yz426 questions

I have recently purchased a 2002 yz426f. I have not owned a yamaha thumper before and had some questions for the experts.

First, I will be changing oil and coolant; any suggestions on what oil and coolant to use?

I will be using the bike mainly for woods riding, does the 426 have any overheating problems while riding slower trails?

The bike has an FMF Q4 exhaust, is there any way to quite it down just a little? Also, can anyone recommend a aftermarket kick stand?

The bike needs wheel bearings and eventually fork seals; is there anything else that I should specifically check for maintaninance?

Can anyone recommend a good skid plate?

I have read on the forum that a heavier flywheel makes the bike a better woods bike, how much improvement can be expected?

Finally, I think I have figured out the "procedure" for starting the bike; but I have also read that a yz450f or a Hotcams exhaust cam with the autodecompression greatly helps in starting the bike, is it worth the cost and effort?

Thanks for the input!

gsev:thumbsup:

I run a YZ400F which is very similar to the 426.

Provided you change you oil at regular intervals, using any reputable brand of synthetic multigrade oil should be OK (I use 10W-50 from memory). I change my oil every 9-10 hours. Get a Scotts reusable strainer, this will save you expense on new filters as well as providing better filtration.

As for coolant I change mine at least once a year, as I ride in a very hot environment, I usually change it before the hot season. I have found a coolant overflow tank a very good modification, especially when the engine is running in hot conditions. The tank catches any overflow from the radiator should it get very hot, and allows for the overflow to be drawn back into the radiator when the engine is running cooler. The overflow tank also provides additional volume of coolant in the cooling circuit. Motion Pro make a purpose built tank (they call it coolant recovery) and there are posts on this site refering to a modification using a turkey baster.

Trailtech at www.trailtech.net make a kickstand for the 426. This stand is very reasonably priced. I have used one for 2 years now, no problems. You will find the addition of a kickstand most useful.

I have no experience with the silencing of an exhaust or a skid plate (I use the stand fitment but as I ride mostly desert, rocks are not really an issue) however for the silencing matter I suggest you search the threads on this forum, especially the early ones from year 2000 thru 2003.

As for fork seals and wheel bearings, this is over to you really and to what knowledge you have of the previous history of the bike. If it has done work in water/dirty/dusty environments, it is probably best to consider the wheel bearings and seals soon for peace of mind. It will also be good practice to strip, clean and grease the swingarm assembly as well as this is an often overlooked item. As for the fork seals, wait till they start weeping oil and then do a full rebuild with seals and bushings.

The cam mod you mention is very worth while. You will certainly appreciate it in tight woods work as for sure you will fall/stall in some awkward situations.

Other maintenance items are check your valve clearances, and change your cam chain. You will find more information on these items in the sticky at the top of this forum.

Good luck.

Good luck

I have recently purchased a 2002 yz426f. I have not owned a yamaha thumper before and had some questions for the experts.

First, I will be changing oil and coolant; any suggestions on what oil and coolant to use?

I will be using the bike mainly for woods riding, does the 426 have any overheating problems while riding slower trails?

The bike has an FMF Q4 exhaust, is there any way to quite it down just a little? Also, can anyone recommend a aftermarket kick stand?

The bike needs wheel bearings and eventually fork seals; is there anything else that I should specifically check for maintaninance?

Can anyone recommend a good skid plate?

I have read on the forum that a heavier flywheel makes the bike a better woods bike, how much improvement can be expected?

Finally, I think I have figured out the "procedure" for starting the bike; but I have also read that a yz450f or a Hotcams exhaust cam with the autodecompression greatly helps in starting the bike, is it worth the cost and effort?

Thanks for the input!

gsev:thumbsup:

Oil- Mobile 1 4t

coolant whatever

It may over heat if your not moving along............ Boyesen waterpump fixed that issue for me

Wheel bearing pivot works I'm running them on my 426 good stuff

Fork seals not sure...........

Check the Linkage/Swingarm bearings regrease or replace sam with the steering head bearings--- also recommend pivot works bearings for this.

Clean air filter

Get a Devol skid plate also running one on my 426 great product

Don't put a Flywheel weight on it just got to a 50 tooth rear sprocket.

Only do the Hot cams exhaust cam mod if you're gonna race it in harescrambles. If you're just riding around the woods don't worry about it.

If you do decide to do the mod check the valves while you're in there.

Some good reconmendations from the previous 2 posts.

I also have a devol skid plate which is great.

Clean the carb

Q4 is probably as quiet a performance exhaust as you will find. (post some photos of that if you don't mind I've been wanting to see one of these. Is it the new or old style with just a Q4 sticker on the old can?)

ProMotoBillet kickstands are expensive but I would say worth it. They are light and tuck up and away nicely behind the side panel and also don't flop around while riding.

The exhaust cam is a nice luxury to have, but not a need. I put in a hotcam after years of using the stocker. Bump starting is easier that is the main benfit in my eyes because I got so used to the drill it was no big deal to me.

Just inspect everything, keep up on the maitenance and you should have a reliable FUN bike for years to come.

I use Yamalube for my oil. Also the pro moto kickstands are tough. I use my stand while starting it up and I weigh 200 lbs. For the raditor, I recomend Engine Ice. Have fun, 426's are a beast. Love mine. Check out "My Garage" and check out mine.

Thanks for the input. I plan on going for a ride this weekend. Has anyone had to rebuild the rear suspension linkage? Mine seems to have some play in it.

Thanks again,

gsev

All the mods listed above were on my 2000 YZ426, all are great additionas to a reliable bike. For riding tight woods I found the fly wheek weight to be extremely helpful as it reduces the amount of stalls, but thats my opinions.

The one thing that is not listed in this form is Jetting. I purchased a JD Jetting kit mainly because I ride from sea level to 7500 feet. Take a day and spend time tunning the bike in. Once this is done correctly and is matched for your riding conditions it will be the best mod you could do. I wish this would have been this first mod oppsed to the Auto-Decompression Cam and Fly Wheel Weight. Once the bike is dialed in it will be easier to start and will not stall out as easily.

Just my .02$... Good luck, they are great bikes...

Oh yeah engine ice and JD jet kit are also great things. I have both on my bike. So x2 for each of those things already mentioned.

I changed out my swingarm/ shock/ and steering stem bearings but just cleaned and greased my linkage as they were in good shape. I have rebuilt other links before, they are pretty much all the same. Use All Balls or Pivot Works kits for any of the bearings you need. I have used both and both have been perfect. The paly may be coming from your lower shock bearing.

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