El Camexican
01-29-2017, 01:38 AM
Seems every time I drop my float bowls to change a jet I find a fair bit of crud in them, sometimes after just one ride and I can’t understand how it’s getting in there when I have two filters on most of my bikes. I haven’t messed with automotive carbs for ages, but I don’t ever recall seeing the amount of crud my bikes have in them and that’s with a heck of a lot less mileage between bowl drops. Then something happened while fishing with my Dad this past summer that got me thinking about what might be happening…
His normally flawless 2hp Honda outboard was starting poorly and leaking fuel when we were portaging in. When we got to the cabin it stopped working completely, so I pulled the bowl and it was loaded with sand. When I say loaded I mean over half a teaspoon of very find sand and most of it was fairly compacted in the bowl. The motor has never been swamped, so how did all that sand get into the bowl??? I cleaned it up and it ran like a clock. When we got back to town he took it in for a full service and it’s been fine since the few times he’s used it.
My theory at the time was that because the outboard doesn’t use an air filter and my Dads truck bed usually has a bunch of dirt in it that while lying in the bed of the truck going down the highway the air currents ended up drawing air through the carburetor throat and this pulled dusty air in to the carburetor through the overflow vent.
It likely took years for the sand to build up in the bowl enough to start plugging the jets and needle, but little by little it did. He always runs the carb dry before he docks, so there’s no fluid in the bowl to prevent the air from flowing through. Having seen that I’m wondering if that’s not why my bikes bowls are getting so much crud in them? I always shut my fuel off when I trailer something and plug the exhaust pipe. I also try to leave the piston near the top of the cylinder, so that the valves are closed, or the exhaust port is covered to prevent air from being drawn into the engine, or pipe.
So with all that done I think what's happening is that after a few bumps on the road the fuel level drops due to leakage out of the overflow tube lowering the level in the bowl to the point that air currents around the air box can start to suck unfiltered air up through the vent hoses and into the bowl where small bits of dirt that were swirling around in the trailer then drop. The rest of the air then gets sucked up through whatever orifices are open and out the air filer the wrong way.
Thoughts? Comments? Does this make sense? Is it happening to anyone else? I think I’m going to start putting a plastic bag around my vent hoses with a rubber band when I trailer and see it the amount of crud in my bowls drops
His normally flawless 2hp Honda outboard was starting poorly and leaking fuel when we were portaging in. When we got to the cabin it stopped working completely, so I pulled the bowl and it was loaded with sand. When I say loaded I mean over half a teaspoon of very find sand and most of it was fairly compacted in the bowl. The motor has never been swamped, so how did all that sand get into the bowl??? I cleaned it up and it ran like a clock. When we got back to town he took it in for a full service and it’s been fine since the few times he’s used it.
My theory at the time was that because the outboard doesn’t use an air filter and my Dads truck bed usually has a bunch of dirt in it that while lying in the bed of the truck going down the highway the air currents ended up drawing air through the carburetor throat and this pulled dusty air in to the carburetor through the overflow vent.
It likely took years for the sand to build up in the bowl enough to start plugging the jets and needle, but little by little it did. He always runs the carb dry before he docks, so there’s no fluid in the bowl to prevent the air from flowing through. Having seen that I’m wondering if that’s not why my bikes bowls are getting so much crud in them? I always shut my fuel off when I trailer something and plug the exhaust pipe. I also try to leave the piston near the top of the cylinder, so that the valves are closed, or the exhaust port is covered to prevent air from being drawn into the engine, or pipe.
So with all that done I think what's happening is that after a few bumps on the road the fuel level drops due to leakage out of the overflow tube lowering the level in the bowl to the point that air currents around the air box can start to suck unfiltered air up through the vent hoses and into the bowl where small bits of dirt that were swirling around in the trailer then drop. The rest of the air then gets sucked up through whatever orifices are open and out the air filer the wrong way.
Thoughts? Comments? Does this make sense? Is it happening to anyone else? I think I’m going to start putting a plastic bag around my vent hoses with a rubber band when I trailer and see it the amount of crud in my bowls drops