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GasGas EC 200 fouling plugs

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Anyone have any hints or advice? My 2002 GasGas EC 200 is running rough and fouling a spark plug after about an hour of hard riding. It won't start or fire at all. I took it in for service at the local GG dealer and he found the carb needing some adjusting. That done, it rode smoothly for about a 5 minute ride. I loaded it up and took it to a hare scramble this past weekend. I started it up and it immediately was running rough again. I made it through about 55 minutes of the 1 hour race and it died again, fouling another spark plug. I don't know carbs at all, but go ahead and give me the technical stuff if you think you might know what's going on.

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This should give you some good pointers.  http://www.duncanracing.com/TechCenter/KeihinCarbJetting.pdf

 

Question number 1.  Is this symptom new or has the bike always run this way?  This will help us determine if the bike has a problem or if it is just jetted incorrectly.

 

Question 2 - If this is a new symptom, how long has the bike been sitting since it ran well last time?

 

Question 3  Do you know what the shop did to your bike?  Did they just tune the air screw or open the carb and look for debris in the float bowl or rejet it? 

 

At some point it would be helpful to know what main and pilot jets are in it now.  It would be also good to know what is the model number on the slide needle and what position the C-clip is in on the needle. 

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When my XC 250 started fouling plugs one day, a leakdown test indicated a bad wet-side crank seal. When the engine was torn down for a top & bottom do over...the crank seal was bad.

Edited by bowhunter007

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Sorry for the long break. Responding to Shredmasterz, in regards to questions 1 & 2, it's a new problem that started this spring (I live in central Canada and spring comes late here). The bike had been sitting over winter for 7 months. It ran well when I parked it for the winter. As to question 3, the guy at the shop just reset the throttle needle. I took the carb apart last weekend and found tons of dirt in the carb. I cleaned it out, pulled out the jets (the Keihin carb has a 180 and a 45 jet) and cleaned them, replaced the air filter and oiled it. Still, I'm going through a spark plug after every 45-50 minute ride. The guy at the local shop suggested I start by replacing the jet with a 178 instead of a 180 to see how that works out. I should also mention that at lower throttle it runs like crap. As soon as I hammer down, it runs great.

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Ok if it runs well at WOT then do not change the main jet.  The crank seals are a good easy thing to check.  Open the flywheel cover and see if it is wet and smells like gas.  Smell your trans oil and see if it too smells like gas. If either show signs of gas you are likely to have a seal leak.  You may want to double check your carb float level.  If it is too high it will cause the bike to run rich. If you confirm the float is set correctly and the crank seals are ok you may want to install one size smaller pilot jet. 

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I'll update this now. Every time I thought I had the problem figured out last year, I was disappointed again. I changed the jets 3 different times. I changed the fuel that I was using. I clean out the carb. I adjusted the needle. I played with the floats. I rebuilt the top end. On and on and on. It just kept fouling plugs. I thought it might be the stator, so I ordered a replacement stator and a new plug end cap. When I got the stator, it was the wrong one, so I put the new plug end cap on. Well listen to this.................. THAT FIXED THE ISSUE!!!! The damn plug end cap gave me a full 4 months of fouling plugs and it was replacing the plug end cap that cured it! Son. Of. A. Bitch!!

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