346OE idle issue

[Yotaismygame]

I took in a first year 1999 346xp on trade. Owner said it was a good running saw. (need to talk with him to confirm). When I got it compression felt good, started right up and ran. I only ran it for maybe ten seconds than tore it apart for porting. What I found was a scored piston. So in went a new piston and vac/pressure tested it...more than once. No leaks. From there I replaced the fuel line/filter. Took the carb apart and put it in the ultrasonic. Carb looked clean before it took a bath.

Here's the symptoms: If the low is adjusted a little lean it will stay running but the idle seems too high. Can clearly hear its idling lean. If I richen it up at all it will act like fuel is pooling bringing the idle too low then it dies. Takes three pulls to get her going again and sometimes the high idle is needed. Frist trigger pull it acts slightly flooded. The high side seems completely fine and is consistent. It doesn't seem like a air leak based on testing and how consistent it runs. Just seems like there is no happy medium between a lean idle and too rich. I played with the low jet for at least 30 minutes and never came to a conclusion. I have read about the tank vents on these being an issue especially after porting. I cracked the fuel cap on it while running and it made no difference. All the threads I read about the tank vent and modding it were not about this specific model/year.

I'm open to suggestions on what's going on here. Seems odd the piston was scored but it also looked like someone had cleaned it up and the cylinder maybe tossed a new ring on and ran it. Air leak? I tore it apart and found no bubbles while under pressure. I'm leaning towards a carb issue. ?????

Edit: I did find a leak on the intake boot when I first tested it after porting. Replaced the clamp with a better one and it solved that issue. Maybe that was the cause of the original scoring.

 

[cuinrearview]

99.9% the boot clamp caused the lean condition. If the vent was the problem you'd know it at WOT or the end of a long cut. Did you kit the carb? Re-set metering lever height? If yes to both try a different carb. That one IS 21 years old after all.

 

[RED-85-Z51]

What brand piston/cylinder?

Sent from my LM-G820 using Tapatalk

 

[Yotaismygame]

99.9% the boot clamp caused the lean condition. If the vent was the problem you'd know it at WOT or the end of a long cut. Did you kit the carb? Re-set metering lever height? If yes to both try a different carb. That one IS 21 years old after all.

I don't know if the boot clamp was the original issue. I did not test it until after I ported it. Leak could have been caused by myself. But who knows. Should have tested it as soon as I saw the scored piston. I took the tank off, filled it up, and shook it around and could see it was venting. I did not kit the carb or mess with the metering lever. It was nice and clean inside. Diaphragms were soft like they should be. I'm tempted to buy a china carb for testing purposes only. I should also make some cuts with it and see how it does.

 

[sean donato]

I'll echo the metering lever and spring, that is what largely keeps the saw from flooding at idle. If the replacement spring had a different rate, or the metering lever was set too high, the saw will show poor adjustability from the low jet. I cant remember a pop.pressure for the carb, but I can say it should hold 15 psi wet.

 

[Yotaismygame]

What brand piston/cylinder?

Sent from my LM-G820 using Tapatalk

Oem with meteor piston. I don't mess with AM cylinders.

 

[sean donato]

I don't know if the boot clamp was the original issue. I did not test it until after I ported it. Leak could have been caused by myself. But who knows. Should have tested it as soon as I saw the scored piston. I took the tank off, filled it up, and shook it around and could see it was venting. I did not kit the carb or mess with the metering lever. It was nice and clean inside. Diaphragms were soft like they should be. I'm tempted to buy a china carb for testing purposes only. I should also make some cuts with it and see how it does.

These carbs (if walbro) have accelerator pump issues as well. A new zama is cheap to get.

 

[Yotaismygame]

These carbs (if walbro) have accelerator pump issues as well. A new zama is cheap to get.

I'll check tonight which carb it has. I'm not 100% sold its the carb but the consistency it has while running is pushing me to think its a carb issue. I can tune it either way and it will do the exact same thing every time.

 

[Old2stroke]

I took the tank off, filled it up, and shook it around and could see it was venting. I

Are you saying that when you shook it, fuel came out of the vent? Vent is supposed to let air in not fuel out.

 

[Yotaismygame]

Carb that’s on it is a walbro HDA 159A. Metering lever is just below flush with the carb body

 

[drf255]

Did you pull and replace the Welch plug when you did the carb? That’s where the L circuit is fed.

Make sure you don’t have any lips in the intake tract from porting. Need a smooth transition, or it will cause fuel pooling. Then when you are at optimal L tune, the saw will suddenly die when you move the saw around or the puddle gets big enough. Common issue on the Stihl 024/6 by design.

 

[sean donato]

Carb that’s on it is a walbro HDA 159A. Metering lever is just below flush with the carb body

Cant remember off the top of my head if the hda is flush or down below a bit. I'll have to look at my gauge when I get home amd get back to you.

 

[RED-85-Z51]

Cant remember off the top of my head if the hda is flush or down below a bit. I'll have to look at my gauge when I get home amd get back to you.

HDA HDB and HDC i think are all flush

Sent from my LM-G820 using Tapatalk

 

[RED-85-Z51]

HDA HDB and HDC i think are all flush

Sent from my LM-G820 using Tapatalk

Yes, flush

Sent from my LM-G820 using Tapatalk

 

[Yotaismygame]

Talked with the last owner and it ran just fine for them. Said he put around 8 tanks through it. The 159 carb appears to be for a 350. Do you think it was switched out at some point or did the early 346's come with that carb? I'm thinking of moving up to the 199 carb. There's a new one on ebay now for $48

 

[cuinrearview]

159 was OEM on a 346 too. It went hda-159>el-18>el-32 on pretty much all of them on that chassis.

 

[sean donato]

Honestly, the zama isnt a bad option, get rid of the pesky accelerator pump.

 

[Yotaismygame]

Swapped a zama knock off on it and same deal. Slightly less dramatic but still the same. Can tune it, seems fine but eventually the idle will fall and it dies. I can even keep the idle high and it will do the same thing. Then once I do restart it, it will nearly die until I punch the throttle a few times. Won’t restart unless I activate the high idle most times. Do I need to revisit the the tank vent? Not sure where else to go with this except revisiting what I’ve already done.

 

[Yotaismygame]

Forgot to add with this fake zama I didn’t have to lean out the low like before.

 

[RED-85-Z51]

Give it a shade more low fuel and bring up the base idle...see if that makes any difference. I did a 440e this morning similar to yours and i finally relented and gave it a big swing out on the low...it started to dive, raised the base a turn and it was much happier

Sent from my LM-G820 using Tapatalk