1983 XV750 midnight front cylinder not firing (Southern Maine)

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Importrunner
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1983 XV750 midnight front cylinder not firing (Southern Maine)

Post by Importrunner » Sun Nov 21, 2021 10:44 am

Bike: 1983 xv750 midnight basket case.

Bought bike as a “non” runner. Seller got the bike in a bundle of motorcycle parts

I checked for spark and got it to run on starting fluid. I pulled the carbs out and the were filthy. Had white residue in the float bowls. One passage in the float bow was 100% blocked.

Micro screens on fuel inlet was pretty blocked. Cleaned the carbs blew out all the ports reassembled and installed.

Bike fired right up and I test drove it for a bit after and oil change(under 5 miles). I noticed some white/grey smoke coming from the tail pipe.

I removed the stock mufflers so I could isolate weather it was the front or rear cylinder. What I found was shocking. The front cylinder wasn’t firing at all!! There was actually fuel shooting out of the front pipe!

If I pull the vacuum line for the front petcock, the cylinder will run low on fuel and fire until it runs out of fuel. Pulling the plug it is soaked.(they are new plugs) strong spark when checked. It’s not flooding the cylinder when off (I don’t think). Not sure what to check next.

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ViragoJoe
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Re: 1983 XV750 midnight front cylinder not firing (Southern Maine)

Post by ViragoJoe » Mon Nov 22, 2021 7:34 am

Importrunner wrote:
Sun Nov 21, 2021 10:44 am
Bike: 1983 xv750 midnight basket case.

Bought bike as a “non” runner. Seller got the bike in a bundle of motorcycle parts

I checked for spark and got it to run on starting fluid. I pulled the carbs out and the were filthy. Had white residue in the float bowls. One passage in the float bow was 100% blocked.

Micro screens on fuel inlet was pretty blocked. Cleaned the carbs blew out all the ports reassembled and installed.

Bike fired right up and I test drove it for a bit after and oil change(under 5 miles). I noticed some white/grey smoke coming from the tail pipe.

I removed the stock mufflers so I could isolate weather it was the front or rear cylinder. What I found was shocking. The front cylinder wasn’t firing at all!! There was actually fuel shooting out of the front pipe!

If I pull the vacuum line for the front petcock, the cylinder will run low on fuel and fire until it runs out of fuel. Pulling the plug it is soaked.(they are new plugs) strong spark when checked. It’s not flooding the cylinder when off (I don’t think). Not sure what to check next.

Importrunner,

Not knowing your mechanical prowess in repairing carburetors, we need to know a little more on how and what you did inside the Carburetors.

Here's an excerpt taking from our pal Dr. Piston:
(Note: the word "carburetor" is a French word. In English it refers to the fuel mixture dispenser residing near a cylinder. However, you should be aware that the meaning of this word in the native French language is quite different. In French it means: "Don't mess with me".)
Do you have a Repair Manual for this 1983 XV750?

Carburetors clogged that much really should have been ultrasonically cleaned. Cleaners and compressed air don't always do a thorough enough job of cleaning the carburetors.

What were the floats set to when you reassembled the carburetors?

Were any components replaced? Jets, needle and seat, etc.

Hitachi had three different flavors (versions) of carburetors. I'm pretty sure your bike carbs are Version 1's. We'll approach the other two if needed.

Why float height is important

https://www.youtube.com/watch?v=yN1Wpm9_Xs4&t=4s

Did you check the inside of the fuel tank for rust and other contaminants, since it was a basket case? Rust can loosen and flake off and clog petcocks, fuel lines, and Carbs. Fuel tank must be clean, if not done so already.

