My 25 year old XV250

[fazil]

Today i celebrated the 25th birthday of my other bike, a 1992 year produced Virago 250.
Here is a photo of her.







And a question about carburator. I changed the carb 2 years ago with a newer model, I also changed intake manifold with a brand new one.
But since then, the chooke is no longer working fine.
In cold winter days, first start takes time, after 4-5 tries, it starts without chooke and i have to keep the gas a little open for her not to stall while she's cold.
If i give it any chooke, (half-full no matter) she dies. What might be the problem?

 

[TownsendsFJR1300]

Is the new carb jetted the same as the old one?

 

[fazil]

Yes i guess so. I've put it 2 years ago. I remember that main jet and pilot jet were the same as original.
Is it possible that, pilot air screw is not adjusted properly, i can try to adjust it tomorrow.

 

[TownsendsFJR1300]

They didn't make a 250 here in the states so I can't even bring up a part fisch of the the carb to look at.

What type of choke?, ie cable on the bars that you can pull out at varying degree's or one right on the carb-basically a plunger

Have you checked your spark plug for how the engine is running over time, IE black, tan white, etc?

Does the bike start fine(no throttle) warm?

Cold start, plz clarify are you using the choke at all or simply crank with some throttle several times....

Lastly, where the chock plunger goes into the carb, have you ever had that out and inspected it, the orifice, etc?

 

[FinalImpact]

If you still have the old carb, compare full choke air flow area to existing carb. Do the same for 1/2 choke. The flow area should be the same.

Also look for any other mechanism that interacts with slide/butterfly. Perhaps the linkage can be bent to open the throttle and achieve a higher cold idle speed.

Off hand it sounds like it no longer closes (chokes) or raises (opens) the main throttle position.

Perhaps a picture of the carb and choke mechanism?
Old and new?
And why was it replaced?

 

[fazil]

They didn't make a 250 here in the states so I can't even bring up a part fisch of the the carb to look at.

Virago 250 is still on sale in the US market. Here is the partzilla link:

Yamaha Motorcycle Parts 2015 V STAR 250 - XV250FCB CARBURETOR Diagram


What type of choke?, ie cable on the bars that you can pull out at varying degree's or one right on the carb-basically a plunger

cable on the bars, you can adjust variably.


Have you checked your spark plug for how the engine is running over time, IE black, tan white, etc?

They look a bit black but not too much.

Does the bike start fine(no throttle) warm?

Yes easily starts after warm up.

Cold start, plz clarify are you using the choke at all or simply crank with some throttle several times....

While cold, if i use chooke it never starts. When cold, it starts after 4-5 try with some throttle and if i don't give it more throttle, it sputters and dies. I have to give it gas for 1-2 minutes. After warm up everthing seems ok, no problem, if i open chooke after warm up, rpm goes high for a while then engine dies.

Lastly, where the chock plunger goes into the carb, have you ever had that out and inspected it, the orifice, etc?

I've not inspected it. Chooke plunger is part #13 in the partzilla link.




If you still have the old carb, compare full choke air flow area to existing carb. Do the same for 1/2 choke. The flow area should be the same.

How can i measure air flow area?

Also look for any other mechanism that interacts with slide/butterfly. Perhaps the linkage can be bent to open the throttle and achieve a higher cold idle speed.

Mechanism seems alright, without any stuck parts.

Off hand it sounds like it no longer closes (chokes) or raises (opens) the main throttle position.


Perhaps a picture of the carb and choke mechanism?
Old and new?
And why was it replaced?


It was very old, Diaphram was not good, the place chooke plunger installs has lost its treads, and broken. I had some sputtering problems expecially in cold and humid conditions, later i discovered that was because of the iginition coils. Changed them.

Here is a video of the same carb (mikuni 26mm)

[video=youtube;neaBAYm8iss]https://www.youtube.com/watch?v=neaBAYm8iss[/video]

 

[TownsendsFJR1300]

AS posted earlier, in 1992 it WAS NOT available here in the states.

The parts link you posted above, being it's 25 years LATER, is it the exact same style carburetor, diagram the same??

(The link above doesn't work)....


With the new information above, please post a good pic or two of your spark plug. Being blackish, it's running rich.
Weather it's the main jet too rich or an open choke orifice, etc, some digging is needed..


Once the engine is to temp, that choke lever assembly, when slowly activated SHOULD start loading up the engine with extra fuel. Will it do that? (You should also be able to smell the excess fuel as well).


What setting is part #2 at? That needle adjusts the fuel mix for just off idle and idle.

(1) As you adjust(raise it), the make the mix RICHER..
(2) As you lower it, it makes the mix leaner.. You want that set to where there's no hesitation, BUT
not to where it's still too rich. IE, set it as low as possible with good throttle acceleration off idle


Looking at the parts fisch, you have TWO main jets for some reason, parts #19 and # 7.

As you got the carb used and don't know what the previous owner did to it (very possibly drilled out those jets)
put YOUR old jets (if not modified) back in this carb..


