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Need help with XV250 carb settings

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Need help with XV250 carb settings

PostAuthor: Dark Angel » Tue Sep 12, 2017 5:41 pm

Hi folks,
I'm working on a '94 Virago 250 and have run into an issue I've never faced before. I just cannot get the fuel height set right and it's running very rich.
Normally I'd just bend the tang on the float until the fuel matches the required height, a little fiddly but no drama. This time something's different. If I bend the tang far enough to get close to the required fuel height (16.5 to 17.5mm down from the cast in mark on the outside of the float bowl) the float contacts the inside of the bowl and pushes the needle completely closed. If I bend it back to where there's enough needle opening to get sufficient fuel flow to run the bike (about 2-mm off the seat) the fuel height is nearly 10mm too high. This is with brand new OEM float and needle and seat assembly.

A little background. The bike itself sat for several years before the previous owner got it. He was a butcher and the guy before him seems to have been a mug as well. They did things like hacksaw the intake funnel off just above the carby and drill holes in the frame (not drill and tap, he just wound the stock screws into the holes) to relocate the choke lever, and no maintenance was done on it for years (the brake fluid had turned to white slime). I've been replacing worn or damaged parts since I got it. I tried to clean the air filter yesterday only to have it disintegrate. Thankfully I already ordered a replacement. There's every chance one of them did something stupid to the carby that's caused this but I'm at a loss as to what it might be.

Does anybody have any ideas on what needs to be done to get this right? A new carby is pretty much out of the question at the moment, but surely there has to be something that can be done.
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Re: Need help with XV250 carb settings

PostAuthor: CX Rancher » Tue Sep 12, 2017 7:52 pm

Dark Angel wrote:Hi folks,
I'm working on a '94 Virago 250 and have run into an issue I've never faced before. I just cannot get the fuel height set right and it's running very rich.
Normally I'd just bend the tang on the float until the fuel matches the required height, a little fiddly but no drama. This time something's different. If I bend the tang far enough to get close to the required fuel height (16.5 to 17.5mm down from the cast in mark on the outside of the float bowl) the float contacts the inside of the bowl and pushes the needle completely closed. If I bend it back to where there's enough needle opening to get sufficient fuel flow to run the bike (about 2-mm off the seat) the fuel height is nearly 10mm too high. This is with brand new OEM float and needle and seat assembly.

A little background. The bike itself sat for several years before the previous owner got it. He was a butcher and the guy before him seems to have been a mug as well. They did things like hacksaw the intake funnel off just above the carby and drill holes in the frame (not drill and tap, he just wound the stock screws into the holes) to relocate the choke lever, and no maintenance was done on it for years (the brake fluid had turned to white slime). I've been replacing worn or damaged parts since I got it. I tried to clean the air filter yesterday only to have it disintegrate. Thankfully I already ordered a replacement. There's every chance one of them did something stupid to the carby that's caused this but I'm at a loss as to what it might be.

Does anybody have any ideas on what needs to be done to get this right? A new carby is pretty much out of the question at the moment, but surely there has to be something that can be done.


How do you measure your float height?
How do you measure your fuel height?

How do you determine how much you change the float setting?

If I bend the tang far enough to get close to the required fuel height (16.5 to 17.5mm down from the cast in mark on the outside of the float bowl) the float contacts the inside of the bowl and pushes the needle completely closed. yes. is this not correct? Older Hondas had a spring dampened needle and you were to set initial float height as the needle contacted the seat without loading the spring. The Virago has no spring and will seat fully.

Sure could be other issues but the fuel height, not the float height, is the primary setting to start at.
G'Luk !
---Rancher


B Good! GearUP! TwistOn! GearTall RideSmall
Homage to Those We Follow - Rest In Peace Ride At Peace
but Race the Urn, Man

(Corrections to my Speeds and Mileage posted before 5/2014 (-10% above 50mph) and (-1.8%mpg) Your Stock Speedo Variation may vary) Corrected by MoDot and TrailTech on Utah Tour. Truth in Posting Law
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Re: Need help with XV250 carb settings

PostAuthor: Dark Angel » Tue Sep 12, 2017 8:05 pm

1- How do you measure your float height?
2- How do you measure your fuel height?

