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Dolmar 6400 converted to a 7900

Started by rat362, August 06, 2018, 08:39:11 PM

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rat362

Has anyone changed the cylinder head and piston on a Dolmar 6400 to convert it to a 7900?  Are the jets in the carb the same for both, or will I need a new carb?  The 6400 handles a 24" bar ok but that's all I dare to use, I would like to go longer.  If the conversion is doable, what's the longest bar that it could handle efficiently?

sawguy21

It's a straight bolt on, bottom ends are the same. Properly tuned it should handle a 30-32" bar easily. Your carburetor will work fine although it will need to be richened a little. Open up the muffler while you are at it.
old age and treachery will always overcome youth and enthusiasm

joe_indi

6900, 7300, 7900. They are identical except for the cylinder and piston.
When upgrading or down grading carb will need adjustment.
(experts correct me if I am wrong) The settings on a 6900 may be too rich for a 7900 (increased air velocity of the latter causes more fuel to flow into the air:fuel mixture)

Coffee_Creek

I put the 7900 cylinder and piston in my 6400, easy conversion, huge improvement, runs a 32" bar with no issues, uses same carp with a little adjustment.

rat362

Thanks everyone for your input.  It's nice to hear from professionals with real world experience and not salespeople pushing product.

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