Author Topic: 707D compression/pressure  (Read 285 times)

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Offline dynodave

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707D compression/pressure
« on: April 03, 2014, 07:05:14 pm »
Any one know what is cranking pressure for these old saws? My 707D blew just shy of 145psi. It has a new piston and rings running in a scratched, but not severely scored cylinder. It has now run Idled and throttled up for a total of about 10 minutes.
I have to send off my dead new tinytach and hope to get a warranty replacement, so I can set up the governor to 6K. Then I can cut wood and get it tuned to break from 4 stroke into 2 stroke...yeah baby...
pix of the patient here...
http://atlanticgreen.com/images/707da1t.jpg
32 saws
ECHO-HOMELITE-HUSQVARNA-McCulloch-PIONEER-POULAN-STHIL

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Offline Eccentric

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Re: 707D compression/pressure
« Reply #1 on: April 04, 2014, 06:00:34 pm »
The Homelite Service Manual tells us to refresh the engine when compression falls below 100 psi.  You're doing very well to have 145 psi with a scratched cylinder.
-Aaron

For older saws:
Tune the H side so that it 4-strokes (burbles) at WOT unloaded and just cleans up when under load.
When you lift cutting load, the saw should immediately revert to 4-stroking.  Fine tune the transition point for the wood you're cutting.

Offline dynodave

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Re: 707D compression/pressure
« Reply #2 on: April 04, 2014, 08:15:01 pm »
Thanks Aaron
I got curious and tried a pressure test on my 7-19C (82cc) also, and got just shy of 165psi. Both saws were converted to new std (no skip) 404 chain. The 7-19C is a 20" hard nose bar and the 707D is a new 30"carlton bar.
I've got a 15' piece of red oak 28" at the big end for testing cookies. I need the 707 running and cutting good for a maple at another property that is much bigger.... ;D
32 saws
ECHO-HOMELITE-HUSQVARNA-McCulloch-PIONEER-POULAN-STHIL

 

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