450 has me at the end of my witts

If it's something major, for the Yammie 450 this would by far be the exception not the rule. I own a Honda and they are great bikes, particularly with the way they handle, but Yammies are by far the most reliable MX 4 strokes, and I repeat, BY FAR.

i'm glad you added the "MX 4-strokes" part of that sentence. i'll use my XR400 as an anvil to smash your CRF and your WR 450 and still ride it home. :p

of course... it's as heavy as an anvil, too :applause:

but that's alright, the weight keeps all 32 screaming h.p. in check. :ride: just for grins, i only know three fellows who have CRF450R's and two have had valve/head issues, hell, one is about an 8k$ bike.

If you did not mess with the carb this can't be it, but it sure sounds like you may have the slide in upside down.

The slide is prescisely where it needs to be. Thanks

The slide is prescisely where it needs to be. Thanks

He wasn't being smart, this is actually a valid suggestion. The slide looks like it's in correctly when it's in backwards, but of course it doesn't run properly (if at all). Many people have made this mistake. Since your bike quit was it was running I don't think this is it, but otherwise it's a valid suggestion.

Drain the 94 octane ( I guessing it is from Sunoco?) Go to a Citco, Sheets etc.. and get 93 octane. Sunoco and BP have ethanol in them and will file plugs all day long in Yamaha's. Try it and see could be the problem. Is there any head work done to the bike? You may want to throw some U4 in it and see if it runs if the above doesnt work.

Just curious why does everyone seem to get an oil pump when this bearing fails?

I replaced everything in the oiling system: pumps (primary & secondary), oil O'rings, seals, check ball and spring. I believe my rod bearing starved for oil. Why it starved, is what I don't know, so I changed everything.

Also was your bearing excessively tight or sloppy?

It was toast by the time I took the crank out, so there is no telling which way it went.

Also the only rod bearing failures I have found for a 450 is yours.

In the countless searches and posts I read I did find a couple other 450 failures. There definitely where more with the 426's, but I'd chalk that up to the age and quantity of 426's out there.

Hey, I'm not saying this is your problem, in fact I hope it's not :applause: . It's just your symptoms looked a lot like mine, so I figured I'd share my experience.

BTW: I put 3hrs pit/trail riding on the 450 yesterday and all is well with the beast now. :ride:

He wasn't being smart, this is actually a valid suggestion. The slide looks like it's in correctly when it's in backwards, but of course it doesn't run properly (if at all). Many people have made this mistake. Since your bike quit was it was running I don't think this is it, but otherwise it's a valid suggestion.

I wasnt being smart either. But it stopped running before the carb was taken apart like I stated in the first post.

And I bought U4 because thats what its jetted for and still no results.

Thanks all.

The carb I think needs a serious douching...not a spritz here and a wipe there...its got U4 thats tarnished in an air passage somewhere or there's a tiny piece of crap in one of the air jets.

Have you taken the carb off and completely disassembled it, soaked it with a good carb cleaner and then blown out the passages with compressed air?

The nice thing about the FCR is you can take the Primary air jet and main air jet out of the mouth of the carb and get a really good shot at it when blowing it out with compressed air.

And go up the hole for the fuel screw too. Every dang hole in the carb needs blasted out. The FCR is a fantasic carb, but if its fouled..it'll drive you nuts...

i'm glad you added the "MX 4-strokes" part of that sentence. i'll use my XR400 as an anvil to smash your CRF and your WR 450 and still ride it home. :p

of course... it's as heavy as an anvil, too :applause:

but that's alright, the weight keeps all 32 screaming h.p. in check. :ride: just for grins, i only know three fellows who have CRF450R's and two have had valve/head issues, hell, one is about an 8k$ bike.

You are correct. That's why I specified "MX Bike". XR's are incredibly reliable. As are most Hondas and Yams. You have to admit, the Japanese have their sheite together. I was stationed in Sasebo for 3 years and I saw their work ethic first hand. I only wish we would/could do the same from a manufacturing stand point.

have you changed the fuel drain all fuel and try with new or fuel from mates bike

Shawn I already cleaned the carb.. but Im thinking I could be a little more thourough. I will try soaking it.. didnt think of that. I will try anything so that I dont have to take the top end off.

