# Stihl HS45 Hedge Trimmer



## jsouth (Jan 31, 2008)

I rebuilt the carb.The trimmer lacks power.I check the muffler and spark arrester is clean,the trimmer when running is is spitting gas out of the throat of the carb.I adjusted the high needle3/4 out and the low needle 1 turn out.The carb. is zama c1q s70,I put a RB 100 kit in it.I ran out of ideas.

Thanks,
Jerry


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## Rentahusband (Aug 25, 2008)

Depending on how much throttle you are giving it, you will see fuel being sprayed into the throat of the carb. If it is more than that then there maybe an issue with the metering diaphram. Try playing with the H speed screw a little more. Turn it another 1/4-3/4 of a turn. I usually set both H and L at 11/2 turns and adjust from there if needed.
I am sure there will be others with suggestions.


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## jsouth (Jan 31, 2008)

Rentahusband,I have turn the high and low needles out from 3/4 turn to 2 turns and back,still the same.The diaphram is new and the metering lever is set correctly.The compression is 120#.The carb. is spraying gas out through the throat of the carb.and would soak the air filter in no time.I use a ultrasonic cleaner to clean the little carbs. with great success,but this one,is still giving me problems.I use simple green as a cleaner,and also use brake parts cleaner.


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## paulr44 (Oct 14, 2008)

I've worked on a lot of these. Usually just rip out the exhaust screen. Check the port too, and if the muffler feel heavy it may be clogged. All piston ported (as opposed to reed valve) engines produce an amount of spitback. Many of them have a spitback cup or flange to help capture and recycle the spitback. How much that occurs that is considered normal is subjective to the person observing it. HOWEVER, a worn piston skirt and/or cylinder WILL produce more spitback and usually make for idle issues, often wont' idle low at all.

I know you're pulling your hair out, but please check the exhaust port for restriction, perhaps even run it briefly without the muffler (I know there's plastic downstream which will melt eventually if you run it a long time).

You sound like you've done more than a few carbs before. Except for the inlet needle lever height, a carb. shouldn't provide excessive fuel. That leaves the exhaust restrictions and piston skirt condition as issues to look at. For what it's worth, I've never seen a worn out piston on an HS45. Still, it could happen but hedge trimmers usually don't have that kind of issue.


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## paulr44 (Oct 14, 2008)

P.S. Forgive any speeeeling errors or grammatical problems. I'm tired. Thanks!


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## jsouth (Jan 31, 2008)

paulr44, I am the worst when it comes to grammar.The spark arrester screen had come off in the muffler.and I had to fish it out.There is just the screwed in fitting left in the muffler.Anyway the customer came to pick it up,said he did not won"t to spend any more money on it.I only charged him for the parts,not labor.I do this has a hobby,but a times seems more like a job,not a hobby.

Jerry


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## paulr44 (Oct 14, 2008)

P.S. Even as a hobby, you can afford a Mity-Vac which would allow you to test the inlet needle valves on carbs. Don't listen to anyone about a pop-off pressure. What you want to look for is the fact that it will hold pressure. You need to see at least .25 to 
.3 bar (that times 15 = PSI (4 to 6 PSI)), and have it hold steady with no leakage. If you're handy, you could make block-off plates for intake and exhaust with one having a typical fuel line nipple (NPT thread), and make your own CC pressure / vacuum test set. You would need rubber flaps to seal the plates, pieces of old inner tubes work okay but Stihl sells 'em real cheap. I test engines almost daily for CC leaks in the busy season, but if they run a down-and-dirty test is to use carb spray around seals and gaskets, being mindful of hot-mufflers and creating and un-indended fire mind you!


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## jsouth (Jan 31, 2008)

Thanks,Paulr44,I will check into a Mity-Vac.

Jerry


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