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Author Topic: Ordered a new 7900 OEM Cylinder and Piston  (Read 888 times)

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Offline KilliansRedLeo

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Ordered a new 7900 OEM Cylinder and Piston
« on: July 27, 2013, 12:42:11 pm »
E&E sent it out quickly as usual. So, when it arrived I noticed there were some differences between it and others I have installed.

1) the piston is slab sided not windowed like I was expecting
2) what looks to be a steel base gasket was included

Anyone know what the deal is with this new setup?
Could it just be that Dolmar is supplying the 7901 kit for both saws? The part number for the 7900 kit and the 7910 are different however.

PS-7900 030 130 070
PS-7910 030 130 071
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Offline 660magnum

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Re: Ordered a new 7900 OEM Cylinder and Piston
« Reply #1 on: July 27, 2013, 01:08:11 pm »
They did away with the windowed piston and started with the metallized base gasket about two years ago (2011) before the 7910 came out.
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Offline farmboy

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Re: Ordered a new 7900 OEM Cylinder and Piston
« Reply #2 on: July 27, 2013, 02:30:49 pm »
My last 2 7900 P&C kits had slab sided pistons.  I wanted windows so I bought 2 AM pistons.  The new piston is a lot lighter and skirts are a couple mm wider.  No reports of anyone saying loss of power with them.  The ex port is completely diff. on the 7910 cyl.  has a tube that stick inside the ex port.  Look @ muffler.
http://www.partsnationwide.com/ARI-PartsSearch#/Dolmar/PS-7910_Chain_Saws_-_Gasoline/Hood%2c_Air_Filter%2c_Muffler/2S01440003/2S01440002C
Ex. can be ported same as 7900 cyl.
Shep
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Offline mdavlee .

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Re: Ordered a new 7900 OEM Cylinder and Piston
« Reply #3 on: July 27, 2013, 06:36:49 pm »
Randy/mastermind ported 2 at the same time with the windowed and slab sided and the slab sided made more power.
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Offline KilliansRedLeo

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Re: Ordered a new 7900 OEM Cylinder and Piston
« Reply #4 on: July 28, 2013, 11:21:58 am »
Cool! Randy knows what he is doing! Does anyone know what the intent of the metalized base gasket is or was?
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Offline 660magnum

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Re: Ordered a new 7900 OEM Cylinder and Piston
« Reply #5 on: July 28, 2013, 02:55:24 pm »
They came up with the metallized gasket because of field reports of the base gasket sucking in on the sides.
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Offline KilliansRedLeo

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Re: Ordered a new 7900 OEM Cylinder and Piston
« Reply #6 on: July 28, 2013, 03:09:04 pm »
Thanks for the info 660Magnum.! May send a BN  7300 off to Mastermind for a port job using the slab side kit. We don't normally make one-off modded saws however this is my own saw.
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Online Cut4fun

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Re: Ordered a new 7900 OEM Cylinder and Piston
« Reply #7 on: July 29, 2013, 07:40:58 pm »
I've never ran any Dolmar done up by Randy. 

But I have ran some of Ed Heard's in Canada EHP 7900 and he does up some strong work saws using the stock parts that come with them.  Not like some (not talking about MM Randy) having to switch in other makers pistons, coils, thicker shims and  base gaskets etc to get the gains. 
You might also check with Dan Henry dozerdan in PA. I know he used to be a dolmar dealer and may have ported them too. Know he does a heck of a job on the huskys.
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Offline farmboy

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Re: Ordered a new 7900 OEM Cylinder and Piston
« Reply #8 on: July 30, 2013, 09:20:17 am »
Dan has done a bunch of 7900's.   He is the one that told me about all the crank failures in the Solo 681.  681 is a 7900 with a 1mm stroked crank.
Shep
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