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[pintailslammer]

Hi Guys
I have a 1990 Suzuki LT250F 2wd Quad Runner that I picked up on trade for some truck tires I had.The guy informed that the quad ran but hadnt been ran for a year.I removed the carb and cleaned it all out. I then re-installed it and the quad fired up. I took it out and it seemed to run fine but the next day the cylinder was completely full of fuel. I drained the oil and replaced the filter and oil.I then ordered an after market carb kit and had it installed by a mechanic. The carb wont hold a vacuum test though. It has been taken apart and i cant see anything wrong with it,Had it dunked in a cleaning tank.All ports are clear as a whistle. The quad will run with the choke on but as soon as I try to shut it off,it quits.

Do you guys have any suggestions other than getting a different carb

Thanks
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[leeaspell]

Is it still filling with fuel or is that issue fixed?

[JohninAB]

If the quad will only run with the choke on it usually means you are running too lean. Check your air fuel mixture setting. Should be a screw with a spring on it. Gently turn it in till it is seated then loosen 1 and a 1/4 turns. Try there and then adjust accordingly. My long distance prognosis!

[Ddawg]

Originally Posted by pintailslammer

Hi Guys
I have a 1990 Suzuki LT250F 2wd Quad Runner that I picked up on trade for some truck tires I had.The guy informed that the quad ran but hadnt been ran for a year.I removed the carb and cleaned it all out. I then re-installed it and the quad fired up. I took it out and it seemed to run fine but the next day the cylinder was completely full of fuel. I drained the oil and replaced the filter and oil.I then ordered an after market carb kit and had it installed by a mechanic. The carb wont hold a vacuum test though. It has been taken apart and i cant see anything wrong with it,Had it dunked in a cleaning tank.All ports are clear as a whistle. The quad will run with the choke on but as soon as I try to shut it off,it quits.

Do you guys have any suggestions other than getting a different carb

Thanks


Pin

I would also check your fuel line for cracks, it may be pulling air, I have had to change out the fuel lines on two quads, due to cracked lines, fuel rots the lines over time.

[pintailslammer]

Fuel leak has been repaired,all fuel lines have been replaced,fuel pump has been replaced,air fuel mixture setting are set as per service manual specs

Hope this is more help
I dont know what else to do besides replace the carb

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[lannie]

You could have a vacuum leak between the carb and the cylinder. The rubber that fits between the cylinder and carb needs a perfect seal. You could check this by turning the motor over and blocking the intake end of the carb with the palm of your hand. You should feel all the vacuum on your hand. If it does not have this you would indeed need to have the choke on to get it to run.The Mikuni carb is a very easy one to do with a good exploded diagram. Make sure nothing has slipped etc. If the Vacuum is good and you are sure the carb was done properly I would look at the reed valves next if in fact they were tampered with or touched. Change the spark plug in a 2 stroke at the first sign of any trouble too.

[lannie]

Originally Posted by pintailslammer

Fuel leak has been repaired,all fuel lines have been replaced,fuel pump has been replaced,air fuel mixture setting are set as per service manual specs

Hope this is more help
I dont know what else to do besides replace the carb

Pin

Dont replace the carb pintailslammer. Needle and seat are set properly?

[pintailslammer]

Originally Posted by lannie

Dont replace the carb pintailslammer. Needle and seat are set properly?

How do you set the needle and seat properly? Are they not just put in place and then the small screw tightend down?

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[lannie]

With the float, needle and seat together flip the carb upside down and the "tabs" on the float should be aprox. level with the float bowl. You would bend the small tab that pushes up and down on the wire that is connected to the seat. I am doing this from memory of the Carb. When the carb was rebuilt or the kit put in it was the position of the little circlip changed that is attached to the "long rod". There is actually not that much to go wrong with that carb. Maybe your tech guy built in a small problem? Easy enough to happen, everyone can make a mistake? The needle and seat leaking in the beginning could cause the cylinder to fill. It does sound like things took a wrong turn at the repair to carb stage maybe. Is there anything online for your Carb?

[turbo mulcher]

Do a suction test/ pressure test on the needle and seat also check the tank for particles of rust or dirt, blow carb cleaner through all passages and then air,

[m3mhunter]

If the choke is needed to keep it running I would check your pilot jet. I know you said everything has been cleaned but I had a troublesome mikuni in my Polaris and another in my can am and it took 3 and 4 cleanings respectively to finally get everything if the machines had sat for a long time. The pilot jet that controls the choke circuit sometimes gets plugged solidly and dipping doesn't always get it. Pull the pilot jet screw - count the number of turns it takes to first bottom it out - gently! Then remove, then run a garbage bag twist tie wire (stripped to a bare wire) through the jet. Reassemble and give it a go.

[tommyguitar]

Originally Posted by m3mhunter

If the choke is needed to keep it running I would check your pilot jet. I know you said everything has been cleaned but I had a troublesome mikuni in my Polaris and another in my can am and it took 3 and 4 cleanings respectively to finally get everything if the machines had sat for a long time. The pilot jet that controls the choke circuit sometimes gets plugged solidly and dipping doesn't always get it. Pull the pilot jet screw - count the number of turns it takes to first bottom it out - gently! Then remove, then run a garbage bag twist tie wire (stripped to a bare wire) through the jet. Reassemble and give it a go.

That's right

[pintailslammer]

Originally Posted by lannie

You could have a vacuum leak between the carb and the cylinder. The rubber that fits between the cylinder and carb needs a perfect seal. You could check this by turning the motor over and blocking the intake end of the carb with the palm of your hand. You should feel all the vacuum on your hand. If it does not have this you would indeed need to have the choke on to get it to run.The Mikuni carb is a very easy one to do with a good exploded diagram. Make sure nothing has slipped etc. If the Vacuum is good and you are sure the carb was done properly I would look at the reed valves next if in fact they were tampered with or touched. Change the spark plug in a 2 stroke at the first sign of any trouble too.

