Newbie Here, 83 CV80 running issue

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thiscarcrash1
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Newbie Here, 83 CV80 running issue

Post by thiscarcrash1 »

Hi All.
Picked up an 83 CV80 the other day.
Starts and idles fine with the key switch in the start position.
Will run fine for a while in the non-choke position, however, eventually bogs to a stall.

Yesterday I took out the carb and sprayed it down with carb cleaner, checked all the fuel lines and reinstalled. It started right up, and i drove it around the city for about an hour without issue.
This morning, I made it about 3 blocks before it bogged to a stall.
At that point, it will start right up, again at the 'Start' key position, but as soon as i turn the key to the run position it dies.

Any pointers?
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Re: Newbie Here, 83 CV80 running issue

Post by thiscarcrash1 »

Narrowed this down to the fuel petcock, as it will idle smoothly and without issue forever, but when under throttle it occasionally acts as if its not getting fuel.
This would point to the vacuum mechanism not functioning reliably, yes?

Will any vacuum operated petcock work as a replacement?
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Re: Newbie Here, 83 CV80 running issue

Post by Dan Durston »

My understanding of the CV80 is that the start position the same as the run position on the ignition except in the start position the redline is about 2000 RPM so you can't rev high enough to actually go anywhere - supposedly a safety mechanism. Moving the switch to run raises the redline to normal (8000 or so).

So I don't think the ignition position has anything to do with the carb choke. The choke is an auto-choke that shuts off once the engine gets hot enough, regardless of ignition position.


I wonder if it's a main jet or carb needle problem that is adversely affecting your air/fuel mix under throttle.

Was the temperature/weather roughly the same when it would run well one day and not the next? Perhaps it's just lean and doesn't do well in the cold? It could be the petcock...just try bypassing the petcock and running the fuel line straight to the carb. Cap off the vacuum hose from the intake so it's not sucking dirty air too.
Scooters Owned: 2003 Ruckus, 2006 Ruckus, 1983 Yamaha Beluga 80, 2007 Vespa LX 150, 2009 Yamaha BWS 125, 2008 Ruckus
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Re: Newbie Here, 83 CV80 running issue

Post by thiscarcrash1 »

Thanks dan.
I'm going to try bypassing the petcock, and ensuring all my vacuum lines are going to the right location this evening. I tested it last night with the mouth method you described here (or maybe it was on the cv80 page) and it seems to be working fine.

The weather was the same here (PA) all week, so i don't think its related. Its not really acting like a lean/rich condition... it literally runs perfectly for hours, and then the next time i start it, it acts fine and then bogs to a stall a block down the road. You would think if the carb settings were off, then it would run predictably bad since they wouldn't change sporadically , yes?

Have you ever heard of the BVS failing?
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Re: Newbie Here, 83 CV80 running issue

Post by thiscarcrash1 »

vacuum lines were hooked up correctly.
idled fine for a bit then died off. I removed the vacuum line from the BVS valve and provided vacuum via my mouth, which kept her running as long as i occasionally did that.
which leads me to believe that:
1. The petcock is not functioning up to snuff, OR
2. The BVS valve is not providing enough vacuum.

I already have a replacement petcock, AND a bypass shutoff valve on the way, so we'll see if that fixes it.
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Re: Newbie Here, 83 CV80 running issue

Post by thiscarcrash1 »

ok. My 'scooter style' fuel petcock came in the mail from ebay. Hooked it up, tested it with mouth vacuum, works fine.
hooked the vacuum up to the BVS (crankcase valve thing) and it wasn't pulling enough vacuum to open the valve. If i sit on the seat and suck, it'll run forever.
So Dan, do you suggest just tossing the petcock and mounting up a manual valve like you've described??
Do you have any pictures of your setup that i could use as a guide?
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Re: Newbie Here, 83 CV80 running issue

Post by thiscarcrash1 »

update #100.
Chucked the replacement petcock. Went for a straight forward fuel shut off valve and an inline fuel filter.

Starts perfectly, still has trouble switching from START to RUN. When it does switch, it runs great for a few minutes then dies out.
Was running obviously rich for a while (popping and backfiring), so i'm tearing the carb back apart and cleaning it like crazy.
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Re: Newbie Here, 83 CV80 running issue

Post by thiscarcrash1 »

Tore the carb apart. The top plunger and rubber bladder piece are in good shape, and move freely. throughouly cleaned all the jets and every port. Slide functions as it should. Put it all back together, and after adjusting the throttle stop screw (with spring, side of carb) it idled fine in the run position. I let it warm up for a good 10 minutes just idling, then took it out. Did about 30 minutes on it and it ran perfectly. no studdering, or backfiring i was experiencing.
Let it sit for about 2 hours, and when i came back to it, it started right up, idled fine, made it about a block, and died instantly.
If i hear it dying and flip the switch to start, it'll stay alive and idle (obviously coming to a stop)
i can sometimes switch it back to run, and ride another block, other times i have to wait or it will die as soon as i flip it to run.

VERY FRUSTRATED at this point. ANYTHING I SHOULD TRY GUYS????
I was confused about which vacuum line goes to the top port on the carb (for the auto choke plunger), i currently have it on the BOTTOM of the two side by side ports on the bi metal valve. is this correct?

HELP HELP HELP haha.

83 cv80. completely stock, sans an inline fuel filter and fuel shut-off valve instead of vacuum petcock.
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Re: Newbie Here, 83 CV80 running issue

Post by thiscarcrash1 »

SOLUTION:

broken lead on the rectifier. Was feeding the battery straight AC while it was running, thus the good initial run, then the temperamental subsequent run.
also fried the cdi as a byproduct.
All parts located on ebay, and on their way.
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Re: Newbie Here, 83 CV80 running issue

Post by Dan Durston »

Wow you did a great job sorting this out. Hopefully these new parts work wonderfully.
Scooters Owned: 2003 Ruckus, 2006 Ruckus, 1983 Yamaha Beluga 80, 2007 Vespa LX 150, 2009 Yamaha BWS 125, 2008 Ruckus
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Re: Newbie Here, 83 CV80 running issue

Post by thiscarcrash1 »

Dan, the one thing i learned from restoring my Triumph, is that with a few bloody knuckles, a couple of decent beers, and enough swearing to send a pope to his grave, you can sort anything out.
I wasn't thinking electrical at all, so once i sorted out the carb and was left with no possibilities, i had to step back and reevaluate.
was a good time
i'll update when the parts come
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Re: Newbie Here, 83 CV80 running issue

Post by gar.rocko »

Hey there! Sorry to drag up an old Post but this exact thing is happening to me too. Did the rectifier fix this issue? How did things end up for you?
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Re: Newbie Here, 83 CV80 running issue

Post by raygirardi »

Hey, had the same issues when I first got my 82 beluga. Decided to replace the carb and petcock with a good brand name larger carb, but not so large as to cause problems so I went with a 19mm and a straight fuel valve(on/off) and had to adjust the carb jets(which took a while to get right) but this alleviated the vacuum system which helped.
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