WR 450 does not idle or run well. Need help!

[bterp67]

I need help or any suggestions!

At Summer Bummer Sat event , my son hit a tree on the left side of his 2004 Yamaha WR 450. The radiator was leaking, but not that bad, I thought. We tried to finish the loop to get water, but we came up short about a 1/2 mile from the end and the bike quit running. It kicked over and seem to have good compression, but hard to tell with the auto decomp.

When we got home, the bike started right up, so I filled it with water to see if any bubbles were coming out the top of the radiator, to check for a leaking head gasket. No bubbles, looked fine.
Next day, come home from work, go to start bike and no start, not even a blubber.
Replaced spark plug, has spark but no start
Checked for fuel in the bowl, good. Seems to be getting fuel. Accelerator pump even squirts.
Air cleaner in tact, no blockage.
Disconnect kill switch on left side handle bar, still no start.
Pulled valve cover and checked valve clearance, intake and exhaust are absolute perfect to specs, all five valves.
Plugged off all coolant lines and pressurized the cooling system for a leak test. went up to 40 psi and it held it, no leaks.
A couple days later, bike starts but will not idle or run smooth. I have to have the throttle cracked abount an 1/8 to get to start.
Maybe the TPS, so I disconnect it, no difference.
It sounds like it may be no fuel on the idle circuit, take off bowl, pull all of the jets, main, idle and starter jet and they look clean, but cleaned them anyway, and still runs rough and no idle.
In the mean time I notice the hot start cable plastic nut is busted off from the top of the carb(result is pulling the plunger up). The choke pull is also bent(left side crash into tree??). I bought a new choke pull assenbly, and pushed the hot start plunger all the way down in the hole where it is suppose to be, and no difference, still runs rough and no idle and very hard to start.(I'm still waiting for the plastic nut)
When it does start the bike will rev like crazy if I want it too and sounds good at a higher rpm.
Do a compresion test and realize the auto decomp gives me a very low reading. I take the spring off the exh. cam for the auto decomp to be disabled, get a higher reading but still seems too low. Now I think it is a head gasket ,sticky valve or stuck rings from the overheat. Pull the top end off and every thing looks brand new. I can't belive running it that low on water didn't even leave a scratch in the piston skirt.
The head gasket shows no sign of leakage, and the valves look to be all closed(I need to check to see if the valves seal with liquid)

I need to pull the flywheel and look for a sheared woodruff key(ignition timing). But I don't have a puller right now.
I'm going to completely disassemble the card and look for any dirt in the fuel circuits.
I also need to look for any possible pinched wires.

After this I am out of ideas. If anyone has any suggestions or expierience with something like this, please reply. I always thought I was a good troubleshooter, but this has me stumped right now. I'm also prepared for the simple/stupid solution that I have not thought of, and I'll have to post it and embarass myself. I just want my kids bike running so we can go to Stumpjumper. :bang:

 

[YZMAN400]

I doubt this is your issue but you saying it wont start without being at 1/8 throttle soundes like what my YZ400 was doing when I spun a intake came gear. The cam gears are just press fit onto the cams. No keyway or splines. Its possible for the gear to spin on the cam. When you check timing it all looks good by the marks but the cam lobe will be pointing in the wrong direction.

This is what your cams should look like when timed correctly. You should be able to put a straight edge on the top of the lobes and have it sit pretty much flat from intake to exhaust

Here is what mine looked like

See how the cam lobe on the intake side is pointing straight back instead of slightly up like the exhaust.

This may not be your problem but its worth checking as its a hard issue to detect. Maybe depending on how bad you overheated it you coulda loosened up the gear and had it spun..

Othwewise maybe an air leak from the loose hotstart/choke that you were talking about.

 

[bterp67]

Wow. I would have never guessed to look for this. How did you ever know to look for that? And how did you fix it? Did you buy a new cam?
It would make sense that the over heat could loosen the cam.I'll check it out when I get home tonight.

 

[nickolino]

Junk It and Buy A KTM ORANGE

 

[24mph,m/l]

Time to burn

Nicolino, you have time at 12:57 to be on this site ? You should be tending to some of those snowmobile customers whom you love so well.

 

[bterp67]

Junk It and Buy A KTM ORANGE

The kicker is that someone I knew let my kid ride his exc 200 on Sunday at Roselawn. He liked it, but I still can't sway him to ride orange, but I'm getting closer. It's the bike I originally wanted my boy to buy, but he wanted blue.

My cam (the boys cam) timing lined up at the dots looks like this. It's a bit off, but not as far as the pics YZMAN400 posted.

 

[E_Langen]

It's a bit off, but not as far as the pics YZMAN400 posted.

It doesn't look like his first picture. How do they look with the cam chain on and the chain tight between the sprockets.

There's a thread on another forum about a WR450 that "misses and bogs down up to 1/4 throttle with no load on the engine". His exhaust cam was off one tooth.

 

[bterp67]

With the cam chain on, the dots on the cam gears lined up where they were suppose to, right at the top of the head. The engine has never been apart before, so I don't have to worry about someone elses mistakes. (just mine now)

So for now I lined up the dots and put a piece of paper on the bearing journal to lock it in place. When my gaskets come in and I can get the cylinder and head back on, I'll look at them much closer when the cam chain is back on.

Everywhere I look on other forums, everyone says to "Check the cam with a degree wheel". I understand how to do this, but I am having no luck finding the stock cam specs. I can only find hotcam specs for their cams.

I had to order a flywheel puller, so I can't check the $3.00 key that may be a problem yet.

