XR400 Must run on Half Choke

[gtcollins]

I ride a bone stock 1997 XR 400 (except for kibble white valves and dual sport conversion). I ride this bike because it is the best bike ever made and because I'm basically lazy and don't want to work on any more than cleaning the air filter and changing the oil on a regular basis. If  I take time off I would rather ride than be in my garage.  So I show up at the track to partner with my son on the 6 hour St. Valentine massacre Hare scramble and do my normal start routine and to my surprise it doesn't start on the 2nd kick. Ran perfect on a trail ride last month. Eventually it starts with full choke but won't run on anything less than half choke. If I take the choke off completely she stumbles and dies. So I ride the whole race on half choke and have to full choke to start it even when it's hot.  Air cleaner was clean, oil has less than 6 hrs on it.  Anybody else have this happen? What's quickest easiest process for cure? (keep in mind I'm basically lazy)  Have a hare scramble I'd like to do this coming weekend so it will have to be simple or I'll be racing on half choke again. Thanks in advance for your most excellent advice and comments.

[Oil Baron]

Lazy? You have the wrong bike.  You need a fuel injected bike for that.  When you let your bike sit, the jets plug up in the carb because of ethanol in the gas.  You could also run race fuel without ethanol.

[Trailryder42]

BR is right.

 

When this happens, pull the fuel screw, its spring, washer and oring and blow out that passage with carb cleaner. It's easier than removing the float bowl in order to pull the pilot jet, and most often will get it back running right.

[oregon_rider]

Lazy? You have the wrong bike.  You need a fuel injected bike for that.  When you let your bike sit, the jets plug up in the carb because of ethanol in the gas.  You could also run race fuel without ethanol.

 

  In many states you can buy "clear gas" - fuel with no ethanol (aka E0)...    The originator of this thread lives in kansas.    So look here...

 

http://pure-gas.org/index.jsp?stateprov=KS

 

   With ethanol free fuel the bike will run cleaner, cooler and the fuel won't go bad as quickly.   I would recommend this over race gas for a stock XR...  

 

   I always drain the carb and the tank before storing.  I store my fuel in steel jerry cans with a little sea foam in it to stabilize the fuel.

 

jeff

Edited March 4, 2015 by oregon_rider

[SquareAce]

I had the same trouble on an older bike, 86 xr250. I cleaned the carb two ti es with no change. The third time I discovered the air cut off valve the last time. I cleaned the dirt and crud out of it and it's ran like a top ever since.

Now that could be coincidental with the third cleaning of carb and jets being the charm.

Air cut off valve is number 14 on this diagram.

http://www.partzilla.com/parts/search/Honda/Motorcycle/1997/XR400R+A/CARBURETOR/parts.html

[AZ-520]

Carb problem  for sure, time to get the tools out and clean. Plug check would be advisable, don't be lazy, lol

[crazyfast]

Lazy, you sound like a UAW buddy that I have . He just rides them and doesn't fix them or has a clue how too. Fine a buddy like me that will work on the bike for fee out of sympathy for the bike. Other wise, clean the carburetor, takes about an hour. I pull the muffler, swing down the sub frame and pull the carb. Good luck.

[ScottE]

Ever get your problem fixed? My bike is doing the same thing. Runs great with 1/2 choke. Once warm, dies with choke off or full. Been searching posts and yours was the most promising I've found in an hour of looking.

 

1998 XR400. Sat with gas in it for 3 years. Dissassembled carb and cleaned 3 times now. This last time, I soaked the disassembled parts in carb/parts cleaner for 40 minutes and assembled with a new oring kit. All passages seem clear. Only thing left I can think to replace is the air cut-off valve diaphragm.

Edited September 28, 2015 by ScottE