2 stroke running out of gas - damage to top end?

[KTM Mike]

HI all - I recently bought a new toy hauler trailer with the cargo area that is open to the living area. To help minimize the risk of fuel spills and odors, one thing I hear many guys do is turn off fuel petcock, let bike run until it dies. This gets fuel out of float bowl, reducing any chance of gas coming out the carb overflow tubes. (while on a rough road for example).

Most suggesting this ride 4 strokes. All the bikes I will haul are 2 strokes - relying on the fuel to supply lubrication. Is there legitimate (not just annecdotal (sp) ) support for concern of top end damage (or accelerated wear?) from a two stroke being ran out of gas like this? I know when my bike runs out of gas, it is not a prolonged drawn out thing - it is just WHAM - engine dies. This seems to suggest it is less of an issue?

Any comments appreciated?

 

[RVL]

It won't hurt your bike. Lots of oil in there migrating around on the surfaces...

If you do that, it doesn't get all of the gas out of the carb. It also takes less time to just loosen the 17mm float bowl cap and let it drain out.

 

[KTM Mike]

RVL - Thanks. It does make sense there would be some "lingering" fuel/oil inside. I understand not ALL would be out of the carb, but almost certainly, highly unlikely with a "nearly" empty carb for any to come out over flow tubes.

Another option I thought of was to time approximately how long to stall - (actually, I loosely did, two of the 3 took about 1.5 minutes, the other about 2 minutes riding at a fairly slow putt putt around and around the garage. So if I were to let them all run for just short of those times - I would have minimized the amount fuel in float bowl, just short of stalling, eliminating any top end risk.

Yeah, I thought about just loosening the drain as well, but it is a rather awkward fit to get a wrench in there without loosening the clamps on the carb...and doing that, means a greater chance of somehow forgetting one is loose and sucking dirt in! This weekend I plan to take a closer look see to really see how easy i can or can not get to the drain on each of our bikes (05 KTM 250, 03 KTM 200 and 99 Kaw. KDX 200). Maybe all I need to do is ever so slightly reposition each carb such I can get to drain easily without rotating carb.

 

[KTM Mike]

oh oh...I see you are a 4 stroke guy...maybe I better get a second opinion huh? ;^)

 

[Papakeith]

Mike,

If you're worried about it just shut the petcock off and lay the bike over to let the fuel flow out of the overflow. You could use a small jug to catch the overflow if the thought of spilling it on the ground bothered you.

 

[adam728]

Another thing that might make you feel a little more comfortable, when your bike dies withe the petcock off it's not like it runs 100% out of gas and oil. It just becomes to lean to promote combustion. Like RVL said, there's a lot of oil lingering in there (I was really surprised on my last teardown how much there was!).

 

[John Cena]

I'm not sure but wont the 2 stroke scream like it's doing 15,000 RPM becuase it's lean? Thats what happend when I ran out of gas with the petcock on.

 

[bad96z71]

yes it will scream like it's nailing 15,000 rpm i would not recomend letting it run out of fuel better to be safe than sorry , and just lean the bike over like papakeith said

 

[rmc_olderthandirt]

There is a big difference between running out of gas when riding hard and letting the engine idle until the float bowl runs dry.

For either case, the crankcase will be fine, there is so much oil hanging around that the crank & rod won't be bothered at all.

The top end, however, can overheat and sieze as the mixture leans out due to the lowering fuel level in the carb. It isn't just the instant that the fuel runs out, the mixture will gradually lean out as the fuel level drops. If the engine is already hot and you are riding it hard it could be a problem.

On the other hand, if the engine is cool to warm and you simply run it at a fast idle it won't bother it.

 

[adam728]

A bike will only scream when going lean if the jetting is wrong.

If you are jetted rich on the lowend you need to crank the idle speed screw up to get to a resonable idle rpm. As the air/fuel leans out it gets closer to the ideal ratio and the rpm begins to climb, because you have the idle screw set too high!

When setting the air screw you usually set the idle speed screw to one point, then adjust the air screw to the point where the bike idles the highest (or just slightly rich of there depending on throttle response). This means if the bike runs richer/leaner than that the rpm will drop, not race sky high.

 

[John Cena]

Just be ready to apply the back break and pop it into 1st. I've had my bike run out of fuel at a stop and the kill switch don't seem to stop the motor when it's screaming. :|