Good news, I replaced everything we talked about and got it running. Bad news is it won't idle. I rebuilt the carb with that kit but is there something else I should do. I turned each screw one full turn. It starts when I put the on off lever all the way down then ot runs like a banshee. Then I have to keep hitting throttle to keep it running. I'm really pumped it's running though. Now just gotta get it to idle.
Rebuilding a Stihl 034, should I try it?
- Thread starter dabills
- Start date
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SteveSr
Addicted to ArboristSite
Which position of the master control lever is it in when it runs like a banshee? If it is in part throttle (starting position) it should run like a banshee (almost). Check out the owners manual for just about any Stihl saw for proper Master Control Lever operation. It only works correctly if operated in proper sequence. You should be able to sequence it without starting the saw.
Once you hit the throttle from starting position it should drop into idle position and the saw should idle. If it is in this position and you have to keep hitting the throttle to keep it from stalling the LA screw may be too far out. Try cranking it in a few turns as it sets how far the throttle plate is open at idle. If closed it obviously won't idle. If the LA is cranked all the way in and it still won't idle you have another issue.
Yes in part throttle position. Then it will only stay going only if I rev it. Do I need to clean out some jets on the carburetor? Seems like it would need it after sitting 10 years. Everything I could see I cleaned but I'm reading there are more under the welch plug, in particular the idle jet?
Edit: I did mess with the LA screw a few turns but didn't want to mess with it too much as I couldn't find any info on factory settings. I'll try cranking it in a few more turns tomorrow.
On a positive note this saw sounds like a beast!
Thanks!
SteveSr
Addicted to ArboristSite
The idle circuit is under the welch plug. However, I have NEVER had to pull the welch plug due to clogging under there. If you pull the welch plug you'll likely be in a heap of trouble as you'll never get the new one to properly seal. If you want to test the idle (or HS) circuit find a piece of RUBBER wire insulation that fits tightly over the straw on a can of carb cleaner. Cut the ends flat with a razor blade as this will have to seal with the hole in the metering chamber. Open the "L" screw 3-4 turns and inject carb cleaner into the idle passage hole in the metering chamber. You should see carb cleaner coming out of the idle hole(s) in the venturi of the carb. You can also test (& clean) the "H" circuit the same way. You'll likely need 3 or 4 hands for this or put the carb in a small vice (with a couple layers of duct tape on the jaws) to hold it.
The LA has no factory settings. If too far out it will stall at idle. If too far in it will idle too fast and the chain will turn. Aim for the second scenario and then back off the LA screw until the chain doesn't turn and then a bit more.
BTW, uncontrolled or stalling at idle can also be an indication of an air leak somewhere. Did you do a pressure and vacuum test after you put everything back together?
I'll mess with LA screw later. Hopefully that does it. I did not pressure test after putting back together didn't even think of it. Thanks for your help.
cuinrearview
Red saw lover
More than likely the idle was turned down once the air leak started.
That screw did look like it was way out I'll give it a look later, thanks.
Like the Chinese say "sum ting wong"
SteveSr
Addicted to ArboristSite
A stock saw SHOULD run just fine at standard carb settings. So you have either got a bad carb or an air leak. Those carbs are pretty simple so I am betting air leak. I wouldn't run the saw much, if at all, until you can verify pressure/vacuum status.
BTW, the best way to test the whole saw at once is to block the intake behind the carb, the muffler, and test at the spark plug with a spark plug adapter. You may need to visit the hardware store for a suitable sized o-ring to put on the spark plug adapter to prevent leaks here.
Before you do this you are just guessing and may roach your new top end. 2-strokes run best... right before they seize up!
cuinrearview
Red saw lover
I'm betting carb. I had one of the "good" OEM China Zamas that did the same thing. No amount of cleaning and re-building would make it run right.
I just read this entire thread.dabills,im really pulling for ya man,hope you get her going soon.Sounds like you are close.My first rebuild was an old 028 fb.I swear after buying tools,parts,and cleaners,I could have bought a brand new saw.But it sure was a lot of fun.
SteveSr
Addicted to ArboristSite
Easy enough to verify "L" and "H" circuits are clear with above procedure. Not much else but metering lever height which I wouldn't think would keep it from idling.
cuinrearview
Red saw lover
Leaky welch plug?
SteveSr
Addicted to ArboristSite
Personally I have not run into these but know that it can happen. However, I would think that it would take an awfully BIG leak to make it so rich that it wouldn't idle at all. And if that was the case it would be so rich that it would run at part/full throttle like a turd which contradicts the OPs "banshee" account.
On an old carb where the welch plug sealant has de-laminated, chipped off, or otherwise disappeared. I just take a toothpick and some water THIN superglue and run a bead around the plug and then let it cure for a day or so before putting the carb back together.
cuinrearview
Red saw lover
Had it happen, with this specific carb. That's why I asked.
Also, be very cautious suggesting "superglue". Not all formulas of that very generic term are impervious to gas and oil. I got a story about that one too
.Uhhh I may have messed up. I watched a video of an 036 carb rebuild so I tried to make mine look like his, nice and shiny, scrape everything off. I thought the sticky gunk, amber in color needed to go because it was old gas remnants on top of (what I think is the)Welch plug. Did I destroy the seal that was meant to be there? Lol, only me.
cuinrearview
Red saw lover
Possibly
SteveSr
Addicted to ArboristSite
Yes, and probably no. On mine it was already brown and de-laminated from the floor of the metering chamber so it wasn't sealing anything anyway. I would scrape off any remaining old sealant with the tip of an x-acto knife in the joint between the carb and plug. Next, clean with some brake cleaner on a Q-tip. Now apply a small amount of thin super glue and spread it around with a toothpick.
Now the hardest part - Put the carb (metering chamber up) in a warm/damp location probably at least overnight to let the super glue cure fully. Super glue polymerization (cure) time is directly proportional to the gap being filled / thickness of the glue. Since you have some open sitting on a flat surface it may take a relatively LONG time to cure fully. You'll know it when it is fully cured it will be hard and might have some "frost" looking outgassing components around the joint. Only now put the carb back together.
If you do this you'll know for sure that the welch plug isn't leaking but it probably wasn't leaking to begin with! Even the carb manufacturers didn't always seal them, but then they also have special tooling for inserting and crimping them into place so they shouldn't leak. Now with EPA they are sealed for consistency and to increase yields and reduce rework.
Other carb things to verify...
1. Correct assembly of the metering diaphragm and gasket. Should be carb base, metering gasket, metering diaphragm, metering chamber cover.
2. Metering lever height. If you used the old metering lever as I recommended, it should be correct but you should verify it. If you used the new lever it will need to be set.
