WR400 suddenly lean. Any Ideas?

7 replies to this topic
  • wr400woody52

Posted September 06, 2003 - 09:45 PM


I have a 1999 WR400. I just completly rebuilt the motor including new crank, piston, cylinder, ect. It started up great and ran fine for the first two heat cycles. On the third time out aprox 40 min on the new motor it started acting supper lean even stalling and not wanting to run. When I did get it started it had no power at all and wouldn't even pull me back to the truck. I retouqed the head, checked the air filter, checked the fuel flow and the carb fuel delivery (all checked good), I changed the spark plug and cap because I had new ones around. Nothing has made a diffrence yet. I was hopping that someone who might have had to deal with this or a simular problem might share some gray matter. I have pounded most of mine out on the engine cases. Thanks

  • MN_Kevin

Posted September 07, 2003 - 12:48 AM


hmmm... :)

You could very likely have an air leak. If you have that conglomerate of hoses on your (shift lever) side of the carb, you can remove that garbage. This is known as "de-octopusing". The octopus (air cut valve) is a disaster in the waiting. Get rid of it. There is a step by step procedure on how to get rid of it. (see my signature)

With the bike idling, spray around with carb cleaner. If your idle goes up...BINGO >> air leak.

Check your air filter (mice ATE my Ninja's air filter :D)

After that, I would pull the carb and thoroughly clean the whole thing.

Be sure to also pull the air horn on the airbox end and blast carb cleaner AND compressed air through the main and pilot air jets.

These have been known to plug up w/ air filter oil. Common sense would lead you to believe if the air jets plug up, the bike runs rich. I do not believe this is necessarily the case.

As sick as I have gotten (gotten - is that REALLY a word...???) pulling the carb, this IS where I'd go after the really easy stuff.

Once the carb is out of the way, you have ignition and valves I suppose...

  • Indy_WR450

Posted September 07, 2003 - 06:33 AM


I suspect it is not a carb issue. Check your ignition timing to see if it has slipped out of phase with your engine crank position. I suspect you are firing the spark at wrong cylinder position and verify you are getting a good spark voltage at the spark plug. :)

  • wr400woody52

Posted September 07, 2003 - 11:53 AM


I was thinking that it must have something to do with the crazy amout of hoses on the carb. I had allready checked the airfilter, but at this time I can not get the bike to run well enough to even try the old carb cleaner trick. I am very interested in the deoctopusing of the carb. However I am very new to the forum and chat thing. In fact this is the first time I have ever tried it. So I could not find the step by step instructions that you mentioned for deoctopusing of the carb. I would appreciate a link to that if you have the time. Thank you for the info.

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  • wr400woody52

Posted September 07, 2003 - 11:56 AM


I will also check the timming and spark again. That sound very logical. Thank you, for you insight.

  • MOmilkman

Posted September 08, 2003 - 06:40 AM


I had the link saved in my favorites to the old TT website where the de-octopussing inst were. That link is dead now. :)

However, if you look at my sig line below you can see what the ACV looks like when its taken off the bike.

  • dkwok

Posted September 08, 2003 - 02:45 PM


jus rebuilt, maybe u didnt run it in properly?
u have a seizure??? :)

  • dooweb2

Posted September 08, 2003 - 04:31 PM


check both exhaust gaskets also


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