You didn't provide any pictures, so we are working in total darkness here.
ViragoJoe 🇺🇸
1996 XV1100SH Virago Special
"Never ride faster than your Guardian Angel can fly!!"
;)


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Importrunner
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Re: 1983 XV750 midnight front cylinder not firing (Southern Maine)

Post by Importrunner » Mon Nov 22, 2021 7:45 am

I have been a auto mechanic for about 15 years. However this is my first motorcycle and carbureted engine(besides lawnmowers). I do not have a service manual yet. I have been referencing this site and a couple other media outlets to get a general idea. I did not install any new components when i disassembled and cleaned the carbs. basically I removed float bowls, jets, needles and blew compressed air and carb clean through all ports. I did not check float height on initial cleaning merely due to inexperience and just wanting to witness the bike run to confirm it would be worth the time and effort to repair. I'm planning to remove the carbs again and check float height. Side note I found two washer on each jet needle is that normal? what pictures would be helpful? I truly appreciate your help. I love learning new things and tinkering. This bike is my gateway into motorcycles and I'm very excited to get out on the road.

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Re: 1983 XV750 midnight front cylinder not firing (Southern Maine)

Post by ViragoJoe » Mon Nov 22, 2021 9:00 am

Importrunner wrote:
Mon Nov 22, 2021 7:45 am
I have been a auto mechanic for about 15 years. However this is my first motorcycle and carbureted engine(besides lawnmowers). I do not have a service manual yet. I have been referencing this site and a couple other media outlets to get a general idea. I did not install any new components when i disassembled and cleaned the carbs. basically I removed float bowls, jets, needles and blew compressed air and carb clean through all ports. I did not check float height on initial cleaning merely due to inexperience and just wanting to witness the bike run to confirm it would be worth the time and effort to repair. I'm planning to remove the carbs again and check float height. Side note I found two washer on each jet needle is that normal? what pictures would be helpful? I truly appreciate your help. I love learning new things and tinkering. This bike is my gateway into motorcycles and I'm very excited to get out on the road.
Importrunner,

If she popped with starting fluid sprayed into the spark plug holes. She'll run when all problems are corrected.

Always take pictures as you are dismantling for reference later.

Main jet has a washer.

Consult a dealers part micro fiche on parts and assemblies, it'll help take the guess work out.

We have electronic copies of repair manuals you can down load.

Always a good idea to have a hard copy manual near the bike when working on her.
ViragoJoe 🇺🇸
1996 XV1100SH Virago Special
"Never ride faster than your Guardian Angel can fly!!"
;)


NOTE TO ALL:
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Also: If this website was helpful, please consider donating to help keep this site here for yourself and future Virago owners.

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Importrunner
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Re: 1983 XV750 midnight front cylinder not firing (Southern Maine)

Post by Importrunner » Tue Nov 23, 2021 4:44 pm

Got a chance to work on the bike Tonight. Found the float height on the front cylinder way off!! I adjusted to 19mm. Then found out both needles had 3 washers in them. So the needle was sitting approx 2.5mm high. Waiting on a new battery probably won’t be able to test it till after the holidays!

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Re: 1983 XV750 midnight front cylinder not firing (Southern Maine)

Post by ViragoJoe » Tue Nov 23, 2021 5:10 pm

Importrunner wrote:
Tue Nov 23, 2021 4:44 pm
Got a chance to work on the bike Tonight. Found the float height on the front cylinder way off!! I adjusted to 19mm. Then found out both needles had 3 washers in them. So the needle was sitting approx 2.5mm high. Waiting on a new battery probably won’t be able to test it till after the holidays!
================================================
found out both needles had 3 washers in them. So the needle was sitting approx 2.5mm high.
The Float Needle and Seat that controls the fuel entering the float bowls had 3 washers in it?!

Washers or O-ring(s)
ViragoJoe 🇺🇸
1996 XV1100SH Virago Special
"Never ride faster than your Guardian Angel can fly!!"
;)


NOTE TO ALL:
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Importrunner
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Re: 1983 XV750 midnight front cylinder not firing (Southern Maine)

Post by Importrunner » Tue Nov 23, 2021 6:13 pm

The main jet needle I believe it’s called. The one you access through the top of the carbs. And they were washers.

