Engine woes, cooling system, cylinder head

[DaleRidesAll]

Hi guys, recently got myself another bike. 1999 wr400 supermoto. when i went to look he said just needed carby tuning, got it roll started quite easily and just ran like it was very rich. when i got it home i dicovered quite a few problems from just worn out parts to leaky gaskets. once i fixed the fuel systems etc i discovered there was no coolant, so i topped the coolant up and kicked it a few times, then i heard coolant in the header, so i stripped the top end down and sure enough, blown head gasket. replaced base and head gasket and put back together. new coolant and oil. next we tryed to start again, got it roll started wwent up and down the road 2 or 3 times came back noticed a bit of coolant on the floor. went for another lap and came back and confirmed it was the weep hole. when i drained the oil there was coolant in it. assumed the seals in water pump were that bad that the preassure from the waterpump couldnt push coolant out the weep hole so it pushed it in the coolant one. so new oil aswell as brand new waterpump seals and shaft and try to start it again, before it even got started noticed coolant on the floor. and also in the pipe. when i took it back t the shed took coolant cap off and strangly had preassure holding the cap on instead of trying to push it off. this is where im sitting at the moment. when the head was off there was no cracks etc but i noticed 2 very small areas where it seemed half the thickness of a wall was i guess smooshed a bit, like it was soft metal getting hit by a hammer. there are a few problems ive explained in there just need help please

[DaleRidesAll]

to make it quick, something is not right wit the head, is leaking cooling into pipe. in worst case new head etc, what heads will fit onto my 1999wr400, do they need diff cams etc. and also if anyone knows if i buy an exhaust hot cam for auto decomp do i need both and are they just bolt on and go? Cheers in advanced ?

 

Pic of bike incase of curiosity ?

[DaleRidesAll]

okay its a wr yes but i assume it is the same on the yz. to make it quick, something is not right wit the head, is leaking cooling into pipe. in worst case new head etc, what heads will fit onto my 1999wr400, do they need diff cams etc. and also if anyone knows if i buy an exhaust hot cam for auto decomp do i need both cams and are they just bolt on and go? Cheers in advanced ?

[grayracer513]

Heads from any WR/YZ400F or WR/YZ426F will fit.  Your problem is probably nothing more than a warped head and/or deck and a new gasket.

[DaleRidesAll]

Will be using an old tecnique todat to check for warping even thetiniest bit but in a worstcase scenario will all my valves and stuff fit in a new head

[grayracer513]

The valves and springs, etc., are interchangeable within the heads I listed.

[DaleRidesAll]

its not looking too good, not warped but there is some damage in 2 little spots, when they resurface a head any idea how much they can actually take off?

[grayracer513]

There is always a practical limit to what can be removed, and usually a limit specified by the manufacturer.  In the absence of any such spec, most shops won't remove more than about .008" (0.25mm)

[DaleRidesAll]

oh okay, it is around .25mm that needs to be removed if not a tiny bit more, looks like theres a chance i need a new head after all, and btw there was no warping just two bits that are damaged no idea how they could have gotten there, if curious ill take a few photos

[DaleRidesAll]

Hi guys, i am posting this on both yz and wr forums, the head is screwed on my 99 wr400 needs a new one, first the head gasket was blown and run like that without coolant, got so hot that now th head is weak and will kee screwing up according to the local head guyi brought it to. i got sold the bike like this but i was not told it was F&*#ed. so just to make sure what heads will fit on the bike, and is all the parts inside the head to same as the wr. cheers in advanced.

[William1]

Multiple cross posted threads merged.

Please, one post per topic in the proper area.

[DaleRidesAll]

Multiple cross posted threads merged.

Please, one post per topic in the proper area.

it could go in both because apparently the engine are the same but gearings and timing is different?

[William1]

Your bike is a WR400, it goes in the WR400 forum

All the threads are about the head. Same bike, same topic.

 

People mod a bike all the time. But the bike does not change, just a few of the parts. Saying it could go in both is akin to saying because it is a Yamaha, it could go in all Yamaha forums. There is a distinct reason for the individual areas.

