Strange noise at high rpm and very low power.

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crashing_sux
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Strange noise at high rpm and very low power.

Post by crashing_sux »

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?
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Post by scheckaet »

Looks shady to me. You should be able to wheely easy with all the mods you have and it's a 220.
If it was me, I'd check the KIPS to see if it actually works and eventually check the cylinder for damages.
Wiseco piston installed by previous owner about 40 miles ago
Are you sure about that? Is he any good with bike? always worth to check it out imo.
Good luck.
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Post by 2001kdx »

I had a similar problem. My powervalve was sticking shut. I am lazy and I did nothing to correct the problem, except for changing oils. That alone made the bike act correctly at high RPM's(approx 6K where the kips activates)
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Post by crashing_sux »

>|<>QBB<
scheckaet wrote:Looks shady to me. You should be able to wheely easy with all the mods you have and it's a 220.
If it was me, I'd check the KIPS to see if it actually works and eventually check the cylinder for damages.
Wiseco piston installed by previous owner about 40 miles ago
Are you sure about that? Is he any good with bike? always worth to check it out imo.
Good luck.
While I have no way to be sure I do believe the previous owner when he said he replaced the piston with a Wiseco. I'm not sure if he was just a lurker or a poster but he told me that he replaced the piston before there was a problem because he had read on the forums that the stock piston was fragile. Overall the bike appears very well looked after. He added radiator guards, a pipe guard, a skid plate and even added a fuel filter (which is a little thing but a small sign to me he cared about the bike). Replacing the piston before it broke seems in character with someone trying to build a very reliable trail bike, although replacing the piston and then selling the bike 40 miles later makes me wonder if he realized someone was wrong and decided to just sell it. No way to know really, the reason he gave me for selling the bike was that his girlfriend quit riding so they were both getting out of dirt biking.

Looks like it's time to get a manual, I was just hoping the noise only at high rpm was a symptom someone had heard of before.
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Post by Indawoods »

Get an online manual at the top right of the page...

Sounds like the KIPS is stuck like others have said... or he snapped the actuator when servicing....
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Post by Jeb »

I second the online manual - it's very good, well worth the 12$ or so per year.
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Post by Colorado Mike »

Also make sure he didn't put the piston in backwards.
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Post by crazybrit »

>|<>QBB<
Colorado Mike wrote:Also make sure he didn't put the piston in backwards.
Yeah, that wouldn't be good. Arrow on the piston head points towards the exhaust port (front of bike), in case this helps.

You can respray the top cover gasket so you can pop it off and check the piston without having to get a full gasket kit. Also you can pop off the slotted slide cover, should show if the KIPS is sticking. I'd do that first.
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Post by canyncarvr »

Re: 'FMF Gnarly Pipe'

That doesn't say anything about the pipe profile..just what it's made out of (metal gage...NOT 'sic' btw). Is it a torque or rev profile? The 220 with a torque profile won't have any top end.

But...it will land you on your behind in a hearbeat if you crack the throttle in first (and probably 2nd and 3rd and maybe 4th) gear.

Classic: No power down low (re: the wheelie comment)..Stuck/broken KIPS.

Do you know how to check that it works?

Re: 'The power feels OK at low rpm..'

No it doesn't You said it wouldn't pick up the front wheel in first gear. That is NOT OK. Not even close.....

Not like an RM250? Well..it never WILL be, either.


Best chance of what's happening: The KIPS actuator shaft was not supported when the cylinder was removed..it's at the least bent and not operating the KIPS, at the worst, it's broken.

IF it's broken (well..or if it's not) you need to find out for sure RIGHT NOW!. The broken piece may find a safe place to sit and not cause further damage...it may grenade the whole bottom end of the engine.

Remove the slotted cover on the LH side that crazybrit mentioned. Put a socket on the nut you're looking at, test the KIPS for free movement. It will easily move CCW. It is sprung against manual movement, but not hard to move..and should return to 'rest' when you let off the tension. I'm talking about a few inch pounds...not arm-wrenching force.

If that part doesn't work..either won't turn or has NO resistance to movement..it's broke.

If that part works...

Start the bike. When somewhat warm, rev it to around 6000RPM, watch for movement of that nut. It should move as it did when you manually moved it.

I'll bet it doesn't. You will need to take off the RH cover (not the clutch cover..the engine cover) to inspect the actuator shaft.

Read THIS:

..and THIS!


There are some great pics of damaged KPS shafts on this site....I looked, didn't find 'em. But then, I don't generally find things I'm looking for.

Someone else care to show the way?

BTW...seeing the nut under the LH cover move doesn't mean the KIPS is OK. You will need to at least remove the pipe to LOOK inside to determine if the subvalves/main valve move as they should and that they are timed correctly.

Done yet? :wink:

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Post by crashing_sux »

Wow, lots to check there, thanks. Before reading this I took a look at it yesterday and found air filter is clean, the airbox lid is off and the powervalve is at least moving. I removed the cover that says KIPS on the left hand side (resonator?) and at idle exhaust gases were being pumped out of the port there. When I twisted the throttle the port was blocked off (I'm assuming by the powervalve?) almost immediately. I have no way to check the rpm but if I had to guess it was closer to 3-4k, not 6k like I've read.

