mending plastic fuel tank

[agg221]

Stihl fuel tanks can be welded, but it's not ABS, it's Nylon (Polyamide) with 8% glass fibre filling for the white part - if it's the transluscent part at the front where you can see the fuel level I'm not sure of the composition as I don't have any saws that new!

 

This means that ABS and similar are not compatible with it. It also means that you need to get a lot hotter (360degC welding temperature) and Nylon picks up water, which you have to drive out to get a good weld, otherwise you get porosity.

 

The best bet is to get hold of another piece of Nylon, not glass filled, to use as a filler. Dry the tank out fully so there is no oil residue or fuel vapour - swill it out with acetone if you can get it, cheap vodka if you can't, to remove the oil. Scrape the crack out clean to form a very slight V (this can be done with a Stanley knife) and then point a hot air gun at it on warm and gentle for a couple of hours, to dry it.

 

Once dry, you ideally use a very high temperature hot air gun with a fine nozzle, or if you don't have access to one it can be done with a high temperature soldering iron whacked on full. Heat the tank plastic to soft and glistening, whilst keeping the filler hot, then feed it in to the crack and let it fuse everything together. There are some videos on Youtube of plastic welding which are worth watching, but if you've ever tried TIG welding it's rather like doing aluminium.

 

Hope this helps (guess where I work as my day job.....!)

 

Alec

[Marc]

It's the plastic section on the bottom of saw, I think I might have dropped it on a stone or something. If I can't fix it, it would be a very expensive repair bill as its the whole handle, air filter and carb section will need to be replaced.

 

It's about £50 to repair it properly, although repairing the hole if you can is cheaper still.

[Warners]

[ame=http://www.amazon.co.uk/Quiksteel-Plastic-Tank-Repair-Kit/dp/B001C69CLE]Quiksteel Plastic Tank Repair Kit: Amazon.co.uk: Kitchen & Home[/ame]

 

Try this.....

[landrover 101]

Have you actually priced a new one up?

 

Only asking as stihl only wanted around £70 + vat for the ms660 tank if its going to cost £50 for a repair I would be tempted to spend the extra £20 and just have a new tank

 

 

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[hedgesparrow]

I mended mine by running a hot electric soldering iron along the cracks then smoothing the hot material back over the top,doesn't leak at to my surprise

 

when inn the printer game used to get plastic bits break as other posts had a sodering iron that ran off butane so had a smallish tip just ran it over crack going sideways this sealed it up and worked ok

[TimberCutterDartmoor]

Fibreglass repair kit? Did an oil tank for a tipper trailer proper job; guess it would be fuel proof - like rock once it's set.

 

edit: yes of course it's fuel resistant; had 2-stroke spillages in fibreglass boats loads a times no issues...

[ThrustSSC]

Fibreglass repair kit? Did an oil tank for a tipper trailer proper job; guess it would be fuel proof - like rock once it's set.

 

edit: yes of course it's fuel resistant; had 2-stroke spillages in fibreglass boats loads a times no issues...

 

Spot on. There are adhesives available in the fibreglassing world that will do the job - just abrade the tank for a mechanical bond, then glue it up.

[2stroke-ady]

Araldite rapid will do the job, but of course it won't be permanent.