Water in my carb?

After dusting of my 2001 WR400F and installing new air filter and sparkplug. My bike is starting with absolutly no problems. With the cold choke pulled out the throttle response is very good. However, when I push it back in and give the throttle a couple of twists, it chokes and sometimes stalls. I'm not the best mechanic so I'm not sure where to look next.

Could there be water in my gas tank? in the carb? I don't see a drain screw to let the gas flow out of the carb.

Any suggestions would be very helpful.





There's a bolt on the bottom of your carb float bowl. Remove that and you can clean any any water and debris from the bowl. You can also spray some carb cleaner in there to dislodge some stuff in the jets. You may have some varnish built up from letting it sit w/ fuel in it. I would also run some fuel system cleaner through the bike. Techron works best. Hope this helps! :naughty:

Thanks xcracer123

I try it out tomm. and see how it goes.



Ok. I took off the screw from the bottom of the carb. You were right. The gas that came out was tacky or sticky aka like varnish. I have completely changed all the fuel. And have sprayed some cleaner up there and have added some fuel system cleaner.

I assume that I'll have to run it a little. After the first run. It is still not running right.

I also have noticed that it's backfiring way more than it did last year. Last season maybe once a ride it would backfire. Today I went for a run around the neighbourhood and it backfired a lot.

I'm not quite sure what backfiring is, but I would think that its fuel mixture that has not sparked and is igniting in the exhaust. Therefore, the fuel didn't spark because of 1) bad wires, 2) maybe bad sparkplug, although it's really new. 3)????? Not sure where else to look.

If any one has any ideas that would be great.!!

Cheers :naughty:

Do you mean it is popping on deceleration?

This is from a lean mixture and will need to be rejetted.

Where are you in Ontario?

Yes it it's popping on deceleration.

Is there a good site so I can learn how to rejet my carb?

Actually, I'm from Toronto and never had a chance to own a dirtbike. For the last three years I have been living and working on Sakhalin Island, Russia. It's just north of Japan. Since, I have been here, I have shipped over a snowmobile and am now on my second dirtbike. My first one was an 91 Honda XLR250. There's a bunch of us who go out on the weekends and just ride. We are 2 minutes from the country and once out there, there is nothing, maybe the odd Russian miltary base and tank training area. Since the Russian military is broke, the tanks aren't out too often. It's actually pretty cool out here. Once I was pulled over for speeding. 45 seconds later, and 200 rubles poorer I was on my way. 200 rubles is $10CDN. Hows that for an efficient police system. 7 out of 10 stops result in a bribe.

I'm coming back to Canada in a week. And I want to drop by a Yamaha shop. Do you know any good ones east on Toronto? Where are you?

It does NOT need to be re-jetted...just pull the existing jets and clean the varnish out of them so they flow fuel.........since the gas evaporated in the bowl, they're clogged!

Rich is right if the bike dried out then for sure the jets are varnished. Clean them and you should be right back up and running. :naughty:

OK thats reassuring. Cleaning the jets would make more sense since it ran fine last year. Since, I have never taken a carb apart, I think I'll wait a couple of weeks for a more mechanically inclined friend of mine to return from vacation. I can see myself pulling it apart (no problem), cleaning it (no problem), and putting it back together with one or two extra parts sitting on my workbench (problem). I'll read up on it.

Quick question?: Do I need to strip it down or just open it up get at the parts to clean it?



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