Did this test this morning,sucked my palm of my hand right in. I think I might need 40 sticks of dynamite

Any other suggestions.
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[lannie]

Does this help? Is this the Carb you have?


https://sites.google.com/site/suzuki...-s/carb-tuning

[pintailslammer]

Lannie,

No mine is the square top style with 4 screws on it

Hope this link works

http://www.google.ca/imgres?q=lt250f...:23,s:300,i:73

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[lannie]

It really seems like there is a problem with the carb kit install. I think you should take it apart and put it back together yourself. Use a camera or your phone and take many pictures throughout the diss assembly. If it starts with the choke on and will not run after it is running way to lean or there is not fuel at all after the choke is taken off. I know it is frustrating beyond... but..
You don't have a friend around with a bit of know how for a second opinion?
Does not need to be a mechanic just another point of view.

[pintailslammer]

Lannie

I have taken it apart again and re-installed it. I re-vacummed tested it. I have had a mechanic friend look at again as well. do you think i should buy a new needle and seat?

Thanks for your help
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[Zanzibar]

The needle and seat won't stop fuel flow if they are faulty, just let fuel leak past, which was your 1st problem. Everything you have described, points at the pilot circuit.

[pintailslammer]

To shorten things up a bit.The carb wont pass a vacuum test. Does this mean that the needle and seat are leaking? I've taken this carb kit out and re-installed it myself. I am getting frusted a bit to say the least.
Should I just throw the carb back on and run it?

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[pintailslammer]

So I was told to throw the carb back on and run it, I did still runs like crap. Have sprayed the carb down with wd40 to check for leaks,Engine didnt rev up at all. I have also been told to check it for leaks using ether. Has anyone tried this? Is it safe?


Please let me know
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[Brent_reid]

I had a can am dirt bike that would only run with the choke on tried everything then a buddy removed the baffles from the exhaust and it took off like a bat outta heck just a thought

[lannie]

Originally Posted by pintailslammer

So I was told to throw the carb back on and run it, I did still runs like crap. Have sprayed the carb down with wd40 to check for leaks,Engine didnt rev up at all. I have also been told to check it for leaks using ether. Has anyone tried this? Is it safe?


Please let me know
Pin

Does it run better now if you start putting the choke on? If you use ether you are going to spray it on the outside of the carb on every spot that could leak from the outside to the inside. If you start spraying on the outside of the cab and it starts reving up you have a leak. I doubt you have a leak because you said when you out your palm over the carb it "sucked hard" which would indicate it is sealing well. Did you change the plug in it? I did mention that before as 2 strokes are very hard on plugs. How about the fuel getting into the carb from the tank selector switch? That would be shut off to take the fuel line off the carb. Make sure you are getting fuel to the carb in that circuit. The fuel in the tank is good clean gas/oil or injected and not water etc? I know how frustrating it is but you will get there.

[lannie]

Originally Posted by Brent_reid

I had a can am dirt bike that would only run with the choke on tried everything then a buddy removed the baffles from the exhaust and it took off like a bat outta heck just a thought

Excellent suggestion ! The cylinder did get filled with fuel so the exhaust might have been too. Just try starting it with the exhaust pipe loose off the cylinder.

[tullfan]

Ok, hope this helps. If this quad was on my bench and for the symptoms the OP described I would fo this.
Pull carb and remove all jets.
Pilot, main, and air mixture. Be careful of the oring and washer under the spring.
My carbs get put in the ultrasonic but manually cleaning them works too.
Ok so the carb leaks fuel. Thats the job of the float needle and seat. They always come as a set if removable. If not sometimes there is corrosion in the seat that needs to be cleaned. A Q tip and solvent can smoothe the seat out a bit.
Now if the float valve will not hold at least 5 psi its bad, get another set. The fuel in cylinder is an indication of leakage.
Next, float height. Check and double check it. Too high a level and it will make the unit run rich, too low it will run lean. Càuses all kinds of tuning issues and is always over looked.
The pilot jet. Controls 0 to 1/8 throttle. Usually, but not always there is a hole straight through. Dont go sticking anything in there to clean. If uou oversize the hole it will run like crap at idle and wont improve. It will be rich.
Emulsion tube is where long needle travels to work with main jet. Make sure its clean. It gets crudded up and has to be manually cleaned.
Needle controls 1/8-3/4 throttle. Move it up or down as needed to tune.
Main jet 3/4 to wide open. Adjust as needed to tune.
Carbs are easy as pie or frustrating as heck. It sounds like your issue is float height, pilot jet, float needle and or seat. Wish I had it in front of me. Let me know if you need any more info.
Good luck,
Tullfan

[pintailslammer]

Tullfan quoted :Wish I had it in front of me. Let me know if you need any more info.

That could be arranged::sHa_shak eshout:

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[pintailslammer]

Well Fellows, I picked a another quad for parts,removed the carb from it,took it apart and cleaned it up. vacuumed tested it and it passed. Installed it on quad and it runs fantastic now. I dont know what is wrong with this other mikuni carb, I was gonna to strip it down again, or should I throw in the bush?


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[deanmc]

Originally Posted by pintailslammer

Well Fellows, I picked a another quad for parts,removed the carb from it,took it apart and cleaned it up. vacuumed tested it and it passed. Installed it on quad and it runs fantastic now. I dont know what is wrong with this other mikuni carb, I was gonna to strip it down again, or should I throw in the bush?


Pin

There is still a blockage in the pilot circuit. You need to soak it overnight in a good carb cleaner and blow compressed air through every passage. It can take a lot to remove old varnished fuel.