I'll take another look this weekend, these tips should really help.
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Post by crashing_sux »

And you're right, it'll never be an RMX250, I was just hoping it would have 80% of the power of an RMX, not less than half. Also, as to my "it runs good down low" comment, I should have said it feels like it runs clean down low, certainly doesn't make the power I would expect, top or bottom.
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Post by 2001kdx »

Inspect that powervalve!
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Post by GS »

Very sound advice from the others, but don't forget to at least confirm that the installed fuel filter is not hampering fuel flow. May not affect bottom too much, but sure can flatten the power.

When all else fails....ck the petcock screen for debris too.

Now, you have to let us know what you learn....deal?

My moneys on the kips......

:lol:
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Post by canyncarvr »

Exhaust flowing/not into the resonator tells you the LH subport drum is moving anyway.

Common KIPS failures (read: broke from lack of maintenance or improper wrenching) will have nothing in the cylinder moving.

Hard to say what is 'good' bottom end on a bike. For one thing, don't know what your comparison value is. My 200 runs far better than it did with all original stuff, but it's still no comparision to the YZ250 I rode awhile back.

No way it's ever going to be in the same ballpark (planet?) as a CR500!

Did I miss this?....what pipe is on it.

Jetting plays a big factor in performance, natch.

IF the KIPS is indeed operational, the jetting is even close and you don't have an 80psi cranking pressure number.....maybe it just can't stand up to....oh....say :hmm: ....a bike well over twice its size!

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Post by Colorado Mike »

I dunno CC, I think my 220 could go toe to toe against a friend's KX500 in a lot of areas.. Let's see; greeness.. they're on par there. lightness... well no, the KX feels lighter, umm... handling.. uh, axially no the KX felt better to me there. The motors were nearly identical though. Well right up until they are running. Then the KX completely flattens mine from idle to redline.

I think on greeness though they're pretty close. :rolleyes:
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Post by crashing_sux »

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. Maybe I'm just reading the plug wrong? A friend told me that I shouldn't be looking at the tip of the insulator and that I should actually look further down into the plug. I had always thought you looked right by the electrode but a 172 is huge for this setup, I know FMF recommends a 142-148 so the initial 148 was probably close.

It also sounds almost like it has a rev limiter at high rpms. These bikes don't have a rev limiter do they?
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Post by crashing_sux »

I didn't check the petcock or fuel filter for flow this weekend but at first glance it isn't reacting like a fuel restriction. I've had bikes that has fuel flow problems before, they ran great for a couple of seconds until the float bowl was empty, then had a lean couch. Mine runs the same the whole time, and for some reason runs about the same with a 148 or a 172 main in it.

I'm not expecting a CR500, I actually bought the KDX to be a slightly more powerful replacement for the CRF230. There are days when a 500 is just too much and a 230F is not enough.
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Post by canyncarvr »

>|QBB<[/url]
crashing_sux wrote: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. Maybe I'm just reading the plug wrong? A friend told me that I shouldn't be looking at the tip of the insulator and that I should actually look further down into the plug. I had always thought you looked right by the electrode but a 172 is huge for this setup, I know FMF recommends a 142-148 so the initial 148 was probably close.

It also sounds almost like it has a rev limiter at high rpms. These bikes don't have a rev limiter do they?

Sorry..too many questions..and too many of them backwards to know where to start.

Re: Plug chops

You DO look down INside the thread ring. Without a tool designed for that purpose it's easier to just cut the threads off. What you're looking for is a ring around the base of the insulator that will only be a couple mm wide if you're close jetting-wise.

White is the color you can easily see..and this what you DO see with a new plug run through a plug chop.

172 is way too big for the 33mm 220 carb.

Well...IS THIS a 33mm carb? If it had a 148 in it, I would guess so...although I've run a 148 a good bit in my 36mm (modified) carb on my 200.

There is no rev limiter other than the 2-stroke 'tune' that makes any 2-stroke run better at one RPM than another due to pipe effect and such.

This is a pic of a 'good' plug:



Image


That is NOT what you see with a plug chop. There won't be any of the 'color' you see above. The pictured plug has been run a good bit. A plug chopped plug will be white to the casual observer. The dark ring you see at the bottom of the insulator in the above plug? THAT is what you check after a plug chop...and as you see in the pic above, the thread shell has been completely removed.

A KDX that isn't 'bad' somewhere will kick the pants off any CRF230.

If it runs 'about the same' from a 148 to a 172, something is indeed wrong.

A check for flow as you suggest and a good dip in some Berryman's would be good..............

Sorry to not be more specific to you situation. Right now there is WAY to wide a view of things. Need to focus on SOMEthing.

Flow check and a thorough cleaning sound like a good place to start.

Maybe cut the threads off one of those plug chop samples and post a picture?

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Post by JMETTEER »

I'll bet anyone $100 it is a plugged silencer...

It happened to me on my 87 Banshee...


Later,
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Post by crashing_sux »

Looks like I owe that Banshee rider $100.

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 jmetteer above 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. JMETTEER 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.
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