I've had nothing but trouble with this model. Lately, I've replaced the carb, spark plug, air filter, fuel lines and filter, put fresh gas in, and decarbonized the spark arrestor. It will still start and run for about 60 to 90 seconds before stalling out. I think the only thing left is to replace the gas tank , cap, and muffler.
Recommend you use a metal can to store fuel for any period of time. The fuel literally leaches through plastic cans, so they're only really good for short term storage.
very helpful video, do you have info on setting the 3 screws on the carb, I know one screw adjusts the idol speed but the others don't seem to do much for me? in fact when I look closer at the idol screw its not even touching the throttle stop, probably have to do as you say and invest in a new full service kit, thanks
I had a problem with my fs38 bogging down. It was a struggle to tune...but I eventually got it. Runs great now...I'd buy it again in a heartbeat. I use the commercial line on a daily basis and the torque is insane...but they are significantly heavier. STIHL my first choice after decades of experience. Running low RPMs is known to cause some issues...my 2 cents.
Need more people like you ..instead of tossing a machine that's still almost new but has a dirty air filter so it finally stalls...they toss it in the local landfill and buy a new one ...wow thats expensive..there is no second owner of anything I have from cloths , rc cars , atvs vehicles, mowers trimmers you name it . I use it till its junk...well my ex wife escaped with a second owner but she had alot of hard miles on her anyway lol ..she like a diesel ....ok enough anyway good vid bro.
*****DIFFICULT- engine bog down problem if anyone wants to try to diagnose. Stihl FS 51 AL Bog down when open throttle and only sort of idles so i suspected carb or fuel starvation So as i done before, i open carb and all parts looked ok but i cleaned and replaced all the diaphragms ect and it run for 10 mins idle and full power and then starved off. I also put a brand new carb on just to eliminate the carb and same problem. I then suspected the pulse hole leakage or engine leaking at oil seal or gaskets causing air to get in maybe when warmed up and leaning the mixture. Put vac of 9 psi and it held steady after blocking off inlet and exhaust so the engine isnt leaking. i tried compression next and got 120 psi ? is that enough to make pulse hole work ? i attached a vac gauge to the little pulse hole and pulled rope and got about 2 psi vac and pressure on the gauge so dont know if thats enough? I notice when i try to start , there is no fuel being drawn through the fuel line to the carb so how can it even idle? Also i bypassed the filter to make sure fuel was available from the tank above the carb. This weed machine dosent have a prime bulb so does the 2 little pump flaps have to have fuel in the carb to start pumping? It worked in past as it is so i guess it will pump until fuel gets to carb but i dont see any going down the line so PULSE line issue not making the pump pump anymore? I used new gaskets and made sure the little gasket hole lined up ect to reach the carb and complete the air pulse circuit. I am at a loss on this machine.
I’m not familiar with that trimmer exactly, but have you tried replacing the fuel lines? They may still be providing enough to idol, but maybe not enough to run fully?
@@LaceyFamilyFarm Hi, i just come back from using the machine for an hour after i got it fixed finally ! As suspected it was starving for fuel especially above idle and the machine was always a little temperamental from first day before i understood the operation and worked on them. I made a thick card gasket and punched out not one but a run of holes from left to right on both top and bottom so they would have to line up with the tiny pulse hole in the carb and engine plastic boss. If you dont get enough pulse action, the pump action will be minimal- supposed to be 5-7 psi pump? . I also bent up the metering pivot tab to far to try and get the carb to flood first to prove good flow and then backed it off till the screws were adjusting about 1-full turn for change. The correct book tab setting was a bit lean as i can only guess the worn engine isnt producing enough vac and pressure through that pulse hole so book figures needed to be modified. Interestingly i sealed off the engine and drew 9 PSI vac through the crankcase and didnt lose any vac with old seal and gaskets including that pulse hole. amazing! Also pull start compression was 120 PSI?? i read thats quite good over 90 psi? I did put a set of rings in it years ago so maybe that helped with todays readings- not so worn perhaps. Its such a durable machine, ive already cut fresh steps in the plastic spool using a soldering iron for the start teeth to engage as they were all rounded and slipping and oiled the bearings and greased the drive shaft down to the spinner. Pretty well serviced the whole machine in total. People complain about the little Walbros but i seen them still pumping even when the little flaps and diaphragms are pretty hard. Little carb cleaner through the adj screw holes and a few dollars for a kit and they work pretty well and i never had one stop which wasnt starving for fuel like mine did.. Hers a pic of one i found for online same as mine. Stihl dosent make parts anymore as too old.. us.letgo.com/en/i/stihl-fs-51-ave-weed-eater_d7d5850c-e5ca-4fab-9717-e9dcfcbb53ac
DifferentialTim well dang. Lol. I’m glad you got an answer! These little trimmers can be so utterly infuriating sometimes but they are actually really good and reliable!
I've had nothing but trouble with this model. Lately, I've replaced the carb, spark plug, air filter, fuel lines and filter, put fresh gas in, and decarbonized the spark arrestor. It will still start and run for about 60 to 90 seconds before stalling out.
