EVO from stock to 103

[Boatsteve]

I am thinking of putting 103 cylinders and pistons on, do I need different heads? do I need and lower end changes? or can I just change cylinders and pistons?

[stroker800]

   To build a 103 with a stock 80" ,,you will need to go with 3 13/16 bore or bigger to keep the stroke at a reasonable length.. The ol school 103 was a 3 5/8 bore x 5" stroke, it might be easier and cheaper to install a big motor,,parts and machining will add up.
Dave

[Boatsteve]

Dave I was tinging of adding diamond cut heads and cylinders and the set I found is 103 cylinders and pistons storck would not change? I do not know

[1997bagger]

We would need a little more info on those cylinders on what you are looking at.

Your going to have to split your cases in any direction to get those cubes on an Evo. I would also vote for an aftermarket engine for cubes.

Headwork needed, fuel changes, cam matching - valve springs, clutch slippage, starter cranking ability, do your homework.

[Boatsteve]

Bagger 1997  Thanks  I Will keep looking for the diamond cut parts on stock parts or buy without and have them cut, I was not looking for more power I like the look

[Hillside Motorcycle]

If you are not looking for more power, and go from 80 to 103 you sure will find it.
Very potent set up correctly.

[TheSwede]

Myself have 95.4 kit  Wonderful setup

Regards TheSwede

SPUTHE CYLINDER KITS COMPLETE*

95.4 CUBIC INCH EVO BIG TWIN

Sputhe’s most popular kit.  The cylinder kit offers the most performance per dollar because the entire displacement increase comes from the increase in the bore size.  RPM potential is not reduced and since Sputhe piston assemblies weigh less than the stock pistons, engine vibration and bearing loads are reduced.

Flat top pistons have valve reliefs for both stock and STD big valve heads.

Oval dish crown pistons maintain squish when using STD, Branch #4 or Revtech Heads.

With oval dish crown pistons
1984 to 1989 compression ratio = 8.6/1 @ 80cc chamber.
Part #4001A

With flat crown pistons relieved for stock and STD heads.
1984 to 1989 compression ratio = 9.6/1 @ 80cc chamber.
1990 to 1994 compression ratio = 8.8/1 @ 90cc chamber.
Part #4001B

104 CUBIC INCH EVO BIG TWIN

For the man who thinks too much is just right.  This kit uses the same stock length Sputhe cylinders as our 95-inch kit.  The difference is the pin location in the piston.  They are to be used with 4 5/8 inch stroke flywheels.

With oval dish crown pistons.
1984 to 1989 compression ratio = 9.0/1 @ 80cc chamber.
1990 to 1994 compression ratio = 8.3/1 @ 90cc chamber.
Part #4003A

With flat crown pistons relieved for stock and STD heads.
1984 to 1989 compression ratio = 10.3/1 @ 80cc chamber.
1990 to 1994 compression ratio = 9.5/1 @ 90cc chamber.
Part #4003B

* Kit includes: 2 cylinders with pistons and ring sets, head and base gaskets, O-rings, wrist pins and snap rings.






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