Bike dies down on me.

[golem]

My geezee seems to die down on me at random interval.
I had the needle shim mod done by a professional but could this be the reason for it not to work so good anymore?
Before that I also had tried to do it myself and went as far as removing the tank myself before realizing what I was doing and putting it back. I know the engine works with a vacuum, is there a step where you have to put the engine under vacuum after putting the tank back maybe? Or this has nothing to do with my problem?
My battery is new so I don't think it's that and the ground wire is well connected to the battery. What else could it be?
I don't lose power when it happens, it always seems to happen on an incline for some reason but this might be unrelated. When it happens, I play with the petcock and it seems to bring it back to life but once again, not sure if it's related. It happens when I accelerate.
Please let me know if you have any idea on what it might be, thank you.

[jonathan180iq]

I know the engine works with a vacuum, is there a step where you have to put the engine under vacuum after putting the tank back maybe? Or this has nothing to do with my problem?

My battery is new so I don't think it's that and the ground wire is well connected to the battery. What else could it be?
I don't lose power when it happens, it always seems to happen on an incline for some reason but this might be unrelated. When it happens, I play with the petcock and it seems to bring it back to life but once again, not sure if it's related. It happens when I accelerate.
Please let me know if you have any idea on what it might be, thank you.

First, your idea of a vacuum isn't right. You don't have to do anything when you install the tank. The vacuum that we all refer to is the sucking power of the engine as it's working. The internal pumping of the piston creates a vacuum, drawing fuel and air into itself so it can compress it, blow it up, spin the crank, turning the front spocket and making you go down the road :)

Tell me this, when you get on the the throttle and really accelerate on flat ground, do you have the same problem with the engine cutting out?

Sounds to me like it's a fuel flow issue - probably a float height issue. The bike is starving for fuel on an incline because the float is too low.

Take the handle of a screw driver and whack the float bowl a couple of times. If this helps, then you need to run some carb cleaner through your tank... Come to think of it, do that anyway ;)

[golem]

The engine doesn't seems to die on flat ground.
Where could I find that float bowl, so I can give it some tough lovin ?
(edit : float bowl in in the carb, right? So I just gently hit the carb?)
Also I always put some sea foam or marvel mystery oil in the tank, whichever is the cheapest when refueling.

[alantf]

Jonathan... When he says "played with the petcock", sounds like he put it into "prime". This suggests a vacuum problem. :hmm:

[jonathan180iq]

Jonathan... When he says "played with the petcock", sounds like he put it into "prime". This suggests a vacuum problem. :hmm:

That's possible too, but because it sounded like it was running alright on flat ground, it led me to believe it's a float issue. Putting the petcock on PRI has the ability to bypass the float, raising the fuel level in the bowl to where it should be, which is why it solved his problem temporarily.

Golem, the very bottom of the carb has this bowl shaped piece. Right in the center of that, on the bottom, is a screw. This screw allows you to drain the float bowl.

If you look at the carb, you should see exactly what I'm talking about. Don't knock the crap out of it. Just give it a couple of little thwacks. If your float was sticking, which would not let enough fuel come into the carb, hitting it will sometimes free it up.

I'm just giving you a cheap and easy way to see if that helps anything. If it doesn't then we are moving onto the next step which, as Alan suggested, is probably a vacuum leak.

Regardless though, get some carb cleaner in your tank.

[5th_bike]

Jonathan... When he says "played with the petcock", sounds like he put it into "prime". This suggests a vacuum problem. :hmm:
Exactly, probably needs a new vacuum line if it's brittle, otherwise just wiggle it a bit to make it seal better.

Edit: the "vacuum line" is a little rubber tube between the petcock and the carburator, it opens the petcock (internally) when the engine is running, by using the 'vacuum' (lower pressure) in the carb to move a membrane in the petcock. It only works when you have the petcock on "RUN" or "RES"; when you have the petcock on "PRI" (pointing down) the fuel flows regardless.

[golem]

Turns out the screwdriver trick did it ! I don't know for how long it's going to work but I don't have anymore problem since then ! Thanks everybody for the help !