'02 WR426 starting problems

9 replies to this topic
  • 2in2out

Posted February 11, 2010 - 07:59 AM


I road my bike for the last time in October after a nice ride. I cleaned her up, changed oil, cleaned filters, and parked her in the garage. Started her once in Novemeber, and put Stabil in early December. Since then I have tried to start her to no avail.

I cleaned the carb, all jets clear, AP squirt good, good fuel delivery. New plug in, gapped appropriately, old plug still in great shape, and getting spark.

Kicked for hours with only one fire. Usual start-up routine. I notice it's much more difficult than before to find TDC. Bump starting unsuccessful, because it also seems the clutch is not releasing, and I'm at the max of adjustment.

This week and next I'm looking to check the cam timing and valves, and possibly replace the clutch, and do the auto decomp exhaust cam (Hotcam or '03 YZ450???).

Model/Year: 2002 WR 426
Engine: Stainless steel oil filter, Notoil Air Filter
Carb: White Bro. fuel screw 1 3/4 turns, MJ 162, PJ 42
Exhaust: Jardine RT4 Can and Mid, FMF PB SS header
Fluids: Maxima 10-40 4 stroke
Suspension: Stock
Chassis: Applied clamps, Protaper 1 1/8
Protection: Devol skid, radiator, frame protection, Acerbis Rally2 bark busters
Tires/Wheels: N/A
Driveline: Stock
Electrical: Grey wire, Vapor Trailtech
Cosmetic: IMS 4.0 Desert Tank
Miscellaneous: Altitude 3500-8500 MSL, Temps 20-60 F (Winter)
Comments: ***????:ride:

Ideas, solutions, guidance....???? What clutch is suggested besides Rekluse? HotCam or YZ cam???

P.S: Should I go ahead and do a Wisco piston upgrade while I've got it apart? Also which gasket kits are best when removing the head as this is my first time since the late 80's I've done any severe engine work. I'm also planning to sell this beast once she fires and runs worthwhile.

  • 2in2out

Posted February 14, 2010 - 08:34 AM


Bump!!! Help please!

  • alfie

Posted February 14, 2010 - 08:47 AM


Hi im on my third yamaha wr ive had a 400 426 and currently the 450.
It could be worth while changing or a good clean of the pilot jet. Also check the kill switch and the grounds on the frame to make sure. Also my old 426 cracked a plug cap and was a pain to fire up. Has for the cam you may be better off with yz auto cam than the hot cam my 426 was a pig to set up with the hot cam and wouldn't run right so i went to old yamaha cam and no more hassle. Ive also used EBC clutches in all my yamaha's with out a problem and they last a long time hope this helps.

  • pablo83

Posted February 14, 2010 - 07:03 PM


If you're in neutral, clutch release shouldn't be an issue when finding TDC. When you check the timing, also check to see if one of the cams seezed (in which case the timing gear tends to spin on the cam shaft.


If your timing is okay, then spray use some starter. This will help determine if the problem is with fuel or spark.

  • 2in2out

Posted February 14, 2010 - 07:18 PM


PJ is clean, MJ clean, good squirt timing, good spark, kill switch ok, plug cap intact. Still no go... Gonna open the valve covers tomorrow and check timing.

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  • kevin1209

Posted February 16, 2010 - 06:41 AM


The problem is that your bike is a "she". They never listen to a damn thing, no matter what you try. If you start calling it a "he", it will start on the first kick, run like crazy, and never complain.:ride:

Sorry for the derailment. It had to be done.

On a serious note, if you are kicking it repeatedly and getting nothing, it is usually fuel or fire. It appears you have cleaned/checked most of the typical culprits. Is it possible that your fuel line is clogged? Or maybe your choke is stuck? Just trying to think of something simple that is out-of-the-ordinary before you tear it down. I just fixed a stuck float problem, but it sounds like you have already cleaned the carb.

  • 2in2out

Posted February 16, 2010 - 09:17 AM


Carb was cleaned, getting plenty of fuel, good squirt, new plug and it fires. Pulled head checking cam timing and valve clearances, all good. Rotated Exhaust cam for YZ timing. Wifes car acting up took my upgrade money. After I reassemble the head, I'll be rechecking the ignition circuits. If that's all good, I may just tear into the carb again, and put a Boysen on.

It may be some time for me to get it figured out, as wifey has made the taxes a priority for me.

  • 2in2out

Posted March 18, 2010 - 06:31 AM


Update: 3 months of frustration come to a glorious end. It starts!!!

The issue: I had inverted the order on the needle spring during my first carb check in Novemebr. Spring washer, Spring, needle, needle nut. I replaced everything in the right order, and she fired up, but jetting was bothersome. Replaced 40 PJ with 38 PJ and she runs like a champ.

Also, the cap gasket to my IMS tank degraded and fell into my tank. Had to filter the fuel and flush out the tank. What a pain.

Still might consider an '03 Auto-decomp cam, but I'm considering selling to get an 08 or 09 WR. Finances will tell.

Year: 2002
Model (400 - 426 - 450): 426
Cam Timing (WR/YZ): YZ
Main jet: 168
Pilot Jet: 38
PAJ: 75
MAJ: 200
Leak Jet: N/A
Starter Jet: 65
Fuel screw (turns out): White Bros. 1 3/4 out
Needle Model/Clip position: Stock needle in clip 4
Grey Wire Mod (Y/N): Y
TPS Connected (Y/N): Y
Airbox Snorkel/Lid (on or off): Lid off
AIS Removed (Y/N): N/A
Airfilter Brand: NoToil
Exhaust Brand: Jardine RT4 w/Jardine mid-pipe, FMF Powerbomb SS Header
Average Altitude: 3500-7000 MSL
Average Temperature: 70
Average Humidity: 7-18%
Degree of Satisfaction (0-10): 8
Additional Mods/Comments:
Still need magic button!!!

Thanks for the help in correcting my stupidity. It's all in the details...

  • pablo83

Posted March 18, 2010 - 08:12 AM


Glad you figured it out. Those issues are the worst to troubleshoot. On the NX650 the carb has a small cylinder piece that sits over the MJ emulsion tube that acts as a needle guide. When I got the bike it was not running. The PO forgot to reinstall this little tube. It took me about a year to figure out what was wrong.

  • 2in2out

Posted March 19, 2010 - 06:59 AM


Sometimes clean is too clean. A coworker of mine said he'd eat off my bike it's so clean.

I took it out for the first ride today. Got 3 miles from the truck and noticed my idle was hanging at 4000-5000 RPM. The idle screw wouldn't turn at all. Rode back down 2000ft drop at white knuckle speed, but at least I didn't boil out.

When I got home, a quick spray of CRC 6-56 on the idle screw and throttle linkage, a little adjusting, and perfection.

Again, it's all in the details.


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