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1982 Virago 750 Will Not Start

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1982 Virago 750 Will Not Start

PostAuthor: rdyeager1 » Sat Jun 27, 2020 8:41 am

I have tried everything I can think of over the last year to get my bike to start, but it just won't cooperate. I've replaced the starter, the starter switch, the computer, the coils, the spark plugs, and the battery, the vacuum lines, and the spark plug wires. I even went as far as purchasing a single carb system and installing it on the bike, had the old carbs rebuilt, and purchased a rebuilt dual carb system on-line, but all to no avail.
I have spark, fuel, and air. The timing isn't adjustable. I just want to chuck the whole thing in a dumpster!
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Re: 1982 Virago 750 Will Not Start

PostAuthor: Flyingdog » Sat Jun 27, 2020 12:53 pm

When say you got fuel..you getting fuel to the heads? Can you smell fuel on the plugs? Have you tried squirting little starting fluid or poured bit of gas in the spark plug hole? Are the valves adjusted correctly? Have you done a compression/lead-down test? Are the timing marks aligning up as they should according to the manual?
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Re: 1982 Virago 750 Will Not Start

PostAuthor: rdyeager1 » Sat Jun 27, 2020 2:12 pm

There is fuel because, rarely, it will start and run for a few minutes and when I've checked the plugs there is the smell of gas. I've not bothered checking the timing marks since every manual says that it's not adjustable. Haven't adjusted valves because it was running until it stopped all of a sudden about a year ago. I don't know what a compression/lead-down test is.
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Re: 1982 Virago 750 Will Not Start

PostAuthor: chrismalm » Sat Jun 27, 2020 4:34 pm

A compression test will determine the overall condition of your engine. A leak-down test is more informative, but it's a costlier set-up. Without good compression, your engine will never start or run right. Once the basic engine has tested good, you can proceed to test the ignition, carburetion and charging systems.

Long distance diagnoses are a shot in the dark. With a 38 year old Virago you have to inspect every component and connection on the bike. There are a lot of safety features that are prone to failure due to age. All connections must be clean and tight. Once your bike is sorted and running, it tends to stay that way until it sits for a long period and ethanol and corrosion cause more mischief.

It sounds like you invested a lot of time and money and have eliminated a number of possible problems. Don't give up. Start with the compression test, follow the ignition and carburetion test procedures in the FSM, and you will eventually chase out all the gremlins.

Also, put your location in your profile. Someone local might be able to assist.
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Re: 1982 Virago 750 Will Not Start

PostAuthor: Flyingdog » Sat Jun 27, 2020 4:54 pm

:yup:

Whoops...meant: leak-down...not "lead-down" Yea shouldn't have mention that as most DIY's don't have the set up for a leak down test. Just a habit of putt'n out options. Like Chris says: long distance diagnosis is a shot in the dark lotta times. I mentions the timing marks, cuz in a least likely scenario, the timing chain can jump a tooth, get overly stretch, cam/timing sprockets deform, break..etc etc. My first thought, besides bad compression, you got a fuel problem. Cuz you've said it does burp once-in-awhile, but doesn't stay running.
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Re: 1982 Virago 750 Will Not Start

PostAuthor: rdyeager1 » Thu Jul 02, 2020 2:34 pm

OK, I'll pick up a compression test kit on my next payday. But in the meantime, here's something strange. When I'm checking for spark and have either the front or rear plug out, the bike will start and run each time. Put the plug back in and it won't start, except very rarely.
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Re: 1982 Virago 750 Will Not Start

PostAuthor: Flyingdog » Thu Jul 02, 2020 2:53 pm

I'm just go'n to throw this out there..When you pull one plug or the other, you're break'n ground to that plug and everything is go'n to other plug. Have you checked coils? Have you ever messed with the primary wiring on the coils? And...you got the right coil go'n to the right plug? What plugs you use'n? How's the connection between secondary plug wire-to-cap? You still have resistor type spark plug caps? Shot-in-the-dark.... :bg:
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Re: 1982 Virago 750 Will Not Start

PostAuthor: rdyeager1 » Thu Jul 02, 2020 2:57 pm

I put two brand new coils on the bike last week. I had tried several used sets and decided to get a new set and try that. I'm using the plugs called for in the manual, BP7ES, or something like that. I tried some more expensive ones but there was no difference. I've made sure that I've always kept the wires to the correct coil by replacing only one at a time. I've replaced the plug wires, but not sure about the resistor plug caps. I couldn't find any originals so bought new NGC caps. Not sure if they're resistors.
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Re: 1982 Virago 750 Will Not Start

PostAuthor: mark75 » Thu Jul 02, 2020 6:44 pm

one of those issues that make you crazy ...

new coils, cables, and caps are giving you spark? double check that your TCI connections are shiny tight [and keep yer battery fully charged]

check your valve lash. if it's way-off valves might not be opening (enough)

if you have an AutoZone near-by, give 'em a call, they have a tool-loan-program so you wont need to buy a compression tester (unless you want to)
>>> https://www.autozone.com/lp/loan-a-tool

hang in there, you're getting close.
"Over the Mountains of the Moon,
Down the Valley of the Shadow,
Ride, boldly ride" ... E.A. Poe


Time flies >>> whether you're having fun __ :bike: or not :fan: ---

Any day above ground is a good day.
so Laissez les bon temps roulez. just roll safely --- Semper Vigilans...always watchful

"I hear and I forget, I see and I remember, I do and I understand." ... Confucius*

If you don't read the news you are not informed.
If you read the news you are misinformed.
... Mark Twain


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Re: 1982 Virago 750 Will Not Start

PostAuthor: Flyingdog » Fri Jul 03, 2020 2:54 am

rdyeager1 wrote: I couldn't find any originals so bought new NGC caps. Not sure if they're resistors.


Come to find out, guess "all" NGK caps, now-a-days, are resistor type and "not" rebuildable as the original caps use to be. How you can tell is, if you look in spark plug end of the cap and see the little brass holder...if it's got a slot, then it can be un-screwed and the resistor "pill" can be replaced with 16d nail or something conductive. But, any caps I've gotten over the years are not rebuild-able.
Good luck on yer quest. Like Mark said, no-spark scenarios are maddening at the very least.
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Re: 1982 Virago 750 Will Not Start

PostAuthor: chrismalm » Fri Jul 03, 2020 10:06 pm

I recently had a similar symptom with a plastic TCI Virago (1983+). I never had it happen with a metal box TCI (1981-82). Non resistor caps + non resistor plugs caused my bike to idle poorly, misfire and backfire when revved. Unplugging one cylinder caused the other other cylinder to run fine. Check the resistance of your plug caps and see if they are non-resistor. If so, you might want to throw another $5 at it and try some BPR7ES plugs.
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