FS 55 not priming

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Mikel1

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jm123 said:
That was my thinking. I don't think that using 92 octane will hurt even though Stihl says to use 89.
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I have used 91 for years now on my Km55 Stihl.
Either way that's a cheap price for a carb. Not a bad idea to change fuel lines and fuel filter for the new carb. Also while waiting on carb you can Google Zama tech guide(PDF) for informational purposes.
 
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jm123

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Mikel1 said:
I have used 91 for years now on my Km55 Stihl.
Either way that's a cheap price for a carb. Not a bad idea to change fuel lines and fuel filter for the new carb. Also while waiting on carb you can Google Zama tech carb(PDF) for informational purposes.
Click to expand...

Thanks for the info! I saved a copy of the Tech guide.
 
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jm123

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Installed the new carb. Same.

Took off the fuel filter. Same.

Hint: Taking off the rear cover and fuel tank (they bolt together) is easy enough. Putting it back together was a three hand type job. Pulling the fuel line assembly with the tank installed is easier. Somebody on Youtube said to uninstall the tank first.

So I guess the next step is a new fuel/return line.

Read in another post that reusing gaskets doesn't work. Wasn't clear on why that would be the case. Assuming that the gaskets aren't damaged.
 
BlazNT

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jm123 said:
Installed the new carb. Same.

Took off the fuel filter. Same.

Hint: Taking off the rear cover and fuel tank (they bolt together) is easy enough. Putting it back together was a three hand type job. Pulling the fuel line assembly with the tank installed is easier. Somebody on Youtube said to uninstall the tank first.

So I guess the next step is a new fuel/return line.

Read in another post that reusing gaskets doesn't work. Wasn't clear on why that would be the case. Assuming that the gaskets aren't damaged.
Click to expand...

Some gaskets lose their ability to compress after one use.
 
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jm123

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BlazNT said:
Some gaskets lose their ability to compress after one use.
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Didn't know that. Are the single use gaskets made of any particular materiel? The ones that came with the FS 55 are kind of like plastic in appearance. Rather than the fibrous ones that I'm used to seeing.

Thanks!
 
BlazNT

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The ones that are considered on use that I have delt with where plastic. They where on cars but plastic.
 
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jm123

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BlazNT said:
The ones that are considered on use that I have delt with where plastic. They where on cars but plastic.
Click to expand...

I guess that I'll replace the gaskets next. I usually put some new oil on gaskets when installing. Getting *really* good at uninstalling the carb on the trimmer!

Thanks!
 
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jm123

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Anybody have thoughts on using a product like Permatex Aviation FORM-A-GASKET liquid sealer on small gaskets and hose connections? Comes in a four ounce can at NAPA. I'll be down there next week to get some Tygon tubing.
 
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bertsmobile1

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jm123 said:
Didn't know that. Are the single use gaskets made of any particular materiel? The ones that came with the FS 55 are kind of like plastic in appearance. Rather than the fibrous ones that I'm used to seeing.

Thanks!
Click to expand...

No they are not plastic.
The diaphragm that make the fuel pump work are plastic.
All gaskets are fiber board of some sort and should be considered as a single use item.
Sealing these cube carbs air tight is quite difficult and reusing the carbs is a sure fire way to inorduce a leak.
 
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bertsmobile1

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jm123 said:
Anybody have thoughts on using a product like Permatex Aviation FORM-A-GASKET liquid sealer on small gaskets and hose connections? Comes in a four ounce can at NAPA. I'll be down there next week to get some Tygon tubing.
Click to expand...

Well it all depends if you want to repair it or destroy it.
If the lattr, the do it properly with a 1/4" bead of silicon on everything.

If that does not work the wrap the whole thing in duct tape and give it a liberal spray with WD 40.

Now I have your attention and just before you send me an abusive flame, how about some better description of what your problem is.

Won't prime means what ?
Primer bulb will not fill with fuel ?
trimmer will not start ?

Did you really buy a new carb, the pull the new carb apart & refit the gaskets oiled ?
If so what on earth made you do this ?
If the new carb did not prime then you take it back for a refund, or try to find the EXTERNAL REASON why it is not working ?

Did you suck on the fuel delivery line to ensure fuel was flowing through it ?

Did you pressurise the tank to test he integrity of the tank & fuel lines ?
do you have the basic tool needed to work on cube carbs, including a vaccuum / pressure tester.
Did you do the work in a very clean room on a clean table covered with clean paprer ?
 
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