splitting the case

I need to replace the crankcase on my 1999 wr400, not the internals just the actual case. So I called my local shop (good mechanics) and they said it will cost about $1100 $635 for the case and the rest was labor depending on how it went. Although it does seem a little high I'm sure some other shops wouldn't be a whole lot less if any. They said if I can get the case cheaper the labor charge won't change (I can get it for $450 online). So now I'm thinking that I could save myself a lot of money if I could do it myself. I'm pretty good with engines, This would be the third time I split a crankcase on a motorcycle, but the reason I'm concerned is that they were both two strokes and I don't know how much more complex a four stroke crankcase is.

-The story- for everybody who is wondering why I have to replace my case

I got this bike about a month ago. The day after I got it I went to change the oil and when I went to unscrew the drain plug I noticed it was held on by JB weld. I started to unscew it and all the jb weld around the bolt fell off, leaving about half of where the bolt threading in gone. I called the owner, he said he had no idea, wether he did or not is beside the point because he offered me $500 back to fix the problem (I now have the cash) So my first though was a welder, I got someone to do it but it didn't work out so well. So he didn't charge me anything but a couple bucks for his time (he did try to weld it). So now I've decided to replace the case, I'm sure there are other ways to "rig" it but I'm the kind of person that likes it to be done right (so I don't have to worry about it anymore)

So I'm just looking for opinions/advise on the matter of me or a dealer replacing the case.



A job like this by a competent wrench should be well under 5 hours time. at $80/hr, that is $400.00 labor. I would think book time is more like 4 hours.

I didn't think it would take them 6 hrs (that's what they told me) I even said I would take the case out and everything off of it. Judging by the time it takes me, a avergage joe, to rebuild a bottom end (of a two stroke)it shouldn't even take them 5 hours to just replace the case. Maybe I'll call some other shops tomarrow and see what they say, but I'd still like to do it myself.


All you need to do it yourself is a case splitter, a press or bearing puller and some ThreeBond. Be sure to replace all seals.

I would JB weld the plug back in and keep the 5 hunnert in my pocket. Why spend all that time and effort on a 10 year old bike?

But if you could split the cases on a 2 stroke (which means you're a pretty smart kid) you can do it on a 4 stroke.

You could strip the cases and bring them over to the dealer and have hime crack them with their case splitter.

BTW most kids your age can't even pick their nose by themselves much less attempt what you are going to. I salute you Jr.

My advice:

I think (depending on how bad the stipped bolt is) adding a heli coil to it will fix your problem - I just had my cases split recently due to a bearing failure and noticed that my drain plug was heli coiled and I have never noticed any issues with it.

You won't need a case splitter, my cases cam apart so easy it's child's play.

There really is no difference when it comes to the internals of a 2 vs 4 stroke other than the valves and timing chain, but that's minor.

The only tool you will need is a flywheel puller and you can just modify a cheapo puller to fit - also child's play.

For replacing the cases you need to consider some things:

You definitely will NOT be moving the bearings from old to new without damaging them, so you need 8 bearings to go along with the case, if you go OEM, you will drop 200-250 bucks. If you can get them directly from a bearing distributor through x-referencing them (good luck), you might save 50-60%.

You will need a gasket/seal kit - I wouldn't be moving old seals over to the new cases, I might keep them as emergency spares, but if I'm doing something this big - I'll go new - so add another 100 for a full seal/gasket kit (TT Store Moose racing).

I would also replace the timing chain (30).

Now since you have it apart, it might be a good idea to check your valves (likely won't need replacing), reshim if required and refresh the cylinder/piston, so you may be into another 100-150 for a new piston, rings and some shims.

While you're in there looking, you might also notice that some of your gears could use refreshing since it's a 10 year old bike, at about 40 a pop, that'll add up fast too.

Then there will be incidentals such as busted bolts - I had a few break way before their specified torque - likely just due to age and use.

Anyways, just so you know, when I lost the 25 dollar bearing, I rebuilt my bottom end and after getting all the bearings, gasket/seal kit, shims, 2 gears, a tranny shaft (50), rings, cylinder honing, and incidentals I spent 600 on my bike doing it myself, and that was WITHOUT cases.

So looking at the above list, it certainly makes a heli coil look like a wonderful alternative.

I'm on the same page as matt4X4, heli coil.

