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1985 Virago XV700 losing power

Have a question about fixing something on a Yamaha Virago XV700? Post it here!
mbiskup
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Joined: Wed Mar 18, 2020 11:17 am
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1985 Virago XV700 losing power

Post by mbiskup » Wed Mar 18, 2020 11:33 am

Hi everyone,

I was having issues with my bike not running well so I cleaned my carbs. I have not cleaned them for the 5 years I have had the bike, and they were pretty clean still. After cleaning and putting them back on my bike seemed to be running better, but after about 5 minutes of riding and coming to a couple stoplights I noticed that each time I let off the throttle my bike was losing RPM's and was on its way to stalling out. It eventually did stall out and I struggled to get it started until I wiggled the carbs a bit. This led me to believe there was an air leak and that I did not properly reinstall the carbs. I took them off again, cleaned them again, and reinstalled them paying much more attention to how everything was sitting. When I took it out for another run I noticed that when I gave her gas the RPM's stayed high for an unusual period, and my throttle cable was not stuck. When it finally died down and I got moving again one of the vacuum caps on my carburetor manifold boots shot off and my bike died pretty instantly.

I am not sure if I have an air leak, I have tried spraying WD-40 around potential leaks and haven't had fluctuation of rpms.

I am not sure if I missed something while cleaning the carbs.

I am not sure why vacuum caps would pop off?

Of course I love riding but I posted my bike on CL. I am now racing to see if I can fix it before someone wants to buy it from me, so I don't have to sell it.

I am a HS Math Teacher and have off because of the Corona, I have time to work on my bike. I just need help, suggestions, or to be called a dumb ass and pointed in the direction I should have been looking in the first place.

Thanks everyone,
Max
1985 Yamaha Virago xv700

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ViragoJoe
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Re: 1985 Virago XV700 losing power

Post by ViragoJoe » Wed Mar 18, 2020 11:53 am

mbiskup wrote:
Wed Mar 18, 2020 11:33 am
Hi everyone,

I was having issues with my bike not running well so I cleaned my carbs. I have not cleaned them for the 5 years I have had the bike, and they were pretty clean still. After cleaning and putting them back on my bike seemed to be running better, but after about 5 minutes of riding and coming to a couple stoplights I noticed that each time I let off the throttle my bike was losing RPM's and was on its way to stalling out. It eventually did stall out and I struggled to get it started until I wiggled the carbs a bit. This led me to believe there was an air leak and that I did not properly reinstall the carbs. I took them off again, cleaned them again, and reinstalled them paying much more attention to how everything was sitting. When I took it out for another run I noticed that when I gave her gas the RPM's stayed high for an unusual period, and my throttle cable was not stuck. When it finally died down and I got moving again one of the vacuum caps on my carburetor manifold boots shot off and my bike died pretty instantly.

I am not sure if I have an air leak, I have tried spraying WD-40 around potential leaks and haven't had fluctuation of rpms.

I am not sure if I missed something while cleaning the carbs.

I am not sure why vacuum caps would pop off?

Of course I love riding but I posted my bike on CL. I am now racing to see if I can fix it before someone wants to buy it from me, so I don't have to sell it.

I am a HS Math Teacher and have off because of the Corona, I have time to work on my bike. I just need help, suggestions, or to be called a dumb ass and pointed in the direction I should have been looking in the first place.

Thanks everyone,
Max
1985 Yamaha Virago xv700
Max,

When you say: I am not sure why vacuum caps would pop off?
Are you referring to the Blind Plug that is located on your Rear Carburetor Mounting Boot?
Or something else entirely?

To get yourself more familiar with the Hitachi carburetors that are on your bike read the below article:

Virago Hitachi Carburetors
https://www.viragohelp.com/virago-hitachi-carburetors/
ViragoJoe
1996 XV1100SH Virago Special
"Never ride faster than your Guardian Angel can fly!!"
;)

mbiskup
Posts: 7
Joined: Wed Mar 18, 2020 11:17 am
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Re: 1985 Virago XV700 losing power

Post by mbiskup » Wed Mar 18, 2020 12:09 pm

Thank you for posting the article, I have read it at least twice already and plan on reading it again a couple more times.

https://www.ebay.com/itm/Carb-Carbureto ... 2111621688

On the boot with two nipples, both caps popped off. Before I bought the bike there was some work done on it, it has always had both nipples capped. The other boot also had its one nipple capped. I could have easily messed something up though while reinstalling them. I did take a couple pictures before I removed the carbs the first time to help me make sure I put everything back the way it was when I took them off.

