192tc bogging off idle

[goatiemon]

good day
I'm pretty new to chainsaw mechanics
but I've lurked here a bit
thanks in advance for yer help

l have a Sthil 192tc that was given to me cuz it didn't run

cleaned fuel/impulse lines and it ran fine
always a little boggy off idle, but totally useable

just replaced the piston and cylinder
(cheap ones)
and it worked great for a day or two

now
it starts cold easily and idles
fine
but boggs super badly when you pull the trigger
to the point of dieing if you don't feather the trigger

and it is really hard to start warm

once you get it going it saws fine

seems like an air leak

my reading seems to indicate the accelerator pump?

l tried a different carb (Zama off eBay)
and it was worse
couldn't get it tuned happily
(perhaps user error)
same bogging/warm start issues

help please

thanks
goat

 

[goatiemon]

any thoughts?

 

[cookies]

I wonder if the new piston/cylinder has good compression and or if your plug/coil is bad or carb is adjusted too lean

 

[goatiemon]

l haven't measured compression
(don't have any way to)
but the thumb over the plug hole test says there is compression

it is a new plug (first thing l tried - it's so easy)

don't know how to test the coil, but the spark looks ok

don't claim to be a carb expert, but l have tried to tune the problem away
l would guess that if anything my settings are rich

just got a new fuel filter, going to try that

thanks
goat

 

[mountainlake]

Is the muff screen clean or gone. Steve

 

[cookies]

l haven't measured compression
(don't have any way to)
but the thumb over the plug hole test says there is compression

it is a new plug (first thing l tried - it's so easy)

don't know how to test the coil, but the spark looks ok

don't claim to be a carb expert, but l have tried to tune the problem away
l would guess that if anything my settings are rich

just got a new fuel filter, going to try that

thanks
goat

when saws fall under 135ish psi compression they also have low vacuum limiting the fuel being drawn in and its atomization. Folks around here suggest setting the plug gap wide then check or even test once warmed up and giving issues. As a beginner I suggest tach tuning our carbs using the service manual directions. A pressure/vac test is mandatory if I build a saw and when diagnosing..some times they only leak when warm.

 

[goatiemon]

I'll see what l can do about pressure/leak testing

spark screen has been deleted

thanks
goat

 

[Brushswamper523]

I have done a few of this in the last month or so. When you rebuilt it, what sealer did you use on the pan? Was it fuel safe? Running good for a day or two then acting up may be something to look at.

 

[goatiemon]

l used some fancy Toyota seal stuff l had around
it's supposed to be fuel safe

thanks
goat

 

[Captain Bruce]

l haven't measured compression
(don't have any way to)
but the thumb over the plug hole test says there is compression

it is a new plug (first thing l tried - it's so easy)

don't know how to test the coil, but the spark looks ok

don't claim to be a carb expert, but l have tried to tune the problem away
l would guess that if anything my settings are rich

just got a new fuel filter, going to try that

thanks
goat

Your thumb is your foundation for a thread that goes on like a stepped on tube of silicone??? SIR! The engine is total junk; prove the world wrong.....a proper compression tester can be rented if you aren't a mechanic Start with, its junk. Maybe saves you 12 Bucks, + tax...

 

[sean donato]

Crank seals, intake boots, carb issues. Add a proper spark tester to your tool list. Checking spark with a plug tells you it makes pretty blue light in thin air. Not under compression.

 

[goatiemon]

sounds like l need spark and compression testers, I'll work on that

couldn't find cracks in the intake boot

I'll do some more carb cleaner leak testing (haven't been able to make it act up that way so far)

changing the carb seemed to make it worse, but l can't say the new carb was "known good" since l don't have another saw to try it on

thanks for all the help
goat

 

[singinwoodwackr]

probably an air leak somewhere in that “cheap” new aftermarket motor.
the cheap aftermarket carbs are just as bad in my experience.
get a copy of the full manual from Benson and do a vacuum test on both the carb and motor. (‘Beg for manuals’ thread)

what was wrong with the OE p&c and carb?

 

[stihltech]

Pick the saw up by the starter handle. Does it hold, go down slowly, or just drop?

 

[goatiemon]

the original cylinder had a big chip out of the wall above one if the ports (intake l think but would have to look)
piston was very scored

it currently has the original carb
(l tried swapping it because l thought that the problem might be due to the accelerator pump - and a different carb might fix it)

l will try the pull cord compression test and report back

thanks
goat

 

[purdyite]

I use an ultrasonic cleaner on carbs...twice recently, after several 8-minute heated baths and carefully blowing with canned air, the problem I was trying to solve was fixed--one on a 192t. Those tiny channels in the carb (I think) were clogged or plugged. I didn't want to remove the welsh plugs. I think that in the past when I thought the carb was clean, it may not have been.

But persistence wins the day every time. My 192t was a pawn shop buy; I also put a new P&C on it. It's working pretty good now.

 

[singinwoodwackr]

Just did the same with 3 200t carbs...sonic tank did the trick.

 

[lone wolf]

Just did the same with 3 200t carbs...sonic tank did the trick.

If you are 3 for 3 on that you are luckey or they were good to begin with. I have piles of them .

 

[lone wolf]

good day
I'm pretty new to chainsaw mechanics
but I've lurked here a bit
thanks in advance for yer help

l have a Sthil 192tc that was given to me cuz it didn't run

cleaned fuel/impulse lines and it ran fine
always a little boggy off idle, but totally useable

just replaced the piston and cylinder
(cheap ones)
and it worked great for a day or two

now
it starts cold easily and idles
fine
but boggs super badly when you pull the trigger
to the point of dieing if you don't feather the trigger

and it is really hard to start warm

once you get it going it saws fine

seems like an air leak

my reading seems to indicate the accelerator pump?

l tried a different carb (Zama off eBay)
and it was worse
couldn't get it tuned happily
(perhaps user error)
same bogging/warm start issues

help please

thanks
goat

You got me at "cheap ones" Now you cant tell what is wrong because China crap is never reliable. If it was all OEM I would say carb is bad but we wont know now. Like it was said do a real compression test or forget it.

 

[singinwoodwackr]

If you are 3 for 3 on that you are luckey or they were good to begin with. I have piles of them .

I ran the disassembled parts in a small tub of Berryman's carb cleaner floated in the main tank.
Just soapy water wasn't cutting it.