No bottom end

[Mostin3]

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?

 

[rvangeel]

Maybe the power valve is stuck open?


Sent from my iPhone using Tapatalk

 

[Mostin3]

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.

 

[pigpen966]

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

 

[pscook]

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?

 

[RBrider]

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

 

[Zman]

You should also check out the reeds.

 

[Mostin3]

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.

 

[Zman]

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.

 

[(F5)]

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.

 

[Zman]

But he just said that the PV rod is stuck up so it not allowing the PV pivot to travel back down which would drastically kill low end.

 

[(F5)]

Oh, so now I'm now like expected to like read and comprehend stuff?
That's not how I roll.

. . , and I had an idea come to me since first reading and didn't check later posts.

My new years resolution is to continue being awesome.

 

[Zman]

Happy New Year!!!!

 

[Joper]

Did you fix the problem with the PV and does it run good again? Last few rides I have noticed the same symptom on my ec200-13. It lacks bottom end power and I need to slip the clutch a lot to pick up rpm, then it runs OK. No play in PV linkage and it closes as it should.

Been fiddling with jetting also but this feels like something else. Currently running:
Pj - 40
Mj - 180
Needle - CCL in middle position
Pilot screw - 1,25 turns out

Hope I can fix this soon

 

[Joper]

Checked some things today but still nothing obvious. Compression 175-180 psi, no play in pv (took that away when changing piston).

Seems weird that it should be jetting since it has appeared gradually last few rides. The plug is still pretty dark so it shouldn?t be a lean condition.

Does the spring in the PV actuator get loose after time and eventually need to be shimmed for better low end? Read that some guys had good luck using a shin but it seems strange that it would change over time?

 

[Joper]

Not much activity here but ill continue posting my results for others to find

Did some testing yesterday to see if it was a lean condition. Tried PJ42 and also lifting the needle one notch, now at 4 from top. I havent mentioned my gearing wich is 13-50. AS is about 2-2,5 turns out after some adjusting while riding.

I think it ran better in the beginning, only rode for 20-30 minutes with no real wot passes. Had some rich blubber because of the needle being raised but the bottom seemed better for the first 15 minutes i think. Then gradually the bottom end power got worse. Hard to know exactly but it felt like i couldnt lift the front in the low rpm in the end.

If Im in second gear at a low pace and open the throttle (not fully but as if you were lifting the front over a log) it respons bad. It doesnt do the "bhaaaa" as if it was way to lean but theres just not much power. More spooge now and the plug is pretty black.

 

[gasser]

Another possibility may be the wrong oil for the way you ride. Here is what I mean. Oils are made with different flashpoints. Flashpoint is the temperature where the oil starts to burn. Too low a flash point and the oil won't give adequate protection. Too high and it will accumulate ,more and more in your power valve and pipe till the bike won't hardly run. Lugging the bike in slow, technical, terrain doesn't let the top end of your motor get hot enough to burn off excess oil like it does at higher revs. Motul is one of the more popular brands of 2 stroke oil sold in bike shops here in the states. Motul 800 is the easiest to find and it's flashpoint is 252c/485f degrees. Motul 710 and Motul 510 have a much lower flashpoint at only 90c/195f degrees. I can't run the 800 where I ride but the 710 and 510 are fine.

 

[Joper]

Thats a very intresting point since I do run the motul 800 oil and my local singletrack is very tight and technical and I only get out of 2nd gear a couple of short sections over a 7-8 km track. I will go back to 40 pj and needle in the middle and try motul 710.

I also noticed yesterday while changing transmission oil that it was quite dark. Usually if the crank seal is bad it sucks in trans oil and not the other way around? Maby its just because I have had to use the clutch quite much with the bike being low on bottom end power.

Thanks for the reply! I?ll report back with result

 

[Joper]

Today I rode some tight technical singletrack again. Weather here in Sweden is cold with -2 degrees Celsius (~28 in Fahrenheit). Tried pj38 and dropping the needle one notch since my plug was black. Seems lean for the weather but the plug says different? Also adjusted the float level more accurate after making a measure tool. Couldn?t find motul 710 or 510 to test if that?s the problem but I did have some shell advance vsx that I rode with instead of the motul 800.

Good idle and a bit less spooge but still runs down the silencer a bit. Still bad bottom end. I don?t even know how it should run anymore since I?m getting used to this..

Maby my silencer packing is saturated with spooge now and that stuffs it and not letting it breath? I?m gonna change it out anyway but could that do this much on the running of the bike?

I also checket the movement of the PV on the left side. It turns about 1/4 of a turn and doesn?t seem to open to early when reving it on the stand. Does the amount of opening seem right?

 

[barossi73]

If you carefully disconnect the actuator rod(top)you can rotate the power valve with fingers to check its moving freely through the entire range.I say carefully because others have found the small stud can crack its weld on back of actuator plate.The safest way is to heat the nut to release the nylock (but youll need a new nut).From memory the pv should open fully once it starts to move,its basically either full open or full shut rpm dependent.(it may flutter a bit if you hold rpm right on the "switch point")