3- How do you determine how much you change the float setting?

4- yes. is this not correct? Older Hondas had a spring dampened needle and you were to set initial float height as the needle contacted the seat without loading the spring. The Virago has no spring and will seat fully.

5- Sure could be other issues but the fuel height, not the float height, is the primary setting to start at.

I've numbered the points to answer in order.

1- There is no float height setting for the 250 carbie in the service manual. Typically I use a steel rule with 0.5mm gradients but that's no use in this case.

2- I use a clear plastic hose attached to the drain spigot, per the service manual. I have scribed a mark at 17mm down from the mark on the float bowl that aligns with the centre line of the main needle, as per the service manual. When I open the drain valve I make sure there are no air bubbles in the line which would give false readings before letting the level come up.

3- Digital vernier calipers. I measure from the flat of the metal float arm to the point of the tang that is getting bent.

4- The needle for the Mikuni carb in the 250 Virago also has the spring loaded pin.

5- I am specifically trying to set the fuel height as that is the only spec I have available. Once I have that correct I can be more concerned with idle mixture etc but not before.
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Re: Need help with XV250 carb settings

PostAuthor: robimisery » Wed Sep 13, 2017 12:00 pm

One question
how to properly measure the fuel level
when the engine is on or while it's off
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Re: Need help with XV250 carb settings

PostAuthor: Dark Angel » Wed Sep 13, 2017 10:57 pm

robimisery wrote:One question
how to properly measure the fuel level
when the engine is on or while it's off

The service manual specifies that the motor is to be running.
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Re: Need help with XV250 carb settings

PostAuthor: Dark Angel » Sun Sep 17, 2017 6:35 am

Had another go at it today. It's as though the pump is pushing the needle open until the bowl is over filled. Lifting the float by hand stops the fuel flow (bowl bottom off, turning the motor over with the fuel tap set to 'on') but it would be very easy to put more force on that than the float would manage on it's own.
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Re: Need help with XV250 carb settings

PostAuthor: Dark Angel » Tue Sep 19, 2017 1:51 am

Nope. There is no pressure relief in the fuel pump. It's just not part of the design.
Really at a loss here now.
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Re: Need help with XV250 carb settings

PostAuthor: robimisery » Tue Sep 19, 2017 10:54 am

I removed the carburetor and without cover I dive it into a bowl of water
I simulated the natural movement of the float and needle
Through the fuel hose I blew air
In that way I checked the sealing of the whole valve set
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Re: Need help with XV250 carb settings

PostAuthor: Dark Angel » Wed Sep 20, 2017 8:15 pm

I lifted the float up till it pushed lightly on the spring with the fuel tap on 'prime'. This stopped the flow of fuel.

The float will sit higher in water than in fuel because water has a much higher density.
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Re: Need help with XV250 carb settings

PostAuthor: CX Rancher » Wed Sep 27, 2017 6:27 am

Dark Angel wrote:
I've numbered the points to answer in order.

1- There is no float height setting for the 250 carbie in the service manual. Typically I use a steel rule with 0.5mm gradients but that's no use in this case.

2- I use a clear plastic hose attached to the drain spigot, per the service manual. I have scribed a mark at 17mm down from the mark on the float bowl that aligns with the centre line of the main needle, as per the service manual. When I open the drain valve I make sure there are no air bubbles in the line which would give false readings before letting the level come up.

3- Digital vernier calipers. I measure mfrom the flat of the metal float arm to the point of the tang that is getting bent.

4- The needle for the Mikuni carb in the 250 Virago also has the spring loaded pin.

5- I am specifically trying to set the fuel height as that is the only spec I have available. Once I have that correct I can be more concerned with idle mixture etc but not before.


2- I use a clear plastic hose attached to the drain spigot, per the service manual. I have scribed a mark at 17mm down from the mark on the float bowl that aligns with the centre line of the main needle, as per the service manual. When I open the drain valve I make sure there are no air bubbles in the line which would give false readings before letting the level come up.

3- Digital vernier calipers. I measure from the flat of the metal float arm to the point of the tang that is getting bent.

