1987 Virago 700 no throttle response after rebuilding carbs (New York)

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cbnymets
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1987 Virago 700 no throttle response after rebuilding carbs (New York)

Post by cbnymets » Wed Jun 09, 2021 9:34 pm

I recently purchased a 1987 Yamaha Virago 700 in March as my first motorcycle, and it ran great when I bought it. I put some miles on it and every so often I would get an extremely delayed throttle response and I had to keep the bike revved up just so it wouldn't shut off. This didn't happen too often, but I still wanted to fix the issue. I took the carbs apart and cleaned them (they were not dirty), blew air through the fuel and vacuum hoses, treated the gas tank for rust and also replaced the petcock with a new one. The bike ran fine for maybe a few days before the same issue occurred.

Next I tried resetting the pilot mixture screws but while doing this accidently left the petcock on prime and flooded the bike. After this occurred I figured to do a carb rebuild and also an oil change since gas got into the oil. I got a carb rebuild kit which replaced everything except for the diaphragms, and also cleaned the tiny jets once again. I had a professional make sure they were clean and also asked him about the floats, he said they looked fine but never measured the level. Then I put the bike back together while also changing the spark plugs and checking the air filter.

This is where I'm at now, as the bike will fire up and idle with some choke but using any throttle basically kills the bike. Sometimes if I use it slowly it will finally jump up to the higher rpms but it is very slow. Another issue is that the idle will jump from 1000 rpms up to 4000 rpms without me touching anything, and then it will stay at 4000 for a while, even after killing the bike and turning it back on. I couldn't find an air leak on the intake boots by spraying WD-40 where the leak would be, but I am going to replace the o rings on the boots anyway. Besides replacing the o rings on the boots, I am at a loss of what to try next. I'm confident that these carbs are clean, especially after paying a professional to clean them. The diaphragms looked okay but they were not replaced.... could a little pinhole that maybe I can't see be causing this issue? Any suggestions of what to try next would be really appreciated.

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ViragoJoe
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Re: 1987 Virago 700 no throttle response after rebuilding carbs (New York)

Post by ViragoJoe » Thu Jun 10, 2021 6:16 am

cbnymets wrote:
Wed Jun 09, 2021 9:34 pm
I recently purchased a 1987 Yamaha Virago 700 in March as my first motorcycle, and it ran great when I bought it. I put some miles on it and every so often I would get an extremely delayed throttle response and I had to keep the bike revved up just so it wouldn't shut off. This didn't happen too often, but I still wanted to fix the issue. I took the carbs apart and cleaned them (they were not dirty), blew air through the fuel and vacuum hoses, treated the gas tank for rust and also replaced the petcock with a new one. The bike ran fine for maybe a few days before the same issue occurred.

Next I tried resetting the pilot mixture screws but while doing this accidently left the petcock on prime and flooded the bike. After this occurred I figured to do a carb rebuild and also an oil change since gas got into the oil. I got a carb rebuild kit which replaced everything except for the diaphragms, and also cleaned the tiny jets once again. I had a professional make sure they were clean and also asked him about the floats, he said they looked fine but never measured the level. Then I put the bike back together while also changing the spark plugs and checking the air filter.

This is where I'm at now, as the bike will fire up and idle with some choke but using any throttle basically kills the bike. Sometimes if I use it slowly it will finally jump up to the higher rpms but it is very slow. Another issue is that the idle will jump from 1000 rpms up to 4000 rpms without me touching anything, and then it will stay at 4000 for a while, even after killing the bike and turning it back on. I couldn't find an air leak on the intake boots by spraying WD-40 where the leak would be, but I am going to replace the o rings on the boots anyway. Besides replacing the o rings on the boots, I am at a loss of what to try next. I'm confident that these carbs are clean, especially after paying a professional to clean them. The diaphragms looked okay but they were not replaced.... could a little pinhole that maybe I can't see be causing this issue? Any suggestions of what to try next would be really appreciated.

Do you have a repair manual for your XV700? Most important tool in your tool box!


Since this is your first Motorcycle and not knowing your carburetor rebuilding expertise. Read these articles:

Virago Carburetor CV

https://viragohelp.com/phpbb3/app.php/v ... 1a3ae0bb5a

Virago Hitachi Carburetors

https://viragohelp.com/phpbb3/app.php/v ... 1a3ae0bb5a


I know the carbs were suppose to have been cleaned etc., however, you may have missed cleaning something in the Pilot or Choke circuits. Below: Engine Stalls Using Choke by Mac McCurdy


Engine stalls using choke
May 14, 2015
This date is when the article was added to Virago Help. The actual article was written back in January, 2006.

Cold Start – Choke Problems
https://www.viragohelp.com/virago-owner ... ing-choke/
ViragoJoe 🇺🇸
1996 XV1100SH Virago Special
"Never ride faster than your Guardian Angel can fly!!"
;)


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cbnymets
Posts: 2
Joined: Wed Jun 09, 2021 8:57 pm
Location: New York
What Virago you Own:

Re: 1987 Virago 700 no throttle response after rebuilding carbs (New York)

Post by cbnymets » Thu Jun 10, 2021 9:08 am

Thank you for the articles, when I have time later today I will take them off again and go through them. I do have the repair manual and it has been very helpful but these articles seem a little more detailed. I will post an update after I clean the carbs again and change the o rings on the intake boots.

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