Couple o questions jetting & top end

[psd]

I've got a 1990 K5 and it runs alright.  I recently purchased it off of somebody that lives near sea level, I live at 3000' or so.  The bike has an FMF gnarly pipe and turbine core silencer, and 175 and 60 jets.  The bottom end seems a little blubbery and the top end under WOT is kind of sporratic for lack of a better word.  I think it is running rich as the plug is black and a little wet.  What size jets would you guys reccomend?  Maybe somebody here has some first hand experience with that exhaust set up at this altitude? I was thinking like a 170, 52.

Also I just did a compression test on it without the carb on it, and I kicked until the needle wouldn't go up anymore.  It got to 90 psi even.  The bike was cold if that makes any difference with the rings expanding or something.  Does that seem normal, because it seems a little low to me.

Any comments are appreciated, and thanks in advance for any help.

[Paul]

If you look over on the right hand side of the screen, just below the random pic block you'll find a "Howto" block. 2nd one down is "Fuel", you'll find loads of helpful stuff under there as well as in the "Jetting" thread under the KX500 section in Maintenance & Technical.

[Danger4u2]

From Kawasaki Serv. Man.
1- Start the engine.
2- Thoroughly warm up the engine so that the engine oil between the piston and cylinder wall will help seal compression as it does during normal running.
3- Stop the engine.
4- Remove the spark plug and screw a compression gauge firmly into the spark plug hole.
5- With the throttle fully open, turn the engine over sharply with the kickstarter several times until the compression gauge stops rising, the compression is the highest reading obtainable.

Cylinder Compression (Usable Range):

KX125 : 770-1200kPa (7.7-12kg/cm2, 109-171 psi)

KX250 : 840-1300kPa (8.4-13 kg/cm2, 119-185 psi)

KX500 : 735-1150kPa (7.35-11.5 kg/cm2, 105-164 psi)

Sounds like you have to low a compression.  Put the carb back on and run the bike, you might find it in the usable range.
Danger

[dcollins4328]

Will a bike run with 75 psi for compression?  I think I melted my piston or something because it won't start?  Will a bike still start with that low of compression or is it another problem

[Good]

Will a bike run with 75 psi for compression?  I think I melted my piston or something because it won't start?  Will a bike still start with that low of compression or is it another problem

It'd be tough to get her started.  Lots 'o kicks.  Maybe a pull-start.  It seems to me that the lower the compression gets, the harder it is to start.  Sorry, though, I don't know the bottom end of starting compression.

[KXcam22]

My rule of thumb is that if u can bump start your KX500 then it is definitely time for a new top end. Cam

[Platypus]

My rule of thumb is that if u can bump start your KX500 then it is definitely time for a new top end. Cam

Cam,  I was able to bump start my bike twice on some semi-technical hills in 2nd gear with a good hard seat bounce.  The compression seems to be fine but I have not done a compression test.  Two other people have tried to start it and could not but I have no problems.  Does hot or cold motor play into your rule of thumb?

[KXcam22]

It's just a rule of thumb - don't want to mislead anyone.  I have never been able to bump start mine, even on pavement it just skids (I am 200lbs).  When I could, I could already notice it being easier to kick. On dissassembly the piston was obviously very worn out.  I never did a compression test so this is all very unscientific. Cam.

[c-152]

Cam, I can bump start mine and always have been able to even after a rebuild (though the conditions have to be perfect and I have to get a good bounce on it).  I have a steahly flywheel though. Think that makes a difference?

[Good]

I've always been able to also, in second or third rolling downhill with a good bounce on the seat.  That's how I start her often just to expedite things, I guess...