New excited and disappointed 07 450 owner

Hey guys!


So excited to be a first time supermoto owner of a 07 wr450!

I've been researching and keeping my eye out of supermotos for 6 months or so I love the look, style, versatility, and sound of a nice 4 stroke dirt bike with street wheels!

It was going to be a husky 510 or wr, I went with the wr cause I love yamaha and have owned r6 and r1 for 10 years or so. And they're less likely to come by in my area. I'm in the boston area and have no intention of putting the wr on dirt.

Although I'm so excited to be on a supermoto, this bike has been nothing but a headache since I got it. Firstly I'm 5'4 and the bike was WAY higher than my 06 r6. I have owned and ridden 9 different street bikes all at stock height never adjusted suspension just dealt with the slight uncomfortable 1 top toe down coming to a stop, but the wr was not rideable. Lowered the forks and yamalink in the back so I can get toes on the ground, that was a little bit of a headache.


The bike idles nicely and sounds good if you can get it running. Electric start almost never works, and you have to kick it 100 times. It might run might not, depends on what day of the week it is, if it does run, idles nicely. runs like crap and the previous owner swears it was running mint before.

If by some chance I get it running, and keep it running by staying on the throttle, I have to wait at least 45 minutes before I ride it to have it be somewhat smooth... Then as I'm riding, if I get in the gas hard it starts to go then dies quick and falls on it's face like fuel is cutting. It does this a lot. If I try to slowly roll the the throttle on, it will still cut out at a certain rpm/engine load, it seems random. Most times I take the bike out, it will do than then just die as if someone turned the key off. I'll roll to a stop and have trouble starting it again. I've been stranded on several occasions! If I get it goin again, it will do the same thing and bog/die all the way home.


I've been doing a little reading and there's so much it could be. I've never owned a carbed bike or car before and don't know what anything looks like or called, but I did notice a few hairline cracks on the intake/carb boot or whatever you call that. I wonder if that is leaning out the mix.. I'd like to replace that piece (can't find that part nor do I know what it's called) and while I'm there rejet the carb since I've read it's cheap and there are specs in the pinned post of recommended jets.

I also would like to add the merge racing AP spring as people said that makes a world of difference; but Merge have stopped producing it! I don't know how to do any of this but seems pretty easy from what I read.

I've read rejetting and adding that ap spring should solve more than half of my issues! The previous owner however said it was running great last season, so maybe the only thing necessary is that boot, but might as well rejet and spring while I'm there.

Does anyone have any further insight, or could perhaps link me to an ap spring/ and or a good place to purchase jets and that boot from.

Thank you!

Likely your pilot jet is just partially plugged up.


Your accelerator spring can be found here


The boot should be a stock intake rubber for an 07' WR450

Edited by stevethe

All of your symptoms are common to maintenence neglect on the carb, harness, battery, valve adjustments, etc.....

You need a service manual.


Service the carb


Use fuel treatment every tank, no exceptions


Tokyo mods and R&D still make a linkage spring upgrade.....but you can't just change one thing and expect miracles....

Edited by KRANNIE

Thanks for the useful reply and links guys. Thank you Krannie, I've seen a lot of

Your posts you've been a great deal of help, thanks for the spring link. The carb was just cleaned I was told. And 2 valves out of spec and adjusted. There is some shady wiring on the kill switch and harness for that matter, that may be worth looking into. Thanks guys

I don't know, but it sounds like a classic valve clearance problem to me.  Hope you haven't been sold a bike with the valves run out.

I have a 07 and has never had those issues. Runs great, you need to go through the list of things Krannie talked about. Something isn't right. I would thoroughly check your carb and valves. Last winter I did have to shim my valves on my 07, they were barely out of spec.

The carb has an accelerator pump so you can easily flood it. Try this, on cold start choke and open throttle once or twice max before trying to start then start with no throttle. warm start with no throttle, works on mine anyway. Also you can run sea foam in your gas @ 1 oz per gallon to help clean up the carb

valves may need reshiming or head work depending on the miles, my 09 WR450 after 15,000 miles 3 valve adjustments it was time for new valves this bikes should be very easy to start good luck

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