You measure the Fuel Level, not the tang or Float for actual Fuel Height.
If you can measure the FUEL height and it is Close to 17mm then you can adjust the tang accordingly to move the FLOAT that same amount up or down as it is upside down against the needle.

I think you stated that you can get the FUEL level to 17mm and it wont run correctly??, then there is a DIFFERENT problem. Plugged main or idles circuits or air bleeds.

CX Rancher wrote:
Dark Angel wrote:I just cannot get the fuel height set right and it's running very rich.
Normally I'd just bend the tang on the float until the fuel matches the required height, a little fiddly but no drama. This time something's different. If I bend the tang far enough to get close to the required fuel height (16.5 to 17.5mm down from the cast in mark on the outside of the float bowl) the float contacts the inside of the bowl and pushes the needle completely closed. A little background. The bike itself sat for several years before the previous owner got it. He was a butcher and the guy before him seems to have been a mug as well.... I've been replacing worn or damaged parts since I got it........
The Virago has no spring and will seat fully.

Sure could be other issues but the fuel height, not the float height, is the primary setting to start at.



If you must measure off the bike, set the carby level and do the test with gasoline and your 'J' tube, all in a large enough catch pan to protect the environment. Its messy and a wee bit dangerous but do it outside for venilation and natural light, or explosion proof lighing.... disclaimer alert, don't catch fire, no smoking, petrol resistant gloves, face shield, etc, if you don't feel comfortable take it to a shop, etc, omg not trying to offend....just specific safe and unambiguous.

Water....sounds safer but there you make contaminated water... different specific gravity. Too elaborate in my opinion. "Well water or treated water?" ( The Python scream before the foot bridge )

Dark Angel wrote: 4- The needle for the Mikuni carb in the 250 Virago also has the spring loaded pin.
[/quote]
I can buy that, as the bale that holds the needle could be considered a spring, and yours may be different, but I meant an internal spring in the needle (Honda style). Mine is solid or seized.
Some carbs set FLOAT height at specific points on the FLOAT to specific points on the CARB, some are set by FUEL height. The XV250 asks for FUEL height setting in the OEM manual.
G'Luk !
---Rancher


B Good! GearUP! TwistOn! GearTall RideSmall
Homage to Those We Follow - Rest In Peace Ride At Peace
but Race the Urn, Man

(Corrections to my Speeds and Mileage posted before 5/2014 (-10% above 50mph) and (-1.8%mpg) Your Stock Speedo Variation may vary) Corrected by MoDot and TrailTech on Utah Tour. Truth in Posting Law
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Re: Need help with XV250 carb settings

PostAuthor: Dark Angel » Wed Sep 27, 2017 11:44 pm

Ok.

1- I CANNOT get it to 17.5mm. I can't even get it to about 10mm from the cast in mark. I have scribed a mark on the outside of the floatbowl at the middle of the specified FUEL height range, 16.5 to 17.5mm

2- I know I'm supposed to be measuring the fuel height, I've talked about that repeatedly. Even the post you quoted shows I'm using a clear plastic hose to read the FUEL height in the float bowl. The calipers are only so I know I have actually changed the tang height when I try to bend it by a fraction of a millimetre.

3- It has an internal spring in the needle. There is a loop of wire that holds the needle to the float tang and there is ALSO a spring loaded pin in the needle. Please see attached image. I will make a video of the pin moving in and out if I need to explain it in further detail.

20170928_143526.jpg


I'm not using water to do anything with this carby, that was someone else's suggestion.
You do not have the required permissions to view the files attached to this post.
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Re: Need help with XV250 carb settings

PostAuthor: CX Rancher » Thu Sep 28, 2017 11:14 am

I see. The float is not upsidedown right?, concerned about contact at the float bowl.

