Stihl tank repair/mod

[Roadhunter1]

Hi all, I am just curious if anyone has tried to remove the transparent section of the gas tank on a Stihl saw and replace it with another section from another tank? Specifically, I’m wondering about the 044 screw cap tanks. But im sure other tanks from other saws would probably apply. I’m just curious if there’s a way to separate the seam on them? Maybe heat? I dunno, I’ve got several tanks to try experimenting on but I would like to at least head in the right direction if anyone has some tips or pointers... I have ordered a plastic welder to try welding some of the cracks but maybe replacing the transparent part of the tank would be a better option? Any help or ideas would be greatly appreciated.

 

[Conquistador3]

I don't know how long Stihl has been doing this, but their clear tanks have long been ultrasonic welded, meaning the only way so separate the seams on their tanks is to cut them.

 

[Roadhunter1]

Hmm, well then maybe cutting the old and new pieces on opposite sides of the seam and then routing a new seam bed with a dremel might work? I don’t have an ultrasonic welder so maybe there’s some sort of chemical solvent that will weld/glue the pieces back together....

 

[Conquistador3]

I don't know what exact material the fuel tank of the 044 is made of, but Stihl fuel tanks are usually made from Polyamide (Nylon 6 if I remenber correctly).

Nylon is not exactly easy to weld at home on the cheap because it's a pretty fussy material: hygroscopic, semicrystalline, with a sharp melting point etc. I am pretty sure some of the ingenious folks here have come up with something cheap and easy, but the procedure I would use a ready-made bonding kit like the one made by Tech-Bond: https://tbbonding.com/product/basic-poly-plastic-kits/
Just be sure to follow instructions to the letter.

 

[Roadhunter1]

Ok great, I’ll check that out. I would assume that the adhesive you mentioned is resistant to gas?

 

[Conquistador3]

Ok great, I’ll check that out. I would assume that the adhesive you mentioned is resistant to gas?

It's not a glue or resin in the traditional sense: think of it as solvent-based welding process you can do at home. If done right it should be every bit fuel resistant as a normal tank.

 

[Roadhunter1]

Oh ok yea, I gotcha. Thanks a bunch for your help.

 

[Roadhunter1]

Do you happen to know if the transparent tanks on the handle assemblies is made from the same material as the handles themselves? I’ve seen some plastic weld filler rod for the nylon 6 you mentioned. But not sure if that applies to both of the plastics used on the handle/tank assemblies or if there even is 2 different plastics used.

 

[Conquistador3]

Do you happen to know if the transparent tanks on the handle assemblies is made from the same material as the handles themselves? I’ve seen some plastic weld filler rod for the nylon 6 you mentioned. But not sure if that applies to both of the plastics used on the handle/tank assemblies or if there even is 2 different plastics used.

The white and colored "plastics" on Stihl saws are usually PA66, aka Nylon 66, often fiberglass reinforced. The transparent parts are usually Nylon 6, but I think on some models PA66 was used as well.
PA66 used in handles and such is usually fiberglass reinforced: the part is often stamped "PA66-GF30" or "PA66-GF25", with the last number indicating fiberglass content.

Bear in mind that using nylon welding rods require some precautions: cleaning both parts to be welded and the rod itself with MEK (aka butanone) and keeping temperature and moisture well under control. It's not something I do because it takes practice and time I lack.

 

[Roadhunter1]

Ok, great info! I’m going to at least try my hand at repairing a couple tanks to see if it’s even something I want to mess with. I was hoping there was some “miracle adhesive” that would fix it but I guess if it were easy everyone would do it lol.