# Crank seal causing fuel leak ?



## theoldwizard1 (Sep 25, 2020)

I have a Stihl BG85, which is probably 15 years old. It starts easy and runs well. For the past year or so, any fuel in the tank when I shut it down leaks out between uses (typically a week). Not immediately, but over a few days. It show now leak if I out it down for 30 minutes and then start it up again.

I took it into a shop and they say it is a leaking crank seal ! *How can a leaking crank seal cause a fuel leak that empties the tank ?*


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## hotshot (Sep 26, 2020)

It can’t. They probably meant to say the carb inlet needle tip seal.


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## theoldwizard1 (Oct 4, 2020)

A "friend" who owed me a favor was going to get this piece of equipment fixed for me. I did not believe the "not worth fixing" so I am doing it myself.
Removing the rewind cover, it was obvious that the crank seal was not in great condition ! Lot and lots of oil and dirt build up. Popped the flywheel and after 1-1/2 can of brake cleaner and rags I could see the actual engine side cover. I removed the seal by using a very sharp pick and some patience. Tiny little thing ! Parts come in next week.
I the mean time, it is sitting on the bench with 3/4 of a tank of fuel. It has not lost a drop of fuel in 4 days so the tank is good ! If it still leaks after I replace the seal, I'll do something about the carburetor. It is hard to believe that the leak _(when not running)_ is from the carburetor. It is located ABOVE the fuel tank.


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## hotshot (Oct 4, 2020)

Good job on getting the tiny seal out, those can be tough to pull without the factory Stihl puller.

If the fuel tank leaks out again in the future, I’d pressure test the carb to ensure that it holds 8 psi or a 1/2 bar, all day long.

May have either a leaky inlet needle/seat or an old dried out metering diaphragm pushing down on the lever...try not to store ethanol laced fuel in it!

Storing equipment in a shed outside, hot days & cold nights, allows the tank to be a thermal pump, even if it’s located below the carb.

The “one way in” air inlet check valve #4203 350 5801 in the top of the fuel tank grommet #4223 353 9201 will cause the vapor pressure to build up during the daytime.


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## lone wolf (Oct 4, 2020)

theoldwizard1 said:


> A "friend" who owed me a favor was going to get this piece of equipment fixed for me. I did not believe the "not worth fixing" so I am doing it myself.
> Removing the rewind cover, it was obvious that the crank seal was not in great condition ! Lot and lots of oil and dirt build up. Popped the flywheel and after 1-1/2 can of brake cleaner and rags I could see the actual engine side cover. I removed the seal by using a very sharp pick and some patience. Tiny little thing ! Parts come in next week.
> I the mean time, it is sitting on the bench with 3/4 of a tank of fuel. It has not lost a drop of fuel in 4 days so the tank is good ! If it still leaks after I replace the seal, I'll do something about the carburetor. It is hard to believe that the leak _(when not running)_ is from the carburetor. It is located ABOVE the fuel tank.


Better order a new carb now.


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## theoldwizard1 (Oct 4, 2020)

lone wolf said:


> Better order a new carb now.


Those "imitation" carburetors are only $10-$15 on eBay !
The parts diagram I am looking lists a couple of different carburetors. How can I tell which one I have ? Also, no rebuild kit is shown.


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## hotshot (Oct 4, 2020)

theoldwizard1 said:


> Those "imitation" carburetors are only $10-$15 on eBay !
> The parts diagram I am looking lists a couple of different carburetors. How can I tell which one I have ? Also, no rebuild kit is shown.



Don’t buy a CaronaChina carb from fleabay! Pull yours off & post a pic of the numbers on the side of the carb.

Then you can search either the Walbro or Zama website for what kit # it uses. Highly likely to be a Zama C1Q series carb, S68 model, but you never know...


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## frank_ (Oct 4, 2020)

i have had carb flooding problems with those blowers
i levered the breather cap off and pricked a hole in the middle of the plastic washer


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## lone wolf (Oct 4, 2020)

theoldwizard1 said:


> Those "imitation" carburetors are only $10-$15 on eBay !
> The parts diagram I am looking lists a couple of different carburetors. How can I tell which one I have ? Also, no rebuild kit is shown.


lots of pictures might help ,OEM carbs aint much maybe 35-40 dollars.


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## theoldwizard1 (Oct 6, 2020)

frank_ said:


> i have had carb flooding problems with those blowers
> i levered the breather cap off and pricked a hole in the middle of the plastic washer


I will concur about flooding ! In warm weather, more than 3 or 4 pulls with the choke on and it is flooded !

My starting procedure is 1 or 2 pulls with full choke. Choke off, 1 or 2 more pulls. Like most 2 strokes, it doesn't like to take throttle until it has idled for 30-60 seconds.


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## frank_ (Oct 7, 2020)

theoldwizard1 said:


> I will concur about flooding ! In warm weather, more than 3 or 4 pulls with the choke on and it is flooded !
> 
> My starting procedure is 1 or 2 pulls with full choke. Choke off, 1 or 2 more pulls. Like most 2 strokes, it doesn't like to take throttle until it has idled for 30-60 seconds.


these were flooding when being left unused tbh
and were hydro-locking when the owners were attempting to start them
i had assumed the tank was pressurising, so punched the pinhole in the breather


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