First Ride, weak

[SweetTea]

Well I finally got home to my new/used (completely stock) 00 KX500.  It's in great shape all & all, no big problems on the exterior, everything looks new almost actually.  It rides good, although it vibrates more than anything I've ever owned lol, the suspension is good, shifts through all the gears perfect and its torquey, just no snap of power at all.

I took it for a spin this evening and it has less power than my ol' KDX220.  The potential is there however I know it, I just need to work on it.  It was a gravel road I rode on, and it did leave ruts in the road, so hookup could be part of it but I'm thinking theres more to it than that.

One thing, jetting seems to be lean, i'm getting a surge on midrange and when I let off the gas, so I'm gonna try jetting first.  The intake boot on the reed valve side is dry rotted a bit, but I don't think its sucking air, but I'm going to replace that pronto anyhow.

I still need to check the compression and reeds, will do tomorrow.   If compression is low I'll go ahead and do a topend.  I guess if jetting doesn't help the power I'll check the KIPs as well.

I'll post more later, I just drove 14 hours straight and I'm a bit worn out and probably not making sense.

Any other suggestions while I'm going over her?

Thanks guys.

[jonny500]

remove the kips cover, run engine, and see if it moves when engine is reved

[SweetTea]

Thanks Jonny.  I checked the KIPs and it appears to be working like it should, the rod goes in and out freely when reving the engine.  Reeds are good.  I checked the compression and it appears to be 95psi.  So looks like the rings/cylinder are worn pretty good.  Looks like I'll be doing a topend.  I should have known, the thing kicks easier than a XR50, I could literally do it in my flip flops.

I took it for another spin after swapping the Turbine Core silencer out for a pratically brand new stock silencer and it ran a lot better.  This thing handles great, feels like it handles better than my 07 WR450!  There is decent power even with such low compression, it will bring the front wheel off the ground pretty easy and dig deep ruts. 

Another question though.  The jetting appears to be good, but when letting off the throttle it still surges, like I've experienced on other two-strokes under lean conditions.  But I think I've read on here somewhere, that it's common to the KX500, any truth to this? 

I know I can't truly jet the bike until I do the top end, so I'm not going to mess with it now.  One thing at a time.

I'll be pulling the jug here soon!

Thanks!

[flyingfitz]

Fixes for your issues based on my experience:

Do a top end. Make sure the cyl plating is good.  Window piston is a good mod if funds are available. 

The seals in the bottom could be bad.  Something to consider.  You have to split the cases to replace the seals.  There are leak methods posted on this forum to check. 

The surge has many theories.  My throttle speed screw was all the way in to get the bike to idle at a reasonable speed.  I jetted down until the engine would idle too fast with the idle speed screw all the way in.  I then adjusted the idle speed screw out to get a reasonable idle.  I then turned the air bleed screw in richening the bottom only to a point where the engine would not surge with the throttle at idle after revving.  I am running a 52 pilot with a fresh cyl and window piston.  N82r needle in center clip.  600 ft elevation.  The settings I have work ok from 45 to 80 degrees.  The plug does not foul and the color is brown.  The bike does not surge and is very reliable. I also set my float level to 18mm.  Hope this helps.

Fitz

[martinfan30]

Fixes for your issues based on my experience:

Do a top end. Make sure the cyl plating is good.  Window piston is a good mod if funds are available. 

The seals in the bottom could be bad.  Something to consider.  You have to split the cases to replace the seals.  There are leak methods posted on this forum to check. 

The surge has many theories.  My throttle speed screw was all the way in to get the bike to idle at a reasonable speed.  I jetted down until the engine would idle too fast with the idle speed screw all the way in.  I then adjusted the idle speed screw out to get a reasonable idle.  I then turned the air bleed screw in richening the bottom only to a point where the engine would not surge with the throttle at idle after revving.  I am running a 52 pilot with a fresh cyl and window piston.  N82r needle in center clip.  600 ft elevation.  The settings I have work ok from 45 to 80 degrees.  The plug does not foul and the color is brown.  The bike does not surge and is very reliable. I also set my float level to 18mm.  Hope this helps.

Fitz

So whats your main # in these conditions?

[flyingfitz]

Main is 168.  Probably could go 170 when cooler on main and down to 50 on the pilot when warm outside.  52/168 seems to be a good compromise. I am not really a puritan on jetting.  It just has to be safe, reliable and close.  A touch rich doesn't bother me.

