# I'm at a loss.. please help.. Stihl FS450



## MagraAdam (Jan 9, 2021)

Hi guys,

So i got a second hand FS450.. love it! heaps of power and great to use.. then the shaft rounds, so i get a new shaft.. it's amazing again! then the bearings in the con rod go, so i order a new crank shaft/con rod and a new cylinder and piston kit. I fit these all up and she won't start at all. I realise that the carby is one of the old fixed jet ones, so i order a new carby too and fit that. It still won't start. it has compression. it has spark. it has air. the fuel primes through the bulb, the filters are all clean. if i put some fuel in the cylinder i can get it to spark a few times, and using some starter spray i can get the same, but it just doesn't run. I have the same symptoms with both carbies. I have tried the adjustable one at 1.25 turns on both screws as instructed on one of the videos i watched, but it isn't just out of tune, it won't start. the old carbie that just had the idle adjustment (the venturi screw i believe) has been set to every possible position and all the same.. a couple of ignitions at best then nothing. I have checked all the hoses and they all don't have any holes.

So.. any help would be amazing, as i'd love to get the beast back up and running.

Thanks heaps!


Adam


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## trains (Jan 9, 2021)

Is the flywheel matched to the coil and correctly fitted to the crank so the timing is correct?
did the flywheel shear the key, and move, thus sparking at the wrong time ?

only thing I can offer at the moment.


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## MagraAdam (Jan 9, 2021)

trains said:


> Is the flywheel matched to the coil and correctly fitted to the crank so the timing is correct?
> did the flywheel shear the key, and move, thus sparking at the wrong time ?
> 
> only thing I can offer at the moment.


Mate you seem to be 100% right, I did manage to break the key.. Weird that it was igniting a bit, but i guess the timing was out. Now to find a replacement part.. seems like it's a weird model to get parts for unfortunately..


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## MagraAdam (Jan 9, 2021)

I'm struggling to find a 41284001200.. i don't surpose a 41344001200 will fit it?


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## funky sawman (Jan 9, 2021)

4134 is a completely different model class than 4128 series


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## frank_ (Jan 9, 2021)

MagraAdam said:


> Mate you seem to be 100% right, I did manage to break the key.. Weird that it was igniting a bit, but i guess the timing was out. Now to find a replacement part.. seems like it's a weird model to get parts for unfortunately..


i usually cut a small slot where the keyway was , then fit the f/w by eye, and then drill down and drive a thin rod down the hole


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## John Lyngdal (Jan 9, 2021)

I think the newer FS480 uses the same flywheel. I sheared a key in my 056 chainsaw and all I had to do was replace the key, the flywheel was fine.
Is your flywheel or crankshaft damaged? It might it be repaired just by installing a new key?


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## cookies (Jan 9, 2021)

can you dremel down the old key into a slot to fit a section of keystock bar?


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## trains (Jan 9, 2021)

MagraAdam said:


> Mate you seem to be 100% right, I did manage to break the key.. Weird that it was igniting a bit, but i guess the timing was out. Now to find a replacement part.. seems like it's a weird model to get parts for unfortunately..


its the taper that holds the torque of the flywheel, not the key, that only indexes it correctly when you assemble it.
So clean up the taper, make sure its clean of oil etc, same with flywheel, fit in correct position, give it a gentle seating tap with long socket, then torque up to spec, and run it.


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## MagraAdam (Jan 11, 2021)

John Lyngdal said:


> I think the newer FS480 uses the same flywheel. I sheared a key in my 056 chainsaw and all I had to do was replace the key, the flywheel was fine.
> Is your flywheel or crankshaft damaged? It might it be repaired just by installing a new key?


The key is cast into the flywheel unfortunately.. well.. it was..


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## MagraAdam (Jan 11, 2021)

trains said:


> its the taper that holds the torque of the flywheel, not the key, that only indexes it correctly when you assemble it.
> So clean up the taper, make sure its clean of oil etc, same with flywheel, fit in correct position, give it a gentle seating tap with long socket, then torque up to spec, and run it.


Thanks mate, I'll give that a try


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## MagraAdam (Jan 11, 2021)

frank_ said:


> i usually cut a small slot where the keyway was , then fit the f/w by eye, and then drill down and drive a thin rod down the hole





cookies said:


> can you dremel down the old key into a slot to fit a section of keystock bar?


I was thinking about trying something like this. Anyone know what size key stock I need? Or a good supplier in Australia for stock?


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## MagraAdam (Jan 11, 2021)

funky sawman said:


> 4134 is a completely different model class than 4128 series


G'day mate, I thought that would be the case. Interestingly I just found this that seems to imply these models all use the same flywheel? 