What if you bend the float pivot straps instead of the tang?
G'Luk !
---Rancher


B Good! GearUP! TwistOn! GearTall RideSmall
Homage to Those We Follow - Rest In Peace Ride At Peace
but Race the Urn, Man

(Corrections to my Speeds and Mileage posted before 5/2014 (-10% above 50mph) and (-1.8%mpg) Your Stock Speedo Variation may vary) Corrected by MoDot and TrailTech on Utah Tour. Truth in Posting Law
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Re: Need help with XV250 carb settings

PostAuthor: CX Rancher » Thu Sep 28, 2017 11:30 am

Although OEM branded , sounds like incorrect float or needle or seat for the carb.
G'Luk !
---Rancher


B Good! GearUP! TwistOn! GearTall RideSmall
Homage to Those We Follow - Rest In Peace Ride At Peace
but Race the Urn, Man

(Corrections to my Speeds and Mileage posted before 5/2014 (-10% above 50mph) and (-1.8%mpg) Your Stock Speedo Variation may vary) Corrected by MoDot and TrailTech on Utah Tour. Truth in Posting Law
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1983 GL650 Std
1983 CX650T
1976 GL1000 Old Skins in New Bones(sold)
The only Cure for Obsession is another.
OR a Divorce, que sera sera
Sex: Male

Re: Need help with XV250 carb settings

PostAuthor: CX Rancher » Thu Sep 28, 2017 12:50 pm

My manual shows that the float pods are taller to the top than the bottom. Intuitively backwards to me. It is a 1995 XV250 G, GC USA manual. Printed 1994.
G'Luk !
---Rancher


B Good! GearUP! TwistOn! GearTall RideSmall
Homage to Those We Follow - Rest In Peace Ride At Peace
but Race the Urn, Man

(Corrections to my Speeds and Mileage posted before 5/2014 (-10% above 50mph) and (-1.8%mpg) Your Stock Speedo Variation may vary) Corrected by MoDot and TrailTech on Utah Tour. Truth in Posting Law
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1983 GL650 Std
1983 CX650T
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The only Cure for Obsession is another.
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Re: Need help with XV250 carb settings

PostAuthor: Dark Angel » Thu Sep 28, 2017 4:15 pm

CX Rancher wrote:I see. The float is not upsidedown right?, concerned about contact at the float bowl.

What if you bend the float pivot straps instead of the tang?


No, the float isn't upside down.

I tried bending the straps. Same effect.
Last edited by Dark Angel on Thu Sep 28, 2017 4:21 pm, edited 1 time in total.
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Re: Need help with XV250 carb settings

PostAuthor: Dark Angel » Thu Sep 28, 2017 4:19 pm

CX Rancher wrote:Although OEM branded , sounds like incorrect float or needle or seat for the carb.


That would be very strange given I confirmed the part numbers from the genuine diagrams.
The needle valve set is the same across a large number of bikes.
http://yamahaoemparts.com.au/part/yamah ... ontentArea
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Re: Need help with XV250 carb settings

PostAuthor: CX Rancher » Fri Sep 29, 2017 12:14 pm

Well I've been no help, and appologise.

I wish I could come over and see it and bring my carb. It's a curiousment for sure. I'm not allowed to be near benzene type chemicals now but I'd love to take the bowl off mine and look around. I leave hospital Sunday.

This sounds a call for an Aussie Super Hero ! I'm not bailing out but I want to give better thoughts next post.

Sure sounds like a basic physical interference. The stack sounds too long or the bowl too shallow but that sounds as ridiculous as my thoughts above. Are used parts cheap and available? even if they are crummy maybe you can find a difference. There could be more than one problem but this is the basic one to correct first logically. grr
G'Luk !
---Rancher


B Good! GearUP! TwistOn! GearTall RideSmall
Homage to Those We Follow - Rest In Peace Ride At Peace
but Race the Urn, Man

(Corrections to my Speeds and Mileage posted before 5/2014 (-10% above 50mph) and (-1.8%mpg) Your Stock Speedo Variation may vary) Corrected by MoDot and TrailTech on Utah Tour. Truth in Posting Law
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1983 CX650C bad-axx
1983 GL650i
1983 GL650 Std
1983 CX650T
1976 GL1000 Old Skins in New Bones(sold)
The only Cure for Obsession is another.
OR a Divorce, que sera sera
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Re: Need help with XV250 carb settings

PostAuthor: Dark Angel » Sat Sep 30, 2017 3:25 pm

I'm at the point of trying to find another complete carb. A brand new OEM from the dealer item costs over $700AUD, so I am rather reluctant to take that route. I'll start enquiring at dismantlers and see if they are less ridiculous in price.
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