Slightly off-topic question on cleaning fuel system

[Andy FitzGibbon]

Not a K specific question, but I figure enough of us have experience cleaning K fuel systems that there may be some good information to be had.

I just bought a 1993 R100GS Paris-Dakar that, like many K bikes, has been sitting and needs the fuel system flushed. The tank on the Paris-Dakar models is some sort of fiberglass. Any experience/advice on what would be best to clean the tank out? On a metal tank, I'd use acetone, but on a glass tank that doesn't seem like a great idea.

Thanks,
Andy

[The Mighty Gryphon]

As a general rule, I start with something gentle and up the ante in stages until I get the desired results.  The safest thing I can think of for a fiberglass tank would be Dawn dish detergent.  Fill the tank with Dawn and water and let it soak for at least 3-4 days followed by a gentle scrub with a ScotchBrite pad. 

Beyond that, you can try ammonia or white vinegar.  You are wise to avoid organic solvents, compatibility with plastic materials can be pretty tricky.

Once the tank is clean and you're running the bike be very careful to avoid leaving that corn crap in the tank for more than a couple weeks.  If you are running the bike regularly and using a fair bit of fuel there should be no problem with ethanol in the fuel, but if you lay up the bike for the winter or long periods it's good practice to run a couple tanks of corn-free gas through the system followed by a full tank of no-corn mixed with a fuel stabilizer like Sta-Bil.

Your tank was made before the government made ethanol mandatory.  That crap is lethal to fiberglass tanks.  It dissolves some of the compounds in the resin and deposits them down stream where they clog carburetors and injectors and jam parts like rings and valves destroying the engine.  I have seen boats that were ruined when the fuel tanks were turned to a sticky goo by ethanol.  Imagine having an entire tank being dissolved like the fuel pump vibration dampers in K bike tanks.

[Skunky]

+ 1 on the vinegar (Cheap as chips too) 

[Gibson]

It is a good idea to find out for sure what the tank is made out of. Poly pro is fine with Gasohol, but fiberglass is made with polyester or epoxy resins. These are not ok with ethanol. They will turn to goo and as mentioned above, the glass will destroy your engine and carbs. 

[Andy FitzGibbon]

Thanks for the replies. The tank appears to be some variety of fiber/resin layup, but I haven't been able to find specs on the exact materials.

Think I may try blasting it out with a car wash pressure wand (off the bike)... it has a more traditional screw cap, instead of the flip-lid of the K bikes, so there's no hand access to the inside for scrubbing.

I fill and run all the bikes with non-ethanol/Stabil mix before winter storage, but this one may end up getting pure gas all the time (at least, where I'm able to find it) just so that I don't have to worry about any future deterioration.

Andy

[Laitch]

The tank appears to be some variety of fiber/resin layup, but I haven't been able to find specs on the exact materials.

What makes it appear that way?

Here's some interesting reading.

[Andy FitzGibbon]

What makes it appear that way?

Here's some interesting reading.

Visible fabric/plies in the interior of the tank, and the fact that it's too inflexible to be nylon or poly.

Andy

[Gibson]

I think there are some tank sealers available that are ethanol resistant. Better if you can get gas without though. Where I am its all 10%. When I was in Pennsylvania, I came across a gas station that had pure gasoline without ethyl. Virtually all fiberglass tanks are either Polyester resin(more common) or Epoxy. Both will dissolve in time. It may be best look into having it sealed.

[Andy FitzGibbon]

When riding locally, I usually fill the bikes from the pure gas pump at the distributor here in town, or from the two 5 gallon cans (of the same fuel) that I keep in my garage... helps keep the lawn mower fuel from sitting around and going stale. On the road, I usually don't take the time to seek out pure gas, but in that situation I'm burning through it fairly quickly and there's no time for the ethanol to sit in the system and cause trouble.

Haven't had time to tear into this Paris-Dakar yet... hoping to get the tank pulled off and flushed out this week.

Andy