Speaking of which is there any way to do that without taking the cams out?

Tubb yes as per my first post I tried new fuel in upstate as well as U4 in my home town.

Check the coil I had mine brake where it "grabs" the top of the plug (on the threads) there should be a piece of metal that acts like a spring to grip the plug tip. Take a look at a old plug and you should see wear. When mine broke the bike ran intermintentally and like crap. I have not read the whole topic so sorry if I'm repeating.

O-ya make sure that plate on the carb slide is on with the hole on the bottom.

Hi I have been spying on your forum for a while now. Hoping to find a freakin yz450f as soon as they are at the dealers. Rode 2 strokes for a while but was converted when I borrowed a yz400f. I think that you have an issue inside the carburator, if you have checked all mechanical (compression, leak down)and electrical(spark) systems. Just putting in my 2 cent but I work on cars all day before that I worked at a moto shop. To check for spark hold the plug in your hand and have some one kick the bike over. JK :applause:

Ok I had a similar problem Have a look at the cam positions at TDC but look at the lobes from the clutch side of the motor. Both lobes should be slighty higher than inline with the head.

The cam sprocket can slip when you have a locked up motor.

Therefore you may have the timing marks correctly alined but timing is out.

My intake cam spun around 3 theeth (similar starting and running problems to yours) once we worked out the problem started first kick and motor still kicks arse.

kinda helps if you didnt blow it up the motor blew i did the same thing on my freind bike the motor blew and the wheel locked up and all it did was kick but nothing sparked or anything you blew the top end of the motor

Ok I had a similar problem Have a look at the cam positions at TDC but look at the lobes from the clutch side of the motor. Both lobes should be slighty higher than inline with the head.

The cam sprocket can slip when you have a locked up motor.

Therefore you may have the timing marks correctly alined but timing is out.

My intake cam spun around 3 theeth (similar starting and running problems to yours) once we worked out the problem started first kick and motor still kicks arse.

Ding ding ding....I was just going to post this same thing. Its not a common problem but it can happen so dont overlook it. Its hard to diagnose if you dont know about it/ what to look for. I spun the intake cam gear on my yz400. Even though the marks on the gears line up the cam(s) can still be out of time causing starting problems.

Here is 2 pictures of mine that I took when I had that problem.

1st one is the correct timing.

The 2nd one is the bad timing.

Notice how in the 1st picture that the cam lobes are pointing slightly upward at a shallow V and that you can just about put a straight edge across the top of the lobes.

Now in the 2nd picture notice that the intake (cam on the left) is pointing straight back. That was because of the spun gear on the intake cam. The gears are just pressed on, not splined or keyed in place so they can spin under extreme stress.

Once I figured out my problem i had the gears welded to the cams in 2 small spots opposite to each other (to keep it ballanced) They aint gonna spin again.

good_cam.jpg

bad_cam.jpg

Well as easy as it is, check the cam timing and the tensioner. Unless you were floating the valves and one smacked the piston the only reason the timing could move is if the tensioner failed to some degree. Pulling the valve cover off and checking it is pretty straight forward. If its off, it should be fairly obvious...

Alright I checked the cams and timing again. Looks alright to me.. if anything maybee the exaust is out a tiny bit not sure. Take a look let me know what you think.

http://www.we-todd-did-racing.com/wetoddimage.wtdr/wMTEyOTQ0MzZzNDEzZGZkMzF5NTQx.jpg

http://www.we-todd-did-racing.com/wetoddimage.wtdr/wMTEyOTQ0NDZzNDEzZGZkMzF5NTQx.jpg

And Yzf all the way... not sure if you can blow the top end and still maintain compression and not have it siezed. If there is plenty of compression and it operates smoothly what part of the top end is blown?

it does look a little off...

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?

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