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austinmation

Any major difference in 99 and y2k wr400 engine?

11 posts in this topic

I blew my Y2K engine, and shipped a 99 Engine.

A peer told me that the Y2K 400/426 engine parts can't go into the 99 engine easily. He mentioned about the clutch, con rod etc, that will not fit in.

Just thought I would ask you guys here if you got any idea cause I cannot tell from the parts manual alone on what had been updated.

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If you got a whole new engine that works why not just bolt up a whole new engine instead of splitting the cases on two engines!

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^^kinda along the same lines as what he said.

just find an entire lower end of a 426

prolly be a bit easier.

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Dumb legislation issues.. I might have to use back the old crankcase with the VIN registered. So almost everything from the 99 engine will be used back on the y2k engine.

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You should be able to take the 426 crank, primary drive gear, balance shaft drive gear (all must be used together as the 426 gears are splined vs the keyed 400 gears), piston (new?...at least rings and clips!) and cylinder and put them into your 400 just fine. A couple of things to consider: You have to use the 426 piston with the 426 crank because the pin size is different. The 426 carb (if you have it) is better than the 400 (internal hot start...plug or cap the nipple in the head), 426 ignition puts out lots more power than the 400 does (probably need the 426 regulator tho). The 426 header will allow you to change the oil without loosening the header. Pretty sure you re stuck with the 400 clutch. The 426 has Ti valves vs the 400's stainless. I wouldn't use the 426 head without a valve job...new SS valves, springs, keepers, etc will drop right into the 426 head (but you have to use all the parts as a set!) and will give you a fresh top end at about 1/3 the cost of the Ti set up. You will need a 426 top end gasket kit ad a 400 bottom end gasket kit. As long as you have the thing apart, do the auto-decomp cam mod if you haven't already!

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You should be able to take the 426 crank, primary drive gear, balance shaft drive gear (all must be used together as the 426 gears are splined vs the keyed 400 gears), piston (new?...at least rings and clips!) and cylinder and put them into your 400 just fine. A couple of things to consider: You have to use the 426 piston with the 426 crank because the pin size is different. The 426 carb (if you have it) is better than the 400 (internal hot start...plug or cap the nipple in the head), 426 ignition puts out lots more power than the 400 does (probably need the 426 regulator tho). The 426 header will allow you to change the oil without loosening the header. Pretty sure you re stuck with the 400 clutch. The 426 has Ti valves vs the 400's stainless. I wouldn't use the 426 head without a valve job...new SS valves, springs, keepers, etc will drop right into the 426 head (but you have to use all the parts as a set!) and will give you a fresh top end at about 1/3 the cost of the Ti set up. You will need a 426 top end gasket kit ad a 400 bottom end gasket kit. As long as you have the thing apart, do the auto-decomp cam mod if you haven't already!

Hey Birdy, thanks for the illustration. Sorry I was not clear about my post.

Mine is actually a Y2K 400, not the 426. The engine got badly ripped with the cylinder and crankshaft broken. I am still not sure what happen that causes it. I was not revving the bike but the crankshaft somewhat snapped and seized. The cam chain tensioner remains functional upon inspection, so is the timing chain, time chain guide. The head cylinder is still fine.

abd8123b.jpg08696374.jpg

I went to buy a 99 motor cause I could not find a 426 motor within my budget. My concern is whether the 99 motor parts will migrate easily into the y2k casing, especially the crankshaft/cylinder/piston assembly and concern if it can spec up to a 426. The 99 motor I gotten has goodies like hot cams , heavy duty clutch and a high comp piston with a 3 axis port job done.

From your illustration, the 99 crank/primary drive/ balance shaft will not take a 426 top. *sobz*

"The 426 header will allow you to change the oil without loosening the header. " I am unclear about this line. In the 99 head cylinder, do we have to crack open the bolt on the metal oil hose to bleed the oil out?

The WR400F in this country were spec with a different A/C regulator, but I swapped it for a Trailtech R/R to run a battery for powering my GPS. I also run a coil on plug ignition instead of using the plug coil. I am not sure if the output is as good as the 426 but everything is neater.

The FCR-MX carb on this bike has already been swapped with one a later model carb when I got the bike, I can't tell if it is an FCR 2 or FCR 3 though.

I just gotta cross my fingers and pray now my crankcase is not damaged from the loose bits off my broken cylinder.

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How often are your motors checked for proper VIN numbers? Here in minnesota the stupid DMV wants to know motor number along with VIN fir registration but as long as you have the correct motor in your possession and you don't plan on selling, I don't see an issue with a complete swap.

And you usually can change registration numbers if need be. What would you do if you broke a case on a brand new bike, junk it?

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How often are your motors checked for proper VIN numbers? Here in minnesota the stupid DMV wants to know motor number along with VIN fir registration but as long as you have the correct motor in your possession and you don't plan on selling, I don't see an issue with a complete swap.

And you usually can change registration numbers if need be. What would you do if you broke a case on a brand new bike, junk it?

Well, money at work here. My legislation needs Yamaha or my local agent to prove it. My local agent will only prove it if I purchase new parts and have them fix it up for me. At around USD$4,000 it ain't helping..

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I guess that was what I was trying to get at as well.......just swap it out and ride, don't make it harder than it is!

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