My 268 xp won't idle

[GWJ]

Not sure what's wrong, but I can't get my 1990 268 xp to idle. It starts fine, but will die if I don't stay on the gas. The funny thing is when I am on the gas, she runs like a raped Indian. And a couple of times, when at full throttle it almost seem to run lean ( Like when you run out of gas). Yes, I have a full tank.

BTW, I bought her from an older gentleman. He said, it has last then 20 hrs on it, and it looks like it too. The compression is 182 psi, and new plug, and air filter. I'm running the Truefuel 50 to 1. Any help with this model would much appreciated!!

 

[GWJ]

Anyone have an idea, other then turning up the idle screw?

 

[Boleclimber]

Search how to adjust your Carb. If the saw doesn't respond to a carb tuning. Look into rebuilding the carb, replacing the fuel line and inspecting the tank vent.

 

[GWJ]

Search how to adjust your Carb. If the saw doesn't respond to a carb tuning. Look into rebuilding the carb, replacing the fuel line and inspecting the tank vent.

It runs great above idle....its when you let it set without the throttle. I would think if the fuel line/tank vent were bad, or pluged, it wouldn't run good above idle. Not sure if I'm correct on that, though????

 

[Boleclimber]

It runs great above idle....its when you let it set without the throttle. I would think if the fuel line/tank vent were bad, or pluged, it wouldn't run good above idle. Not sure if I'm correct on that, though????

You are most likely correct on vent. However, if you have the tank out to inspect or replace the fuel line, you might as well inspect the vent.

The issue is most likely your L side tune. You may be too rich or too lean. With out having the saw in my hands, it is difficult to determine which it may be.

The issue of leaning out, at times, at high RPM is odd. You could have multiple issues going on. Until you get the low side figured out. It will be hard to figure the high side issue. Combat one issue at a time.

 

[SkippyKtm]

Sounds like a possible air leak, could be a carb issue too especially if its been sitting around a long time. I would go through the entire fuel system, fuel line, fuel filter, impulse passage way, clean the carb with a USC (ultrasonic cleaner). Check for vacuum leaks as well.
I wouldn't use it until you get it sorted out, or you could fry your piston....

 

[SkippyKtm]

It runs great above idle....its when you let it set without the throttle. I would think if the fuel line/tank vent were bad, or pluged, it wouldn't run good above idle. Not sure if I'm correct on that, though????

Could be the idle circuit is plugged up, you need to clean the carb with a USC.

 

[GWJ]

You are most likely correct on vent. However, if you have the tank out to inspect or replace the fuel line, you might as well inspect the vent.

The issue is most likely your L side tune. You may be too rich or too lean. With out having the saw in my hands, it is difficult to determine which it may be.

The issue of leaning out, at times, at high RPM is odd. You could have multiple issues going on. Until you get the low side figured out. It will be hard to figure the high side issue. Combat one issue at a time.

Can you help me find my gas vent? I've done a search, but can't find any pictures for the 268. Could it be a plugged fuel filter? Not sure if the original owner replaced it????

The low and high screws should be 1 turn out, right? What about the idle screw? Can you set the L and H screws by a tach? Thanks for the info!!!!!

 

[GWJ]

Sounds like a possible air leak, could be a carb issue too especially if its been sitting around a long time. I would go through the entire fuel system, fuel line, fuel filter, impulse passage way, clean the carb with a USC (ultrasonic cleaner). Check for vacuum leaks as well.
I wouldn't use it until you get it sorted out, or you could fry your piston....

Thanks.....maybe I'll get a carb rebuild kit. Its an 1990 model, and he said, he only had 20 hrs on it.

 

[GWJ]

Could be the idle circuit is plugged up, you need to clean the carb with a USC.

So, if I rebuild the carb, that will take care of the idle circuit???

 

[hammerstrap]

I just replaced the vent on my 266, the vent is in the fuel tank on the right hand side in front of the av mount. The vent is part number 501629601
and is around 10 dollars. You may be able to drive it out from the fuel hole. It is the little black tube in the top of the tank. I replaced mine because it would run on its side with the fuel cap off. After replacing the vent it ran the same way. I took the carb off and found the expansion plug under the diaphragm had come out. I put the plug in and expanded it and all is good now.

 

[GWJ]

I just replaced the vent on my 266, the vent is in the fuel tank on the right hand side in front of the av mount. The vent is part number 501629601
and is around 10 dollars. You may be able to drive it out from the fuel hole. It is the little black tube in the top of the tank. I replaced mine because it would run on its side with the fuel cap off. After replacing the vent it ran the same way. I took the carb off and found the expansion plug under the diaphragm had come out. I put the plug in and expanded it and all is good now.