[Birdy426]

Surface the head enough to clear the "bad spots", then assemble with a thin layer of clay on the piston dome.  "Kick" thru a couple of times, and then disassemble and verify that the valves don't go completely thru the clay.  As you can run an aftermarket 13.5:1 high compression piston on pump premium in these bikes, I doubt you will be able to clean enough off the head to create detonation problems due to higher compression.  Trying that approach will certainly be cheaper than a used head.  FWIW, my experience has been that you almost always need to "kiss" the head to true up the surface to keep the head gasket from leaking...

 

If you have the WR400, you have stainless steel valves rather than the Ti valves the 01 and up 426's came with.  The SS valves can be lapped to fit if you swap heads.  Ti valves can't.  Also, if you end up playing "musical heads", the springs, retainers, etc from the Ti valves need to be used with the Ti valves, and those from the SS valves used with the SS valves.  You can't mix and match between the two.

 

As far as Hot Cams, you really only need the exhaust cam to get auto-decompression and it's a bolt in...you do get a good performance increase with the intake cam, though...

[DaleRidesAll]

Surface the head enough to clear the "bad spots", then assemble with a thin layer of clay on the piston dome.  "Kick" thru a couple of times, and then disassemble and verify that the valves don't go completely thru the clay.  As you can run an aftermarket 13.5:1 high compression piston on pump premium in these bikes, I doubt you will be able to clean enough off the head to create detonation problems due to higher compression.  Trying that approach will certainly be cheaper than a used head.  FWIW, my experience has been that you almost always need to "kiss" the head to true up the surface to keep the head gasket from leaking...

 

If you have the WR400, you have stainless steel valves rather than the Ti valves the 01 and up 426's came with.  The SS valves can be lapped to fit if you swap heads.  Ti valves can't.  Also, if you end up playing "musical heads", the springs, retainers, etc from the Ti valves need to be used with the Ti valves, and those from the SS valves used with the SS valves.  You can't mix and match between the two.

 

As far as Hot Cams, you really only need the exhaust cam to get auto-decompression and it's a bolt in...you do get a good performance increase with the intake cam, though...

Most helpful by far! took it to a head place the other day, head has gone soft around the damage, so i need a new one. as for the the valve stuff, if i bought a 426 head with all the valves and stuff in it already can i just use that, and if its doesnt can i just get EVERYTHING from my current head and put it on the new one? just threw the hotcams things in there but i will be deffinetly getting them both when i get the money, had the same year of bike 2 years ago and it had them in it and it was insane.

[Birdy426]

Most helpful by far! took it to a head place the other day, head has gone soft around the damage, so i need a new one. as for the the valve stuff, if i bought a 426 head with all the valves and stuff in it already can i just use that, and if its doesnt can i just get EVERYTHING from my current head and put it on the new one? just threw the hotcams things in there but i will be deffinetly getting them both when i get the money, had the same year of bike 2 years ago and it had them in it and it was insane.

Yup, that's the idea...if you pick up a used 426 head, though, be sure to take it apart and inspect the valves...after a while they tend to wear where they strike the seats and kinda "mushroom".  That causes them to strike the seat at just a bit of an angle, which puts bending loads on the valve stem, which causes the head to pop off and destroy your piston, head, and cylinder.  The 400 had should have stainless valves, which 1) don't wear like the Ti valves do; and 2) Can be lapped to fit the head you buy.  I just took a look on flea bay, and WR/YZ heas are running about 450-500 bucks...don't know that I'd want to spend that on a bike that old that I didn't know the history on

 

I would look at your existing head carefully...if the area around the water jackets has been annealed because of the water leak (though I'm not sure how the head shop could know that unless they did a hardness test...did they?), you may be able to grind out the bad spots and still have enough "land" left to seal...maybe post up a pic or two?  I assume the idea is to get the bike running as cheaply as possible?

[DaleRidesAll]

alright, so sounds like im a bit screwed money wise. id like to get it fixed as cheeply as possible yes, but if i was to fix and sell or sell as a wreck with supermotos sepparatly which would i get more for?