Might get a 450, have some questions.

2 replies to this topic
  • KAS

Posted August 01, 2007 - 09:35 AM


Right now I've got a 2007 YZ250 smoker. I like the bike, but I want something different (been on a 2-stroke for five years). I really want to stick with a Yamaha, so I'm leaning towards a YZ450F. I've got a couple questions.

First is jetting. Nothing worse than buying a new bike and chasing down good jetting specs just to get it to run. Do they come fairly close stock (sea level-4000ft)? I haven't touched the jetting on my 2-stroke, its been great from the factory.

Next is valves. Do you they need adjusting right after break-in? And then what is considered normal intervals? I'm a slower mid-pack B-level hare scramble rider, so I wouldn't beat on it too bad, say compared to an expert MX'er.

How about overheating? Do they puke fairly easy? Like I said, I ride woods, and I'm not the fastest. I never boil my 250 over, but I know big 4-strokes produce a lot more heat. I had a liquid cooled XR650R that never boiled on me, but MX 450's are a whole different animal.


Visit the ThumperTalk Store for the lowest prices on motorcycle / ATV parts and accessories - Guaranteed
  • gtguy

Posted August 01, 2007 - 10:58 AM


I've got an 06 450F and an 07 250 smoker. I still prefer the 250 for racing. Reliability on the 450F has been great. I've checked the valves once @ 10 hrs and am going to check them again this weekend. Jetting was pretty close, I went to 165 main/45 pilot. They do get hot and finicky when the weather is warm. Hard to beat the smoker for all around riding IMO.

  • Ranger18

Posted August 01, 2007 - 02:03 PM


Change the jetting. 165/45 works pretty good. When it cools down you might want to try a 165/48. I have never touched my valves. They state that you might have to adjust them, just so that you won't get pissed off if they do need adjusting. I don't think I have ever boiled over my bike. I have riden some pretty slow trails with people, and run pretty hard at the track, and no boil. If you have any concerns, just replace the coolant with engine ice. The YZF is a great bike, you won't be disapointed.

Related Content


BIGBORE FOR YZ450F 2006? by Taattie94

Dirt Bike   Make / Model Specific   Yamaha   YZ 400/426/450
  • 5 replies

Should I buy this bike? help....... by Numsa Hul

Dirt Bike   General Dirt Bike Forums   What bike should I buy?
  • * * * * *
  • 10 replies

Snake pit oct 30th by The Anvil

Dirt Bike   Dirt Bike Regional Discussion   California
  • Hot  293 replies

2016 YZ450 by CaptainKnobby

Dirt Bike   Dirt Bike Technical Forums   Suspension
  • Hot  59 replies

James Stewart back on a YZ450F by YamaLink

Dirt Bike   Special Interest Forums   Pro Racing
  • Hot  47 replies

Join Our Community!

Even if you don't want to post, registered members get access to tools that make finding & following the good stuff easier.

If you enjoyed reading about "" here in the ThumperTalk archive, you'll LOVE our community. Come join ThumperTalk today!

The views and opinions expressed on this page are strictly those of the author, and have not been reviewed or approved by ThumperTalk.