Not vmx but help needed

[steve7406]

Went to start my 2000 yamaha wr 400 put foot on kick starter and kicked herd a tink within motor then loss of compression was allright before this any ideas what i should be looking for.

[Paul552]

Decomp cable?
Or decomp mech at top of head?

[matcho mick]

Went to start my 2000 yamaha wr 400 put foot on kick starter and kicked herd a tink within motor then loss of compression was allright before this any ideas what i should be looking for.

your wallet 

[evo550]

What should you be looking for?......a new bike perhaps?...preferably a 2 stroke....

[crossedup2]

The early WR / YZ suffered from sticking valves to valve guides. If they sat for a while they would loose compression. A lot of people put it down to change of brands of oil at oil changes but I won't believe that.
I'd do a proper compression test first. Then I'd check valve clearance etc. After that check valve timing (assuming the chain may have jumped???)

Good luck and let us know what it was.

Peter B


 

[80-85 husky]

Don't take any of those idiots at face value

A "tink" noise EH??? I tink its crapped itself.... sorry couldn't help it.....

obviously you have lost the decomp mechanism or a valve head has fallen off.

you had better get the compression checked or the valve train. but a 2000 model could have suffered a major failure.

pull the plug out and see if it is still in good condition ( light brown color, electrode ends square..) hold your hand over the plug hole and ... sorry I forgot its a 4 stroke , the plug surface is awaaaayyy down in the head somewhere..

would be good to see if there was compression still without the plug in....

Tink noise... could be anytink .....

[JohnnyO]

Take the valve cover off to start with and check the decomp mechanism and also do a valve clearance check, that'll give you some idea.

[John Orchard]

Once a cam chain is stretched it tends to slip on the crank sprocket during the the kick starting process, my guess is the the timing has jumped, the piston has kissed the valves bending them.  If the valves are bent I'd be replacing the cam chain or checking that the tensioner hasn't backed out.

[steve7406]

Thanks guys will look at it tomorrow .

[Tim754]

Please post a report on your findings Steve as I and maybe others are interested in what the problem be . Thanks Tim754

[steve7406]

Finaly got the wr apart its bent a valve i would say the timing chain slipped a cog.Time now for a rebuild
top and bottom end carnt complain its the first time in 13 yrs its been apart.

[80-85 husky]

On the money JO

[steve7406]

Smart cookie jo and a good bloke with it.