Lastly, (for now), unscrew the choke cable/piston from the carb and make sure it moves in and out, spring is installed, no binding when the handle bar lever is moved...

 

[fazil]

Exactly the same
It reminded me of this:

 

[fazil]

 

[TownsendsFJR1300]

Up close pic's of the plugs, can't tell much from that distance....

How old are they?

There's a fair amount of carbon build up on the outside. That engine should be running CLEANER than that

 

[fazil]

Here is a bigger one:




An other question carb non-related. I bought Chinese levers, after breaking the clutch lever. They look very nice but new ones wobble much more than the old ones. Thickness is the same and the hole diameters look identical but i guess the new ones are a little larger, that's why they wobble. A collar could solve the problem may be. But there is not much space for a collar to put in also, should i go to a machine shop for this?

 

[fazil]

I adjusted the pilot air jet, but it didn't work. Still the same. When i pull the chooke, first it responds and rpm goes high, for 2-3 seconds. Then the engine dies, in any case, if it's hot or cold no change.

 

[TownsendsFJR1300]

When cold, the choke SHOULD raise the idle, then you can lower the RPMs with the lever...

I would start by putting your stock (from the old carb) jets in and go from there.


Chinese knocks off levers are cheap because they generally are not machined as well as OEM parts.
I'd personally put an OEM lever back on that fits right and be done with it.

If the levers are LOOSE, machining them down, will make them looser....

Either have neat looking LOOSE levers, or factory correct fitting levers... Your choice...

 

[fazil]

I remember that, i've put the old jets to the new carb. They should be ok.
But i am not sure about the main needle adjustment. I shoud dissamble the carb and chek everthing from scratch.
Also i saw something that can be a problem while inspecting the carb today. The carb air boot that coming from up (frame and air filter) seems a little bit out of the way it shoud fit. It's a bit crooked fit. Can it be the cause, that if it takes some unwanted air, from that crooked fitment?

When cold, the choke SHOULD raise the idle

It raises the idle at first then after 2-3 seconds, whatever it's position is, if i don't close the chooke, engine dies.

 

[TownsendsFJR1300]

I remember that, i've put the old jets to the new carb. They should be ok.
But i am not sure about the main needle adjustment. I shoud dissamble the carb and chek everthing from scratch.
Also i saw something that can be a problem while inspecting the carb today. The carb air boot that coming from up (frame and air filter) seems a little bit out of the way it shoud fit. It's a bit crooked fit. Can it be the cause, that if it takes some unwanted air, from that crooked fitment?
.

The boot from the air filter to the carb would have an affect on one cylinder vs the other but
not to the extent of how your plugs look.

A carb to cylinder boot leaking would cause that one plug to be white / lean

It also makes tuning IMPOSSIBLE with an air leak..

 

[fazil]

How old are they?

There's a fair amount of carbon build up on the outside. That engine should be running CLEANER than that

They are 3-4 months old. Yes the carbon built up seems not normal to me.

Picture of the boot

 

[TownsendsFJR1300]

Hair line cracks, poor sealing surfaces is what you should be looking for.

 

[fazil]

I took off the carb, tried to open the air side but two of the screws has seized. Couldn't check the main needle adjustment. Checked chooke plunger, it looks ok.
Put it back, with caring of the boot to fit nicely. Took around 1.5 hours, started engine, it fired up after 8-10 tries. Nothing changed
When i pull the chooke, first resonds well and rpm increases, then if i keep the chooke, engine dies, If i roll the gas while chooke is on, engine can hold on.
But also i didn't smell unburned fuel.




I guess, in an other day, i should open up that vacuum side screws and look at the main needle, or change it with the older one. May be that needle is not set to stadart position or diferent, that makes bike run rich from the beginning. Is it possible at idle?

 

[FinalImpact]

Do you have an FSM for this? I'm curious what the sensors are reporting. Also that video said that model had an accelerator pump. If that is not working that would make a cold engine die as soon as the throttle is cracked open further. You may be able to roll it on real slow, but too quickly and it leans out and stumbles or dies.
Float level can really impact idle performance if off just bit and I really don't see the main jet impacting cold start or idle performance.

An air leak between the air box and inlet, minimal to no impact except dirt plugging small idle air passages.

Back to the electric wires. If one of those is a solenoid and it isn't working that could be an issue too. Example during cold start it opens or closes a fuel/air passage. If not working, well you get the idea.

As for choke setting, i was saying compare the exposed area in each setting. What mechanism connects the choke to the slide? Anything? Is it adjustable?

Has it ever worked properly?

 

[fazil]

It was working fine in summer. I mean, it was firing up in first or second try. (Never used chooke in summer)
Now it starts at least in 5-6 tries cold without any chooke. With chooke it never starts.

Those wires are for carb icing heaters. Not selenoids or else. Chooke plunger seems fine, accelerator pump also seems working.
I should check fuel level.