MS290 vac/pressure specs?

[half_full]

Hi All, I sold one of my 372's the other day. Unfortunately I offered to look over an MS290 that runs but has no power.

So, it will not hold vac or pressure. I pump up to 5 psi and in 5 seconds it's gone. Same with vac. What should the specs be for this saw once I resolve this issue?

Compression is at 132. It needs an AV mount, spur sprocket and the air leak resolved.

The saw had a new cylinder put on it due to stripped spark plug hole. The cylinder looks great. The piston has very minor scoring as do the rings. I'm guessing from running with an air leak?

The owner wants to get rid of the saw. It looks decent and my labor would cost him a truck load of firewood (his sons cut and sell). Is it worth fixing or should I suggest selling as a parts saw?

Anyhow, it's very unfortunate the search shows great threads on how to disassemble the 290. BUT, THE PICS ARE GONE

 

[Marshy]

Disclaimer, Im no expert.

I was just reading the stickies about vac testing, and granted I did not read them all I did not see a "spec" that quantified leakage. It was more like a pass/fail test. I'd say it needs seals before putting it back to work or it will only get worse and end up destroying the new cylinder/piston or wrecking a bearing. Seems like replacing the seals would be the way to go. Probably cheaper than replacing the saw.

I'll take it for parts if he wants to sell it cheap.

 

[half_full]

The saw is a clamshell motor. So there's more area to leak. I'm trying to think of worst case so I know prior to breaking it down.
I plugged the impulse and put a rubber (motorcycle inner tube) blocker on the carb and exhaust. There is no decompression valve. So, are these known for air leaks anywhere like the husky 55?

 

[sld961]

I read somewhere that a Husky manual specifies that the pass/fail point is 20% of the pressure in 30 seconds. I think that is too much of a leak. When I test saws, they get 10psi and it must have 0 drop in 5 mins, then I do a vacuum at 10" and it must have 0 drop in 5 mins.

If you have a leak, pump it up with pressure (not over 10psi) and spray soapy water all over the hoses, base gasket, carb boot and also on your exhaust and carb block. Identify the leak before you start replacing stuff. If all of the easy stuff checks out, then look at your crank seals.

 

[redunshee]

agree with prior post but I don't wait as long. If it doesn't leak after a minute I feel it won't leak. Clamshell engine likely needs seals and if you're replacing those you might as well replace the bearings. Have you diassembled the saw? If not , when you do, keep in mind you need to remove one of the bar studs first. I believe its the front one but its been awhile since I worked on one.