450 has me at the end of my witts

Any chance you have a picture of the cam gear side? I'd like to compare to my timing marks.


Thanks shawn I checked the timing a few times now and it seems to be in order and the cam chain is pretty damn tight so I belive the tensioner to be alright.

Also if the time comes is there any way to pull the head off without taking the cams out?

Nope cams gotta come out to pull the head. You wont get the chain off unless you do.

That intake does seem a little off dont it. But I doubt that is the problem. As far off a mine was it still ran. Not good but it ran. I think your cam timing is fine. It must be something else.


There you go TD-3. Thats at the TDC mark on the flywheel. The dots might be a tiny bit off either direction as long as its not a whole tooth.

Yeah thats not off that much where it would make it not run.. thanks for the extra input though guys.

Is the chain the only barrier to taking the head off without the cams?

Thanks for the picture.

I've noticed that your chain has 13 pins between the top marks. I set mine at 14. I have read everything from 12 to 14 :ride: Either way, it looks fine.

Taking the cams off really isn't that difficult. Now getting them on with a new crank (gear) and chain was a little scary!

I'm really curious to know what is ailing your bike :applause:

I'm really curious to know what is ailing your bike :applause:

You and me both.

Its wierd especaily since Ive had it running a few times.. and one time it was running weak and the other time it was running strong as hell till I turned it off. I guess I gotta check the big end bearing and a different coil. I dont think it has anything to do with carberation at this point.

Try a new plug and leaner jetting before you finally eat it and tear it completely down.

I know that sounds stupid but I've had symptoms like this (other than the bike die at speed and lockup which seems that might by more symptomatic of a bigger problem :applause: )

Well the jetting worked like a monster until this happend... I was doing 4th gear wheelies about 100 feet prior to it dying. So I dont know how it would require a rejet all of a sudden. Tomarrow I try a new coil from a very helpful TTer in the area. Let you all know how that goes.

Are you dead sure that exhaust cam doesnt need to be 1 tooth clockwise from where it is now?

Just looking at the spread (lobe separation) the lobes are almost 180 from each other. Ive built lots of crazy stuff, never seen one like that before...

PM FFR racing on this one. Tryce knows his shit. Its been so long since I peeked under the valve cover of a YZF that I cant tell 100%

Looked at your pics all looks ok

O'well keep trying

The only thing I could add is you said you have good spark, and carb has been cleaned but is the plug wetting wet from fuel????

Have you tried yet another sparkplug???

Blue Spark=Good

Orange Spark=Bad

Good luck!

I will give check out the spark plug again. It had a nice blue solid spark to it. Might be getting blown out in the engine though.

A nice blue spark doesnt get blown out. It starts a big ass fire...

If youve got spark and compression and fuel, its gotta be spark timing then. How you check that with out the engine running Im not sure...

Could the flywheel have sheared the key off and moved?

That could drive you nuts!

Do you have access to a flywheel puller?

Shawn pulling the flywheel is one of the first things I did because I thought it would be something simple like the keyway. Not so lucky. Thanks

have you tried push starting it? not that you should have to, but if it starts to run it may lead you a direction...

Alright tried a new coil and no results. I think I must accept reality and tear down the motor. Knowing how much God hates me Im almost positive its the big end bearing. Thanks all.

There is a quick and easy way to check for the loose bottom end bearing without total didasembly.

Pull the tank off. Pull the plug. After turning the engine over by hand...... stop while it is in either down stroke. Using a long screw driver...... threw the plug hole.......lightly set the tip of the screw driver on the top of the piston........now push down on the handle of the screw driver..........If you hear a dunk sound........there is play in the big bearing. No sound and everything feels tight.....It probably is.

gday Diode663,i had a wr250 that done the same thing,it drove me nuts for a week before i got it worked out,i had pulled my carby apart a couple of times and cleaned everything,well i thought i did,it turned out to be a speck of crap in one of the two small jets in the back(the two that you see when you pull of your airbox boot)of the carby,after cleaning them out along with rest of the carby again she started first kick,then i thought to myself how easy that was,i hope thats all it is for you as well.good luck.

Diode663: If you take out the plug, does the motor turn over smoothly? Try kicking it over by hand several times and feel for any unusual resistance. Mine would turn over smoothly a couple times, then start to bind (resistance), then move freely again. It was not consistent each time.

I've had these kind of wierd problems twice on my 250f.

1: The first time, I drained the tank a few times and nothing improved, finally I took the tank off, shook it out, and let it air dry overnight. Bike ran perfect.

2: The 2nd time was really bad. Turned out to be the rubber intake manifold boot was split under the hose clamp, causing an air leak.

Hope you figure it out.

Any new updates?

Hopefully you've been too busy riding to post your findings! :applause:

Havent had a chance to get to it yet. Friends came home from college and figured I would give my mind and leg a rest.

TD-3 when ur bearing died and you pulled it apart was it a little too tight or was too loose? I ask because lumpy suggested how to test the crank with the motor in tact, but that would only work for a loose bearing (still gonna try).

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