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View Full Version : Strange problem... fouling plugs.



85V8XJ
09-23-2005, 09:24 AM
I'm new to the whole ATV thing, so I'll apologize in advance for any stupid questions.
I just picked up an '02 400EX to cut my teeth on, got a sweet deal on it. Asthetically, and mechanically, it's damn near perfect. Never been on it's lid, hardly a scratch. I should mention that it's BONE stock.
The day I brought it home, it ran GREAT. The previous owner had just put a new plug in it, but said that it was probably due for an oil change, and the gas in the tank (about 1/2 tank) was 8 to 12 months old.
I'd fired it several times during the first couple of weeks we owned it, but didn't have a chance to ride it. Then, the day before we'd intended to ride it, it wouldn't fire. It popped a couple of times, but then nothing. Ended up running the battery down over the course of two days trying to get it running. I'd pulled the plug, which appeared to be newer, and confirmed that it had spark. There was some evidence that it was running lean, but it didn't seem too bad.
So I picked up a few new plugs (they're cheap, worth having spares around), popped in a new one. The bike fired on the first push of the button. Took it up and rode it, ran great all day.
We're going up tomorrow, so I'd decided to get everything ready last night. I tried to fire the bike, and I'm getting the same thing. It actually fired and ran for about 15 seconds, but died and now it won't light. I'm sure that installing a new plug will fix the problem, but I'd rather correct the problem than just treat the symptoms.
The only bad thing I'd found on the quad is that the previous owner had absolutely HOSED the stock foam filter with filter oil. So much so that the lower portion of the airbox had a bit of standing oil (filter oil). I'd replaced the filter since even filter cleaner couldn't get most of the oil out of the original unit. Could all that filter oil have plugged up the carb? Could the remnants of the oil simply be fouling the plugs? Like I said, it ran fine on my ride. Restarted all day long with no problems.
Any suggestions? Tests that I could perform at home?
All this aside, I'm very impressed with the 400EX. My wife and I are currently sharing it, our intent was to pick up a bigger machine for myself later on - considering the Raptor 700, but I'm not a very aggressive rider, the 400 seems to have enough grunt for my purposes. That, and my wife is a little too small for the 400, so we're looking at a 250EX for her.

Pappy
09-23-2005, 05:49 PM
cant say for positive, but id pull the carb and clean it very well, and remove the float bowl and inspect everything for any signs of build up.

ofsoto
09-23-2005, 10:08 PM
Like Pappy said, take apart your carb and clean it throughly. It may not only have oil residues but also gum/varnish deposits from the old gasoline. And also don't forget to get all that old gas out of the tank and fill it up with fresh gasoline before you fire it up again.

frankiedizzle56
09-23-2005, 10:21 PM
i am not sure u didnt make it clear r u still run the same tank of gas. the old gas seems to be the problem i had that happen on my old quad i ran a few tanks of good gas(93oc) through it and it ran fine. empty out the old gas if u didnt already and put some new gas in it and clean your carb b/c old crappy gas will clog it up like they said b4

85V8XJ
09-26-2005, 08:10 AM
Hey guys, appreciate the responses. The old gas in no longer in the tank. Things got a little stranger with the EX over the weekend. I worked on trying to get the bike started for a few hours Friday night since we were to ride on Saturday morning. I'd install a new plug. the quad would actually fire and idle for a minute or two, but would not clear out. The moment I'd touch the throttle, it would die. Pulling the plug, it was dry and black - no doubt it's running rich. I called the previous owner to verify he'd never rejetted the quad. It's bone stock, he's never so much as touched the carb settings.
Got up early Saturday morning to start working on it again, but had no luck. We decided to head up to the mountain anyway, since I'd promised my little girl she could ride her quad this weekend. The 400 was loaded in front of my daughter's Kasea 65 on the trailer, so we just decided to leave it where it was.
We get up to the moutain, find out parking spot, and unload the 65. I was joking around with my wife, saying "Watch, the 400 will start with no problem now that we're up here". I turned the key and pushed the button - IT FIRED!!! Not only did it fire, it ran like a champ all day long!!!. Not the slightest sign of the problems we'd had at home.
Our house sits at around 700 feet above sea level, the riding area sits at around 2000. I've been told the stock jetting is good from sea level to 3000 ft. I'm still baffled.
Anyway, thanks again for the advice. Any other ideas? :confused: