Farmertec 660 leak test fail

[wonderwolf]

I'm working on slowly building my 660 kit and following steves "New England Saws" yt build videos.

I'm to the point of doing the leak test and I have the carb adapter, put the piston at TDC per the book and tested and it's dropping from 15 to 8 in 14 seconds. So pretty fast.

I have a stihl decomp valve in and I put better hardware on the intake hose clamp (which ended up breaking the clamp so I'm going to have to replace that)

Is the test only testing the top end? The only thing I haven't done is put a drop of oil on the shaft seals to see if it sucks it in or not but I'm fairly convinced my issue is the decomp valve or intake boot mating with the adapter.

The only other thought I had was block off the adapter and test in the decomp valve port?

 

[2StrokeFondler]

Did you already spray down the usual suspects with soapy water?

 

[stihltech]

You are testing the whole crankcase. I believe Donny Walker did a video on this. The original seals a low quality. Get the oem seals and recheck. Again, put something on the seals and retest, vacuum first. Usually a bad vacuum test is a sign of bad seals. If the pressure test is bad also, then it could be gaskets, rubber components, or all of the above.
Soapy water or a bucket is your friend on this.

 

[wonderwolf]

Did you already spray down the usual suspects with soapy water?

I only have the vac tester so I dropped oil on the seals and it's not picking any of it up. I've got some more parts on the way so if they don't fix it I'll look at a smoke test or something

 

[wonderwolf]

You are testing the whole crankcase. I believe Donny Walker did a video on this. The original seals a low quality. Get the oem seals and recheck. Again, put something on the seals and retest, vacuum first. Usually a bad vacuum test is a sign of bad seals. If the pressure test is bad also, then it could be gaskets, rubber components, or all of the above.
Soapy water or a bucket is your friend on this.

With the adapter for the intake do I still test at TDC? I'll have to look up his video and see his methods

 

[SteveSr]

With the adapter for the intake do I still test at TDC? I'll have to look up his video and see his methods

Crank position doesn't matter. Pressure will equalize across the rings.

 

[wonderwolf]

Crank position doesn't matter. Pressure will equalize across the rings.

No trying to be smart but why does the manual say TDC for the testing position when using the adapter? I was thinking because the vac could cause it to change positions and alter the reading but the ports are under the piston?

 

[Gord404]

I use a piece of rubber and a stripped down small carb as a spacer and and a couple of spacers before the nuts go on that wayI have access to the pulse line and have a plate and rubber for the exhaust so if it is the base gasket I will see it and quite often vac-pres through the pulse line or plug it off and use the spark plug adapter- you have already know you have a leak but without 7-8 lbs of pressure you will have a hard time finding it like the base gasket etc- love my mitiivac

 

[stihltech]

As far as having the saw on tdc, yes Stihl recommends it. Gets the lower end filled up faster from my experience. Depending on cylinder porting and piston position. Will it still get pressure and vacuum to all parts, sure. Just takes a little longer.

 

[grizz55chev]

Air pressure works best for finding hard to find leaks, in my experience. You only need about 7psi to make it work, and a 5 gal bucket of water. Adapt an old bicycle pump if you dont have an air comp.