On another subject, why doesn't any of these Yamaha dealers stock parts I need. Even the simple ones. I have never bought parts for this bike and not had to order them(besides an oil fiter or plug). I called most of West MI looking for all of the gaskets, and no luck. When I call Lansing Cycle for my KTM parts, they have them in stock and shipped to my doorstep the next day. I was even in the U.P. for a week of riding a few years ago and broke a rear hub on the KTM. I drove to Zambon's from Newberry on a Monday morning to get there as soon as they opened, and he had a hub assembly for me. Try that at a Yamaha dealer. I guess I'm a bit sour about not being able to take the kid riding on a holiday weekend.

 

[BadgerMan]

Has the cam chain ever been replaced? They stretch pretty quickly so if you have the original chain still, it is over due for replacement. Put a new chain on while you have it apart.....a new chain is cheap insurance.

 

[bterp67]

This bike has very low hours on it, so the timing chain should be good. We bought it in in the spring of 07, and it still had original tires on it in great shape. There weren't even any scratches on the frame from boots.

I just did the top end in my 01 KTM 400 this past winter, and I put a chain & cam bearings in while I was in there. I compared chains at the time and there was a slight difference in length. I am amazed at how well my KTM looked inside after all these years of abuse.

Oh well, back to yard work untill the parts and flywheel puller come in.

 

[BadgerMan]

I put a new chain on my YZ250F every winter or any time I had the top end apart. It is the weakest link in the valve train and will cause much grief when it wears out. It will cause excess wear on the drive gear on the crank shaft and can cause timing problems when it stretches. It was a twenty dollar part for my 250. It did not make sense (to me) to put the top end back together with a used chain.

 

[E_Langen]

I had to order a flywheel puller, so I can't check the $3.00 key that may be a problem yet.

Pull the rod up to tdc and see if the rotor and cover marks align.

Did you check the valve timing before you took it apart?

 

[YZMAN400]

The kicker is that someone I knew let my kid ride his exc 200 on Sunday at Roselawn. He liked it, but I still can't sway him to ride orange, but I'm getting closer. It's the bike I originally wanted my boy to buy, but he wanted blue.

My cam (the boys cam) timing lined up at the dots looks like this. It's a bit off, but not as far as the pics YZMAN400 posted.

WR's are timed slightly differant than the YZ's are. If memory serves me the exhaust cam is 1 tooth off from the YZ timing (the picture I posted) so what you are showing is probably normal. The intake looks correct anyways.

When I had that problem I had just done a top end and didn't use a torque wrench on the cam bolts ( a highly critical step you cannot skip mind you) I overtorqued the cam bolts and siezed the cam in the head. When the cam siezed it spun the gear. I fought with that issue for over a month trying to figure it out untill I finially stubmled apon the gear issue. I had to get the proper cam lobe positioning from Dubach racing to finially figure it out. I bought a new cam for mine.

The YZ/WR's have very tight clearances between the cam and cam journals. I had to have my head welded and re-machined my a place called engine dynamics. They said that they have seen a lot of YZ's with messed up journals. They add a little more clearance in the journals when they re-do them.

I doubt that is your issue. Its very rare, actually I have never heard of anyone ever doing it besides me. But I throw it out there when people are having odd running issues because it is a very hard thing to detect.

 

[bterp67]

I checked the valve timing before I took it apart, by just looking at the dots on the cam gears and the timing mark on the fywheel and cover, and all looked good. So I don't think the key will be the problem, but I have to rule it out first.

Good idea to bring piston to top, then look at flywheel mark. I'll look at this today

The timing chain for $20 is something I probably should do while I have it apart.

I thought there was a difference in cam timing from the YZ to the WR, but I didn't know if it was both cams or one cam. So just the exhaust cam then? Looks like the WR exh valves will open sooner and close later than the YZ.

When I looked at the cam journals, I couldn't believe they ran these right on the aluminum. I thought they would have had replacable journals like a automobile crank. I heard that the new KTM 450's have valve shim buckets like the Yam and Honda's. I wonder what the cam bearing situation is, if they still use 2 ball bearings, or if they do the same as the Jap bikes now.

When we got the bike, the throttle stop was out, or at least the screw/stop in the carb didn't have that extension on it.
The gray wire was connected, so we disconnected it and it actually ran smoother. I was expecting a change the other way. I also had to richen up the main, idle and starter jet, and I think I also dropped the needle clip a notch (I'd have to look at my notes) but this made a huge improvement in performance. When the bike runs, it's fast, way faster than my KTM400. In my opinion it is too fast and too touchy for woods riding, but it may be better for a faster rider than me.

 

[bterp67]

Fixed It!!!!!!!!!!!!!!

After checking the flywheek key and that being okay, I was baffled. It still missed on idle, would just die sometimes and was hard to start.
I cleaned the carb 3 times and still had no luck. It was just like the idle circuit was plugged or not working.
Then it accurred to me that a friend of mine had the same bike and I could swap carbs and other parts to eliminate or pin point the problem. We swapped out the carb with no difference at all. Next I was going to swap the CDI unit, then I looked at the plug cap/coil unit and thought it was easy to try. Swapped it and it ran like it was brand new! I swapped it back and forth a few times to make sure I didn't just disrupt a wire.
It's the coil for sure! It makes sense that the overheat killed the coil, seeing that it is part of the plug cap. It's too bad I took the whole top end off.
The good news is my son gets to ride Stumpjumper now. :)

Thanks for all of your help and suggestions.

 

[YZMAN400]

Cool deal. Glad it worked out for ya.

 

[KTM Mike]

BT - good news! See you this weekend. It should be a fun event.