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I got a 01 KDX 200 off craigslist, hard to start no compression (around 90). Had no power maybe could go 5 mph when i could get it started. Rebuilt the top end cleaned the carb, rejetted to a 155/45 needle on middle clip, new reeds, fresh air filter. Damn thing still has zero power! Compression numbers didnt really increase either. I am at a loss, I have spent hours messing with this thing and getting nowhere. I do know the kips isnt opening but I want to get this thing moving before i waste any more time fiddling with that. Am I wrong in assuming it should be able to decently move without the KIPS?
Thanks!

Did you do a leak down test or just compression? You rebuilt the top end on a bike with no compression, did you check the lower end crank seals? Unlike a 4T, a 2T needs good seals on top and bottom as both ends are active parts of the engines intake and combustion cycles. And you will need the KIPS operating to get the engine working properly.

It should run ok with KIPS broken, just not much bottom end. At least for me, I didn't notice my left side valve was broken until I started asking it for down low power. I also keep it somewhat wound out when I ride. I made a good dozen hillclimbs before I knew something was up.

I would think something else is going on that has nothing to do with KIPS. BUT, my experience is with E-series (89-94) stuff, which is totally different in form, but function is similar

bufftester wrote:Did you do a leak down test or just compression? You rebuilt the top end on a bike with no compression, did you check the lower end crank seals? Unlike a 4T, a 2T needs good seals on top and bottom as both ends are active parts of the engines intake and combustion cycles. And you will need the KIPS operating to get the engine working properly.

No leakdown test, and im sorry when i said "no compression" it was around 90 psi or so. I am new to this 2 stroke thing. Would worn crankseals cause this much of an issue? Like i said it goes maybe 5-10 mph max full throttle. Looks like a leakdown test is in order. Will not idle and dies without keeping hand on the throttle. Still a beast to get started

What's your compression after doing the top end?

about the same maybe a little better but not much

does it smoke much when its running

jaywhy wrote:about the same maybe a little better but not much

There's a problem in there somewhere then. 90 psi is bad, but after a top end it should be well above 120, closer to 170. May want to take the head off and inspect everything. It also sounds as if you may have some fuel delivery issues. I'd say carb then reeds, but you say you've changed reeds and cleaned the carb. Check the petcock in your tank for good fuel flow (there is a mesh filter that can get clogged up) and then a leakdown test to check your crank seals (yes they can have a big effect on the engines performance).

Yeah, 90 after a new top end is very bad.

Does anyone have a dummies guide to a leak down test? I've searched and found conflicting info (plugging exhaust and intake) some do some don't, some use the 100psi method while others say to use 15psi etc. I do have a leak down tester. A nice rundown KDX 200 specific would be amazing.
I'm starting to despise this bike

Sounds very much like a bottom end issue and another steal of a deal on CL. Not the bikes fault the PO didn't take care of it and I'm guessing you knew the condition when you bought it.

There is plenty of help here, but the best thing to do would be to buy a service manual and go through the motor. Nothing in there is too complicated. You can definitely fix the bike.

When you pulled the top of how did the old piston and cylinder wall look? Did the crank rod have any up/down play?


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jaywhy wrote:I got a 01 KDX 200 off craigslist, hard to start no compression (around 90). Had no power maybe could go 5 mph when i could get it started. Rebuilt the top end cleaned the carb, rejetted to a 155/45 needle on middle clip, new reeds, fresh air filter. Damn thing still has zero power! Compression numbers didnt really increase either. I am at a loss, I have spent hours messing with this thing and getting nowhere. I do know the kips isnt opening but I want to get this thing moving before i waste any more time fiddling with that. Am I wrong in assuming it should be able to decently move without the KIPS?
Thanks!

check the piston to cylinder clearance, and the timing

The old piston and cylinder walls looked good. The piston had a little play when it was wiggled by finger and was a chinese replacement. Replaced it with a weisco top end kit since it was apart and I already had planned on doing the top end.

A vacuum or pressure test is done with the engine assembled.

Slowly build to about 7 psi. 100 is way too much!

Are you regretting saving all that money?? Many of us have been there before.

What did you pay for it?

Do i need to plug the exhaust and intake ports?
I bought it for $700

jaywhy wrote:Do i need to plug the exhaust and intake ports?
I bought it for $700

yes, plug both

look at the Motion Pro set to see what one looks like. ok, here:

and maybe this

So i have found that my flywheel key was sheared off completely. I have ordered another, do I have to set the timing or will simply replacing the key do that for me?
Thanks

Just replacing the key will take care of your timing, but you still have a compression issue if after the top end job you only have around 90 psi. The first issue (key) has nothing to do with the second issue (compression)

If no damage was done to the crank (keyway) or the rotor....