FLYWHEEL FOR STIHL FS120 FS200 FS250 FS300 FS350 FS380 FR350 FR450 FR480 HT250


THIS PRODUCT IS NOT GENUINE STIHL FLYWHEEL FOR BRUSHCUTTERSFOR THE MODELS : STIHL FS120 STIHL FS200 STIHL FS250 STIHL FS300 STIHL FS350 STIHL FS380 STIHL FR350 STIHL FR450 STIHL FR480 ΒΟΛΑΝ




www.gardenparts.gr


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## frank_ (Jan 11, 2021)

MagraAdam said:


> I was thinking about trying something like this. Anyone know what size key stock I need? Or a good supplier in Australia for stock?


you only need a sawblade notch to line it up, then i use a 3mm drill down the keyway on the mowers that i do it to (they have a shearkey to prevent the crank bending) but yours probably needs a 2mm drill and then just drive a nail down the hole, and cut the excess off the top


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## cookies (Jan 11, 2021)

measure the keyslot in the crank, any small engine shop or hardware store worth a hoot will have key stock rod, if they have the wrong size buy the next size up to have the ability to grind it down to size. Like another member stated the flywheel is held in place by the tapers on the crank and bore in the flywheel press fitting and the key aligns them...you could even use a square wooden or aluminum dowel, the reason i suggested keystock is it is generally the same fractional sizes across all manufacturers. You could even draw alignment lines on the crank and flywheel to install without the key but beware of misalignment and shifting during tightening.


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## MagraAdam (Feb 16, 2021)

Ok, so I finally got around to making a key out of aluminium after I found my small files and modified one of them to file a square hole in the flywheel. Both tuning screws are set to 1.25 turns and I put fresh help in it. Exactly the same as before. I can get it to turn over a few times using starter spray, but that's it. 

Any other thoughts before I have to pay someone to look at it? (At which point I will have spent more fixing it than I did buying it..)


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## cookies (Feb 16, 2021)

sounds like the carb is still not fueling properly on the low side


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## bcorradi (Feb 18, 2021)

I think I have a new or like new fs450 powerhead. I got it in a lot of parts at a state auction. To be honest with you, I'm not sure if it ever had gas in it. It appears parts were just scavenged off of it. Send me a msg if you would like more information.


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## Bobby Kirbos (Feb 18, 2021)

Don't pay for labor. There is more available knowlege on this site than you will find at a single repair shop. There are guys here who have brought saws back from the grave.


Throw a tablespoon of mix down the carb. You'll likely get a bit more run time from that then you get from starter spray. The slightly longer run time will give you a better indication of whether or not the timing is correct (which it most likely is). 

It does sound to me like you have a fuel delivery problem at this point.


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## MagraAdam (Feb 18, 2021)

bcorradi said:


> I think I have a new or like new fs450 powerhead. I got it in a lot of parts at a state auction. To be honest with you, I'm not sure if it ever had gas in it. It appears parts were just scavenged off of it. Send me a msg if you would like more information.


Thanks heaps for the offer - I'm pretty sure shipping to Australia will be cost prohibitive. I've also replaced the shaft, the gear box, the carby, the cylinder, the piston, the crack shaft and con rod, the bearings. by now i may as well have bought a new one :/


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## MagraAdam (Feb 18, 2021)

cookies said:


> sounds like the carb is still not fueling properly on the low side


That's what i feel like is the problem too, but i have replaced the carb and both had the same symptoms. I also replaced the carb gasket..


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## cookies (Feb 18, 2021)

compression test it yet?


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## bcorradi (Feb 18, 2021)

MagraAdam said:


> Thanks heaps for the offer - I'm pretty sure shipping to Australia will be cost prohibitive. I've also replaced the shaft, the gear box, the carby, the cylinder, the piston, the crack shaft and con rod, the bearings. by now i may as well have bought a new one :/


Np I haven't shipped internationally for a while so u may be correct.


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## MagraAdam (Feb 18, 2021)

bcorradi said:


> Np I haven't shipped internationally for a while so u may be correct.


Looks like it's about $70-100AUD plus packaging (assuming it weighs 2-3kg)


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## MagraAdam (Feb 18, 2021)

cookies said:


> compression test it yet?


no, it's the one thing i haven't done yet. I don't have one and need to find one..


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## trains (Feb 18, 2021)

does it pop if you spoon some 2t mix down its throat, dont use start ya bastard canned stuff it has no oil in it.
if it does, your looking at fuel delivery issues, we will sort it, just need to methodically work thru it, in the end you will know more about it and have a working unit.


