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Old 12-11-2008, 06:04 PM
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eDJ eDJ is offline
Motorized Bicycle Elite Member
Join Date: Jul 2008
Location: Wayne National Forest
Posts: 531
Default Re: my first build is broke down

Just curious here jimmybking ? How long has the bike sit with the same fuel in it ? I see this happen with outboard motors all the time at seasons end when people pull them out of the water and not run the engine out of fuel. Next spring they go to the water with a fresh tank of fuel/oil mix and have the problem you're having now.

What's happened to them is the varnish built up thru the winter and plugged up the carb and if anything is sticking the float and plugging the jets giving a lean mix which leads to backfire. And most outboards use a 50:1 mix ratio and that's enough to stick them. These bikes use a 20:1 ratio and if the gasoline evaporates out of it in the float bowl the residue will probably look like molasses.

Now that's just my guess.

Down the river from me is the old Ashland Oil Refinery now called the Cattletsburg Refinery where a friend of mine works. He tells me they change the formulation of the gasoline as much as 22 times a year. That's to compensate for climate and temperature changes thru the year. Products like "Sta-bil" are around to add to the fuel if a vehicle is to sit for long periods of time without being started. Varnishes build up quick in fuel tanks and the crud will flake off and get trapped in the sediment bowl of the petcock or fuel filter and ultimately wind up in the carb float bowl where it will likely get sucked into the main jet. Then the lean mix will cause sputters and backfiring.

If your fuel smells of old varnish...pitch it....clean the tank out with a little MEK (Methyl Ethyl Keytone) You can get it at Lowes, and use it outdoors....then flush the tank with some new gas and pitch it too. Then the tank should be good to go again. As far as the petcock, fuel line, & carb.......just spraying them clean with spary start (ether)
outdoors again can clean them up nicely. Make sure everything is open and flowing with the jets and then put it back together. It may solve the problem. Leaving the stuff sitting around is a kiss of death.

Last edited by eDJ; 12-11-2008 at 06:14 PM.
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