mine has always done that.

When in neutral the clutch plates are at rest. Even though the clutch is pulled in the plates are still touching each other and they have stationary friction. It takes more force to break loose the stationary friction than it does for it to slide once it's alreadt in motion. So when you drop the tranny into gear, all of a sudden those plates start turning and have to break loose from the other plates. You'll get a slight jump. It doesn't hurt anything.

Easiest way to avoid the "jump" is to just use the rear brake when popping it into gear.


On the fuel delivery issue.. 1st thing I'd check is to make sure you dont have any clogged vent tubes on your carburetor.