No bottom end
 

Hi folks, I?m trying to diagnose a problem with my bike that?s been present the last few times out on it.

It seems to have no bottom end power, stalls easily and you have to be in exactly the right gear for it to pull into the higher revs and not bog.

I have replaced the spark plug, stripped and cleaned carb and jets, fitted new air filter.

Once it gets higher into the rev range it appears ok but I?m pretty sure it?s lacking there too.

By ideas?

Maybe the power valve is stuck open?


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Hi mate, thanks for the reply.

I?m pretty certain it?s not stuck open as I?ve recently had it apart and had the RHS side cover off to remove freeplay out of the PV governor.

It?s something to check though thanks.

Check the plug wire where it screws into the coil. You can cut a half inch off the wire and screw it back in.

That sounds like a lean condition. Any other recent changes? Have you performed a leak down test of the engine to confirm that the left hand crank seal isn't leaking? Intake boot in good shape without any leaks or cracks?

When I got my used XC 200, it acted just as you describe. I bumped the pilot up one notch, from a 40 to a 42, I seem to recall. That brought the low end to life and really smoothed out the transition from low to mid to wfo.

However, as I learned the hard way, I had a mag side crank bearing starting to go bad which in turn was causing the seal to leak a little.

I was visiting and trail riding with some friends in another state when after a steep hill climb, I shut the bike off to wait & see if everyone made it up that hill.
Once we were all up & over, I tried to start the bike and it was locked up tight.

Thankfully, I kept rocking it back & forth in gear and it finally broke loose. Once I got it started again, I rode it the 5 miles or so back to the truck.

Upon dis-assembly, I found the cage that holds the rollers had come apart and jammed between the cases and the crank. But the deteroiation of the hard face of the bearing race and ball bearings had been happening for a long while.

I'm convinced that bearing was what was causing my lean condition when I bought it. After rebuilding the engine, I needed to go back to the 40 pilot jet.

Not trying to scare you, but just saying if you do have to replace the crank seal, you might want to check out the main bearing as best you can while you're at it.

If it has a hint of looseness or even a hint of any moisture or mud has gotten past that seal, then I'd seriously consider new crank bearings.

RB

You should also check out the reeds.

Hi chaps, thanks for the input, spent the day trying to find the offender.

Stripped carb again just to double check that, seemed ok.

Pulled reeds out, seem perfect.

Pulled exhaust and both PV covers to inspect and something weird it going on with the PV. It?s not stuck, but with full travel from the governor, it?s only moving about 2mm, meaning that?s its ultimately open all the time. I haven?t managed to tear down any further yet to find out what?s going on but something is a miss.

With the actuator taken off, I can rotate the PV manually until it is fully closed, however, when it?s in the closed position, the shaft is 180 degrees out of where it needs to be in order to fit the shape of the actuator arm.

Pull off the larger clutch cover and see what is going on down below. Maybe the adjuster bolt got loose and slipped or one of the balls is dislodged in the PV governor.

Or pull the top cover and observe in action.

Left field; fuel filter? Remove. Does the carb leak when on side stand on a slight slope? If not, adjust it till it does, but not on the flat.

For giggles put in the next size pilot jet. If its better you're looking for an airleak.
With the pilot removed there should be clear hole above it.