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Old 12-06-2012, 05:28 PM   #1 (permalink)
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1985 SRV 540 issues

I have an 85 Yamaha SRV 540 and am having some issues.

First is the tail light. The tail light works but the brake light doesn't. Tried a new bulb. Installed new brake switch. Still nothing. I tested the wires right from the switch to the light and they seem fine.

Second is a starting issue. It seems to take 50 pulls to get the pig to start. It seems like there is no gas in the lines so it has to bring it all the way up from the tank. I out brand new lines throughout. Used scissor clips and zip ties. My thoughts were air was getting into a connection and allowing the fuel to drain out of the lines back to the tank, but im not sure.

Any help would be much appreciated.

Thanks everyone.
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Old 12-06-2012, 06:04 PM   #2 (permalink)
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Did you go threw the fuel pump? Is the polse line full of fuel? Is it getting too much oil? Did you clean the carbs?
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Old 12-06-2012, 07:21 PM   #3 (permalink)
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for the tail light, theres 2 connections under the seat, one at the front of the seat and one where the light assembly connects to the rear of the seat. i would check for continuity between these connections. due to the age and the fact that your seat has a plywood base, not uncommon for the wires to rot out along with the wood, or even one of the connections to fail.

as for the hard start, assuming you are watching the fuel supply lines flow air bubbles, i would check the vent lines for the tank. whens the last time the filter in the fuel was replaced?

dont rule out the needle and seat in the carb as well as the choke plunger adjustment and o-rings.

kc mentioned fuel pump and pulse line, pay attention there as well. if your watching the line fill with fuel, in theory the pump is doing its job. question is where is it bleeding at?
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Old 12-07-2012, 09:46 PM   #4 (permalink)
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Did you go threw the fuel pump? Is the polse line full of fuel? Is it getting too much oil? Did you clean the carbs?
Yes I went through the fuel pump. There is no gas in the pulse line or the delivery line to the Carb. When I start pulling the ropefuel starts to come out into the delivery line. The cCarb has been cleaned twice now.

What exactle does the pulse line do? My book shows it but doesn't say what it does.
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Old 12-07-2012, 10:02 PM   #5 (permalink)
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for the tail light, theres 2 connections under the seat, one at the front of the seat and one where the light assembly connects to the rear of the seat. i would check for continuity between these connections. due to the age and the fact that your seat has a plywood base, not uncommon for the wires to rot out along with the wood, or even one of the connections to fail.

as for the hard start, assuming you are watching the fuel supply lines flow air bubbles, i would check the vent lines for the tank. whens the last time the filter in the fuel was replaced?

dont rule out the needle and seat in the carb as well as the choke plunger adjustment and o-rings.

kc mentioned fuel pump and pulse line, pay attention there as well. if your watching the line fill with fuel, in theory the pump is doing its job. question is where is it bleeding at?
I checked both the connections under the seat. There is continuity from the connection right at the tail light all the way up to the switch.

All of the fuel lines have been replaced and have scissor clips and zip ties to hold them tight, including the vent line. The filter in the tank has not been replaced yet. I can understand how that could possibly restrict flow but I don't understand why that would allow fuel to drain out of the lines. When I pull the cord I see fuel coming out of the pump into the line so I'm assuming the pump is working. What does the pulse line do exactly? Every connection from tank to Carb are tight so I don't understand how the lines can drain back to the tank. Once I get it started it runs fine but if i shut it off and let it sit a couple hours then all the fuel is gone from the lines again. All help is appreciated. Thanks everyone.
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Old 12-08-2012, 12:29 PM   #6 (permalink)
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The pulse line transfers the +/- pressure from the crank case to the fuel pump thereby making the diaphragm pump the fuel.
If that line is not tight or collapses, then you will not get full pressure at the pump.
This is why using the tygon line is not recommended, but reinforced automotive fuel line is and be sure that both ends are securely clamped.
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Old 12-08-2012, 09:04 PM   #7 (permalink)
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somewhere in your fuel supply system you have a syphoning effect happening. could be the filter, could be the main fuel line attached to the filter, could be the rubber cap atop the fuel tank, something in a vent line, or a small leak in any of the hose connections.

take a straw in a soda pop for instance. if you suck through the straw the fluid flows. if you suck then plug the straw, the fluid shouldnt back flow until it gets some air. if your engine is an air pump and it creates a vacuum via the pulse hose, the draw should remain for at least a day or so, depending on how tight everything is. somewhere theres a leak or a reverse suction allowing the fuel to drain off.

back to you brake light issue, does the oil light come on when you pull the brake lever? it should. this will lead you to either the oil tank switch or the handlebar switch.
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Old 12-10-2012, 10:14 AM   #8 (permalink)
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somewhere in your fuel supply system you have a syphoning effect happening. could be the filter, could be the main fuel line attached to the filter, could be the rubber cap atop the fuel tank, something in a vent line, or a small leak in any of the hose connections.

take a straw in a soda pop for instance. if you suck through the straw the fluid flows. if you suck then plug the straw, the fluid shouldnt back flow until it gets some air. if your engine is an air pump and it creates a vacuum via the pulse hose, the draw should remain for at least a day or so, depending on how tight everything is. somewhere theres a leak or a reverse suction allowing the fuel to drain off.

back to you brake light issue, does the oil light come on when you pull the brake lever? it should. this will lead you to either the oil tank switch or the handlebar switch.
I checked the pulse line and there was a crack in it. Replaced it with new line and seems to start up no problem. Now there is an issue with it not moving. It starts fine and idles fine but when I push the throttle all the way down it moves at about 3 MPH. I can walk beside it as it's moving. It's not revving up like it should be. Was working fine before I swapped the pulse line. Any ideas on that? Throttle cable is tight on carb, carb has been cleaned twice and jets are clear (thinking of doing it one more time). I'm no mechanic but like teaching myself and I'm completely out of ideas. Thinking of selling it as is or taking to a mechanic and breaking the C clamp off the wallet. Would like to get it going myself as it still is a good sled.

Thanks everyone.
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Old 12-10-2012, 11:26 AM   #9 (permalink)
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Might have a fouled plug.
Check that!
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Old 12-10-2012, 12:37 PM   #10 (permalink)
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Might have a fouled plug.
Check that!
I guess I had one of those DUH moments. I never even thought of that. But when friends have issues with their sleds that's the first thing I tell them to check. Thanks RJ Gleason. I will check that out this weekend if I get out there and post back.
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Old 12-11-2012, 01:37 PM   #11 (permalink)
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Check your TORS wires as well. If they arent hooked up properly or bypassed it wont allow the engine to rev over 3000 rpms.
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