# Stihls hs45 not starting??????



## vach55 (Nov 10, 2010)

I have a Stihls HS45 hedge trimmer recently the small metal clip that holds the choke lever on inside the air cleaner broke off and was sucked into the intake through the carb the trimmer shut down . I tried to restart but could not pull string . not knowing what was the problem at the time I started to take the machine apart and noticed the clip was gone so thinking the metal piece was in the crankcase I tried to free the piston by turning the flywheel . I was able to get the piston free so I finished taking the machine apart. I I pulled the motor out and took the cylinder head apart from the crankcase . I was able to remove the pieces of the clip out and clean out the crankcase but I never fully pulled the piston out of the head because I have no ring compressor so I put the machine back together with the original gasket making sure the bolts holding the head and crankcase together were tight . I have spark , new plug , I am getting fuel , But now I cannnot get the Trimmer started the key looked ok on the flywheel at least it lined up in keyway. I tried starter fluid with no luck . Please help. ???? timing or should I take apart again and replace gasket.


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## phillipmc (Jan 27, 2008)

make sure you have good compression. at least 100psi if compression is good then replace the gasket.


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## luckyvision (May 24, 2007)

You don't need a ring compressor for most modern Stihls, the bottom of the cylinder is tapered, so you can pull the head off.

You do, however need to make sure the ring ends line up with the pins underneath them. this keeps the rings from turning on the pston & catching a port edge

Phillip is right, check compression, but before that, pull the plug, muffler & carb. With a good flashlight (mini mag) look thru those holes & see if there is any scoring on the piston or cylinder. anything you could catch a fingernail on is bad...

Now the bad news, even out of warrenty, Stihl may still have warrented the machine for a failure like that, if a Stihl tech would agree that it was within a couple of years of the end of the warrenty, & the machine was well maintained & not abused, .. at least my distibutor probably would have (Mid Atlantic Stihl) they're pretty good guys...

They most likely would have wanted it back to examine first. at the very least they would have given you a discount on a replacement 45 with the same length blade... since you took it apart though... they won't touch it 

--Lucky


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## vach55 (Nov 10, 2010)

compression is 55psi (not good ) is it worth the effort????will take carb and muffler off tommorrow to check for scoring. thanks for all the help .


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## vach55 (Nov 10, 2010)

piston scored pretty bad , rings won't even move and cylinder wall scared , flywheel keyway not damaged at all , all other parts are in great shape . will check on cost of jug and piston and rings if not too expensive I may repair since I have it broke down this far , All new gaskets only around $15 would be too bad to throw it away. thanks for your help "Lucky" ? PS: would you know the torque specs ????

---Dave


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## luckyvision (May 24, 2007)

Stihl specs @ 9 Nm... if my brain converted it right, that's only about 6.5 foot lbs or 70-75 inch pounds.

really though, just snug it up & then tighten them down..normal tight, then go around them & tighten just a little more....

i'm a human torque wrench though, I just know when it 'feels' right. my buddy tested me to see how accurate I could be, & I was never more than 7ftlbs off  it's a talent, lol

--Lucky


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## geogrubb (Jul 28, 2006)

Some HS45 spec. Have a good one. Geo

1 Piston displacement cc cu.in. 27.2 1.66 
2 Cylinder bore diameter diameter mm in 34 1.34 
3 Piston stroke mm in 30 1.18 
4 Engine power kW (bhp) @ r.p.m. 0.75 (1.0) 7,000 
5 Air gap between arms of ignition module and flywheel magnets mm 
in 0.2 - 0.45 0.008 - 0.018 
6 Type of spark plug BOSCH NGK CHAMPION WSR 6 F
BPMR 7 A RCJ 6 Y

7 Spark plug electrode gap mm in 0.5 0.02 
8 Overall length of ignition lead in - 
9 Diameter and length of starter rope mm dia. in L 3.0 41 3/4 
10 Standard setting of carburetor L and H adjusting screws H 3)
L 3) -- 
11 Idle speed @ r.p.m. 2,800 
12 Tuning RPM at full load (H screw):
- chain saws with bar and chain - FS units without cutting attachment @ r.p.m - 
13 Maximum attainable RPM on engines with speed governing (electronic cut-off, carburetor with control valve or wind vane). @ r.p.m 9,500 
14 Tightening torque of flywheel nut Nm lbf.ft. 17 12.5 
15 Tightening torque of hex. nut on fanwheel Nm lbf.ft. - 
16 Tightening torque of hex. nut on clutch Nm lbf.ft. 17 12.5 
17 Tightening torque of cylinder base screws Nm lbf.ft. 9 6.5


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