Help I don't know what to look at

My 2006 WR450 began starting with 4 or 5 kicks a few days ago. It used to start first kick each time till then........Then lastnight it acted like it does when you run out of gas unless I kept the RPMs up and it wouldn't it acts like it wants to start but won't by kicking it over......I took the carb apart blew out all the jets and vent lines but it still doen't want to start. I know if I pulled it behind a car it would fire up but won't stay running. I am beginning to think its electrical.......does anyone have an idea?

My cousin's 01 250f started acting like that and 5 rides later it seized. Neither him or me had knowledge of 4 strokes at the time and just thought it was the nature of the bike :thumbsup: How often do you change the oil? clean/oil the air filter? measure the valve clearances? Has it ever overheated? These motors are stout, but they'll pop w/out maintenence.

Check your valve clearances!!!

I change the oil every 150 is very well maintained........I'll check the valve clearances but last check they had plenty of clearance......any other ideas?

Have you still got your fuel screw in place?

Yes Mutu the fuel screw and the whole carb are clean and working. When I get back in a few days, I'm going to check valve clearance. I'm not good with electrical but I need to look at that too.

Also may just be time for a new plug. Another thing to consider would be Cam chain stretch. Did you inspect the throttle slide plate? They can crack and cause strange problems. Honestly though, it sounds like it may be a plug problem. Sounds like it may be a little weak or maybe even fouled. Hope this helps.


Let us know what you find, Hope it's nothing serious

I had similar symptoms on my 2005. Eventually (after cleaning the carb and checking the valves) found the small AIS fitting into the cylinder had fallen out causing a small vacuum leak.

Sounds like the pilot jet, but you said you cleaned the carb, make sure you dumped the gas that was in the tank too.

I had same issue with the pilot jet cleaned it but didnt dump the tank out. Usually you can take a flash light and look in the tank or gas can to see if the gas is bad = brown globs.

Good luck

My buddy had the same symptoms..... Hot Start plunger was stuck open... check it out, you might get lucky and thats all it is:thumbsup:

Is there a spark when you use the E-start?

So far.......only one spark while holding e-start for about 5 seconds

1. Fuse good

2. battery good

3. little or no spark

4. connections seem to all be in tact

5. engine stop button okay

6. main switch appears to work okay

7. a. Primary coil - S/B 0.08 to 0.10 ohm (too small for my meter but appears okay)

b. Secondary coil - 5.71 Kohms (in range of 4.6 to 6.8 Kohms)

8. AC Magneto Pickup coil - 296 ohms (in range of 248 to 372 ohms)

So it looks like the CDI is possibly bad.........does anyone know how to tell for sure if its bad and what options I have......I may go for an an aftermarket one?

The only way I know of to verify a CDI is to install it on a known working machine and see if the problem stays with the CDI, or borrow a CDI from a buddy with the same bike. Hope this helps, and if there is a better way someone please correct me.

My '02 426 had the same problem a few years ago and after changing everything , one part at a time off of a friends same bike , it turned out to be a bad CDI. I contacted Richard Muurling (RichardMuurling : ) at Vortex Ignitions and he informed me that some Yamaha's have been know to have the timing map default to a "retarded timing" position and stay there. I installed a Vortex X-10 CDI and my old WR never ran so good. The cool part of the X-10 was the timing map select switch that it comes with. I set it for muddy conditions ( #4 setting ) and it worked great when coming into a wet corner, or over some wet roots and rocks. You can contact MT Racing ( ) in the US to pick up a Vortex ignition. Good Luck -- WR Dave.

Thanks.....You guys are so helpful........I would really like a Vortex X10 but they are twice as much as the OEM ($419 vs. $200). Ebay has some Vortex X10's for a yz for a good price but none for WR.......If anyone knows where I can get a X10 for cheap, I'm all ears........I'm trying to decide which to go with.

My 450 acted like that, the fuel screw fell out.

I've had 2 ignition coils fail on my 2003 WR450 even though both times, the coil looked "OK" when taking an ohms reading.

The CDI was faulty........I got a Vortex X10 and it has 10 for standard YZ which runs good with my yz exhaust maps 1-3 it runs like a thing about starting, its much easier....before it wouldn't start easy with E-start but in YZ map (#9) it fires right up now when completely cold.

I haved the same kind of probleme few month a go... I have find whent I disconect the TPSon carb every thing goes normaly....when I replug the TPS fire was cut ??? I run without the TPS now.....

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