Hi.I have a STIHL 45S lawn trimmer. It starts easy, idles very well and runs well at 1/2 maximum revs. but dies at any more than 1/2 revs. I have replaced the plug, air cleaner filter and put in clean new fuel. Also adjusted the idle and mixture all to no avail. Can you help please ?
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Re: Lawn Trimmer wont reach full revs.
You might want to check the magnito for rust build up. it also wouldn't hurt to check the float or maybe even the valves. since you adjusted the idle and mixture ur probly gonna have to adjust them again to get them back where they should be especially if rust build up on the magnito is the cause of your problem. it wouldn't hurt to check the fuel filter either.
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inside the muffler there is a screen that gets all gummed up, take muffler assy. apart and clean screen, if you have a propane torch, this works well as you burn crud off it becomes ash and wipes or blows off. first link shows how. press the helpful button and follow me on fixya
Oiless fuel ruins your compression. The trimmer should crank anywhere above 50 psi. A good place to start with the jets is 3/4 to 1 out. You may have damaged the new jets by srewing them all the way in. These small jets are often needle thin and can be damaged when bottomed out.
Try turning the choke off after it tries to start. This is a first for me. I have never ever heard of any type of yard implement, chain saw, mower, weed trimmer, etc that came brand new with fuel( gas mixture) in it or in the package. The fuel mixture for this trimmer I beleive is 50:1. Is that correct? This means that for one gallon of gas, 2,56 ounces of two cycle oil is added to the gas.
My nephew had a problem with his Stihl FS55R trimmer, sez it would run on high for a few then quit. Sez it restarts easy and runs on idle with no problem. I pulled carb & found fuel screen full of fine contaminant. This is the screen you see when you drop the bottom pan of the carb. (single screw does it). Reassembled and the trimmer runs on high speed w/o problems. If your primer bulb doesn't pop right back up when you punch it down, it means that the fuel can't get past that screen....
Make sure the carb settings are correct. Screw both tuning screws all the way in and then turn ot anticlockwise the following settings H 3/4 of a turn, L 1 full turn. (this is set to the standard setting)
You need to clean the carburetor. Remove & disassemble. Use a Den Tek Brush, (http://www.shopping.com/xPO-Lustrasilk-Lustrasilk-Cholesterol-Shea-Butter-Mango-20Oz-Bonus), to clean small portals in carb. Spray carb. with carb. cleaner. make sure the small screen in carb. is free of debris. Reassemble and start. If this doesn't work, buy a carb.kit and replace the needle valve, gasket(s), small screen, & diaphragm.
As with all 2 strokes if you have compression and a reasonable spark, you only need fresh fuel with correct oil ratio) and they must go !(as long as you haven't fiddled first and all gaskets are sealing) I start mine by(1) pumping the primer till it is firm,(2) full choke,(3) pull till it kicks ONCE,(4) half choke, pull till it runs,allow to warm up and(5) switch to run (you may need to apply a bit of throttle while pulling as in (4)(or give it a few more pumps if it dies) If all is ok, check that when properly warmed up there is a smooth transition from idle to full revs, if it hesitates it may need the LOW SPEED mixture leaning (clockwise) SLIGHTLY.If it dies the LOW SPEED mixture may need richening(anti-clockwise)(adjust 1/8 turn at a time) Make sure that motor is just peaking at full revs and is on the RICH side of peaking (HIGH SPEED mixture)(this will avoid seizing it Adjust both till it revs cleanly and is JUST rich at full, and idleing nicely and it should start without too much trouble.(If you have fiddled and are lost,-about 2 1/2 turns out from closed on both needles should get you started)