WR450 2007 top speed problems

Hi, I own a WR450 2007 since 2011 (bought it used) , noticed that the previous owner already did the free mods (AIS removal, grey wire , etc)

it's been running fine since i bought it, but back in 2011/2012 I remember it could reach 120kph (74mph) fine, and if I gave it a little more throttle it would reach 130/135kph (although at very high rpms, but hey, it's normal ) - checking just by looking at odometer

Now, I bough a FMF factory 4.1 and noticed it performs better in low and mid range , but checking with GPS I saw that it could barely get to 90kph (55mph) that it was running already at very high rpm, I've tried connecting the grey wire and somehow i noticed it was even better at low range (dont ask me why)

What might be the problem for not getting nowhere near 100kph ?

PS: i cannot compare the GPS with the odometer now , because the battery of my bike is running bad, and odometer displays 199kph even when im at no movement at all (dont have money to buy a new one for now, and it runs fine just by kick starting it, and sometimes even e-start works) but for "sure" it's not the GPS that's wrong.

A bad battery can affect run quality

So can a worn piston/rings, dirty airfilter, bad gas, etc etc.,

The FMF should not restrict top end.

What is your jetting?

A bad battery can affect run quality

So can a worn piston/rings, dirty airfilter, bad gas, etc etc.,

The FMF should not restrict top end.

What is your jetting?

Battery would affect it ? Because when i'm at 80kph it's running at very high rpm (not reaching rev limiter though but i know it wont go faster than that cause it's already almost redline)

air filter is clean, I have two and exchange them between rides, so one of them is always clean.

Gas is top quality 98 octane 

About the FMF i noticed it makes every gear a little longer(because it's more open that stock exhaust, may be ? ), at least that's what i feel.

About the jetting i dont know, since i never touched the carb

You can't add a pipe without also modifying the jetting and intake

All you are doing is making it louder and leaner


Read the FAQ section

Only 55 mph? I've had my 01 WR250 up to 87. It's had all the free mods done and a Dr. D SS full system on it other than that it is stock. Oh and I run 85 octane non ethanol gas

Try shifting into 5th gear.

But in all seriousness, unless your jetting is WAY off, you should have the power to go faster than 55 mph. I doubt it's the battery, but you could always remove it to be sure. If the pipe really leaned you out that much and you still have the stock pipe, put it back on and see what happens.

In other words, get the bike back to the last configuration that it was running properly. Did you ride it much since 2012?

As mentioned, ensure you have fresh gas and a clean air filter - eliminate the obvious and easy possibilities. Are you sure the carb is clean? Running Gumout through it doesn't count. Have you checked the spark plug recently? Is the throttle opening all the way?

Where else in the power curve is the bike having problems? I doubt it's only top end speed.

A faulty ignition CDI could cause these problems as well. I've seen one crack and get moisture in it and make weird power problems.

If the fuse is blown the display will read something like 199 kph or mph.   If you've changed pipes you probably need to rejet.  I've had my '09 up to 88 mph (141.6 kph).  That's with the free mods, FMF Q4 and Hotcams stage one cams.  Sounds like that top speed is typical of what they can do.  

It's unfortunate that you are using 2 different devices to compare your speed.  Your GPS vs your prior odo. You didn't say if you bought the full FMF system or just the slip on.


Either way, you need to get a baseline using the same device for checking your speed.  Since all you did was change the exhaust, I would recommend putting it back to stock and take a run using the GPS to measure your speed.  You already know what you are getting with the FMF on so that should give you some indication on what is going on.


if you just did the slip-on, while you should change jetting, right now I wouldn't think that is robbing you of that much top-end.  While not ideal running temperature, it's not gonna knock of 20mph.  I think your issue is not using the same device to compare your speeds with.  Give that a try :thumbsup:

I question the accuracy of your GPS. If you are reaching the same rpm in 5th gear then you will be going the same speed regardless of your jetting or pipe. 55 should be easy to get to with out over driving it unless you are not in 5th gear or your clutch is slipping.

 or your clutch is slipping.

If it's not your GPS, I would look at your clutch plates.

If you are able to rev to the same RPM and have NOT changed the gearing. Only a slipping clutch could lower your max speed.

If you need a instrument cluster/ meter, I've got several extra. PM me.DSCN1490_zpscc36445d.jpg

Ok, so i only got the FMF factory 4.1 slip on ! I didnt re jet it because FMF said it worked without  needing to re jet, and since I installed the bike has been running "nice" apart from this "problem"

Thing is I no longer have the stock exhaust... so i cannot test against it.
I have 14 / 52 tooth  (same as before)

Yesterday i've charged my battery with an external charging and got my odometer working.

Today I warmed up the bike for like 5min ,  ride it slow for another 10~15min and then i tried to go top speed and it reached 120kph (didnt confirm with GPS) almost redline or at very high rpm, 

On my way back home (after a 3~4hour ride), i tried again to reach top speed and i could make it to 110kph but already feeling like it was redline.

Well, if we're talking 10 kph/6 mph here, the difference could be how long you're willing to stay on the throttle and where you're riding. 14/52 is more than capable of reaching 120 kph/75 mph. "Feeling" like it's at its redline and hitting the rev limiter are two different things. A few hundred RPM makes a big difference at the top of 5th gear.

Your bike is probably fine.

When i say "feeling" like it's at redline it's because  it's screaming really :o

if only i could get a rpm counter/tach , i could see at what rpms i hit the 120kph line.

Your fine :thumbsup:

That's the one I use, along with their little $15 mounting bracket. Works/fits/looks great - highly recommended.

I've bought one of those cheap tachs from ebay, but i cant get it to read anything...it's always 0rpm, may be i didnt followed the instructions on installation :p might wanna try again tomorrow

It's screaming because you leaned out your motor by adding the pipe.


Pipe/intake/jetting should be changed together

Didnt know that, mainly because FMF says since it's only a slip-on, dont need to re-jet . 
I will see if i can take it to a mechanic, cause i dont know much about carbs and what else... (may be i should read the manual :p )

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