Bought an '04 YZ 450f today

I received a manual and tools with it, along with what looked like two jets. Are they jets? Why do they give them to you, or why would you need to change them? Thanks.

They're jets. Mine came with an extra 160 and a 170. Supposedl there's a 165 installed stock. Mine is running pretty well on the 165, so the 160 and 170 are useless for me.

I ordered a 168 to bump it up a little, but I think with the stock exhaust the 170 would be too rich for me.

They just include those to get you in the ballpark if the bike won't run right with what's installed from the factory.

Be sure to adjust the pilot screw (fuel screw) before you even bother running it. Mine wouldn't idle out of the box until I did it. The screw was set a .5 turns out from the factory, I set it to 2.5 and it finally ran ok. I have since put a ZipTy screw in it and it's worth every penny.

Thanks. I also wanted to add another question. What gearing are you guys running and for what kind of riding? Thanks again.


I actually liked the stock gearing for faster MX...if the going got slow, a tooth or two bigger in the rear made it much better.

I'm using 14-46 for gearing. Mostly race hare scramble races.

I haven't messed with my gearing yet, but I'm thinking I want to either drop a tooth on the front or go up 4 or 5 on the back soon.

For most of my riding it's fine stock, but sometimes I want to putt around and it's too tall for that. I let my Dad ride it again yesterday and he always takes it really easy for the first few minutes and rides the engine on the borderline of lugging it.

I haven't even used 4th gear yet, so it's not like I'll miss the top end for awhile.

I'll probably drop a tooth on the front first. That way I can still use the stock chain until I get a complete sprocket/chain set. A front steel sprocket is only like $20.

I use to run a 13-50 for tight MX tracks. Stock is good, but I found that I was shifting way to much. Had a weird spot between 2nd-3rd and 3rd-4th. Alot of people are running 14-47. Now I'm running 15-50. It is within .005 of 14-47. I love it. Great for MX.

14 - 47 mx

Stock works great for most of the tracks I go to, I tried a 47 but had problems in a few corners that led into some tight doubles much better with stock 14 - 48. The tracks I go to you only hit 3rd gear in a couple of sections everything else is done in second.. Supercross Style.. :thumbsup:

Nevermind what I had before. LOL. I figured it out.

I wouldn't recommend going up 4 teeth on the rear, i did that and it is really a chore to keep the front end down on the dirt, I can wheelie in forth gear with a twist of the throttle, same goes for dropping one on the front.

try changing 2MAX teeth at a time and always replace your chain.

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now