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Discussion Starter #1
After taking a 40mph lowside about a month ago, my '00 SV is dumping fuel through the carbs straight into the engine. While the bike was inoperable after the crash I had it in the back of my pickup while waiting for parts. After sitting for two daysafter repairing all the crash damage the cylinders are completely full and the engine won't crank. I took the carbs out and checked the floats to see if they were cracked, they seem fine. Drained the oil and changed the filter and pulled the spark plugs to clear the engine. Now I'm about to do it again. Any suggestions? Where is the fuel pump and how does it work? I'm familiar with diaphragm style Mikuni fuel pumps and checked that too, but couldn't see anything wrong internally. Is there some sort of vacuum line clogged in the tank or something that's pressurizing the fuel system? Any ideas? Thanks.
 
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Discussion Starter #2
The 1G bike has a vacuum powered fuel pump mounted on the RH side just below the rear of the tank. The vaccuum operated fuel valve is mounted directly across from that, on the LH side attached to the tank (naturally). Pull the fuel line off the valve and see if there's flow with the engine off. Inspection of the fuel valve is similar to the vacuum powered fuel pumps you mentioned.

Sounds like a good starting place...

:)
 
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Only the front cylinder was full so I suppose fuel pump checks out okay. When I pulled the fuel line from the fuel pump to the carbs no gas came out, so if it operates under vacuum only it checks out. I pulled the carbs off and started poking around. Took the float out again and didn't see any cracks. Possibly a small pinhole so I'll see if it floats in a can of gas. I took the float needle and seat out and found a few small flecks of crud inside. Can't see much else wrong. The smal filter element on the end of the seat looks fine with nothing in it though. Possibly the O ring around the float needle seat leaking? Man I hate carburetion. Fuel injection from now on.
 
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Discussion Starter #4
I've never really looked all that closely at the fuel pump. It's there to help drain the bottom of the tank, but if there's no built in bypass it would function as a second fuel valve.

:)
 
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Discussion Starter #6
Excellent spark on the front cylinder. The float seems to be working fine, so I guess I'll just do a new float needle and seat and hope for the best. Maybe a new float too just for fun.
 

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When I pulled the fuel line from the fuel pump to the carbs no gas came out, so if it operates under vacuum only it checks out.
So if I pull the fuel line off the fuel pump and fuel comes out where is my problem? Is the fuel valve potentially bad?

I've discovered that I have gas leaking past the carbs into the cylinder and filling my crankcase with a gas/oil mix.
 

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So if I pull the fuel line off the fuel pump and fuel comes out where is my problem? Is the fuel valve potentially bad?

I've discovered that I have gas leaking past the carbs into the cylinder and filling my crankcase with a gas/oil mix.
It's the job of the float/needle/seat to stop the flow of fuel.

Problem can be a float that is heavy (leaking gas into the float or saturated float - depending on type), a worn or damaged needle, or a worn or damaged seat. Junk from a dirty tank can sometimes get stuck between the needle and seat, keeping the needle from seating and allowing fuel to flow.

That's the basics of it.


Jay
 
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