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MS 192 TC starting problems when mildly warm

#1

G

GearHead36

I have the above chainsaw. Last year, it was hard to start all the time, so I rebuilt the carburetor with an OEM rebuild kit. It then became easy to start cold and hot. When cold or hot, it starts just as it should. When it's in between cold and hot, though, it can be very hard to start. Typically, if I start it within 10 minutes of using it, it starts fine. After 30 minutes, it will be hard to start. After an hour... I usually have to go get my big saw, because this one won't cooperate.

What causes this?

My premix is ethanol-free 87 octane mixed with Echo Red Armor oil, which has fuel stabilizer. I store my premix in reused Trufuel quart cans. I mix a gallon at a time, which typically lasts me about a month. I have full confidence in my fuel. It works fine in all my 2-cycle equipment, including this saw, except in certain conditions.


#2

StarTech

StarTech

Stihl or Zama kit?


#3

Hammermechanicman

Hammermechanicman

When it won't restart (hope you haven't choked it) pull the plug. Is it wet with fuel? Dry? Oily? Have you tried a new plug when it won't start?

When that saw is warm pulling the rope one time with the choke on can flood the saw. FYI


#4

A

Auto Doc's

When was the last time you replaced the spark plug? Also make sure it the one it calls for. Just because a plug fits does not mean it is a correct one.


#5

FixItFrank

FixItFrank

I chased a very similar problem on an old leaf blower once. And it turned out to be the main fuel line from the tank to the carb. When it was cold, the line was fine. But after the engine ran for a bit and everything got warm, the old rubber line would get a little too soft and could collapse or get a tiny air leak when I tried to start it. It wasn't getting enough fuel. A new fuel line for a couple of bucks fixed it completely.
It might be something to check next time it acts up. When it's warm and won't start, just take a quick look at that fuel line to see if it looks soft or pinched.


#6

StarTech

StarTech

Oh well I thinking the OP used the Stihl's gasket and diaphragm kit which has no inlet needle valve. It so it sounds like a leaky one that is leaking under fuel tank pressurization. If so then the OP needs the Zama RB-69 full carburetor repair kit as the needle valve tip is probably ringed worn.


#7

Hammermechanicman

Hammermechanicman

StarTech said:
Oh well I thinking the OP used the Stihl's gasket and diaphragm kit which has no inlet needle valve. It so it sounds like a leaky one that is leaking under fuel tank pressurization. If so then the OP needs the Zama RB-69 full carburetor repair kit as the needle valve tip is probably ringed worn.
Click to expand...
I was thinking the same thing. That is why i asked him to pull the plug and see if it is wet.


#8

G

GearHead36

StarTech said:
Stihl or Zama kit?
Click to expand...

ZAMA - REBUILD KIT RB-69​


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#9

G

GearHead36

Hammermechanicman said:
When it won't restart (hope you haven't choked it) pull the plug. Is it wet with fuel? Dry? Oily? Have you tried a new plug when it won't start?

When that saw is warm pulling the rope one time with the choke on can flood the saw. FYI
Click to expand...
I pull it with no choke, no throttle. Then with throttle. Then with choke, no throttle. I know this will flood it... that's the goal. Then I pull it with no choke, full throttle, which should clear the flood after a few pulls, resulting in the right fuel mixture at some point in the process.


#10

G

GearHead36

Auto Doc's said:
When was the last time you replaced the spark plug? Also make sure it the one it calls for. Just because a plug fits does not mean it is a correct one.
Click to expand...
I've never replaced it. I got the saw a couple of years ago from my sister. Sometimes it runs great so I haven't suspected the plug.


#11

G

GearHead36

StarTech said:
Oh well I thinking the OP used the Stihl's gasket and diaphragm kit which has no inlet needle valve. It so it sounds like a leaky one that is leaking under fuel tank pressurization. If so then the OP needs the Zama RB-69 full carburetor repair kit as the needle valve tip is probably ringed worn.
Click to expand...
I replaced the needle valve. The old one looked good, but my eyes aren't good enough to see microscopic wear, and since I had a new one, I replaced it.


#12

G

GearHead36

FixItFrank said:
I chased a very similar problem on an old leaf blower once. And it turned out to be the main fuel line from the tank to the carb. When it was cold, the line was fine. But after the engine ran for a bit and everything got warm, the old rubber line would get a little too soft and could collapse or get a tiny air leak when I tried to start it. It wasn't getting enough fuel. A new fuel line for a couple of bucks fixed it completely.
It might be something to check next time it acts up. When it's warm and won't start, just take a quick look at that fuel line to see if it looks soft or pinched.
Click to expand...
This sounds like the most likely cause. I'll have to check that. I seem to remember from when I rebuilt the carb that the fuel line was molded. Is that the case? Or will generic fuel line work?


#13

G

GearHead36

Thanks, everyone for the suggestions.


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