Help w/ cylinder swaps dolmar 6401/solo 681 and jred 625 and 670 champ

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ArboristSite Operative
AS Supporting Member.
Apr 7, 2007
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Duluth MN
Been lucky enough in the past couple weeks to come across some tantalizing cylinder swap options. I have a dolly (mak) 6401 sitting on my shelf and stumbled across an excellent 681 cylinder. What do I need to swap this in? I know the stroke is longer on the solo - does that matter - am i good with just a base gasket? What piston should I use?

Second question - Picked up a Jred 625 in really good shape and a kinda junky parts saw 670 champ with an excellent p&c. Is that p&c swap just a bolt on? I assume it is? Just double checking. Thanks!
Can't help with the Dolly but as already said the 625 to 670 is a direct swap but I would add you should take the 670 carb along with the P&C if you want to take full advantage of the upgrade. The 625 will probably have the smaller 237 carb. There were some changes along the way carb wise so depending on your two saws age will determine what carb the 670 will have ....The latest version and the West Coast versions used a 250A which is a nice carb but is a recirculating type so it has two fuel lines which means that if you 625 is not set up the same you would have to bore in a return fuel line...not a big deal to do.
The Solo 681 cylinder isn't going to be a straight swap onto your 6401 chassis. You would either need to swap a Solo crank into your Dolmar/Makita chassis (which is also not a straight swap),
or figure out a taller piston and then adjust the port timing to suit.
Could sell the Solo 681 to fund the purchase of a 7910 cylinder
I you go that route, please let us know where you found it for a reasonable price. I've got a ea7900 in dire need for a functioning P and C. But I'm not willing to spend that 200 euro yet.