New WR owner, a few questions

Hi all :)


I've just acquired a 2007 WR450 with a few "issues", if anyone can point me towards information I'd be very grateful.


My main concern is sorting out the exhaust / jetting etc. I see there are many threads about this topic which I plan to read through, but can anyone summarise the situation? I'd like to ensure my bike is not massively restricted in power, but I really don't want a loud exhaust. The bike at the moment has a stock exhaust but it looks like the baffle has been removed, and it's far too loud for trail use here in the UK.


I also got an FMF system with the bike - which will be my best basis for getting a bike with decent power but a polite sound? The FMF downpipe has one of those expansion chambers (power bomb?) on it.


The other major problem is that the starter motor doesn't work. There's a nasty screeching noise that sounds like the sprag clutch has worn out. I assume this won't be a tricky thing to fix? I've replaced the sprag on my KTM without problems.



Many thanks for any info :)


Stock exhaust mod -

I made my own pea shooter for the end. It is as big as you can go whilst leaving the moose nose on

I didn't do anything to the innards of the silcencer


Also, remove the snorkel from the air box so it is just the plain opening


As the bike comes from Yamaha UK, it is restricted to make it comply with noise & emissions

Some or all of this may have been done, but I will go through it

Replace the throttle stop, which as std allows only half throttle opening, with either a YZF (expensive for what it is or cut down the original to correct length) -

Jet it with a 168 main (std as from Yamaha is 160)

The bike comes from Yamaha with the proper needle in a plastic bag - it is marked DUQ - put it in with clip in middle groove


Much good info in here


With the stock can mod'ed, and the jetting sorted out the bike has more than enough power



Also read these




Starter motor is a known problem, in that people abuse it and it then fails

If the motor stops past where the auto-decompression has closed, then the starter isn't man enough to overcome the motor's compression and it basically stalls. the solution is to rock the bike backwards in gear to bring the piston back down the bore. Abusers just keep there finger on the starter with the result it dies

If you search on here, there are threads about replacing the starter motor carbon brushes but if may be beyond repair

Edited by GuyGraham

Thanks that's a good collection of info, should keep me busy for a while :)

Guygraham the link for the stock exhaust mod is to a drz thread ?

Guygraham the link for the stock exhaust mod is to a drz thread ?


No, WR450F, 2006(?) onwards (WR's with an alloy can as opposed to the earlier welded shut steel thing)

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