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Top End and Compression

Joined
Sep 11, 2000
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4
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#1
Hi,
I have a new 00' KDX 200. I am the only one to ride it. I started riding it in aug. of last year and have probably put 40 hrs. or so on it, including two hare scrambles and a lot of trail riding. I have never owned a two stroke before (last bike was xr4oo) so I do not have any Idea when it is time for a top end. Is it the best way for me to tell now by doing a compression test? If so where is a good place to get a tester (on the internet preferably)? In the KDX service manual it says to move the gas tank back but leave it attached. Is this a clearance thing for the tester or does it serve another purpose? Also how far can you stray from the service manuals recomendation of 95 - 151 psi service limits? Thank you in advance for putting up with my rambeling.
 

Sage

dirtbike riding roadracer
Joined
Mar 28, 2001
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#2
I would opt for the higher side of normal, after a comp. check, a simple way to check the condition of the top end is to pull the expansion chamber off and look at the rings for blow-by & check the plating around the transfer ports while your there.

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Sage Wilkinson, KDX Link 1
 
Joined
Dec 10, 2000
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#3
A compression test will give some indication of the top-end condition, but the only way to really tell is to pull it apart and measure ring end-gap. When I do a top-end, I measure the compression after break-in for a baseline, and then recheck it after every 2 or 3 rides. Once the engine has lost about 10% of the baseline compression, it is time for a rebuild.

With only 40 hours on your KDX, I doubt it needs a top-end yet, they have probably the longest lasting top-end of any two-stroke you can buy (except maybe a PW50 ;) ). My engine is closer to a KX 250 than a KDX 200, and I still get 60-70 hours between top-ends.

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1992 KDX 250-FMF porting,two-stage power reeds, Fatty pipe, Power Core silencer,titanium rod,Wiseco Ultra-lite, Pro-Action suspension...Why didn't I take the blue pill???