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Discussion Starter #1 (Edited)
I have a 1998 Wr400 that has been down for a while. I was riding it about 2 months ago, when it suddenly started to surge in power, then immediately died. I tried to restart the bike, but it had no compression. After i tore it down, I found a piece of the carb vacuum plate (FCR MX 39) stuck in two of the intake valves! I removed the obstruction, cleaned the valves (making sure they fulling seated into the cylinder head) and replaced the broken slide. I have the bike put back together, but now it will not run. I can get the bike to start, but it will only idle for about 15 seconds until it sputters out. The fuel screw is about 1.5 turns out (does not seem to help when adjusted) and the idle screw all the way in. I am thinking i might need to clean out the pilot jet for the carb, but not sure if that will help. Cam timing appears to be perfect.... Any suggestions??



Broken Keihin Slide
 

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Discussion Starter #3
I also noticed that when i kickstart the bike, fuel drips out of the vent lines from the carb. could this mean the carb is partially plugged up with debris?
 

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I also noticed that when i kickstart the bike, fuel drips out of the vent lines from the carb. could this mean the carb is partially plugged up with debris?
Sometimes when you have fuel dripping or leaking from a vent tube from the carb, particularly from a line coming from the float bowl, that's an indicator that the float needle valve sealing rubber is worn out and isn't getting a proper seal. OR (pretty unlikely) is that your float may be fuel logged and not floating which will cause excess fuel to flow out of the vent tube.


IF this is the case, an easy (and alittle messy) way to test this is to remove the float bowl, reconnect your carb and fuel line (if you pulled off the carb) and turn the gas on. Gas should flow through the carb and basically make a mess. If you push the float upwards with your finger, it should stop the flow of gas as it's designed to do. If gas continues to leak, you should go ahead a replace the float needle valve. That's the best way to visually check that particular problem.

Otherwise give your carb a good cleaning to rule out the possibiliy of a gummed up jet or circuit.



Just my .02

Hope that helps.
 

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My mini is having the same symptoms, intrested to see what pans out here.
 

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Discussion Starter #7
Does it run with the choke on?
Yes, it will only start with the choke on.However, it does not idle very smoothly and sputters out after just about ten seconds. it always dies when i take the choke off, or give it any throttle.
 

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Discussion Starter #8
Sometimes when you have fuel dripping or leaking from a vent tube from the carb, particularly from a line coming from the float bowl, that's an indicator that the float needle valve sealing rubber is worn out and isn't getting a proper seal. OR (pretty unlikely) is that your float may be fuel logged and not floating which will cause excess fuel to flow out of the vent tube.


IF this is the case, an easy (and alittle messy) way to test this is to remove the float bowl, reconnect your carb and fuel line (if you pulled off the carb) and turn the gas on. Gas should flow through the carb and basically make a mess. If you push the float upwards with your finger, it should stop the flow of gas as it's designed to do. If gas continues to leak, you should go ahead a replace the float needle valve. That's the best way to visually check that particular problem.

Otherwise give your carb a good cleaning to rule out the possibiliy of a gummed up jet or circuit.



Just my .02

Hope that helps.
Thanks for the suggestion KDog! Definitely an easy test to do, but do you think that a bad float needle valve/seal would affect the performance of the bike or just the excess fuel dripping from the vent tubes? This dripping fuel has not ever been a problem until now...since the bike hasn't been wanting to run :headscrat
 

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Pilot jet needs to be cleaned/replaced.
Not to thread jack... but I figured the same, and I cleaned that SOB out and I still can't get it to work.
 

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Pilot jets need to be replaced. The passage is so small that cleaning is a bit of a gamble.
I'll try it out, thanks bro!

/threadjack.
 

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Discussion Starter #14
she's alive!

Well, the bike is up and running now! :bannana: Unfortunately, I admitted defeat :bs: and brought it to a local shop. They discovered that the O-ring and washer were missing from the fuel mixture screw , as well as it being in need of a new needle jet seat. After the carb was cleaned, and the new parts installed, it started up after about 10 kicks. The funniest part is that nobody at the shop was able to even cycle through the kickstarter (without the decomp lever pulled). They thought there was something wrong with the bike, until i showed up and kicked her the way she likes it! Gotta love that high compression ratio :arsenal
 
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