Super xl... rebuilt carb... runs like new for 5 min or so of cutting, then dies at WOT...

[sliceoflife]

So I got a Homelite super xl it started up with some gas down the throat so I rebuilt the carb now it runs perfect for about 5 minutes I'd assume Until It's Hot then it dies at wide open throttle and it fights me trying to start it back up seems like I have to turn the low carb adjustment all the way counterclockwise super rich and the high all the way clockwise super lean as well as maxing out the idle throttle screw and it's still floods with open throttle and never gets enough gas at idle... but only after it heats up... when cold, the thing runs like a clock.


Any idea what this indicates?

 

[hacskaroly]

I rebuilt the carb

Did you just replace the diaphragms or did you also clean out the jets too? Some other things to check:

• Spark arrestor clogged?
• Clogged fuel tank vent (vapor lock)
• Old/blocked fuel filter
• Potential spark plug or coil problem?

 

[sliceoflife]

Thanks... did replace needle and scrubbed whole thing with carb cleaner. I didn't remove and clean beneath the hammer in plates tho... think doing that may fix it?

I'll check spark arrestor screen and tank vent... as soon as you said it... vapor lock made sense to me.

 

[NSEric]

Does it have good compression?

 

[sliceoflife]

Feels like it. Another tool I still need is a meter, but it feels about right when pulling it.

 

[hacskaroly]

I didn't remove and clean beneath the hammer in plates tho... think doing that may fix it?

Not sure what part you are referencing by hammer, but if it is the inlet needle under the metering diaphragm, then yes, you will want to remove that and clean that spot out, that is the main jet. When using carb cleaner, you should have all the gaskets, diaphragms and the inlet valve out as carb cleaner can damage them and cause the nose of the inlet needle to swell.

 

[sliceoflife]

I mean those little coin like plates that you need to drill through, hook and remove then punch in the replacements after. I didn't deal with any of that; but everything that could be removed without destroying it was removed and cleaned; as well as every jet I could access. Went over it pretty thoroughly; but as mentioned... I never touched those replacement punch in plates.


Google refreshed my memory: "Welch plugs". Didn't touch any welch plugs.

 

[hacskaroly]

Google refreshed my memory: "Welch plugs". Didn't touch any welch plugs.

Yeah, I have not messed with those yet either.

 

[rmfinnern]

So I got a Homelite super xl it started up with some gas down the throat so I rebuilt the carb now it runs perfect for about 5 minutes I'd assume Until It's Hot then it dies at wide open throttle and it fights me trying to start it back up seems like I have to turn the low carb adjustment all the way counterclockwise super rich and the high all the way clockwise super lean as well as maxing out the idle throttle screw and it's still floods with open throttle and never gets enough gas at idle... but only after it heats up... when cold, the thing runs like a clock.


Any idea what this indicates?

I had that exact same problem, was told to replace the crank seals, that solved it.

 

[sliceoflife]

That was my first suspicion, and if it turns out not to be vapor lock, will probably be my next step.

 

[rmh3481]

Check the gaskets to diaphragm order in the carb. Sounds like its starving for fuel. On the pump side (single screw) the diaphragm goes down first, followed by the gasket and then the cover. On the metering side (4 screws) the gasket goes down first, then the diaphragm and then the cover. Finally, check the lever height and replace the fuel filter.

 

[sliceoflife]

Thank you everyone...
So Crank seal was what I feared it would turn out to be, haven't tried that fix yet so it'd be a learning experience...
Vapor lock I hadn't considered but made sense when it was suggested...
Carb diaphragm/gasket flipped I considered but doubted because I literally JUST did that to another saw, and it died after a few seconds; not several minutes of cutting like this saw did.


So Took it out and figured I'd test in order of simplicity... First try and disprove vapor lock, then rebuild the carb again and ensure it's right; and if all that failed; pressure/vacuum test to check the seals....


Started right up as usual @ default 1.25 turns out on both adjustments with idle throttle screw in pretty deep. A minute or two of revving and tuning and it starts dying. So I loosen the gas cap... behaves... different... not fixed, but better? Tweak the L a touch and remove and replace cap entirely... Pull it over again and it runs like a bat out of hell... unscrew the Idle throttle screw a ton and it starts idling nice again... take one cut off a 12" diameter log... seems to be running pretty good so I turn it off.

Pull the cap and give it a good clean; blow it out to make sure the vent hole isn't clogged... back on... start it up and it runs like new and makes several cuts over the next ten minutes with no problems...

Guessing vapor lock was the problem... I'll confirm next time I can get out there and spend a good 30 min or more running it to be sure.

 

[sliceoflife]

So pulled it out today and once again its trouble. It was dying at idle after 1-3 minutes, again played with h and l settings and no better. Realized I never pulled the spark plug, because it fired fine when I got it... pulled it and good god... how that fired I have no clue. It was a blob of carbon... I'd bet money it would never sparked I hadn't seen it myself... cleaned it as best I could and cut three logs down but also ordered a new plug... it still looks pretty bad even after cleaning.

 

[farmhard]

I'd be looking into a coil. We spoke about changing the seals on this one in another post which is a VERY GOOD IDEA. If a seal goes hard it can score the crank and then it is useless. Does this one have the blue coil of death? Leave it in a crock pot on low overnight and see if anything changes. Adjusting the fuel ratio changes the amount of spark needed to fire it under pressure. I just went through this with an 028. I don't bother to pressurize, I just rebuild. It wound up being the coil. I stock the seals so it was no biggee and I get to see inside and check crankcase for corrosion. On a vintage saw it's a very important to check for internal corrosion before it takes out the p&j. Good luck in solving!

 

[sliceoflife]

So; after I checked the carb and reset the lever arm meter; it didn't fix it no matter how much I tried to tune it... spent maybe a half hour adjusting and trying to get it to run... and while it cut; it just didn't want to run well...

Then I took it out the next day and did nothing besides a small adjust on carb settings and it started right up and tuned easily and has been running great since. (3 days in a row, maybe 1-2 hrs total).

One of those mysteries.

 

[farmhard]

Cooler weather

 

[sliceoflife]

Actually it's been near 80 here most of the past week. Wondering if maybe there was a fuel system issue that worked itself out (partial obstruction in line that dissolved or something, perhaps).

 

[Tony Mayhew]

I didn't hear anything about you removing the brass breather screen from the fuel cap and replacing the duck bill behind it? Just remember this, anything like intake boots, duck bills, grommets on homelites are guaranteed melted into a black gooey mess! Gasoline really did a job on that cheap ass rubber that they were using on their equipment. It's a pain in the ass to remove the brass piece in the fuel cap so be very careful what tool that you use for removing it or you will stab a hole in the end of your finger and curse like hell! I own at least fifty homelites and every single one of them needed this done! And if you go visit Leons chainsaw parts and repair videos you will find whatever you need to know about a homelite chainsaw my friend!