- Joined
- Feb 7, 2013
- Messages
- 2,529
On my last excursion to the scrap yard I brought home a Stihl FS90 AVE brush cutter. After looking it over, I could see that it was missing a few carb parts
and the blade end didn't turn. After loosening up the cutter head it was on to the carburetor. I could see two ways of repairing this thing to functionality.
One way would be to affix a different carburetor to the engine or make the missing parts for the existing carb.
Before making parts, I decided to see if it had spark and it did. Then I instilled a little gas mixture into the carburetor and gave it a pull. It fired right off!
The parts are metric as well as the threads on the carburetor so somewhat challenging. I machined up some rough approximations and threaded the
inside of the top cover using a 12x1mm tap. So with that accomplished, I made a 12mm cylinder and grooved it so it would fit in the hole. After finishing that,
I threaded a short piece of brass and tapered it to fit the metering hole. This is all trial and error at this point as I have no dimensions to work with, just
using common sense and trial and error. The 12mm cylinder could be fashioned in brass but the aluminum one will be good enough to see if it will run.
I'm at the point where it is assembled and ready to see if it will run at idle with a little experimenting likely. Then I need to come up with throttle cable
parts which I should be able to come up with. It's probably 30 years old or better so likely hard to find parts.
This is the power head with the parts installed ready to see what happens next.
Below are the small parts ready to install. I left the brass pin a little fat in case I need to adjust the mixture.
This style of carb does not use the new style units with the bulb to press on. They don't hold up well anyway so if I can make this work, it will be a better
setup. The button that says push on it activates the diaphragm and also opens a little valve for easy starting.
It's another snow day and I had to shovel my way to the shop. So, later today when it quits snowing, I will have to move some snow with the skid steer,
an old 12C Hydra-Mac with a 2 cylinder 2ab1 Isuzu engine. I it has 9500 hours on it but still does every job I ask it to.
Y'all have a good day!
and the blade end didn't turn. After loosening up the cutter head it was on to the carburetor. I could see two ways of repairing this thing to functionality.
One way would be to affix a different carburetor to the engine or make the missing parts for the existing carb.
Before making parts, I decided to see if it had spark and it did. Then I instilled a little gas mixture into the carburetor and gave it a pull. It fired right off!
The parts are metric as well as the threads on the carburetor so somewhat challenging. I machined up some rough approximations and threaded the
inside of the top cover using a 12x1mm tap. So with that accomplished, I made a 12mm cylinder and grooved it so it would fit in the hole. After finishing that,
I threaded a short piece of brass and tapered it to fit the metering hole. This is all trial and error at this point as I have no dimensions to work with, just
using common sense and trial and error. The 12mm cylinder could be fashioned in brass but the aluminum one will be good enough to see if it will run.
I'm at the point where it is assembled and ready to see if it will run at idle with a little experimenting likely. Then I need to come up with throttle cable
parts which I should be able to come up with. It's probably 30 years old or better so likely hard to find parts.
This is the power head with the parts installed ready to see what happens next.
Below are the small parts ready to install. I left the brass pin a little fat in case I need to adjust the mixture.
This style of carb does not use the new style units with the bulb to press on. They don't hold up well anyway so if I can make this work, it will be a better
setup. The button that says push on it activates the diaphragm and also opens a little valve for easy starting.
It's another snow day and I had to shovel my way to the shop. So, later today when it quits snowing, I will have to move some snow with the skid steer,
an old 12C Hydra-Mac with a 2 cylinder 2ab1 Isuzu engine. I it has 9500 hours on it but still does every job I ask it to.
Y'all have a good day!