gasket failure, NGK plug query & upgrade advice please.


I went to swap the oil on a brand new (non ridden) 07 wr450f. When removing the engine guard, I noticed green coolant on the guard & on the frame. Not much though. After cleaning up the coolant and re-starting the bike, it appears that the right side crankcase cover gasket has failed. Bummer.

Is an uprated gasket available? Is this gasket prone to failure?

Also, I bought a new spark plug to replace the 'old' one as the bike is not starting up very easily (hence service). According to the manual Im to use an NGK CR8 plug. I picked up an NGK iridium IX plug, numbered CR8EHIX-9 3797.

Is this a straight swap? Are these pre-gapped or do they need gapping?

Whilst the crankcase cover is off, what mods should I consider? Impeller upgrade?

Thanks for your time and help.

are you sure the coolant isn't just coming out of the weep hole on the underside of the water pump cover?

Hi kskyles & thanks.

Im not sure tbh. There was green coolant 'hanging' from the gasket. My best guess was the gasket had failed. Phew.

Could also be (and most likely) a sloppy top off, it is a new bike after all.

Spark plug will be fine, should be pre-gapped but check it. If you do have to change it, be extremely careful of the center electrode, fine wire types do not like to be shoved around.

Right side case gasket - well....actually.... both right and left side would leak oil if they failed, there are two seals that separate the case cover from the water pump cover.

If you look on the underside of the right case right at the bottom of the water pump housing you will see a 1/16" hole - this hole is situated between the oil seal and water seal along the impeller shaft plane, if it leaks oil, it's the oil side seal and if it leaks coolant it's the coolant side seal, if it's dry both seals are fine.

So if you run your machine and see coolant dripping out that hole you know it's a seal.

If you see nothing then it's a sloppy top off like William said.

Thanks very much guys. I've been outside and the weep hole seems to be clear. There is no evidence that coolant has tracked from the weep hole to the coolant/gasket 'interface'. Sloppy top? seems about right. I guess its my fault for leaving the bike for so long. Once the bike is ridden, will the pressure in the crankcase 'bloat' the gasket out so closing the gap? Do I need to bleed or otherwise adjust the coolant system? My sincerest thanks, I've been smashed with illness for a few years and the WR has been a nice focal point during the recovery process. I'll triple check these initial findings tommorow, as my neighbours wont thank me for firing up the bike at night.


crankcase doesn't really build pressure - it's vented so it stays at atmospheric pressure.

Your case and case cover gaskets should be fine - the lower portions are always submersed in oil anyways. These gaskets are pinched in tight enough that you likely won't have to worry about anything.

Run the bike tomorrow for about 10-15 minutes and see if any leaks develop.

sometimes the seals get dry, so when you first spin everything up, htere might be a small leak that goes away - when the seal becomes brittle or has shrunk - it won't go away.

If my bike sat for a year or more, I would change the oil, drain and fill the cooling system with fresh coolant (drain is the bolt with the washer at the pump housing) and bleed the brakes through with fresh DOT4.

Hopefully she wasn't stored in a very humid environment because the internals can rust if not turned over for long periods.

hi matt and thanks. The longest the bike has sat without being started is 6 months. I live in the UK (temperate climate) and the bike is stored in a garage which has a gas boiler at the back. Zero observable oxidisation on the bike itself. Im worried about what you have said about internal rust. If things go wrong, I just hope the bank manager will be in a good mood. I'll get the coolant sorted out tommorow and some brake fluid as well. Hopefully, by this time next month i'll be in a wheelchair with a big grin on my face. Im Looking forward to riding her.

Thanks matt.

you should be fine with that storage - I really just asked because there are a lot of people who toss their bikes into sheds not worthy for the mice that infest them....

hi matt and thanks. I've started her up when I could, but was just to ill to look after her properly. Oil swap now complete:banana: . Man I need a proper bike stand. Getting the WR on a plastic box was a royal PITA. Once that was done all was easy. The spark plug swap was fiddly but easy. Somehow i've managed to break my torque wrench, so treated the bike spark plug like a car spark plug. Its defintely the coolant weep hole that is leaking so im going to get that sorted after doing some research. After cleaning the bike a few days ago, the throttle barrel does not close. I'll lube/clean that the morn.

Thanks guys.

Hey TT - even just pumping the kicker a few will help pump some oil around to recoat the internals.

So if it is the coolant weep hole, I'd do the following (since you've already swapped your oil):

Proper method:

Drain coolant,

lay bike onto LHS (to keep your new oil inside)

remove RHS case cover

remove water pump cover

hold water pump shaft from back side with 12mm (I think) and remove impeller

Pull shaft out to backside and inspect - light grooves can be removed using emery cloth sandpaper - heavy grooves - replace

Replace the two seals from the water pump side - orientation is important to note here (I always replace both although oil side rarely leaks)

Some people only replace the coolant side seal.

Put it all back together - if you were able to save the case cover seal you can probably reuse it.

Improper method:

Drain coolant

remove water pump cover

put bike in gear and spin off impeller (this can damage the balancer shaft key the impeller shaft slides into)

drill small hole into seal surface (do not go too deep), insert small wood screw and pull with pliers.

Grease new seal and install over shaft.(coolant side only)

The problem with method two is that you cannot clean up the shaft or properly inspect it, and you can damage the key way on the balancer shaft upon impeller removal.

Hi matt.

Thats a solid 7.7 on the doh! scale. I remember saying to myself "rtfm in case the seal swap meant dumping the oil":smirk: . Oh well, suppose its part of the learning process.

Im looking at page 5-57 on the 07 manual. Removing the impeller appears not to difficult.

[qoute]Hold the impeller shaft on its width across the flats with spanners etc and remove the impeller[/qoute]

Does that then expose "oil seal 1" (coolant seal?) and can "oil seal 1" then be removed without removing the right side crankcase cover? I totally respect your advice and thank you for it, that said there is at least £50+ of gaskets/fluids if the right side crank case cover needs to be removed. If it has to be done then no problem.

Im also looking at page 5-56 on the 07 manual. Is component 'no 14' on the exploded schematic the problem seal?

Thanks matt/guys

apologies. Just removed the water pump cover and answered the question. Oh well, thats life. That said it would have been nice if yamaha sunk an allen fitment in the impeller shaft so the shaft could be held still whilst spannering the impeller off...With the pound being so low, im going to get hammered at the stealership:rant:

order on line if you can.

If you are careful, many have been successful just putting the bike in gear and using an impact wrench to pop the impeller loose, or use a breaker bar, pre-tension it then whack it fast once and it should pop the impeller loose without doing damage to the keyway - you just don't want to bust the keyway.

Since your bike is an 07 and this is likely the first time it's being done it'll probably work fine to do it that way, then just pull the the top seal (#1) and replace, however, if the shaft is burred, it won't last all that long.

yours may just be leaking from sitting so long and the shaft might be perfectly fine.

Oh, and when I said lay the bike on it's side - I said that so you'd save the fresh oil!!! (it'll stay inside that way)

Greetings matt & my sincere thanks. Ouch $$, I've just ordered the parts and am now walking like John wayne:moon: £40 for the entire right side gasket set, £9 for 1 litre of castrol 10w-40w offroad bike oil, circa £30 for engine ice coolant and castrol oil filter foam. The dealership said not to oil the filter???????:)

Fuel added matt. My total and sincerest thanks.

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