99 wr400 cutting out

i have just completed a rebuild of my 99 wr and after running in as laid down in the manual i went out on a trail ride all was going fine for about an hour when the bike stalled as if out of fuel i stripped and cleaned the carb went up the road and it cut on me again ,i replaced the ht lead and plug it went a couple miles further and cut again i returned the bike to my house stripped carb cleaned again kicked her over nothing, i checked all the leads wires etc all OK except plug cap is a bit rough i prodded up inside the plug cap and kicked the bike over, it started straight away ran for about 5 mins then just cut again no cough nothing just stops like the kill switch has been pushed i suspect plug cap but not sure any one have any ideas

That sounds almost like running out of fuel except for that usually leads to some warning before the motor cuts out (coughing and sputtering, etc). It could be related to the temperature of the motor. After it gets warm, does it feel the same as you kick it through, or is it more difficult to kick? Something could be expanding as the motor gets hot, causing it to stop turning. I don't know the extent of your rebuild so I can't say where to look. I would try to be absolutely sure you are getting proper fuel flow before digging deeper. I hope you find it quickly. Keep us posted. :banghead:

hi slipnslide yeah i looked along these lines to start off with but the motor doesn't have any clearance issues; kicks over fine hot or cold with no leaks etc, all valves are in spec, The rebuild on the motor consisted of new crank, conrod ,main bearings,camchain ,wrist pin and rings all yamaha OEM and fitted as per yamaha spec :banghead: no probs before rebuild that was carried out because the fly wheel puller mullered the thread on the crank whilst removing the flywheel to fit new camchain hence the strip down and it would have been rude not to replace the other items while the motor was apart,alas after initially running perfect and pulling like a train the motor now has this really frustrating problem

hi ,

The problem might be the coil cutting out after you run it and it gets hot, it puts a load on the coil. All of the " older " yami's 98-02 yzf's and 98-02 wr's had a problem with there coils after some time on them. Make sure there isn't a lot of rust around where the coil bolts to the frame and on the coil.

Thanks jjjyyz 450f :banghead: ill get right on to that i reckon its something to do with either that or the plug cap as Ive been right through the fuel system thanks though i didn't think of checking coil to frame contact you no what its like when your on your own going through stuff bloody frustrating : :banghead: thanks again

Filed the surface rust off the earth poles on the coil and fitted ngk plug cap fired up first time. :banghead: Ran it up to temp and hasn,t died yet hope this was the problem thanks for your help guys

If that doesn't take care of it. Disconnect the kill switch and see if that does it. I was having the same problem on a ride a while back. Would run/start perfectly. Then, would just stop while riding as if I hit the kill switch. I disconnected (actually just cut) the switch on the trail. Never had another problem. I have sinced replaced the kill switch ($10).

Thanks jchantz ill remember that one just in case, I do recall having a problem with a kill switch on a yamaha outboard motor a couple of years ago , i remember mucking around with the motor for ages before ripping the kill switch out and solving the problem thanks again

Is the gas tank vent on the cap plugged?

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