Intermittant gas leak on start-up

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Intermittant gas leak on start-up

Postby HandKPhil » Fri Aug 20, 2010 7:50 pm

Anyone else have an occasional gas leak from the carb overflow tube, right after starting your Helix up? Mine does this only once in a great while, and it usually happens if I don't give the bike time to fully warm up (3-4 minutes) before taking off.

It happened again this evening, when I tried to take off right after a cold start. I might have let the bike warm up for 30 seconds. Outside air temp was around 80 degrees. I got about 50 yards from the house and smelled gas. Bike stalled, and would not stay running. Where I came to a stop, about 3-4 ounces of gas came out of the carb overflow tube below the bike. This is the tube that plugs onto the carb overflow nipple on the upper right-hand side of the carb. This line has a tee in it, just below the overflow nipple on the carb. The line from the tee runs under the carb and plugs into the bottom of a round doohickey located on the upper left side of the air chamber, left side of the bike, under the seat. This line appears to be some sort of vapor return line, I think. Another line runs from the round doohickey mentioned above, over to the air box.

I pushed the bike home, let it sit for two minutes, re-started it, and went on an uneventful 40-mile cruise, with no further problems.

Anyone else experienced this? Think it's anything to worry about?
Last edited by HandKPhil on Fri Aug 20, 2010 8:14 pm, edited 1 time in total.
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Doohickey Identified!

Postby HandKPhil » Fri Aug 20, 2010 8:12 pm

The round doohickey (on the air chamber) that I mentioned in the post above is called the EVAP Purge Control Valve
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Postby crazychile » Mon Aug 23, 2010 9:04 am

I had an intermittent gas drip a few months ago. Make sure it really is coming out of that tube, because I originally thought that also but it turned out my gas pump had a slow leak and needed to be replaced. It was dripping and hitting the bottom frame and then leaving a spot on the pavement near the drip tube.
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The leak has become a stream

Postby HandKPhil » Mon Aug 23, 2010 10:40 am

I took my Helix out yesterday and it drove fine for about ten minutes. Then I did a brief high-speed run, and when I stopped gas came pouring out of the overflow tube, and the engine stalled.

It's starting to seem like the fuel pump is periodically going nuts and over-pressurizing the fuel system, to the point where the volume of gas coming into the floatbowl is so much that it's getting past the float needle and pouring out the overflow.

It runs fine one day, and the next day it does this. I read somewhere once that there was a timer on the fuel pump that controlled how long the pump came on at start-up. If I remember correctly, this allowed the pump to "pressure up" the fuel system for a few seconds. Could it be that the timer is malfunctioning, and/or coming on intermittantly? What sort of electronic doo-dad controls this timer?

I'm at a loss what to try next. Do I replace the fuel pump? Anyone have any ideas?
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Postby Cruiser » Mon Aug 23, 2010 4:44 pm

I fought something simular to this all last summer. It turned out that the main culpret was a sticking Piston Slide in the carb.
http://cgi.ebay.com/ebaymotors/Honda-CN ... leQ5fParts
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Problem persists

Postby HandKPhil » Fri Aug 27, 2010 2:25 pm

Funny you should post something from that seller. I just bought a new carb from that guy, thinking that my fuel leak problem was probably a bad float needle/seat. It wasn't, because the new carb worked perfectly for a couple of rides, then gas started pouring out of the carb overflow again, ten minutes into the next ride.

In other words, I replaced the carb after this fuel-leaking problem increased in frequency, thinking the problem must be carb-related. Apparently the problem is somewhere other than the carb.

Anyone else had this problem, or do I have the one-in-a-million Helix that sprays gas out of the overflow tube on every third ride?
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