mystery fuel leak

[rdp5008]

Hi guys, a little background. I'm at about 900 miles on the RX3 and loving it! I did the first oil change around 200 miles and then the valve adjustment at 500 miles. Cleaned and lubed the chain at 500 miles. About ready for another oil change.

Yesterday was the first time I have had the bike on a real highway with sustained speeds above 70 mph. I noticed a strong smell of fuel when I stopped and saw a few drips of fuel under the bike (confirmed by smelling). The fuel was pooling on the skid plate (upgraded version) and then dripping on the ground. There is no fuel drip when the bike is parked in my garage (that I can see) and I never noticed this issue when using the bike around town at speeds of 50 mph and under.

I was about 100 miles from home when I first noticed the issue and I pulled the gas tank in an auto parts store parking lot. I thought one of the connections to the tank came loose but the hoses seemed fine and the bottom of the tank was dry. I added some better hose clamps to the vent lines just to be safe.

So my question is where to begin troubleshooting? I think I will pull the gas tank again in the comfort of my own garage so I can inspect it more closely. Is it possible to have reconnected any of the fuel hoses incorrectly after my valve adjustment? I am unsure if this is due to something I did during maintenance or has always been there but only noticeable when traveling at high speed for long distances. Are there any common places for a fuel leak on these bikes?

[Working_ZS]

I would revisit the fuel filter quick connects, it is possible that they are not fully seated and locked. I've had this happen on cars that I have done fuel system work on and then started leaking. The connectors require more force than you realize to click the locks into place. Barring the fuel filter, check the routing of your fuel lines.

Another thing to consider is the OCS drain hose. That is the clear plastic tube that hangs down from the Oil Contaminant Separator with the black plastic plug. You are supposed to open and drain it every 100-150 miles. It contains a mixture of fuel and condensed water from out of the engine crankcase. The plug on yours may not be sealing, instead letting the fuel and water mixture leak out as you are riding the bike. The wind would then blow it back onto the skidplate. If you are not seeing an inch or two of condensate in your tube after a 100 mile ride, then yours is most likely leaking.

[BlackBike]

Originally Posted by Working_ZS

I would revisit the fuel filter quick connects, it is possible that they are not fully seated and locked. I've had this happen on cars that I have done fuel system work on and then started leaking. The connectors require more force than you realize to click the locks into place. Barring the fuel filter, check the routing of your fuel lines.

Another thing to consider is the OCS drain hose. That is the clear plastic tube that hangs down from the Oil Contaminant Separator with the black plastic plug. You are supposed to open and drain it every 100-150 miles. It contains a mixture of fuel and condensed water from out of the engine crankcase. The plug on yours may not be sealing, instead letting the fuel and water mixture leak out as you are riding the bike. The wind would then blow it back onto the skidplate. If you are not seeing an inch or two of condensate in your tube after a 100 mile ride, then yours is most likely leaking.

Excellent

[SpudRider]

Welcome, we are glad you joined us.

With only 900 miles on the odometer, I would reconsider running the NC250 engine at sustained speeds above 70 mph. Everyone is different, but I prefer to vary the engine rpms, and keep the rpms in the lower range for the first few thousands miles during engine breakin. I don't remember exactly; what does CSC recommend for running the engine during the breakin period?

[fjmartin]

Standard break in was to vary the throttle for the first 500 miles and keep the RPMs under 5000. Which for my bike was a max speed of 42mph.

[rdp5008]

Yes, I stayed under 5000 rpm for about 600 miles but that limited me to under 50 mph. It is my understanding that after the first 500 miles the engine can be revved to higher rpm. I was riding state highways so there were twists and hills and only a few stretches of straight highway so hopefully the RX3 can handle that.

On the fuel leak... I noticed my fuel filter was wedged in under the tank causing one of the connections to be at an odd angle and potentially causing strain at the connection and a leak at higher rpm. Also a few of the bolts holding the fuel pump into the bottom of the tank were loose so I tightened them a bit. And lastly the overflow tube was empty so I zip tied the plug to see if maybe it was the cause of the apparent leak. Also disconnected and reconnected all of the quick disconnects.

Thanks for the tips! Next ride is tomorrow morning.

[rdp5008]

I managed to sneak in a quick 30 minute ride tonight. After securing the OCS drain plug with a zip tie along with the standard clamp it started filling with liquid. The hose still leaked fluid that collected on the skid plate, but I'm pretty confident there are no fuel leaks anywhere on the bike. Thanks for that suggestion.

So is it normal for the OCS drain hose to be nearly 25% full after about 25-30 miles of riding? Based on the color and smell it seems that the fluid is mostly if not all gas. Is this normal as well? I can smell the fuel when I stop and inspect the bike.

[Working_ZS]

Originally Posted by rdp5008

So is it normal for the OCS drain hose to be nearly 25% full after about 25-30 miles of riding? Based on the color and smell it seems that the fluid is mostly if not all gas. Is this normal as well? I can smell the fuel when I stop and inspect the bike.

Yes, perfectly normal.

The bike runs very cool for the North American climate, so you get a lot of crankcase vapors condensing out of the OCS. Some RX3 owners have installed higher opening temperature rated thermostats to increase the operating temperature of the engine. Others use radiator blocks. I fall into the latter category. Currently, with riding temperatures in the 50-70 Deg F range I have the right radiator completely blocked off to airflow. In still lower riding temperatures, I block off half of the left radiator, too.

[rdp5008]

Great community here. Thanks for humoring my paranoia!

[dpl096]

The OCS issue is one in which you can spend hours reading about here and over at adventure riders. A lot of ideas on what, if anything, to do about it. A lot of knowledgeable folks at both web sites .....good people all around! Point being...I don't believe you are experiencing anything abnormal at this point.