where does the oil go now?


Interesting introduction to four-strokes.

First of all, Yamaha didn't make a 00 YZ400. It was a 426. If you have a 400, it's a 99.

Next, the factory design is a dry sump system with a 52oz capacity. This can be converted to a wet sump system using a 32oz (950ml) capacity.

However, I've yet to see a general aftermarket conversion for this, which means it sounds like someone has does some custom work to this machine. The oil will either have to go into one of the two cases. If they have not added a filler hole, you could lay the bike on the right side and use one of the timing plugs.

BTW - 32oz is not much oil (1 quart) for an engine like this. Works fine for single moto sessions, but trail riding and the like, it may not be a good idea. Consider converting back to a dry sump system. Perhaps you can do a temp reading on it and make sure that it statying within the operating range of your oil.

As for the rear hub, the factory design is two bearings. The drive side is a beefier bearing, but again, only two. Sounds like the hubs have been switched out as well, but I don't know of any one that uses three bearings. Assuming of course, that you're not counting the spacer as a bearing.

Good luck. Sounds like an interesting machine.



You're right, it's a '99 YZ (registered as WR 400 '00).

I'm going to use it as supermoto race bike. And no, I didn't count the spacer, there are three bearings (some mechanic said the YZ250 has those three bearings and thinks someone might have swapped wheels??).

As I had 17" rims laced up, I had the bearings replaced.

It also lost first gear, which is quite annoying, since i was gonna change gearing to >15/<39 to increase topspeed, but i also want to be able to make good starts. Or will it be strong enough in 2nd?

Cannot get bigbore kit, since 400cc is the 4stroke limit in the 250cc class, and I can't imagine racing this against the CR500's I used to race.

Thanks for your help!


I would love to have the wet sump system in mine. I hear that BBR can come up with the parts, but knowing them it will be pricey. Yes, my '95 YZ250 had 3 wheel bearings, 2 on the sprocket side. And yes, it has the beef to do 2nd gear starts. Which rule book limits 4 strokes to 400cc? I know the new AMA rules are 450, that's why the CRF is 450cc.

Dave is right about the oil though, you will need to change it after every ride. I do on my stock '00 anyway. Just think of the weight you save though, besides the oil you have all the oil lines as well. You might go to the BBR website and see if there is anything there about their wet sump system, maybe that will give you a clue as to where to add oil...


I'm relatively new to 4stokers, and kinda regret having made the switch. I bought a YZ400 '00, and found out that the oil resevoir in the frame has been sealed off. This may sound a stupid question, but where do I get the oil in now?

Someone has written 950ml on the sidecover (left), so I guess this is the 'new' oil capacity.

Another one: I read somewhere that the rear hub has two bearings, I just replaced three (two on the sprocket side)!

I need this info since i'm gonna race this thing and the first race is almost there...



European championship rules:

- 250 series: 250 2 stroke and up to 400cc 4stroke

- 500 series: 500 2 stroke and up to 990cc 4stroke

2cyls (first thought of racing a suzook SV650N project/SM, you've all seen the drawing, right?-> and if it's good enough for some Paris-Dakar nutter...)

Why would you want wet sump? Less oil? No oil pump? Less hoses? Quicker oil changes? What and why would you bother? Are there that many advantages? Where's the BBR website?

This year will be more of a °we'll see how it goes with the 4stroke° year...


Although this engine is defined as dry a sump, it does have a wet sump pickup. In fact, the engine has two oil pumps, one for taking the oil from the frame, and the other for pulling oil from the spill off, or wet sump.

Traditionally, wet sump system lubricated the crank journals by splashing the oil onto the crank. This robbed power from the engine.

For many race applications, the preference was to have the oil outside of the engine to prevent this, as well as to increase oil capacity and cooling, while still maintaining clearance issues, such as a low application race car.

For the YZF machine, the conversion is done soley to reduce weight. It drops one quart and you can remove all the plumbing. This removes about 2 to 3 pounds.

The conversion involves plugging the holes into and out of the engine, and re-routing the two pump system into a single wet sump pickup.

The conversion should be mostly small parts, so I can't imagine it would very costly, however, converting back to a dry sump system could be costly if you did not have access to all the parts removed.

If you are just racing the bike, you may want to keep it as is, and just exchange the oil after each one or two session.

Hope this helps.


Like Dave said- the mod would only be useful for a full on race bike. There are lots of disadvantages. I would like to look into doing it to my bike. BBR is here:


I looked around and couldn't find the kit, but I am sure I either saw it once on their site but it could have been in an article I read about these guys. It's cool looking at their work anyway and you could email them for more info...

Thanks for all the info guys!

they made 2000 wr400

i would just drink a quart of oil before each race and screw the extra bearing you dont need it.

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