I take it, I need to strip all the panels off to get to the vent?

 

[272super]

Just crack open the fuel cap while you are trying to get it it idle. If it does not change anything,the vent is not the problem. Does it idle if you turn the idle screw up? Adjust the low speed screw a quarter turn each way and see if it makes any difference. There probably is not much wrong with your saw,just a simple carb adjustment. If nothing helps,then pressure test,for an air leak. That that can cause your problem too and can ruin your top end if left unrepaired.

 

[Cliff R]

I had exactly the same problem with my 268XP. I did everything to solve the problem, which included crank seals, intake gaskets, carb kit, fuel line, and tank vent. It still refused to hold an idle adjustment and would stall out. Drove me nuts. So I cleaned out the carb and kitted it again, no improvement. I was advised by someone on this site to remove the welch plug in the carb, as there may be a spec of debris under it. Sure enough, that was the problem. It's ran flawlessly every since.....Cliff

 

[GWJ]

I had exactly the same problem with my 268XP. I did everything to solve the problem, which included crank seals, intake gaskets, carb kit, fuel line, and tank vent. It still refused to hold an idle adjustment and would stall out. Drove me nuts. So I cleaned out the carb and kitted it again, no improvement. I was advised by someone on this site to remove the welch plug in the carb, as there may be a spec of debris under it. Sure enough, that was the problem. It's ran flawlessly every since.....Cliff

Does the rebuild kit come with a welch plug, and how do you get it out, the right way???? Thanks in advance!

 

[GWJ]

Just crack open the fuel cap while you are trying to get it it idle. If it does not change anything,the vent is not the problem. Does it idle if you turn the idle screw up? Adjust the low speed screw a quarter turn each way and see if it makes any difference. There probably is not much wrong with your saw,just a simple carb adjustment. If nothing helps,then pressure test,for an air leak. That that can cause your problem too and can ruin your top end if left unrepaired.

I didn't want to change the setting, because I'm sure the original owner didn't. So, first I want to check the vent, then the welch plug, when I do a carb rebuild. I don't think its the vent, because I ran it for 5 min, and opened the gas cap, but I didn't see or here the positive pressure escaping.

 

[038magslinger]

just a tip

this is a tip passed down by an old friend of mine who had worked on saws for years ,after cleaning the carb and replacing the welch plug take a small amount of clear nail polish and brush on over the seams of the plug, works great and it does not affect your carb or breakdown overtime.

 

[GWJ]

You are most likely correct on vent. However, if you have the tank out to inspect or replace the fuel line, you might as well inspect the vent.

The issue is most likely your L side tune. You may be too rich or too lean. With out having the saw in my hands, it is difficult to determine which it may be.

The issue of leaning out, at times, at high RPM is odd. You could have multiple issues going on. Until you get the low side figured out. It will be hard to figure the high side issue. Combat one issue at a time.

You might be right. I pulled my carb off today, and checked the L and H screws. The L was set at 1 1/4 turns out, and the H was 3/4 of a turn out. Does that seem right?

One other question, when I unscrewed my idle screw, it was like 4 turns out. Is that in the normal ballpark, and does the idle screw have a ball in the same location as the idle screw???

 

[fearofpavement]

You might be right. I pulled my carb off today, and checked the L and H screws. The L was set at 1 1/4 turns out, and the H was 3/4 of a turn out. Does that seem right?

One other question, when I unscrewed my idle screw, it was like 4 turns out. Is that in the normal ballpark, and does the idle screw have a ball in the same location as the idle screw???

Those screw settings may or may not be correct. They vary from carb to carb. You should have tried adjusting the idle mixture before pulling the saw apart. It may be that the problem could have been resolved by adjusting the screw 1/4 turn. At least that could/should have been eliminated FIRST. Always start with simple cheap stuff and then up the ante as necessary. The carb screw settings can be checked with the saw assembled by gently turning them in and counting turns and then returning them to the original location. Most chainsaws have a starting point of about 1 turn out from lightly seated and then get adjusted from there.

 

[SkippyKtm]

Be sure the impulse passage way is not plugged-- its a tiny hole that runs from the pump side of your carb through the manifold and down into the crankcase. It provides the energy (pulses) to the pumper side of your carburetor so it can pump fuel to the metering side of the carb. I use 15psi compressed air on the passageway and listen to hear the sound of the air making its way into the crankcase.