One thing to pay attention to when reassembling the cases. There are some small orings between the case halves - two I think - that seal the oil passages to/from the oil pump. Make sure you install them. Other than that it's basically like putting a 2 stroke case together. I do have to agree though if you can helicoil it I'd just do that. It will be better than original and if you're careful you can probably do it without splitting the cases.

you can definitely do the helicoil without opening the cases up - just tap the case, flush the engine out a couple of times using the oil that was drained to do the tapping (before inserting the helicoil because the heli coil sticks up off the case bottom, so it will block the debris from flushing out if installed already) it'll get 99% of any debris left around the opening, install heli coil and replace the oil with fresh oil, change after 1-3 hours the oil filter will get the remainder.

X4 on the Helicoil! OR, just find a bigger plug and get a tap to match it.........

Helicoil or similar (there are other brand names on the market). Splitting the cases is probably not necessary. Stripped oil drain plug threads are a common problem on car/trucks. It is SOP to repair with a Helicoil. Use the $500 to buy beer.

When i first went to change the oil and found the problem there was a big chunk of jb weld where the crankcase was originally. There is a spot on the crankcase that comes down to give the bolt a place to thread in, half of that was broken off completely and in stead of the crankcase being there it was a big chunk of JB weld. The welder grinded the rest of the spot off and welded a big chunk of alluminum there and drilled it and tapped it out. Right now the oil is leaking out the pinholes in his weld, so I put a little jb weld where it was leaking but it didn't stop it. That now leaves me having to replace the case.


Got any pic's that you can post?

I never took a pic of it before the welder went at it. If anybody wants to see a pic of what the welder did I could take one.


Austin, you have your head on right. Replace the case.

JB weld and the ilk are fine for emergencies. When you do a repair, there is a right way and a wrong way. A klugey fix may 'work' but often, they become more of a problem later on.

HeliCoils are great. The threads you end up with are stronger than those before the HeliCoil. In aircraft, nearly all threaded holes in soft alloys like aluminum are automatically HeliCoiled for this very reason. But on a bike engine case, you do not need stronger threads, you need to not over tighten the bolt. In your engine, the threads did not pull out, the case cracked. This is because the bolt size is capable of whitstanding more compressive forces that the alloy can. Something had to give, hence the crack.

Drain bolts are like spark plugs. With a proper washer/gasket, they are seated and then tightened about 1/4 turn more (about 7 ftlbs.). If the washer/gasket is a compressible one, the flat side should go towards the case. This prevents the 'wedge effect' of the washer from placing addition side loads on the casting.

Ok, so now that we know it's a little more than a stripped drain plug but rather a broken off chunk - go ahead and replace the cases - take my advice and replace the bearings too at a minimum.


Get BC3 to weld it - he's really good and won't leave pinholes.

I'm ordering the stuff tomarrow. A case, bearings, a complete gasket set, and all the oil seals (probably not needed but they are cheap enough) anything else that needs replacing I'll order after I have it apart. I know I'll feel better knowing it's fixed right and I won't have to worry about it. After I get the parts and have the case apart I'll take a couple pics.

Oh yea, I have a puller, a cheap hardware store model that does the job, and my buddy has a case splitter if I need to use it.

Wish me luck,


I think you will be fine. A few hints to make it easier. Have a box of sandwich bags handy. As you take secions apart, put all the parts in the bag. Then do the next section. If you can, line them up on the bench in the order they came off. Cleanliness is next to godliness or sammiches, depending on how you view things. Clean hands, clean parts. No debris anywhere. Have some naptha/benzine nearby and a roll of paper towels. Make sure all gasket surfaces are completely clean. The naptha does a pretty good job of removing traces of gasket and threebond. If some gasket is really stuck, use something softer than aluminum (I use plastic scrapers) to carefull scrap it off. Do not force anything, if things are not going together, there must be a reason. Understand why and resolve. Think. Read the manual. Think some more.

Have a box of sandwich bags handy. As you take secions apart, put all the parts in the bag. Then do the next section. If you can, line them up on the bench in the order they came off.

I like taking digital pictures while disassembling something new to me. Take lots of pics with good resolution and you can review them later. A factory shop manual is also invaluable.

if you still need the case, i have a good used one that i'll sell ya. it is from a 99 wr400f. as a matter of fact i'll make ya a killer deal on both sides. $200 for both sides. or i'll toss in all the internals including the crankshaft for $250. it is already apart so all ya have to do is split yours.

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