Stihl 028 - Why is the carb spitting at me?
- Thread starter kscycler
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If I had to guess then the metering lever is too high.
Most of 'em are flush with the chamber floor or flush with the gasket surface, depend on brand/model.
Most of 'em are flush with the chamber floor or flush with the gasket surface, depend on brand/model.
I will take a stab at this one.My guess is that you "MAY" have worn rings.The mix should go into the cylinder but is slipping past the rings and going out the carb. I may be wrong, but I have seen this sort of thing more than once. Best of luck, Ken
First turn the high in about 3/8 of a turn and see if that helps, then adjust from there. It could just be pig rich. As mentioned it could be a worn piston but some carb spitting is normal and gets worse with the high set to rich. Steve
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Thanks, Ken. I took the carb off (again) and cleaned the idle jet well. I don't think it's clogged, so you may be right. From your knothole, how would I check for worn rings? A compression check? If I chose to replace them, would I need to change the piston or cylinder as well?
kyle.kipple
ArboristSite Guru
I have been working on my 028 super for a few now and realised it was spitting at me the last time she was running... Took my muffler off and seen my piston and rings where shot...so my guess is we have the same problem...rings and piston...36-40 bucks as long as you don't need the cylinder.
That's a good place to start. I'll take the muffler off when it cools down (it's 105 right now) and take a look.
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Please keep politics out of the chainsaw threads.I deleted any and all of the political crap in this thread,I hope it stays on topic.Dave
SkippyKtm
The Lorax, my FIL rip...
While you're at it, Make sure your muffler screen is not plugged, That will cause excessive carb spit back as well.
While you're at it, Make sure your muffler screen is not plugged, That will cause excessive carb spit back as well.
Another good idea. I'll look at that, too. Thanks...
What was it running like before you rebuilt the carb and points? When you try to rev it up does it blubber or just die? I'd think if the piston and rings were that far shot it wouldn't even start.
Exhaust screen plugged.
Adjusted to rich
Points opening too far and floating at higher RPM (Fish)
Could be piston and rings wore but I'd sure check the easyier things 1st. Steve
Exhaust screen plugged.
Adjusted to rich
Points opening too far and floating at higher RPM (Fish)
Could be piston and rings wore but I'd sure check the easyier things 1st. Steve
This 028 was a parts saw I picked up and revived, and I ran it only one time before rebuilding the carb. So, I replaced the points and gapped them using an old flywheel cut out to leave the hub only, added the missing muffler, and cleaned it up. Compression seems good, and the saw will hang on the starter rope without dropping. From what I recall, the piston and cylinder looked OK to these untrained eyes, but I'll need to look again.
The saw will start, and will idle. It spits just a bit, a fine mist, onto the handle (I have the air filter removed to see what's happening) as it idles. When I try to rev it up, the spitting increases quite a bit and the saw won't rev. It doesn't stumble, but doesn't increase in RPM. When I let off the throttle, it idles again.
Exhaust screen plugged - possibility, and I'll check this
Adjusted too rich - possibility. I'm set at 1 1/4 turn out on both L and H, and I'll try to suggestions above to see if anything changes.
Points openint too far and floating - unlikely, as it hadn't reached higher RPM and it spits at all RPMs
Piston and rings - possibility, and I'll look more closely after I get the muffler pulled off.
Great troubleshooting ideas, all. Thanks for all the suggestions. I'll report back when I get some sleuthing done...
Really sounds like a clogged muff, check it out good or try running it for a bit without the muff. Steve
Yeah, hadn't thought about that. Should be fun, and it'll wake up the neighbors. Easy to check, too...
Sheared Woodruff Key
Replaced the piston and have 130 psi. Still wouldn't start, and then it backfired on me. That gave me the clue I needed. Pulled the flywheel, only to discover the woodruff key had sheared off and the flywheel (apparantly) had rotated on the crank, resulting in bad timing (and the backfire). So I'm thinking the only thing wrong was the timing caused by a sheared woodruff key. D'oh! should have checked that first....
Replaced the piston and have 130 psi. Still wouldn't start, and then it backfired on me. That gave me the clue I needed. Pulled the flywheel, only to discover the woodruff key had sheared off and the flywheel (apparantly) had rotated on the crank, resulting in bad timing (and the backfire). So I'm thinking the only thing wrong was the timing caused by a sheared woodruff key. D'oh! should have checked that first....
Several things here. First of all, you will always get some spitback. Excessive spitback is a symptom of worn piston skirts, not rings. 1 1/4 turns is too rich for a stock saw.
albert
Addicted to ArboristSite
The flywheel and crank stub needs to be oil free and dry before reinstalling. Nut shold be torqued. If done correctly the key won't shear. Points are seldom an issue on these, but usually the condenser causes the most problems. The saw will idle well, but will bog and run ragged at above idle. It is better to put a atom type ignition or a stihl electronic coil on it.
Thanks, and I'll do just as you say. I will try to find a woodruff key at the local Sthil dealer on my way home from work. And I may have a Stihl electronic coil to put in, too. Should be running by tonight...thanks again..
Fish
Tree Freak
Yeah, the electronic coil is the best easiest solution, you don't even have to remove the flywheel and worry about messing that up......
Brad,How can the piston skirt have any wear?The piston's only contact is between the ring and cylinder?Ken
