Yet another 4t stalling thread....

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NCJ8
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Yet another 4t stalling thread....

Post by NCJ8 »

After reading through (I think) all of the 4t stalling threads, and noting how common it is, I'm wondering: have we figured it out? Since this has been such a persistent problem, is there a common cause and equally common solution?

There appear to be at least four common situations, and perhaps some are related:
1) stalling with a full tank
2) stalling after extended WOT
3) stalling with a passenger
4) stalling at idle

My issue is #s 1-3, especially #1. I just shortened my fuel lines, but that didn't solve the issue. My evap was disconnected by the previous owner, so can't be that (and I plugged the tube coming from the tank...perhaps that was helpful for venting?). Next move is to try a vented 2t cap. The carb cleaning...

These seem like the typical things to try but...does one ever get rid of stalling problems completely? But for this issue, this would be the perfect bike for me, yet it's admittedly difficult to trust something that stalls or feels starved at WOT. Any advice from you 4t gurus would be most appreciated!
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Post by NCJ8 »

I should also note that, if plugging the line coming out of the tank for the evap is a problem, I'm considering adding a one-way valve (as was done by someone else in 2013...I forget who): https://www.napaonline.com/p/NDP7301347

https://imgur.com/FJRtsDw
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phunksoulbrotha
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Post by phunksoulbrotha »

Many of the stalling issues are due to some sort of vapor lock in the tank. Even after drilling/venting my fuel cap and getting rid of the entire evap system, I still get stalling issues occasionally. Luckily I know why and mine is an easy fix. I have a vented cap but my new seat sits right on top of it, effectively covering the vent. So long as I'm paying attention, I can hear it start to struggle and I can raise my seat just a touch while still riding, and it goes back to running normal. The problem gets worse if the tank is full or if I am on a steep incline/decline as it puts the fuel up against the bottom of the cap and effectively plugs it from inside the tank. Still working on a permanent fix but for now, lifting the seat and letting it breathe solves it for me.
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Post by NCJ8 »

Thanks @phunksoulbrotha. It looks like we have the same "racing" style seat, so its good to hear that this is a short term solution. When you got rid of the evap system, did you plug the tube coming out of the tank? I did because mine was leaking gas when the tank was full, and this made stalling much worse (even after trying a vented cap yesterday). I unplugged that tube, put a shop rag there to catch gas drips, and so far, so good.

My next thought, and this might work for you too, is to put on a one way valve at the end of the evap tube coming from the tank so that air can get in but gas can't get out. Here's the link - we'll see how it goes: https://www.napaonline.com/p/NDP7301347
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Post by BigDaddy SnakeOiler »

Did you vent your gas cap?
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Post by NCJ8 »

@BigDaddy SnakeOiler, I am currently using a buddy's 2t cap. It didn't make a difference until I unplugged the disconnected evap tube coming from the tank, but perhaps I had overfilled to the point that the vented cap wasn't able to breathe.

Two things: would you recommend drilling out my cap (and where should I do that) or just getting a 2t cap? And what is considered "overfilling"? I tend to put as much fuel in as possible so I don't have to make frequent pit stops :wink:
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Post by phunksoulbrotha »

Yeah, I threw a vacuum plug on that tube. I also get a little fuel leak from that spot but it hasn't made it past the trim ring between the tank and the paint so I haven't worried about it and wipe it dry when I refill. Let me know how the one way valve works out for you.
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Post by BigDaddy SnakeOiler »

I used a 1/16th drill bit and went right down the center.
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Post by johnk »

NCJ8, can you report back about the one-way valve on your EVAP? I'm considering doing the same. Thanks!
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@johnk

Post by NCJ8 »

@johnk I just tagged you in and re-upped my posted solution. It's worked perfectly. Good luck!
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