Here's another question. Has anyone who has gone pumpless had an issue with gas puking?

Probably something you need to ask on the Forum.

Not enough traffic here to get a representative response.

Doc

Just got back from doing that.

Here's my idea. If we had some kind of fuel pressure release at shutdown we wouldn't have this problem. Has to be a way to do it. But if pumpless doesn't stop the problem then I'm barking up the wrong carb.

If you're speculating that the pressure in the fuel system (2.5 lbs) is the cause of the gas overflow then you would see this happening for pretty much any bike that has the fuel pump.

I doubt that it would happen in the pumpless situation as the pressure is very small. It's just the difference between the height of the fuel in the tank and the float bowl. This is not enough pressure to unset the float needle.

One of the theories for puking (besides to much beer) is that the heat from the engine causes the fuel to 'boil' which would increase pressure in the fuel bowl. The fuel bowl has a 'vent' to the carb and the increase in pressure would force the fuel through this vent. This could also occur for the pumpless situation.

On the other hand, is there is dirt in the seat then the system is open and I can see it leaking out (vs puking).

Doc

Well I'm kinda thinking that the pump holds the pressure and keeps feeding what gas is in the line into the carb as it boils. If the pressure was released at shut down it woun't keep feeding the problem and once the level in the bowl dropped it wouldn't over flow.

I sense my whole idea is boiling away

Musky wrote:
Well I'm kinda thinking that the pump holds the pressure and keeps feeding what gas is in the line into the carb as it boils. If the pressure was released at shut down it woun't keep feeding the problem and once the level in the bowl dropped it wouldn't over flow.

I sense my whole idea is boiling away

I agreed with you. What I added was that .... in that case every bike should have this problem. I never experienced it myself nor did my riding buddies.

I'm partial to gas boiling theory, especially if the pumpless carbs do it also. This would also explain the smell of gas some people sense but don't experience the 'vilolent' expulsion of fuel from their carbs.

Doc

I agree with your agree and I'll bump you an agree. Everyone should have it if is the pump that causes the isssue. That's where I see my idea boiling away. But then again why doesn't everyones gas boil? There are people who have had it happen it realtively cool weather. So I could conclude that ambient temp isn't the cause.

Geez I'm using alot of big words (for me) in this thread.

Ambient is relative.

If you have winter gas then the gas will boil at the "relatively cool weather." I haven't looked at the posts carefully but I get the impression that most of the guys are getting puking this time of year when the temp is higher than what winter gas is intended.

That's not to say that it can't happen in the summer with summer gas. The temp would, however, have to be much higher.

To get an accurate picture you would need better info than we have now.

Doc

To get an accurate picture you would need better info than we have now.


Sorta the point of all these questions

Just kidding

If it's winter gas then shouldn't everyone who lives in the winter gas climate be having this problem? I'm not finding any common denominater here. Anyone got a spare denominator laying around? 04 to 07.

I've got two replies from the RSR so far and both of them said no problems since going pumpless.<br><br>Post edited by: Musky, at: 2007/03/28 17:17

I talked to the service department today and they said that they fielded phone calls all day on Monday about this problem. He said it was the winter gas causing it to happen. Hopefully he's right and the problem goes away. But still there should be a fix for this. It seems to me to be a very dangerous problem and that Yamaha needs to come up with a fix before someone goes up in flames!

We should all be posting this problem to NHTSA and get this problem looked into.