New '03 YZ450...What to do?

I just picked up a new '03 model. Are there any 'must do's' that I should take care of right away?

Yep...change the oil. Check the valves. New tires. And Make sure your bucking bronco does not throw you off its back.....put a Gripper Seat Cover on that beast.

You will go through the rear sprocket really quick if you dont get a good chain. After that a new bike just needs to be ridden, at your break in point 3-5 (Thats my interpretation of broken in) tanks of gas do a good maintenance on the thing, check valve clearance, change oil, lube the rear axle and headset change out the fork oil yadda yadda. Then look at all the fun after market stuff... Triple clamps, front forks revalved new pipe bars fun stuff like that.... Have a killer time with your new ride. :thumbsup:

There are a lot of people on this site that give out advice to toss the oem chain. Usually without even finding out what kind of riding they do.

I ride strictly MX and bought my first 4 stroke this spring. A new left over 03 yz450. The stock chain is great. Best oem chain I have ever seen on an MX bike. If you ride off-road I would not recommend any non o-ring chain though. Stock suspension is also great for MX. I am 165 lb fast B rider and am using the stock springs. I may try a bit heavier on the front on my next oil change. I will be riding A class next year and doubt I will have my suspension done unless whatever bike I am riding comes with poor factory suspension. The suspension on todays MX bikes are great for MX. Disregard this advise if you don't ride MX(in which case there are better bikes out there) or fall well outside the intended weight the bike is set up for. Of course if you want to spend the money and the down time, I am not advising against having it done. There are a lot of reputable shops out there

The only things I have done to my bike (other than maintenance..grease..) is a 50 tooth rear sprocket, CR High Pro Tapers, and disconect the TPS. I also fixed the clutch for about $35 with a 426 clutch plate and spring. It was horrible from the factory. I am also running the GYTR MX flywheel. I would like to try the 4 oz Dr. D unit which is slightly lighter than the GYTR flywheel.

Of course when the stock tires wore out I put on better rubber for my type of riding.

Change Oil often. External adjustable air screw. That's all I can think of.


1) Fork springs, Up from .46 to .47 (I'm 160 Vet A class).

2) 47 Tooth sprocket, I know it doesn't sound right but try it first (unless you race supercross and of course only after you wear out your stock stuff).

3) Aluminum bars & better grips (I prefer renthal dual compound) - stocker bars are soft heavy steel.

4) Gripper seat cover made a bigger difference than I would have imagined (I went with the complete seat for 89.95 and really like it).

5) Twin air air filter, stocker is not so good.

6) Honda front brake line routing. I did mine for 59.95 and it really does make a difference.

I rode the bike stock as long as I could. I wish I would have made some of the changes sooner, like the gearing and seat cover but at least I got my money's worth out of the stock crap (I like the stock tires).

I also put on a Hinson pressure plate (can't afford the whole clutch) and it seems to help the chattering.

Change your oil often, it's cheap, motors are not. Take your time and do it right and be careful not to strip or over tighten.

The bike is so much easier and funner for me to ride with these changes it's hard to believe. With the taller gearing I can just leave it on instead of having to be so respectful of the big hit. (of course some people want the big hit) :awww:

What ever you do have a blast, be safe and smoke a Honda today! :thumbsup::lol::devil:


Were the 426 clutch parts $35 retail? Also, what are your clicker settings on the stock suspension?(help from anyone)


The best investment you can make is a zipty fuel screw or equivilent. I didn't realize how much I would use mine.

Prime example is right before a rain. You have to lean it out before the rain, then when it starts raining you have to richen it up. It's very noticeable. The screw makes it very easy.

Were the 426 clutch parts $35 retail? Also, what are your clicker settings on the stock suspension

$42.50 is the Retail price on my reciept - $10 discount +$2.10 tax $34.43. This was the biggest improvment(and cheapest)I did to this bike.

I started with about 10 comp and 12 rebound. I have dialed in some more compression on the fork. I go up or down a click or two depending on conditions.

Almost forgoto that I also got rid of the stock front brake cable because of lousy performance. It's sometimes hard to remember the little things


Did you replace just the aluminum and fiber clutch plates plus springs? Is that all it takes to get rid of the chatter? I've also heard of drilling holes in the clutch boss. Guess I should check past threads on this topic.



I replaced one fiber plate, the clutch boss spring, and the seat plate. The clutch was a POS and is now silkey smooth and I hammer on that clutch. A few of the steel plates were really blue when I did the fix and I did not have much time on the bike at all. Drilling holes may help cool and I may do that when/if I replace the clutch, but is not needed to solve the chattering.

Part#'s 5JG-16383-00




Thanks Craddock! :thumbsup:

In addition to the things already mentioned, let me suggest a heavier flywheel if you find the engine a bit too snappy for your tastes. The 03 450F quickly earned a rep for being difficult to control exiting tight loose turns and similar situations. Yamaha corrected this on the 04 by amking the 03 GYT-R +5oz flywheel OEM stuff. I recommend the 4 or 6oz Dr. D unit. ( I run a 4oz on mine. Sometimes I think I'd rather have the 6, but it's way better than stock, and not a bit slower). Ride one and see.

As for the OEM chain, ride the OEM three real good hard days, take it off and lay on the floor next to a six month old Regina Gold or DID X-ring and see which one is longer.

Hey, thanks everyone for the input. I rode yesterday at the track for the first time and I am one happy dude. Glad I made the choice to move to the YZ.

I know now what everyone ment when they said this bike has a 'snappy' engine :thumbsup:

The 47 tooth sprocket is cheaper to try than a flywheel with similiar results. :devil:

I put a Hinson pressure plate in the clutch cause motocross action says the stock one is whimpy and flex's causing chatter. Not perfect with just the plate but definately better and it doesn't cost that much (compared to the whole clutch) I paid about 135 through my dealer. :thumbsup:

I put the lightest GYTR flywheel on strictly to help with stalling when lugging the motor in tight corners. A 47 tooth sprocket would only amplify the problem. I run a 50 tooth and it is great. I could run a 52 for supercross. But hell, I think the stock chain is great.(I have never ran an o-ring chain though)

My clutch is perfect with the stock parts except for the three I mentioned, but if I ever break something before I sell it I will replace with a hinson

Never had a problem stalling - pick up your corner speed. :thumbsup::devil::awww:

But seruiously, with the 47 it is LESS prone to stalling. You tell me why. Doesn't make sense to me but MXA made the same observation. With a 50 or 52 I would think 2nd gear would almost be useless. :lol: I've tried the 47, 48 & 49 and like the 47 way best. But hey yeah, all comes down to personal preference. :D

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