wr 426 egine shagged after 800 km

can anyone tell me if they have had any problems with this years 426 as mine had a major meltdown after 800 km i bent 3 valves,took the tops off the cam lobes ,piston slopping around in bore,big end gone and the camchain stretched enough to slip the cams this all happened at idle with the bike only 3 months old does anyone know of this happening to anyone else and why it would happen thanx pesh

Sorry to here about that. :) I haven't read any posts of anybody having a problem like that. Man, I hope you can at least salvage some parts from it. Good luck :D

Has anyone been inside the motor yet? Anyone change it to YZ cam timing?

Hey Pesh,

There was some posts about 3 months ago about breaking valves and destroying the tappet bucket cavity in the cylinder head. I'm not sure but I think there were two members with trashed top ends. Try an archive search for 'cylinder head' you might be able to get some more info.

Sorry about your motor,

I YZ Timed my 02 WR426

Hauls butt too! No problems..Works well too, ask WRoost I did his bike and now the poor guy almost did himself in at Riverside. Fractured hip, 2 broke ribs, punctured lung, ect.ect...Called me the hospital to tell me how great his bike runs now :)

SoCal

pesh

i don't think this has happened at tickover. i think you may have found it there but the real damage was done with you riding it around giving it a good thrashing. you've an oil circulation problem or you ran out of coolant. the problem could be;....

a dingo! apparently they're absolute bastards for doing this and find it all very funny. they syphon off about a litre of oil and replace it with a very acidic form of piss which is highly corrosive.

you should be able to spot the little bastard because he'll be the only one running through the bush at 75mph and ****ting like a goose.

Taffy

Pesh,

Bummer! This is the same thing that happened to my Kaw. In my case, it was an oil circ problem. The oil line that lubed the cams quit emitting oil and resulted in a partially lunched top end due to a siezed cam. I didn't get near the damage you did, but it easily could have. Check the oil lines to the head to see if they flow any oil.

Pesh,

Bummer! This is the same thing that happened to my Kaw. In my case, it was an oil circ problem. The oil line that lubed the cams quit emitting oil and resulted in a partially lunched top end due to a siezed cam. I didn't get near the damage you did, but it easily could have. Check the oil lines to the head to see if they flow any oil.

Taffy,

You crack me up man!

Mike

:D Taffy......you are an evil man my friend...evil (But very funny! ) ROFL :D:D:)

I have a 01WR426 exactly the same problem!

During a top gear long distance wheelie it nipped. It had chewed all 3 inlet valves, bending the conrod too.

The top of the piston shows semi circular polish marks where the inlet valves had been kissing the piston for some time before one gave way.

I know that the 01 models have titanium valves - maybe they just cant take long term revs??

Should part of the £700 rebuild be to use the 00 year valves??

Luckily the bore is untouched so its "only" head, rod and piston required.

400s never did this sort of thing did they??

My 2000 WR400F completely grenaded even worse than yours! Yamaha Canada still wont or cant tell me what happened. They think the chain skipped. Crank, cylinder, head, piston, valves etc...$5000 to fix. Yammy gave me some parts from tech school and paid part of the labour. Cost me about a grand. They replaced everything but the tranny and cases.

OOPS!

[ December 28, 2001: Message edited by: Stefe9999 ]

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