HELP!!! Won't start.

I'm at my wits end and ready to throw the bike off a cliff (yeah, right). Bought new in Feb 01. Has run and started perfectly up until about a month ago. Over two or three rides, became more and more difficult to start. Now it won't kickstart at all. Only way to get it fired is to bump start it (what a hassle)! Once started, it runs perfect. I've had the carb completely apart three times, removed all pieces, cleaned, blown out with comp. air, etc... Only thing I have'nt checked/verified, was the throttle posn. sensor. Ill give you my baseline settings, but I've tried everything richer and leaner within a reasonable range, only making small incremental changes. Elevation is 1000', temp around 70-90. Taffy/James Dean, I suspect this may not even be a jetting problem. What do you recommend?

YZ cam timing (have checked twice to verify chain did'nt jump a tooth)

Vortex ignition (switched back and forth with stock and no difference)

170 MJ (have tried 165, 168, 172. 168, 170 work best)

EMP#3/4/5 (#4 is best)

PAJ Screw: 1 1/2 out (tried 1 - 1 3/4 turns out)

48 PJ (tried 45)

Pilot Screw 1 1/4 (tried 3/4 - 1 3/4)

Float height stock

Accelerator pump stock (hav'nt done Taffy mod yet)

What's the air filter look like?

Try a fresh spark plug/ check for good spark.

Does it start OK after it's hot?

does it idle OK when it's running?

Did you do anything to the bike before this happened?


I put in a brand new DT air filter and a clean stocker. No change. I put in a new NGK CR83. The one that came out looke fine. Turned engine over and it has good spark. It won't kickstart whether it's hot or cold. Before the problem, when it was cold, pull the choke out and it would start on the first or second kick every time. When warm, pull out the hot start, and first or second kick, she'd start. The bike runs great once it's running (after push starting it). It idles very nice, no flat spots, excellent snap, etc... I made all of the changes (YZ timing, carb jetting, Vortex ignition) over a year ago and hav'nt had any reason to change it because it ran so good. That's why this situation is really bumming me out. The bike runs perfect, then over a period of three rides, becomes progressively more difficult to start, now won't kick start at all. If I did'nt change anything, what would cause this? What's even more strange is the fact that it runs great (as it always did) once I bump start it, so I nothing to zero in on as far as trying to diagnose the problem. The little voice in my head says the TPS may be doing something weird? Any ideas would be greatly appreciated.


My bet is your valves tightened up. Check the clearance. For reasons I don't understand, they don't tighten up linearly, they do it in fits and starts.

Good luck,


Originally posted by Mark Cantrell:


My bet is your valves tightened up. Check the clearance. For reasons I don't understand, they don't tighten up linearly, they do it in fits and starts.

Good luck,


Mark, I would have to say you're right. Mine tightened up on me too.

Foz, You need to have your valves checked!!! It's totally normal. Do you hear a clicking sound at all? This is my bet...

Originally posted by Foz33:

I suspect this may not even be a jetting problem. What do you recommend?

Jetting just doesn't start to go bad. Valves..........

Just out of curosity, when removed the carb didyou check the operation of the accellerator pump to see if the carb is being primed? Your problem sounds very much the same as one I had after the first year of riding my WR. The pump diaphram had a hole in it and refused to start.

Just thinking out loud here.....You do have a filter inline between the tank and carb right? Any possibility that a small piece of sand or trash got inside of the pilot or the Starter Jet? If you have an ACV is it sealed against air leaks?

Just need 3 things to light the fire....

Spark...which you have

Air....Which you have


From your description you have compression....Which means the valves are not sticking in the open position. You say that you had been able to previously been able to bump start the beast....Bumping causes the bike to inhale deeper than kicking and the suction could be the priming mechinism. You can rule this out or in 100% my getting a can of either and spay just a little in the airbox inlet(with filter out) (Make sure the airbox interior is clean) If you kick it and it starts the problem is in the carb. I would then completely disassemble the carb completely and flush each jet and the passage ways.

good luck...

Bonzai :)

If the valve clearances and compression are OK, then double check that spark, should be nice and bright blue. I had a problem like this with a DT175 and SR500 where the stator was going down. It would give a yellow spark when kicking, but thats not good enough...there is only a good enough spark once the motor is really spinning.

Mark and Dan,

I last checked the valves in Jan. (about 500 miles ago). Two of the intake valves and one exhaust valve were right in the middle of the tolerance range. The intake valve closest to the cam sprocket was close to the limit (tight) and the exhaust valve next to the cam sprocket was right at the limit of the minimum allowed tolerance. I did'nt change the shims bacause I did'nt have any and wanted to ride. A little laziness probably had something to do with it to. Anyway, I will check the clearances and I suspect the two that were marginal are probably way too tight now.


I don't hear any "clicking". Would'nt that be a sign of a "loose" tolerance (cam lobe smacking into valve bucket)?


I did have the carb apart (several times), removed all jets, needle, slide, everything! Soaked everything in carb cleaner, blew it all out with compressed air. The AP is definately working! Way too much though, as I plan on doing the BK or Taffy mod as soon as I get this starting gremlin fixed. If a valve adjustment does'nt fix it, I'll try ether in the airbox as you mentioned.


The spark is bright blue. Do you think I should check the stator anyway?

Thanks to all for the good ideas. I'll keep posting as changes/adjustments are made. Hopefully we get this figured out and then the next guy with this type of problem won't have to go through this.


if we didnt get the technique right to kick start it, can we push start it down a ramp?

it would not ruin the engine or anything rite?

btw, my son can kick start the wr4 wifout any problem, only ihave weaker legs???

yes,aftermy son taught me how tokick start it, i can do it even wif weakerlegs???


[ August 06, 2002: Message edited by: dkwok ]

[ August 11, 2002: Message edited by: dkwok ]

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