Tips For A New Yz400f Owner

Hello everyone,

this is officially my first post here on TT... looks like a great site! Ive been a thumper fan sense my first bike (74' XL250) Had an 86' XL600R's for twelve years after that... ended up on a sand bar called florida for a while... no good riding and sold my XL. Back home here in the Bay Area now and picked up a 98' YZ400F thats in pretty good shape for $1,650. I'll be camping this weekend, but when I get home next week I want to do a mild tear down on it, flush and replace all the fluids, asses any damage, make repairs and so forth.

Id love any tips from people who have expreiencs with the YZF's if possible. Things I need to look out for, good upgrades, good set up and whatnot. I need to get a new seat, this one has a tear and is hard as a rock! The rear shock seeems kinda worn out and sounds rough when put through its stroke. Missing a few fastners here and there, but the plastic seems pretty good.

Ok... I'll check up on this thread sometime soon. Thanks in advance for all the tips and tricks! Oh.... I live in San Jose by the way, and will be looking for some new riding pals soon... so hit me up!!!!

Thanks again,


I agree with you on the seat. Yamaha should have just used a 2x4 and taken the price of the bike down a bit. I haven't replaced mine yet. Oh well, you learn really quick to stand up more. (if you ride trails)

i have a 99 400, so I will fill you in on what i have learned.

I took my seat to a local auto upholsterer and he took 1 inch on hard foam out and put 2 inches of soft foam in and it is 200% better.

these bikes do not like to be rode slow or idled for any amount of time, they will overheat very fast. I put engine ice coolant in mine and watch my ride/ idle time and have not had an overheat prob. since.

If you read in the sticky's at the top of this forum, they will give you a ton of info. There is also a download for a manual there. The best mod I did to mine was the exhaust cam mod to do away with the manual decomp. If you don't know if the cam chain has been replaced, it would be a good idea to do that.

have fun and welcome to TT


The guy I just bought my '99 400 from mentioned something about "clutch exploding and blowing a hole in the case"... Any ideas on what he is talking about here?:thumbsup:


I have had no clutch issues at all with mine. He would amost have to be talking clutch basket, but I would try to pin him down alittle.

You might hit the search thing, I know there is a mod to update on the 426 clutch, not sure about the 400.


I too have a 1999 YZ400F, and the stock seat on mine is nice and soft...Did I get the only good one or something?

And as far as the bikes, be sure to check the valves maybe every 5 rides, it doesn't take too long, and will alert you of any problems that you could have in the future. And change the oil, and clean the oil filter every 1-2 rides.

My 450 has got an edelbrock quicksilver pumper carb on it I heard it is a good mod to do because a lot of the yzs had serious hot start issues and if they fell over they were impossible to start. I think it's about a 400 dollar carb though. Also the renthal fat bar seems to hold up really well when jumping... I would also put on strong aluminum or alum/plastic brush guards because they protect your levers and are much cheaper than asv. I would also put on a good skid plate, frame guards, case savers, and a shark fin (if you don't already have them). There are also some really trick looking anodized blue pieces that look pretty trick and shave off a little weight eg: axel blocks, fill and drain plugs, wheel hubs, most bolts can be replace, front and rear brake fluid covers etc etc etc...

a really good idea also if you have the money is to get a good hinson, barnett or billet clutch set up of some kind. They are really pricey though eg: basket about 300, inner hub 250 or so, and pressure plate about 150 or so... New clutch springs can really liven up an old clutch too... I've also heard good things about the rekluse auto clutch but haven't ever used one myself.

There are lots of cool mods it just all takes money.... good luck happy hunting. :thumbsup:

Good info so far... thanks. I'll certainly be taking the seat to a local auto aphulsterer for some mods. Think I'll flush the cooling system and fill it up with engine ice or similar antifreeze. Just bought the Clymer manual today, will tear the bike down and go through it next week when I get home from Clear Lake. Cant wait to get it out on the trail. Think I'll probably look into maybe putting a WR flywheel and stator sense I do mostly trail riding, and it would be nice to be able to put on a head light as well. Might try to track down some black plastics to.... going to be fun putting my personal touch on the YZ....

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