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## MagraAdam (Feb 18, 2021)

Bobby Kirbos said:


> Don't pay for labor. There is more available knowlege on this site than you will find at a single repair shop. There are guys here who have brought saws back from the grave.
> 
> 
> Throw a tablespoon of mix down the carb. You'll likely get a bit more run time from that then you get from starter spray. The slightly longer run time will give you a better indication of whether or not the timing is correct (which it most likely is).
> ...





trains said:


> does it pop if you spoon some 2t mix down its throat, dont use start ya bastard canned stuff it has no oil in it.
> if it does, your looking at fuel delivery issues, we will sort it, just need to methodically work thru it, in the end you will know more about it and have a working unit.


OK, i put some fuel (about half to 1 table spoon) down the carby and it did pop a bit, better than with the starter spray, but still not for very long. 

The primer bulb works and will fill the carby then overflow down back into the tank, if that helps.


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## trains (Feb 18, 2021)

So did it start, sort of run, rev a bit then once the fuel was consumed, stop ?
when you first try, its like its flooded, then runs, then goes lean.

if it does that, then you know your spark side of thing is sorted and ok.

any chance the fuel lines are put on backwards ?
not being a smart arssse, just trying to step by step thru this so you dont leap frog over it.

check pm, give me a ring if you want, can talk a bit more thru it if that helps.


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## MagraAdam (Feb 19, 2021)

trains said:


> So did it start, sort of run, rev a bit then once the fuel was consumed, stop ?
> when you first try, its like its flooded, then runs, then goes lean.
> 
> if it does that, then you know your spark side of thing is sorted and ok.
> ...


yeah, first few pulls nothing, then 1 spark, then a few sparks, then it ran for about 1 or 2 seconds then stopped, then nothing (as i assume it was out of fuel). 

Fuel runs in from the bottom of the carby, out through the top next to the adjustemnt screws, into the bulb, then out of the bulb and back into the tank.


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## Bobby Kirbos (Feb 19, 2021)

Bad/leaking primer bulb (been there, done that)? Primer bulb hooked up backwards?


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## lone wolf (Feb 19, 2021)

MagraAdam said:


> Thanks heaps for the offer - I'm pretty sure shipping to Australia will be cost prohibitive. I've also replaced the shaft, the gear box, the carby, the cylinder, the piston, the crack shaft and con rod, the bearings. by now i may as well have bought a new one :/


Is it a aftermarket carb?


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## MagraAdam (Apr 24, 2021)

Hey guys, time for an update. I finally had time to take it apart again and it looks like either I put too much grease on the bearings, or have load on the bearings, as it doesn't want to spin. But here are some photos of taking it apart if anyone is interested.


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## trains (Apr 24, 2021)

That base gasket will need replacing too, see its torn in the 2nd last pic at 3 O clock.
is it the original gasket, looks like its blocking off some transfer ports too ? not sure if the ports start in the case halfs, or if they are above the gasket.

just looked at an online parts list, and it shows the plain gasket that you have, and no ports in the case halfs.


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## MagraAdam (Jun 6, 2021)

Ok, status update.

After spending many hours with @trains I have torn it right down and cleaned out the heavy grease that I put in there, out the bearings on using the correct method, used the right lube, sealed the crank case (which was not done last time), put new grease seals in, put the crank case bolts in (as I seem to have forgotten to do that last time..), and discovered that the Chinese carb was terrible. 

Here is it running with the original carb on it



And now here is is after reading down the carb and cleaning it all up and putting it back together. 



I'm very happy with this, and will look to get a genuine adjustable carb. 

Thanks again to @trains - I really couldn't have got this far without your help.


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## Ripandsplit (Jun 6, 2021)

Good on ya for sticking with it mate all paid off . It's end results like this that makes this site great !


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## MagraAdam (Jun 6, 2021)

Ripandsplit said:


> Good on ya for sticking with it mate all paid off . It's end results like this that makes this site great !


Absolutely right. I love this site and the good people on here.


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## Clyde85 (Jun 6, 2021)

Glad it all worked out.


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## Vintage Engine Repairs (Jun 11, 2021)

MagraAdam said:


> Ok, status update.
> 
> After spending many hours with @trains I have torn it right down and cleaned out the heavy grease that I put in there, out the bearings on using the correct method, used the right lube, sealed the crank case (which was not done last time), put new grease seals in, put the crank case bolts in (as I seem to have forgotten to do that last time..), and discovered that the Chinese carb was terrible.
> 
> ...



You’re in very good hands with @trains. Having been a professional mechanic spanning many different fields including aviation and racing and now a full blown chainsaw nut, I’m forever picking his brains. If it wasn’t for him teaching me what he has and continues to do so I wouldn’t be able to have repaired the countless chainsaws, strimmers, edgers and now small Villiers. Glad you’ve build up a friendship, wonderful to see his guidance once again has been invaluable. I’m just waiting for him to start charging us, or not answering his phone


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## trains (Jun 11, 2021)

Oh Goodness, I hope you dont think of me as a Lumberg.

shudder

ewwww


And its my red stapler


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