Fuel Line Maintenance

TextDuring a recent tranny maintenance I noticed that the fuel line had chaffed through about half its thickness where it emerges from under the airbox. Further inspection showed more chaffing under the airbox itself, with the marks corresponding to the ribs cast into the top of the tranny.

The line was from Bing Agency, some of their black alcohol proof stuff, installed after the MOA National in Oregon several years ago. I elected to replace it with a fresh line, also from Bing, but this time in clear (well, it's more of a transparent, uncooked egg white color) but I wanted to be able to see fuel flow so it's good enough. The old line was still flexible, hadn't split, and was not leaking at any of the fittings, and since the new line is made from the same alcohol proof plastic, I figured I'd get the durability of the old line and be able to see through it as well. To prevent, or at least slow down, the chaffing, I covered the portion of the fuel line under the airbox with two layers of electrical shrink tube. This not only provides some protection for the line, but also makes it a much tighter fit under the airbox, which may reduce vibration and hence the chaffing. It's too soon to tell if this strategy will work in the long run, but with a thousand miles on the new set up there are no problems. I also used a burr in a Dremel tool to radius the edges of the airbox and transmission housing where the fuel line emerges from the bike.

The Bing line isn't cheap (I think I paid about ten bucks, including shipping, for six feet of the stuff), but it's the right size and seems to last (at least in the absence of chaffing) for a long time.

When it came time to push the new line under the airbox (several trials were needed to get the length just right) I came up with the idea of using a chamfered bolt as a guide to help keep the end of the tube from catching on the tranny ribs and the inside edges of the airbox. Seemed to work just fine, even with the added thickness of the shrink tube making for a lot of resistance as the line went under the airbox.

While I was at it, I made up a couple of washers from some black Delrin I had laying around, and per Snowbum's suggestion slipped them over the barbs on the in line fuel filters before I installed the fuel lines. This makes removing the lines very easy, as the washers compress the line, causing it to open, as opposed to contracting the line when you try to pull them off (a bit like Chinese hand cuffs). Makes draining fuel for starting campfires at Airheads events and rescuing your buddies with stock R80G/S tanks very easy. And unlike a metal washer, there's no chance of a spark (however unlikely that event might seem) or abrading the fuel filter barb with the plastic washer.

As mentioned by others on the Airheads mailing list, I have seen bubbles coming up the fuel line from the portion under the airbox, particularly when the bike has been running a while and it gets parked. Probably happens all the time, but with black fuel lines you can't see it. I assume that's just fuel boiling from the transmission heat. So far I haven't noticed any problems with hydraulic lock, even though I run with only the left petcock open. Sure looks funny, though; sorta like those old style Christmas lights Uncle Dick used to have on his tree all those years ago...