I think the key for mine was to jet the pilot down to the point where the idle speed screw was actually functioning.  With the idle speed screw all the way in I think that the slide was open far enough to be more or less off the pilot and on the slide/needle.  I found that the air bleed screw was  responsible for correcting the surge.  A richer air bleed screw would cure the surge reguardless of the pilot jet. This was all confusing because the surge would go away with the throttle opened the slightest bit above idle in the original configuration.  I found myself going down steep hills in the woods with the throttle cracked a little to keep from surging.  Crazy.

Everything I knew before this told me to use the air bleed to fine tune the mixture at the idle stop.  If the bleed screw was in a turn or so from the 1 1/2 reference then richen the pilot.  If it was out then lean the pilot.  What ended up happening was that I was surging at around 1 1/2 turns.  I would richen the air bleed at idle to kill the surge but would have a very unreiliable idle, foul plugs and backfire sometimes when starting.  By jetting down the pilot, I was able to compromise the system to allow the air bleed screw to be my "anti-surge screw".  It is not far off from 1 1/2 turns but I dont really know where it is and I dont care.  I adjust it in from the 1 1/2 turn reference until the surge stops. If the idle speed screw is in too far lifting the slide abnormally high, I jet down another step until I have an "adequate" amount of idle speed adjustment.  I stopped trying to think about this in the traditional sense above and found this method works.  Use care not to over lean the system!

Hope this helps.

Fitz

[Polar-Bus]

Well I finally got home to my new/used (completely stock) 00 KX500.  It's in great shape all & all, no big problems on the exterior, everything looks new almost actually.  It rides good, although it vibrates more than anything I've ever owned lol, the suspension is good, shifts through all the gears perfect and its torquey, just no snap of power at all.

I took it for a spin this evening and it has less power than my ol' KDX220.  The potential is there however I know it, I just need to work on it.  It was a gravel road I rode on, and it did leave ruts in the road, so hookup could be part of it but I'm thinking theres more to it than that.



One thing, jetting seems to be lean, i'm getting a surge on midrange and when I let off the gas, so I'm gonna try jetting first.  The intake boot on the reed valve side is dry rotted a bit, but I don't think its sucking air, but I'm going to replace that pronto anyhow.

I still need to check the compression and reeds, will do tomorrow.   If compression is low I'll go ahead and do a topend.  I guess if jetting doesn't help the power I'll check the KIPs as well.

I'll post more later, I just drove 14 hours straight and I'm a bit worn out and probably not making sense.

Any other suggestions while I'm going over her?

Thanks guys.

I run almost the same jetting down to 60's F temps, and my 500 runs almost perfect. The fact you are jetted at 168 is right in the ballpark. Your comment that your 500 has less power than your old KDX is definately telling me you have a major issue elsewhere. Like I comment over and over, check all the simple tests FIRST. adequate fuel flow ?   Squeeky clean carb/jets ? Fuel tank cap check valve working properly ? Next your immediate simple test should always be a compression test. You need to be around 155 psi. My 500 tests at about 170 psi, but I run the optional .2 mm thinner head gasket. You can also yank the exhaust pipe and shine a light up into the cylinder and get an idea of what the piston and cyl looks like. It's not a 100% ideal test, but again quick. Other members have posted issues with the ignition coil generating a weak spark once up to heated temps, but this is more rare, and can be investigated further after all the other basic tests are carried out.

[SweetTea]

Thanks for all the helpful input.  This is becoming an expensive project lol!  I yanked the jug and the cylinder and piston looked decent.  No major scoring, but the Nikasil was worn away pretty good.  I sent the jug off to US Chrome and have a piston kit coming.  Hopefully once I get everything back, we should have a brand new beast.  Crank looked good, no major play, everything is within specs. 

I'm also going to fashion together a Leak Down tool to test the crank seals just for extra comfort.  I'm pretty sure the wet side would be good cause It doesn't smoke bad at all or foul plugs.  The ignition flywheel side should be okay, I didn't see any oil behind the ignition, looks brand new.  But I suppose we'll find out for sure.

Good thing I pulled the jug, the circlip on the left side of the piston wrist pin was getting ready to pop out, not sure how that could happen.  The engine has never been apart from the factory until now.  The previous owner just rode and rode and rode her with not much maintenance.

I've spent a lot of money, and I just keep finding more things that need replacing :p, lol.  Gotta love it!

Thanks again!