Thread: Fuel system rebuild
05-06-2008, 09:47 PM #1
Fuel system rebuild
I've decided to do a complete tune-up including rebuilding/renewing the fuel system on the wife's SLT 780. It runs great when it's warmed up, but it seems to take longer and longer to warm up each time we go out. The machine only has 140+/- hours on it. Compression is 140, 139, 140. And it's getting good spark, so I figure there's junk in the fuel system. I'm building up the courage to take on the carbs, so I decided to start with the fuel lines and fuel pump. I found some kind of green growth in the lines and replaced all of them with standard 1/4" fuel line from Advance Auto. The fuel valve seems to be clean and works fine. When I took apart the fuel pump, I found gas mix behind one of the diaphragms and was thinking that this might be causing some of the hard starting and rough idle.
05-06-2008, 09:58 PM #2
I also changed out the plugs and cut about 1/4" off the end of each plug wire. The plugs were dark brown, telling me it's running rich, but from what I can see, (after reading the article about piston wash that CrazyA pointed out to me), the pistons look dark in the center with light, sort of shiny spots on the edges. It's tough to see in there with a flashlight. my next move will be to remove/inspect the fuel pick-up, however, from what I've seen in diagrams, there isn't much to it. I keep reading about gas-logged floats, but I don't see a float in the pics. Her MFD does, however, show 'FUEL' alot. Even with a full tank. I don't think the rev limiter is causing problems, though, because even when it says 'FUEL', she still runs at about 6400 r's.
05-06-2008, 10:34 PM #3
- Join Date
- Oct 2006
- Cleveland OH
2 strokes don't read the same as 4 strokers. Dark brown would be a lean condition. A clean or very light brown plug would be considered rich. Get a good look at piston crown as plugs tend to lie IMO.
The float is most likely gas logged. Randy at Watcon.com sells replacements for around $20. Not sure why the limp mode isn't working. Maybe that year didn't have it, or someone removed the grey or tan wire to bypass limp mode?
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