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Old 07-04-2008, 12:36 AM   #1
drfong
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Default 83 500 virago won't start

Hi all, I'm new here. I hope I have problem some of you can help me with. I have a 83 Yamaha Virago 500 that I just picked up and it won't run. The starter clutch was bad and it had been sitting. The guy I got it from said it ran until the starter clutch went out, but I have no way to know for sure. I replaced the starter clutch. When I put the flywheel back on I checked to make sure the cotter key was in place and everything lined up. I then pulled the carbs to clean and they really did not look too bad, but are now well cleaned. The bike still would not run. It really does not sound like it is trying to start. I replaced the spark plugs and set the gap to spec. The spark does not look real strong, but I would think it would be enough to run. I removed the coils and checked them with a coil tester, they were fine. I also used a spark checker inline with the plug installed and when turning the motor over I do get a spark that jumps the tester gap of about 3/8th inch. I did a compression test, and even cold the compression is good. When trying to start it does absolutely nothing except an occasional backfire. I tried reversing the coils to make sure they were not wrong and no luck. I pulled the cam gear covers off each side and turned the crank with a wrench to see if the cam timing was off. With the flywheel on the 1st cylinder TDC mark the dot on the cam gear is straight up (in relation to the cylinder) and when I turn the flywheel to the other cylinder TDC mark, the cam gear dot is straight up on the front cylinder. There is no mark for the dot to line up with, but I assume that 12:00 is correct. It won't even try to start with some starting fluid; it just turns over until it backfires. Any ideas of where to look would be appreciated. I also have a few more questions and hope someone might have some insight. I was wondering why this bike even needs a fuel pump with the tank located above the carbs. Also there is the fuel line that goes out of the petcock to the pump. Then from the pump to the carbs and then from the carbs back to the petcock. I am not talking about the vacuum line for the petcock. Is the extra line a return bypass? Can you run this bike without the fuel tank with an aux tank on a stand? Maybe run a fuel line from the carbs that would go back to the petcock to a fuel can to catch any extra fuel. I have emptied and replaced with fresh fuel in the tank and I know I am getting fuel to the carbs because I can open the drain screw and fuel runs out. I also took the fuel pump apart and cleaned/checked it. There are no rips or cuts in the membrane material. Also, it will not start on starter fluid either. Doesn't even act like it is trying to start until it backfires or after fires when you crank it for 5 seconds or so continually. It also spins over well, doesn't seem to drag or anything.
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Old 07-04-2008, 11:32 AM   #2
LowRiderGhost
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Sounds to me like you definitely know you're stuff already so I can only go by the things you haven't already written. Have you done a Compression Test on it already? Obviously you won't get a totally accurate reading on a stone cold engine but least confirm you at least got a motor that's even capable of making any?! Of course you know already about the Oil Squirt test: If the readings go up after a squirt of oil, you've got shot rings. If no difference, odds are good valve problems. Sorry, I am just a suspicious old grouch and I wouldn't take NO previous owner's 'word for it' (or anything else for that matter!) that it was running just fine before the Starter problems.

All I can add is I agree, I can’t either see any reason for a Fuel Pump (Electric or Mechanical) being present unless the assumed Fuel Tank is really a dummy (and the real tank is beneath the seat, like say Gold-Wings) or except for Electronic Fuel Injection (to feed the Injectors). My Victory has such a set-up, and in fact has a Return Fuel Line to the Fuel Tank. The bike has a huge Electric Fuel Pump which I’m guessing just runs at full bore the moment the Ignition switch is turned on, and just feeds away to the Throttle-Body / Throat Mounted Injectors, excess fuel pressure being re-routed back to the tank.

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Old 07-04-2008, 01:02 PM   #3
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Thanks, compression is good, about 150 per cylinder stone cold.
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Old 07-04-2008, 09:43 PM   #4
Dan631
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You've got good compression, spark, fuel and I'm assuming the air filter is clean. What's left???? I would get a service manual for the bike and re-check the timing.
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Old 07-05-2008, 10:20 PM   #5
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It certainly seems like a timing issue, but the yamaha service manual is vague. It shows checking it running with a timming light, I do not know if it would check right just turning it over without starting. Also it says that if it is not correct to see chapter 6 (electrical) yet there is no mention about timing and setting it. I have not had time to remove the side cover again to see if there is any adjustment in the mounting of the pickup coils. That's the only thing I could think could adjust the timing. The flywheel is fixed with a cotter key, so there is no adjusting that. The manual also gives no clear direction about how the cams should be timed. It really is not real helpful, like most of Yamaha's manuals. I gues I should look for a copy of a clymer and maybe it has better instructions.
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Old 07-06-2008, 01:13 AM   #6
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I tend to concur with a timing issue. Is there anything that might have been installed 180 degrees off? Uhhh...well...let's just say I been there and done that...once to twiced before. Ignition wires on right plugs?
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Old 07-30-2008, 10:44 PM   #7
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Here's a first for me. I read somewhere in a different thread, maybe a different forum, that resistor plugs may keep on older bike from running. I did not even know what was in it. I bought new plugs from advanced auto, just asked for the plugs for the bike. The guy sold me what he said were the right plugs. I didn't check with manual for the correct plug number. The bike calls for bp7es. (non-resistor). I checked today and they had infact sold me resistor plugs. BPR7ES. Funny thing is I called and asked for plugs for the same bike but didn't say anything about their last mix up. The girl told me the correct part number and sold me the correct plugs. I can only guess that they were out of the right plug last time and so he sold me the others without telling me they were not what was called for. Either that or he just didn't read the boxes right, close enough I guess.

Anyway, I put in the new plugs and got great spark and now it starts. The bike won't stay running and it's in the carbs. I cleaned them but it seems the float level is extreemly low. Based on how the manual describes how to check them, they were atleast 1/2 inch low. I pulled the carbs again and set both floats on the bench. I'll see tomorrow if I got it right. It should atleast be close enough for the bike to run now.

Whoever mentioned the resistor plugs somewhere, thanks. I would never had thought to check that.
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