2008 Yz450F Jetting 1

Alright I just got done tearing down the entire back end of this 08, and let me tell you, I'm glad I haven't broken it in yet. There was no grease in it. Nowhere! I torn the back end down to get to the carb to jet it and I just couldn't believe it. I packed every bearing and got it ready and torqued. It's perfect and what a difference. Anyway I am at 535 ft elevation and I put in a 168 Main jet with a 48 pilot jet. Stock everything with GYTR fuel screw at 1.5 turns out. I haven't started it yet but I will tomorrow. I believe it will be just about right. Stock I could hardly start it. It was so lean. I will keep you posted on how it runs. By the way we have had warm weather in Charlotte, NC and is about 73-76 degrees.

Im at same altidude as you and and my bike was perfect stock, and now with Dr D its even more perfect. Rember this is not like a 06-07 things have been changed. My bike was reak hard to start at 1st after 2 or 3 rides it was 1st kick. I think you have gone way to high. I might go up on my pilot for winter but as off last ride I went to 2.5 turns out it was 44 degrees and she ran like a champ with no decel popping. I like a little decel popping myself. I have had zero bog issues with this bike. My 06 I have to jet alot more often. I think you missed on your guessing here.:banghead: ASK TODD he likes his factory jets as well

Im at same altidude as you and and my bike was perfect stock, and now with Dr D its even more perfect. Rember this is not like a 06-07 things have been changed. My bike was reak hard to start at 1st after 2 or 3 rides it was 1st kick. I think you have gone way to high. I might go up on my pilot for winter but as off last ride I went to 2.5 turns out it was 44 degrees and she ran like a champ with no decel popping. I like a little decel popping myself. I have had zero bog issues with this bike. My 06 I have to jet alot more often. I think you missed on your guessing here.:banghead: ASK TODD he likes his factory jets as well

Factory jetting for the 08!!!!!! I got mine stock but 2 1/2 turns on the screw. PC Full system. I tried a 165 main but went back to the 160....Lean is mean.

I did get everything together and started her up tonight. Seemed to of course bog with quick blip on throttle. Now the bike is not broken in either and should have the pipe soon. I did hear somewhere that you should go up one size or 2 sizes with a pipe and vp fuel. What's your experiences.

I did get everything together and started her up tonight. Seemed to of course bog with quick blip on throttle. Now the bike is not broken in either and should have the pipe soon. I did hear somewhere that you should go up one size or 2 sizes with a pipe and vp fuel. What's your experiences.

If you are going to run straight race fuel you will need to bump the main one size maybe two...so for you either a 165 or 170. If your running race fuel you might be ok with that 48 pilot also. I have a friend running the VP ultimate 4 and his jetting is 170 main 45 pilot 45 leak jet.

If you are going to run straight race fuel you will need to bump the main one size maybe two...so for you either a 165 or 170. If your running race fuel you might be ok with that 48 pilot also. I have a friend running the VP ultimate 4 and his jetting is 170 main 45 pilot 45 leak jet.

Man, I can't wait to ride Saturday to try out this 08! I was riding a perfectly set up 06 with full suspension upgrades, coatings, ect. Totally stock engine though. I have a friend who bought it, so needless to say I want my 08 to run with the old.:banghead: Well See! I am going up to a 50 tooth on the rear. Got the rear shock set at 96 mm sag and 1" static sag. Stock shock. I weigh 195. The rear spring on the 08's are slightly oversprung compared to the front.

The changes to the linkage on the '08 require a higher spring rate than the '06/'07. Because of that, they aren't directly comparable.

Well I ordered MY PIPE!............. I ordered the DR.D pipe for a couple of reasons. Price is good, and from what I understand it only takes about 10-15 min to repack! @ 10-15 dollars each time. I did however call Dr.D to get the jetting specs for this pipe, so I would be ready and there was a lady who went to the back asked someone what the jetting specs were, when she returned she told me that to go to 162 on the main and go to 4th clip on the needle. She didn't ask me gas, altitude, ect. When I asked her about altitude she told me that was up to 4500 ft. ele. I also asked her about gas, because with race gas gas VP U4.2 I believe you go up 1-2 sizes. She told me that it didn't matter. I thought I would let you guys know.:busted::banghead: I believe with race gas and at 500-700 elevation I should come back down from a 168 main and 48 pilot to 165 main and stock pilot then move the clip to the 4th. what do you think?

Be an oddball and try what you have first to see how it works. Seriously.

Be an oddball and try what you have first to see how it works. Seriously.

I will! Supposed to rain and be cold Sat. :banghead: We'll see

PS 4th clip on the needle will lean it out right?

Depends on where it is now. #1 is at the top, lowering the needle to the max. #7 is at the bottom, raising it. The easy way to keep it straight is that, like the jet sizes themselves, the higher the number the richer the setting.

Review the tuning section of the manual regarding carbs, the adjustable components, and their effects on the overall picture. This link may help as well:

http://www.thumpertalk.com/forum/showthread.php?t=404426

The changes to the linkage on the '08 require a higher spring rate than the '06/'07. Because of that, they aren't directly comparable.

Thats a very good point Gray....Where i needed a 6.0 spring on my 06.....my 08 required a 6.7. My 06 also had .50 fork springs......the 08 has .52's

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