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Carbs flooding. Does this make sense?
- Mellvis
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The carbs were still nice and clean inside. We have a major fuel leak where the fuel valve mounts to the tank. I assume that when the tank was filled up that the rubber seal (being 36 years old) finally gave way. I can't really see what the exact cause of the problem is, but my far-fetched theory is that when the seal started leaking it was flowing right into the #1 and #2 air filters, causing them to flood out. When the choke (which is actually an "enrichner" causing MORE fuel to go into the cylinder) was applied cylinders #3 and #4 were able to run. At high RPM #1 and #2 could burn the excess fuel. Sound reasonable?
The bike is getting strong spark, the plugs were fresh (Fuel fouled after this mess) and all four are firing. Anyone have any other thoughts?
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- Old Rider
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Old Dogs never Die.
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- LineArtist
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Good analysis!
'79 KZ650B3 (stock)
'79 KZ650B3 (parts bike)
'06 HD 883R
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- bountyhunter
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After doing that, install good inline filters. As long as there is any crud in the tank, it will flow downhill and cause all kinds of problems. Carb flooding is often caused when a piece of crud gets under the needle valve and it can't close.
1979 KZ-750 Twin
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- Mellvis
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LineArtist, The fuel valve leaks a steady drip right onto the #1 filter/pod. I think filling the tank and extra pressure of about 4 gallons of gas on the seal (if that makes a difference) caused the leak as I had the bike for over a weak with no leaks at all. Lets say it sat leaking for about five minutes right on the filter and then was started to ride away. That filter is now fuel soaked and sucking fuel right down the throat of the #1 carb. Once moving and still leaking, where all is that fuel getting to? Plugs #1 and $2 were SOAKED by the time I got there and he had gone less than 3 miles.
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- Mellvis
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bountyhunter wrote: Was the tank and petcock assembly thoroughly cleaned? Petcock removed and cleaned? Tank cleared of rust and sediment?
After doing that, install good inline filters. As long as there is any crud in the tank, it will flow downhill and cause all kinds of problems. Carb flooding is often caused when a piece of crud gets under the needle valve and it can't close.
I made the mistake of trusting the owner when he said the tank and petcock were spotless. It has a new filter inline that had no signs of sediment that I could detect. I am personally going to rebuild the valve and replace all lines and filter. As I said, the carbs remained spotless after a complete disassemble and scrub. The needles and seats look great and don't even show a wear ring on the needles. I payed real close attention when taking them apart this time to check for debris, as I DON'T want a repeat of sending it away to have it come right back!
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- LineArtist
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'79 KZ650B3 (stock)
'79 KZ650B3 (parts bike)
'06 HD 883R
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- Mellvis
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- Mellvis
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- 650ed
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1977 KZ650-C1 Original Owner - Stock (with additional invisible FIAMM horn)
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- Mellvis
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- 650ed
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1977 KZ650-C1 Original Owner - Stock (with additional invisible FIAMM horn)
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