Garbage in Float Bowl

[El Camexican]

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

[Scootertrash]

I've pulled many fuel tanks off of wheelers, sleds, and various small engine type applications such as mowers, weed whips, tillers, etc, and they all have some amount of crap in the tank as well as the carb bowl. Lots of time I find water also, probably condensation from half empty tanks sitting for a period of time. In smaller engines like chainsaws and concrete or cut off saws I've found crap in between the diaphrams and between the various layers of the carb (If you've had one apart you know what I mean, can't find the proper terminology right now :P).

My theory is dust, dirt, etc, falling off of dusty, dirty fuel containers. Fuel cans riding around in the back of trucks and trailers, stored on shelves in sheds, garages and barns not being used for weeks or months, all the while collecting dust and dirt, not to mention years of using the cans but never cleaning the top of the gas can before pouring in fuel. Also leaving gas cans in close proximity to where you rider or are working collect dust and debris. I've started blowing off the tops of my gas cans with the air hose before I fuel up. I don't know if it helps, but I'm sure it can't hurt.

[Scootertrash]

Sorry, but you can not access barnett468's profile

This user was banned from the site, and the profile related to it is blocked by the administration.

The reason given for the banning is: Tedium beyond medium

[El Camexican]

Yea I like it too. That's a copy paste from a Mustang site he was banned from. You should see some of the stuff he's posted in other places. It's the same as it is here. A couple people find him helpful and the rest think he's a dick. Then someone who knows more about something posts and a pissing match starts. The only real difference is that he gets permanently banned on all the other sites, but I figure that's coming here pretty soon. In fact after yesterday's warning I decided to buy a bottle of champagne and put it in the fridge.

[El Camexican]

Ok, I get the part about crud in the fuel getting into the tank, but how does it get past two filters and into the carb? I'm wondering if trace contaminants could be entering as liquids and combining into small solids when left to sit for a while? Like scale in a water pipe.

[Scootertrash]

He got a warning yesterday? Link?

Yea, I don't get how it gets past the filters either. By 2 filters are you counting the one on the petcock too or would that be 3 filters?

I think some of the stuff is so fine it gets past the filters. I've found chunks of deteriorated rubber from old gas lines in the bowl, but I get how that gets there. I get your theory about the vent lines, but that seems like a long distance to travel without developing a good vacuum to pull it thru the vent hose and into the carb bowl.

[El Camexican]

He got a warning yesterday? Link?

http://www.3wheelerworld.com/showthr...ng-and-keyways

Yea, I don't get how it gets past the filters either. By 2 filters are you counting the one on the petcock too or would that be 3 filters?

I think some of the stuff is so fine it gets past the filters. I've found chunks of deteriorated rubber from old gas lines in the bowl, but I get how that gets there. I get your theory about the vent lines, but that seems like a long distance to travel without developing a good vacuum to pull it thru the vent hose and into the carb bowl.

Petcock and one inline. If those filters are that porous I may as well get rid of them. I was using a paper filter in a glass tube and it was struck by a rock on it's maiden voyage and broke open, fortunately I smelt the fuel early on and had a piece of hose that was long enough to replace it or I'd have had a 40 mile hike through the mountains in my MX boots After that I went to triangular plastic ones that use some sort of pumice looking filter. No room for a large plastic automotive type filter on a bike.

I think enough vacuum could be created in an air box while trailering at 70mph to draw air up through the vent lines. The dust that is kicked up off the tow vehicle is very fine. Like I mentioned earlier, I'm going to cover my vent hoses and see if it makes a difference.

I should have mentioned that I use a water impervious filter to fill my tanks when I'm at home, so that's like a third filter at times, but I don't have it when I'm fueling up on the ride.

[muthey]

I have a theory for you to ponder over with your thoughts Camexican. take into consideration that there are no filters on your breather hoses when riding and that the motor is not only creating a vacuum draw from the air box but also from the breather hoses on the carb as it is emptying fuel in the bowl. In essence yes they should be pushing pressure out as the float allows fuel in but could there not be a point where they are allowing air back into the carb bowl before the floats drop? if the bags over them when hauling doesn't change the amount of debris maybe putting aquarium air stones on the end of the breather hoses will work to prevent dirt entering in. I have noticed on my machines when the ground turns dusty here that they will collect a large amount of dirt around the breather hoses. Just an additional thought and with you fathers boat it could be as simple as the sand blowing in the wind off of the beach getting sucked in as I believe you said there is no air filter on the outboard.

[El Camexican]

Thanks Muthey, maybe I'll try wrapping a piece of pantyhose around the vent hoses and see what happens. As far as my dad's outboard is concerned, there is almost s no sand where he uses it, everything up there is granite. The box of his truck is the only place there is sand.

[86T3]

I'm going to agree with Muthey here. When I bought my klx the guy was showing me all the stuff he did to it, one of the things was to put little filters on the ends of the vents. He said dirt gets in there and makes its way to the valves and wears them faster. Idk if it's true or not but the motor seemed pretty tight

[Rob Canadian]

Just guessing. As it is a 2HP engine the tank is on the engine. Vent lines will get a bit of dirt from in the back of the truck etc. Maybe the engine is still warm and as it cools it is drawing vacuum into the vent hoses and drawing in a small bit of dirt/debris at a time(?)

Are you laying the engine on it's side during travails in the back of the truck?