One of my buddies just bought a new 05, YFZ 450. Do you have any advice for him??? I heard that the bike is jetted from the factory to be run without an airbox lid, and you get 2-3 free horsepower, right there. What are the best motor mods??? Thanks!

 

Any Advice for a New YFZ Owner ???

From what I've heard, try no lid, take the baffle out, rejet and that is supposed to be a great boost. Also the "cam mod". Things to look out for is the decrompression plug popping out. Check outYFZ Central .com They have all the best known mods and problems figured out.

 

I would definitely rejet right away, especially if you removed the air box lid. When ya add the air, you have to add the fuel. These yfzs run hot out of the box. I've heard the main jet from the factory is about 10 sizes too lean and the pilot about 3. Go to the daddog jetting page for other info on jetting. I took some of their advise and it worked great.

I'd also get the replacement decompression plug. The old one is just a rubber cap and the new one is only about $20.00.

 

I removed my air box lid on my prairie and lost power.
It would be best to have an area that you can make runs and compare the mods you do.
This was with a Kawasaki and I think it would pertain to all machines. I actually lost 6 mph in a 300 foot run with air box lid off.
So jetting is very important.

 

yeah... investing in a jet kit will probably be the best 20-40 bucks you spend on that quad. And it'll thank ya for it. [img]i/expressions/face-icon-small-wink.gif[/img]

pipe
header
jet kit
airbox lid off
air filter

fer around 400 - 600 bucks, you'll have a pretty sweet setup that will keep you ahead of most of the local riders....

 

trade it in before he puts to many rides on it.... [img]i/expressions/face-icon-small-smile.gif[/img]

 

no, its not jetted for no lid from the factory.
no, its not 10 sizes to small on the MJ and 3 on the PJ
the decompression plug problem has been fixed on the 05's... no need to worry about that.