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Discussion Starter #1
Hey guys I finally got around to getting my vulcan running that I bought in March, but have an issue. The bike starts and idles good, but taking it for a ride I found it was low on power. Now I'm coming from a 07 gsrx600 so I'm used to something quick, but thats not it, I'd be surprised if I could get the bike up to 70mph right now. The other day I realized after running the bike for a couple minutes the rear cylinder's exhaust was barely a little warm so i grabbed the front exhaust and damn it was hot. I checked spark and have it at both plugs. Pulling the plugs showed me that I was getting fuel, they were cleanish but wet with fuel compared to the front plugs. I swapped both the rear plugs with the fronts, started it and still no change. I thought maybe I had a weak coil so I swapped it with the front... still no change. Then I got to thinking the worst and maybe compression, tested it and is right in check with the front cylinder. I am running out of ideas.

Another symptom I have that may or not be related is a "knocking" sound coming from the rear head. I tried the Gambo trick but it didnt change the sound or help the rear cylinder.

The bike has 16,000 miles on it and its an 88 if this makes a difference, also when I put the new carbs on I also de-eared and rejetted. When I removed the airbox and installed the coasters, one bolt broke off in the head on the rear... right now I just have one bolt holding on the rear coaster and it is not sealing completely, could this cause a problem? My understanding is that it pushes air out of the head and into the exhaust through the valve which I removed, so I am thinking that it is not that urgent right now to drill and tap.

Sorry for the long post I am just running out of ideas, the only other thing I can think of is a rocker maybe popped off the intake but it doesn't look like the valve cover wants to come off with the motor in the frame :mad: Anyway any help is appreciated thanks :beerchug:
 

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Check for spark on the rear plugs. If you don't have spark make sure the back coil is getting power. If you do have spark it must be a fuel problem, likely too much. Make sure the enrichment valve "choke" isn't suck open. If a rocker was off the intake valve I wouldn't expect wet plugs.
I'm also very new to motorcycle maintenance so anything I said may be wrong. Hopefully one of the experts will chime in.
 

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Discussion Starter #3
Yea your probably right about the if the rocker was off the plugs wouldnt be so wet I didnt think about that. I do have spark in the rear for sure, I just thought maybe the coil was "weak" or something so thats why I tried to swap it. I also checked the choke and everything its moving as it should, at least on the outside of the carb
 

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Disconnect the vaccuum line on the rear carb. Plug the nipple with your finger. Has the niose stopped? Sometimes it is the air valve under the seat that makes a knocking noise.
 

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Discussion Starter #5
I have that vacuum line capped off since i deleted the airbox and reed valve, It seems like the rear cylinder isnt firing at all..
 

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Have you changed the ACCT to the MCCT, if not I wonder if the chain slipped making the timing off ? I'm new to this too with a 96 and have been reading alot about the chain tensioners.
 

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Discussion Starter #8
Spray some carb cleaner into that capped openning and see if you get a hit off the cylinder.
Ok I'll try that out


Have you changed the ACCT to the MCCT, if not I wonder if the chain slipped making the timing off ? I'm new to this too with a 96 and have been reading alot about the chain tensioners.
I was thinking that but if the chain slipped my compression should be showing it
 

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In the OP you said "new carbs". You think maybe the rear carb might have a sticking float? You might drain both carbs into identical containers and compare the amount of fuel, or since the ears are gone just see if you smell gas in the rear air filter. When I got my bike it had a stuck float along with black plugs in the back and the identical pathetic performance you describe. One you get the other half of your engine running you will be amazed at how peppy it is.
 

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I had similar problems with mine and after cleaning and di-electric greasing all the connections and installing iridium plugs the problem was solved.
 

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Discussion Starter #11
Ok so I took niterider's advice and sprayed some carb cleaner into the rear carb and sure enough it fired up, man do I feel stupid. I guess now I'll start in the front and work my way back to check for fuel starting at the petcock. Is there anything obvious I can check on the carbs with them still on the bike or am I pretty much looking at pulling them if I don't luck out with the petcock? (not very knowledgeable with carbs)
 

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Discussion Starter #12
Ok it turns out I have no fuel coming from the petcock to the rear carb :doh:

I have two petcocks, the one on the bike I believe is an older version, it says prime/on/reserve. The nipple going to the rear carb doesnt look the same as the nipple that goes to the front carb maybe this is my problem.

Anyways I have a spare petcock however the it flows fuel no matter if there is vacuum to it or not. For now this should work and not flood or anything correct? I'm a big of a dummy with carbs but my understanding is that nothing negative will happen unless my float is stuck then it could flood the cylinder and out the air intake .
 

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newer petcock has on, off, reserve.
I am assuming the "off" still stops fuel flow.

theoretically it should stop fuel flow as long as the floats are working properly. you could just turn it "off" if the cards flood out due to bad seals in the float needle.
 

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Discussion Starter #14
Awesome just swapped it over and all is good! Thanks a lot for the help guys. Im gunna go take it back to work now and see how its supposed to ride :beerchug:
 

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Good to hear it is working. You can probably salvage the other petcock by taking it apart. There is a circular rubber gasket that perhaps has failed or whatnot. You can buy a new one or trace out a new one from an inner tire tube with a razor.
 

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glad it worked out!

I would keep an eye on the oil level just in case the carb does have a bad float and dumps fuel into the case. just get into the habit of turning it to the "OFF" position if the fuel flows even without vacuum to the petcock.
 

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Discussion Starter #17
Yea its a completely different bike now thats for sure... now I just have to tackle changing the tires and I'll actually feel safe on the road with her haha
 

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Glad to hear you got it working! My only lingering question is why were the back plugs wet if they weren't getting fuel?
 

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Discussion Starter #19
I honestly have no idea, I'll be keeping an eye on the coolant level for the next couple of weeks though..
 

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I honestly have no idea, I'll be keeping an eye on the coolant level for the next couple of weeks though..
coolant level?? You mean engine oil level...right?:smiley_th
 
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