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Strange noise at high rpm and very low power.

Joined
Jan 5, 2007
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#1
I just bought a 2003 KDX 220 and while it started up easy and felt nice on my test run I didn't run it hard and now that I own the bike and have been on the trail I'm finding it is waaaay down on power. This isn't just the old "these bikes make their power down low" or "they're pretty tame stock", this bike feels like it has less than half the power of a friends RMX250 I was swapping back and forth with, about the power of my girlfriends CRF230F. On steep hills it actually has trouble pulling me even in first gear, and will barely wheelie in first.

I've done some searching and my best guess is maybe a powervalve issue but because of the noise it's making at high rpm I figured it was worth a post as none of my searching found anyone complaining of noise that kicks in only at a certain rpm.

Here's what I know:
2003 KDX 220
FMF Gnarly Pipe
FMF Silencer
V-Force Reed Cage
Wiseco piston installed by previous owner about 40 miles ago. I'm wondering if he messed something up when doing the top end and decided to sell the bike instead of fix it.

After a long pull at full throttle up a hill I checked the plug, looks just about perfect. Not quite chocolate color (don't think I've ever seen that on a two stroke, I keep hearing about it though) but the plug was a lighter gray/tan, didn't look too rich or lean.

The power feels OK at low rpm, not impressive but I actually bought this bike because I wanted a weaker bike as my primary is a CR500. Doesn't pull any rpms, no hit at any point, and it never feels like it makes full power. Full throttle doesn't feel much different than half throttle. Wheelies are tough even in first gear.

If I try to really wind it out (can't tell what rpm I'm at) on a long hill (because it won't pull the next gear) as the rpms climb at a certain rpm it starts making a ticking/grinding/ratcheting noise. It's hard to describe, at first I thought it was detonation but it doesn't sound quite like detonation and it's strange how it seems to come on at a certain rpm, not throttle setting. Maybe the powervalve is trying to open and it's stuck?

Has anyone heard of this before?
 
Joined
Aug 24, 2006
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#2
Human error is usualy the cause of most mechanical problems. I say tear it down and make sure everything is its right place. Before you do that make sure your kips saft is moving by removing the right side cover. It might help if you get a manual also.
 
Joined
Jun 25, 2000
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#3
crashing_sucks said:
at a certain rpm it starts making a ticking/grinding/ratcheting noise. It's hard to describe,
My 98 200 is doing it also and when climbing long steep hills it starts out ok then bogs down at high rpm's but runs fine after I clear the top of the hill.
 

G. Gearloose

Pigment of ur imagination
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Jul 24, 2000
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#6
Open it up before it frags. The 230f should feel like a scooter, comparably.
 
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Jan 24, 2004
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#7
I've only had my KDX for a month. It is a low hour bike, but to be safe, I just finished the top end last week. After going through the manual and learning about the timing on the KIPS, I'd tear it down and look it over. It would be very easy to get the timing off on the KIPS system. Also, check to make sure the "resonator" bolts are tight and the gasket isn't leaking. The resonator is the rectanular "box" on the side of the cylinder that says KIPS. It has 3 bolts. The engine will have almost no low end, and will have little on top too if you have a leak there.

If the timing is off on the KIPS, I think the symptoms will vary depending on how the cams are out of time.
 
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Jan 5, 2007
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#8
Interesting, might be a timing issue. I pulled that cover off on the resonator and found that it let exhaust into the resonator box at idle but almost immediately off of idle, (feels like 3-4k rpm but that's a WILD guess) the valve slides shut and exhaust stops coming out of that port. That makes me think the KIPS is working, but maybe the timing was off? I didn't even know the timing was adjustable until you mentioned it but it did strike me as closing pretty early, almost as soon as I flicked the throttle.

Air filter was clean, airbox lid was removed so intake doesn't seem to be the issue. I was thinking I'd repack the silencer and if that didn't help things I'd tear into the top end.
 
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#9
I still haven't had time to tear it down (working on getting the engine back in my CR500 this weekend) but I did have time to put a new plug in and do a test of the WOT jetting. When I checked it before I didn't use a clean plug, oops. The main was a 148, I threw in a 165, did another run, the plug still looked white. I then swapped in my biggest jet, a 172, and the plug still is pure white. What could be happening? Maybe a crank seal leak leaning it out? Now that I see how lean it is I'm amazed I didn't burn it up on my last ride where I was holding it full throttle so much.

Doesn't a 172 seem like way too big of a main to be running in this bike? It has the airbox cover removed, a vforce reed cage, and fmf gnarly pipe and silencer, from reading other posts I expected something around a 165 main, but didn't expect a 172 to be so lean the plug is still white after a good 6 seconds at wide open throttle.

It also sounds almost like it has a rev limiter at high rpms. These bikes don't have a rev limiter do they? Could this just be a result of being so lean?
 
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Jan 5, 2007
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#10
Disregard my last post, I just found out from a friend I wasn't reading the plug right. He said the tip of the plug is expected to stay white and that I should look further down into the plug for the color. I've never heard of reading a plug that way before but figure I'll give it another shot before I make any conclusions.

FMF says to use a 142-148 on the main so it seems the original main was pretty close. Strange that jumping up to a 165 or 172 didn't make much difference, I guess I'm not even making it far enough into the top end to make use of the main jet.
 
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#11
I've been out of town for a couple of weeks dealing with the death of my father and when I got back in town I found my friend Jake had bought a KDX220 for himself, then got together with another buddy of mine and fixed my KDX while I was gone.

You just don't run into friends like that very often, there I am out of town dealing with a horrible situation and Jake and Josh made sure I had something nice to come home too.

Turns out the perforated tube that run through the center of my FMF silencer had broken off near the front of the silencer, forcing most of the exhaust to be pushed through the packing material. Jake loaned me his stock silencer he picked up with the KDX he bought and got the bike running great again, now I just need to call FMF and see if I can get a new center section, otherwise I'll just pick up a new silencer. Either way, it's great to finally have the bike running right, and as expected it works perfectly in the tight singletrack.