Thanks,
Max

mbiskup
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Joined: Wed Mar 18, 2020 11:17 am
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Re: 1985 Virago XV700 losing power

Post by mbiskup » Wed Mar 18, 2020 12:20 pm

OK pictures of the setup before I took the carbs out.

Thanks

Click Images to Enlarge and Correct Orientation:
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ViragoJoe
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Re: 1985 Virago XV700 losing power

Post by ViragoJoe » Wed Mar 18, 2020 12:38 pm

mbiskup wrote:
Wed Mar 18, 2020 12:20 pm
OK pictures of the setup before I took the carbs out.

Thanks

Click Images to Enlarge and Correct Orientation:
Max,

If you blew off any Blind Plugs or vacuum hoses there is more going on there than meets the eye.. Those Crab boots brass ports are to allow vacuum to be created as the piston is on its way down during the intake stroke. On the way up for the compression stroke would create pressure and if the Intake valve isn't completely closed would create enough pressure to blow the vacuum hoses or Blind Plug off.

Is it just happening to one Cylinder? Like the Rear Cylinder for example that may have both a Blind Plug and maybe also a Vacuum line (hose)?

Edited at 12:40.
Are there two Blind Plugs on the Rear Cylinder Boot Brass Ports?
ViragoJoe
1996 XV1100SH Virago Special
"Never ride faster than your Guardian Angel can fly!!"
;)

mbiskup
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Re: 1985 Virago XV700 losing power

Post by mbiskup » Wed Mar 18, 2020 12:51 pm

ViragoJoe,

For the short trip I took, only the plugs on the rear cylinder shot off. There were two on the rear cylinder boot brass ports.

Thanks,
Max

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ViragoJoe
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Re: 1985 Virago XV700 losing power

Post by ViragoJoe » Wed Mar 18, 2020 12:57 pm

mbiskup wrote:
Wed Mar 18, 2020 12:51 pm
ViragoJoe,

For the short trip I took, only the plugs on the rear cylinder shot off. There were two on the rear cylinder boot brass ports.

Thanks,
Max
How does the bike run. Missing? Does it blow the plugs off every time? What about sitting still and throttling the bike up some? Does it happen then?
ViragoJoe
1996 XV1100SH Virago Special
"Never ride faster than your Guardian Angel can fly!!"
;)

mbiskup
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Joined: Wed Mar 18, 2020 11:17 am
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Re: 1985 Virago XV700 losing power

Post by mbiskup » Wed Mar 18, 2020 1:03 pm

Before I took it for the short ride I let it idle for a couple minutes to see if the RPM's would drop, because that was initially why I took the carbs out. The bike seemed to be ok. I throttled it up some and the RPM's rose and fell seemingly normal. Nothing blew off until I started riding. Should I try firing it up again? Any recommendations on things I should test? I appreciate your help and troubleshooting attempts so far!

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ViragoJoe
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What Virago you Own: 1996 Virago Special XV1100SH
"Never ride faster than your Guardian Angel can fly!!"

Re: 1985 Virago XV700 losing power

Post by ViragoJoe » Wed Mar 18, 2020 1:26 pm

mbiskup wrote:
Wed Mar 18, 2020 1:03 pm
Before I took it for the short ride I let it idle for a couple minutes to see if the RPM's would drop, because that was initially why I took the carbs out. The bike seemed to be ok. I throttled it up some and the RPM's rose and fell seemingly normal. Nothing blew off until I started riding. Should I try firing it up again? Any recommendations on things I should test? I appreciate your help and troubleshooting attempts so far!
Those Blind Plugs should also blow off when you rev the engine not just when riding.

Have the valves ever been adjusted?

Do you have any valve train noise down at the cylinder heads. You should have some rocker arm clatter down there.

If there is no clatter of the Rocker arm tappets at all. Then you need to check the valve clearances.

Only do this on a completely cold engine.
ViragoJoe
1996 XV1100SH Virago Special
"Never ride faster than your Guardian Angel can fly!!"
;)

mbiskup
Posts: 7
Joined: Wed Mar 18, 2020 11:17 am
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Re: 1985 Virago XV700 losing power

Post by mbiskup » Wed Mar 18, 2020 1:41 pm

I have never adjusted the valves, I am not afraid to try using a my Clymer manual as a guide. They may have been adjusted by a previous owner. I am not familiar with valve train noise, I will begin researching.

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