A tale of two KDX's: 03 vs 00

[farcry2]

My nephew and I have 03 and 00 kdx 200’s.
My 00 has an FMF gnarly woods pipe, procircuit spark arrestor, airbox lid removed, 45 pilot, needle clip raised one position, air screw 1&1/2 out, and a 158 main. The low-end response is great, the mid range seems linear, and the top end has an okay hit with respectable over rev. My bike revs quickly and seems like it goes from a great low end to mid punch right to a decent pulling top end.

Until recently my nephew’s 03 engine was stock. Compared to my modified 00 his 03 was a slug, almost like riding a 4 stroke. Recently I modified his 03 with airbox lid removed, 45 pilot, air screw 1&1/2 out, and a dyno port big volume pipe. What an improvement these mods made to his 03! It is smooth down low with a really nice mid range punch (powervalve opening) and strong pulling top end. I actually liked the mid range so much, I wanted to see if I could duplicate the same power characteristics on my 00. :yikes:

Here is where my dilemma begins:

I figured the dyno port pipe must be responsible for the great mid range on the 03, so I put the dyno port and stock silencer on my 00. This changed the power delivery somewhat but a marginal improvement at best, nothing like the meaty mid range it provided on the 03.

Next, maybe my carb is a little gummed or the float level is a bit off, so I swapped carbs from the 03 to the 00 to eliminate the carb as a potential problem. I inspected my reeds while I was at it, all okay. Marginal improvement at best again, still no mid range like the 03.

My 00 has about twenty more hours on it than the 03 (nephew rides more), so I don’t think my slightly more worn top end could cause that much of a difference, could it?

Then, I figured my powervalve might be restricted as compared to the 03. I operated each from the linkage and inspected through the exhaust port and the operation seems about the same on both.

I have a revloc auto clutch (will post review soon) and an impact wrench, so I went back to my almost new stock clutch for the comparison to eliminate that as a variable.

Can two KDX’s with the same setup be that much different in power output? In 1990 I bought two new identical YZ 250’s (consecutive serial numbers), power was the same on both, no detectable difference. In 1983 I bought two new Suzuki PE 175’s (manufactured 6 months apart). One bike had a great low-end and midrange, while the other was a top end screamer. Upon doing top end jobs on both, I discovered that these same model year bikes had different head gasket designs explaining the different power characteristics. It doesn’t appear that Kawasaki changed anything in the KDX 200 motor from 00 to 03. What other factors could contribute to the 03 having so much more power than the 00. :think:

 

[canyncarvr]

You're asking a question to which conjecture can be the only reasonable answer, imo.

I wouldn't expect an '00 to be at all in the same shape as an '03. I'd suspect that the reported 20 hr. difference is a considerably bigger number. Unless you keep excellent records that would be kinda' hard to guestimate over years of time. At the least your bike is inarguably years older than his.

Some things are hard to determine without somewhat involved testing equipment. Reeds are one of those things. Just because they aren't obviously sprung/frayed/chipped/split doesn't mean they are good as new or as good as a 2-year newer bike.

Also to consider; if your bike has been modified from the gitgo and his has not been, it would seem reasonable that your bike has been ridden harder over the years difference in age.

Who says the ignition timing on the two is the same? Maybe it's set to the same physical mark, but that doesn't mean it's actually the same.

I'd expect them to be similar if similarly equipped. If they aren't then something must be different, 'eh? ;)


re: '..I don’t think my slightly more worn top end could cause that much of a difference, could it?'

Guess that would depend on 'slightly' and 'much difference.'

I'd say, 'Yes.'

I don't think you willl get definitive, factual answers. Merely ruminations.....as the above.

 

[DougRoost]

A simple and quick test between the 2 would be a compression test. Might be enlightening. Just make sure bikes are equivalent engine temps and hold the throttle wide open when you kick them over.

 

[Robcolo]

I've had several KXs and now a KDX and the difference in quality control is night and day. Kx internals are nicely cast and finished whereas the same KDX parts are extremely crude --pistons, clutch parts, cylinder. Most KDXs vibrate like crazy when you release the clutch as those crude rotating parts are poorly machined and unbalanced and ill fitting. The cylinder passages need all kinds of die grinder work to get them matched and aerodynamic. The KIPS valves rattle like crazy because of loose sloppy fits. It's no surprise to me that 2 different KDXs respond completely differently. Since some KDXs overheat badly and others don't, I suspect that the factory squish clearances vary widely from bike to bike. "Correct" squish can make a huge difference in engine performance - and as mentioned a compression comparison would be another good thing to know. Actually,a higher compression ratio increases the low to mid range hit of an engine whereas a lower compression ratio enhances the high end power.