I think the only thing left is to replace the gas tank , cap, and muffler.
Recommend you use a metal can to store fuel for any period of time. The fuel literally leaches through plastic cans, so they're only really good for short term storage.
very helpful video, do you have info on setting the 3 screws on the carb, I know one screw adjusts the idol speed but the others don't seem to do much for me? in fact when I look closer at the idol screw its not even touching the throttle stop, probably have to do as you say and invest in a new full service kit, thanks
I had a problem with my fs38 bogging down. It was a struggle to tune...but I eventually got it. Runs great now...I'd buy it again in a heartbeat. I use the commercial line on a daily basis and the torque is insane...but they are significantly heavier. STIHL my first choice after decades of experience. Running low RPMs is known to cause some issues...my 2 cents.
So true. I have been happy with mine even with all the issues.
Thanks for your thoughts and help! We appreciate it!
Helpful. Thanks!
Your welcome!
Need more people like you ..instead of tossing a machine that's still almost new but has a dirty air filter so it finally stalls...they toss it in the local landfill and buy a new one ...wow thats expensive..there is no second owner of anything I have from cloths , rc cars , atvs vehicles, mowers trimmers you name it . I use it till its junk...well my ex wife escaped with a second owner but she had alot of hard miles on her anyway lol ..she like a diesel ....ok enough anyway good vid bro.
Lol! Thanks!
Cool
Where was the tune up 😐
*****DIFFICULT- engine bog down problem if anyone wants to try to diagnose. Stihl FS 51 AL
Bog down when open throttle and only sort of idles so i suspected carb or fuel starvation
So as i done before, i open carb and all parts looked ok but i cleaned and replaced all the diaphragms ect and it run for 10 mins idle and full power and then starved off. I also put a brand new carb on just to eliminate the carb and same problem.
I then suspected the pulse hole leakage or engine leaking at oil seal or gaskets causing air to get in maybe when warmed up and leaning the mixture. Put vac of 9 psi and it held steady after blocking off inlet and exhaust so the engine isnt leaking. i tried compression next and got 120 psi ? is that enough to make pulse hole work ?
i attached a vac gauge to the little pulse hole and pulled rope and got about 2 psi vac and pressure on the gauge so dont know if thats enough?
I notice when i try to start , there is no fuel being drawn through the fuel line to the carb so how can it even idle? Also i bypassed the filter to make sure fuel was available from the tank above the carb. This weed machine dosent have a prime bulb so does the 2 little pump flaps have to have fuel in the carb to start pumping? It worked in past as it is so i guess it will pump until fuel gets to carb but i dont see any going down the line so PULSE line issue not making the pump pump anymore?
I used new gaskets and made sure the little gasket hole lined up ect to reach the carb and complete the air pulse circuit.
I am at a loss on this machine.
I’m not familiar with that trimmer exactly, but have you tried replacing the fuel lines? They may still be providing enough to idol, but maybe not enough to run fully?
@@LaceyFamilyFarm Hi, i just come back from using the machine for an hour after i got it fixed finally ! As suspected it was starving for fuel especially above idle and the machine was always a little temperamental from first day before i understood the operation and worked on them. I made a thick card gasket and punched out not one but a run of holes from left to right on both top and bottom so they would have to line up with the tiny pulse hole in the carb and engine plastic boss. If you dont get enough pulse action, the pump action will be minimal- supposed to be 5-7 psi pump? . I also bent up the metering pivot tab to far to try and get the carb to flood first to prove good flow and then backed it off till the screws were adjusting about 1-full turn for change. The correct book tab setting was a bit lean as i can only guess the worn engine isnt producing enough vac and pressure through that pulse hole so book figures needed to be modified.
Interestingly i sealed off the engine and drew 9 PSI vac through the crankcase and didnt lose any vac with old seal and gaskets including that pulse hole. amazing! Also pull start compression was 120 PSI?? i read thats quite good over 90 psi? I did put a set of rings in it years ago so maybe that helped with todays readings- not so worn perhaps.
Its such a durable machine, ive already cut fresh steps in the plastic spool using a soldering iron for the start teeth to engage as they were all rounded and slipping and oiled the bearings and greased the drive shaft down to the spinner. Pretty well serviced the whole machine in total.
People complain about the little Walbros but i seen them still pumping even when the little flaps and diaphragms are pretty hard. Little carb cleaner through the adj screw holes and a few dollars for a kit and they work pretty well and i never had one stop which wasnt starving for fuel like mine did..
Hers a pic of one i found for online same as mine. Stihl dosent make parts anymore as too old..
us.letgo.com/en/i/stihl-fs-51-ave-weed-eater_d7d5850c-e5ca-4fab-9717-e9dcfcbb53ac
DifferentialTim well dang. Lol. I’m
glad you got an answer! These little trimmers can be so utterly infuriating sometimes but they are actually really good and reliable!