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ViragoJoe
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Re: 1983 XV750 midnight front cylinder not firing (Southern Maine)

Post by ViragoJoe » Wed Nov 24, 2021 10:03 am

Importrunner wrote:
Tue Nov 23, 2021 6:13 pm
The main jet needle I believe it’s called. The one you access through the top of the carbs. And there were washers.
==============================================

Hold on my friend we are not talking about the same animal here. I'm talking about the Float bowl needle and seat.

Not the Diaphragm Slide Needle. That jewel slides up and down in the emulsion tube.

Are you speaking of E-Clips or shims as being washers? Though they are washers in this case of Adjusting the needle they are considered shims. They are adjustment devices. Don't mess with those just yet. Take pictures of where they are set now.

Attach pictures of them here, so we can all see what you are talking about. Basically, we have two needle assemblies in the Virago Carbs.
1.) Float Needle and Seat that meters the in Flow of Fuel to the float bowl. That I'm addressing.

2.) Diaphragm Slide Needle has no seat. But has a Main Jet, Emulsion Tube, and the Slide Needle that meters how much fuel will be allowed to enter the Carburetor Venturi as it Slides up and down. Adjusting the Slide Needle adjusters can make the Fuel Mixture Rich or Lean. Remember, so can the Float Bowl Needle and Seat by adjusting the Float Bowl Fuel Height. Know what you are doing before you do anything.

All circuits (for lack of a better word) depend on one another. Anything you do to one circuit effects all the others.

Do you have a manual yet?!!!


Remember the video I attached regarding:
Why float height is important
If you move those slide needles via the E-clip and/or shims you will throw off the Rich and/or Lean mixture that was preset at the factory to run properly.

Slow down, remember everything you do in there can and will create consequences?! Usually, all BAD!

Remember what Dr. Piston said earlier "Don't mess with me!"
(Note: the word "carburetor" is a French word. In English it refers to the fuel mixture dispenser residing near a cylinder. However, you should be aware that the meaning of this word in the native French language is quite different. In French it means: "Don't mess with me".)
This Chap refers to the "Emulsion tube" as part of the main jet he refers to as "brass guy"
Needle jet removal XV750 Virago What he really meant to say was, removal of the Slide Needle, Main Jet, and Emulsion Tube. The Emulsion Tube is what he tapped out with the hammer and center punch.
https://www.youtube.com/watch?v=U4419xQJOWE

What Position For My Needle Clip?

https://www.youtube.com/watch?v=ggHx4nb4SKM

Inside A Motorcycle Carburetor - Needle Height Tuning Adjustment | MC Garage
In this video he is calling the EMULSION TUBE (the needle Jet Nozzle)
https://www.youtube.com/watch?v=7U0Cf15ZbW4&t=4s

Carburetor Emulsion Tube - Why it is needed - How it works - What they do?

https://www.youtube.com/watch?v=IGPg51AtIEE

Carburetor Shims:

I've heard that these are the best washers to use as shims for carburetors requiring Shims:
CARBURETOR SHIMS M3 Metric Flat Washers STAINLESS.jpg

In Hand View Below:
CARBURETOR SHIMS M3 Metric Flat Washers STAINLESS In HAND View.jpg
You do not have the required permissions to view the files attached to this post.
ViragoJoe 🇺🇸
1996 XV1100SH Virago Special
"Never ride faster than your Guardian Angel can fly!!"
;)


NOTE TO ALL:
:arrow: Please edit your profile with location (State/Country) & Bike Information. It will aid us in assisting you!


Also: If this website was helpful, please consider donating to help keep this site here for yourself and future Virago owners.

Yamaha Virago manuals for download. Left Side Panel
or Click this Link:
https://viragohelp.com/phpbb3/viewtopic.php?f=64&t=1722

supercub
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Re: 1983 XV750 midnight front cylinder not firing (Southern Maine)

Post by supercub » Wed Nov 24, 2021 6:30 pm

Someone added the washers to raise the needle to richen the fuel mixture for better off-idle performance. I have added one .060" thick plastic washer on 80s bikes to help the off idle lean condition and it helped but there is too much.
81 XV750

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