Anyone got a 2003-2006 WR450F?

[CAPP0]

As per title, if you have one of these could you help me with a query about the engine please!

In the pic below, can you tell me:

- is there anything bolted to the threaded hole inside the red oval? (The hose behind it is connected to something, it's an optical illusion that it's hanging there!)

- what's in the end of the little cast boss that the arrow is pointing to the end of?

The reason I ask is that mine has a slightly wappity black rubber/plastic plug in it, which does prevent some oil from leaking, but there doesn't appear to be anything retaining it. I've checked the Yamaha parts catalogue and the Fowlers parts catalogue (same fiche I think) and they don't show anything at all. Googling for pics of the engine seem to show that some engines have some sort of little cylinder arrangement there.

Any assistance welcome, it's doing my head in trying to work out whether there is anything missing or modified or whatever!

TIA

[Krikkit]

It looks to me like that casting is for an oil return down into the crankcase, possibly a take-off for an oil cooler on some models?

Edit: It's plugged for access to the camchain, possibly a casting requirement, or used in the factory assembly to lock the cams/chain? https://www.fowlersparts.co.uk/parts/4186596/wr450...

I wouldn't expect that lughole to go right through into the head internals though, usually that kind of lug is for bracketry or something, although it has been decked in the head cleanup process, could well just be another assembly aid.

Edited by Krikkit on Wednesday 22 December 09:47

[HustleRussell]

Krikkit said:

usually that kind of lug is for bracketry or something, although it has been decked in the head cleanup process, could well just be another assembly aid.

This.

[nunpuncher]

I've got a 2005 250 I can check if you want. Not sure how closely related the engines are but my guess would be they are near identical from the outside

[Tribal Chestnut]

Will try and have a look tomorrow/Fri. Mine’s in a few pieces though so mightn’t be overly helpful.

[CAPP0]

Krikkit said:

It looks to me like that casting is for an oil return down into the crankcase, possibly a take-off for an oil cooler on some models?

Edit: It's plugged for access to the camchain, possibly a casting requirement, or used in the factory assembly to lock the cams/chain? https://www.fowlersparts.co.uk/parts/4186596/wr450...

I wouldn't expect that lughole to go right through into the head internals though, usually that kind of lug is for bracketry or something, although it has been decked in the head cleanup process, could well just be another assembly aid.

Edited by Krikkit on Wednesday 22 December 09:47

Thanks for this and thanks everyone else for the replies.

That's weird that Fowlers include the part in the cam chain fiche because the cam chain is on the other side of the engine so there's no access to it from that boss? That's why I couldn't find it - didn't look at that section. Weird thing is, if the plastic plug is out, it leaks oil at a rate of about 2 drips a minute, albeit obviously under some degree of pressure (but not full oil pressure) because it hits the back of the rad then drops onto the header in a puff of smoke, but if the plug is in, and it's just a soft push fit, the leak stops. At least I know where to get another now if I need it, so many thanks for that.

If anyone does get a chance to look and take a pic that would be great, thanks, just so I can see. I think the 250 lump is very similar, yes, so should give some idea.

[Krikkit]

I wonder if they insert a tool into that portion to hold the cam during assembly (allowing clear access to the gear on the opposite side), then remove and plug.

Anyway, I'd stick a dowty washer and small caphead in the hole and be done with it. Or just fill it with Loctite sealant.

[Drabbesttunic]

My 03 250 has an earth strap to the circled part of the picture and has a rubber plug in the arrowed, the plug is a tight fit.

[Tribal Chestnut]

Just a little angle retaining the wappity plug.

[CAPP0]

Perfect, thanks TC, that makes complete sense. I couldn’t see what would stop the wappity plug from popping out. No such bracket on mine and I don’t think (without checking) that it’s on the fiche, so I’ll knock something up myself.


Cheers, much appreciated.

Edited by CAPP0 on Sunday 26th December 18:35