372 logy

[stumper]

One of my 372's is what I'll call logy.  It start fine, has clean air filter, good compression and spark but does not want to rev up or have power when it does.  It is fine for one or two cuts but once warm is runs poorly.  If I just open the throtle normally is kinda bogs down.  If I open it slowly it revs to full scream, but if I give it a load and fall from full rpm is goes to no power.

I have sprayed the carb with carb cleaner pulled the top plate sprayed that.  Adjusted the high and lower jet still runs like crap.

Any thoughts?

[Satamax]

Last time i've had this type of prob, it was the air screw on a stihl.

[John Mc]

I'm not exactly the first person you'd want to ask on engine troubles, but it does sound as though it could be running a bit lean. Low speed mixture too lean can cause the problems you described on acceleration from idle. High speed mixture too lean might cause the lack of power under load? If it's not caused by mixture settings, maybe an air leak or something causing it not to get enough fuel (bad fuel line, bad diaphragm, plugged fuel filter)??

As I said, there are others on here far more qualified than I to diagnose this.

[barbender]

Check your gas tank vent- if it plugs up with bar oil and saw dust the carb can't pull fuel.

[lumberjack48]

Check the screen in the muffler, that was the first thing i took out of a saw.

[stumper]

Thanks

Fuel filter - good
tank vent - good
Muffler screen ???  What is a muffler screen?  It seems to be missing.  This saw has some age on it.  I have rebuilt it once.  Add to that the fact that I no longer cut in the woods except for my own firewood or a small harvest on my own land.  My primary use is in support of my stump grinding business so the Forest Circus does not have any reason to check my saw so the screen went missing years ago.

[Al_Smith]

The best thing to do if you suspect carb problems is just rebuild the thing right off the bat .

People play with them,take them apart a zillion times then finally rekit them and all is well .90 percent of fuel delivery problems are carb related and of those another 90 percent is just simpley the carb innards have gone stiff on you from old age .

[lumberjack48]

Its the spark arrester screen in side the muffler, you have to take the muffler off the saw than take the muffler apart, if theres no screen in it, thats good, just throwing out things stumper.
Throw a another carb on it, thats most likely the problem.
Good luck with it, its usually something simple.

[Ianab]

What Al says.

If the saw is an older one, all sorts of perishable bits in the fuel system could have gotten hard ,or soft, or split etc.
You could spend all day figuring out exactly which one. So just go through and replace them all. It's not like they are expensive parts, and even if the fuel line is OK right now, it might split in 6 months time. Same for all the other little bits in there. Replace em all, you will have got the faulty part, and the next 3 that were going to fail as well, and the saw should then be reliable for many more years.

Ian

[Al_Smith]

There's a lot of places on line that sell rebuild kits for carbs .I often refer to Baileys because they're a supplier most people are familiar with .

However there must be a couple of hundred others ,Google it if you want .

Usually when I order kits I get at least two of every  type I need and of the more common such as a Tilley HL or Walbro HK perhaps half a dozen .Then again in addition to being a collector I might work on any number of saws during the year which varies .Some supply houses have a flat rate shipping it doesn't cost any more to ship 20 than it does one .Of course you can by kits locally too at sometimes not a bad price excepting anything that says Stihl on it .You kinda gotta pay for the name although the parts aren't any different .

Through my crystal ball I see  Stihl dealers getting red in the face at the mention of that ----good . :D

[Caloren]

Through my crystal ball I see  Stihl dealers getting red in the face at the mention of that ----good .

Went to my Stihl dealer [local Ace hardware] to get a carb kit for my MS170 last year, he told me "you can get one on the web cheaper than I can get one". Sort of like the guys down there.

Loren

[Al_Smith]

There are a few dealers ,the good ones that stock a variety of parts ,mostly OEM like Tillotson and Walbro kits which retail for a lot cheaper than OEM Stihl parts .

There are some that sell a variety of products to the general populace and provide excellant honest service. Then there others who sell to the suburbinite home owner who really isn't knowlegable .Sort em out ,deal with the good ones and let the others find another kind of business .Works for me .

[jcbrotz]

I would bet on you rfuel line being checked/cracked.