Engine flooded & leaking gas

[mxmatthew]

Ok, I had a strange problem over the weekend. Hopefully someone might have some insight on this.

I'd say I have about 20-25 hours on my KTM. Up until this last weekend it has run flawlessly....

So the story goes......It was a hotter day than any of my previous rides on my bike, but I don't think it was enough to cause my problems. I start the bike up to warm it up, it's idling fairly normal with me giving it tiny bits of throttle. I notice that it's smoking a little more than usual and then all the sudden it stalls out. Flooded.

So as I'm kneeling down to change the plug I notice that the carb is leaking fuel out of the overflow hose. Not just a few drops....flowing out. Put the petcock to off, it stops. Reserve and on its still flowing.

I throw in the new plug and it fires right up. I run it for a little with the gas off to drain the float bowl a bit. (I'm thinking the float is stuck at this point)

Everything seems good now. We go out for a good 1.5-2 hour ride with a bit of everything. Super slow stuff and some wide open sections. Then all the sudden I feel the bike sputtering out, I hold the throttle wide open with the clutch in to hopefully clear it out. It revs up and down for a few seconds and then dies again.

So I throw a new plug in again and away we go for about 15-20 minutes to get back to the truck. The day is over as I'm on my last plug.

Also my 11 liter tank looks like it is damn near on reserve at this point and my buddy's 7 liter still has lots to go, so I must have been leaking more fuel.

Took the carb apart today and cleaned everything and didn't notice anything out of the ordinary. I guess I'll try it again this weekend and see what happens.


Anyone got any ideas before I waste another weekend? Any ideas would be much appreciated!!

 

[SpeedyManiac]

Simple. Check your jetting and float height. I'm guessing you're too rich (causing spark plug fouling and fuel range issues) and the float level is too high (causing the overflow issues and fuel issues). Time to rejet and adjust the float height.

 

[SpeedyManiac]

Oh, when's the last time you cleaned your air filter?

 

[mxmatthew]

filter's cleaned every ride or 2.

It does seem like jetting when it fouls, yet then I can be riding 5 minutes later and it is running perfectly, no bogging or anything for more than an hour and it's also been running great since I got it.

I may try the float level, but as for jetting I'm not sure where to start as it feels like it's jetted correctly..... when it's running.

 

[John Harris]

Your Jetting has gotten rich since it has been hot. I suspect that it is now at least 40 degrees F hotter now than what you are jetted for. With a highly tuned 2 stroke, which KTMs are, jetting is critical and temperature and altitude make real differences. Ride safe John

 

[SpeedyManiac]

Check what jets are in it, then lean it out one step at a time and see how it runs.

 

[_JOE_]

Sounds to me like the float valve isn't seating for whatever reason. Check the face and seat of the valve.

 

[btm1948]

ya it sounds like its a problem with the float i would start there

 

[whenfoxforks-ruled]

Not the floats, the float valve and seat. Fix that before trying anything else.

 

[Wolferl]

I agree! The Float valve doesn`t close correct!
You can test it:
Take out the carb and combine it with the fueltube. Open the float chamber and hold it in working position. Then move the float upwards. Open the gas tap - no fuel should come down. The float valve should close now! If not check it and clean the fit.
The second bug chould be an leaking float. Look carefully if there is gas in it.
After you successfully repaired the carb change the gear oil, its possibly mixed with fuel.

Good luck to you!
Wolferl ;)

 

[whenfoxforks-ruled]

Testing the float valve can sometimes be a waste of time. It may not do it all the time. This is really a part that should be changed yearly. Just to prevent issues just like this!

 

[Wolferl]

After 20 to 25 hours?! Its nearly new! :nod:

 

[_JOE_]

It's quite possible you got a small piece of dirt or something in between the needle and seat. That could have damaged one or both components. May still be in there. 25 hours is enough to start thinking about at least changing the piston rings.

 

[rmc_olderthandirt]

sounds to me like the classic bad float valve.

You might have gotten a little bit of dirt or something in the gas that has worked its way into the float valve and is causing the needle valve to stick. Just taking the carburetor apart and cleaning may clear the problem up. It is also possible that the valve seat has been damaged and it just won't seal properly, like a leaky faucet.

The damaged valve seat is usually a slow leak, and since you had a situation where the gas flowed I would suspect a sticking valve.

If I was out camping / riding I would just take the carburetor apart and try to clean the needle valve. If I was at home and preparing for an upcomming ride I would buy a carburetor rebuild kit, including a new needle valve & seat and fix the carburetor properly.

Rod

 

[whenfoxforks-ruled]

Most of the time its the little things. 25 hours, what does KTM recomend on a top end?

 

[MrLuckey]

One other thing that I didn't see mentioned is to see if you have a check valve in the gas cap. If you have a check valve stuck and it's real hot out you might have been boiling gas and it can get pushed into and completely through the carb. Pretty much exactly the same symptoms as a stuck float.

 

[mxmatthew]

Well I'm hoping it is the float valve. That's what I figured from the start and that's what I took special care in looking at when I had the carb apart. I guess I will find out.

I really can't see it being an issue about how hot it was and the jetting. It was at the most 30 Celsius (i think thats around 85 F) at the peak of the day. Just a bit hotter than the rides I had before that. This also wouldn't explain the leaking fuel.

As for the gas cap thing, I'm not sure that I know what you mean. I just have the stock KTM cap:

Thanks for the ideas!

 

[whenfoxforks-ruled]

Make sure your as tank is vented. Take the cap off, clean it and blow through it. If your gas tank is sealed, it will build pressure, and blow it by the float valve.

 

[MrLuckey]

Exactly.

 

[mxmatthew]

Well, rode all weekend with no problems. Gas tank was fine so it must've been the float valve. Thanks guys!