Pistons

This bike will be stroked from 45CI to 57CI using chief flywheels.

I'm using some 1934 standard scout cases so the chief flywheels will need to be ground down to fit with sport scout barrels & rods.

As the stroke is longer we need to make sure the pistons wont come out at top/bottom. So we need pistons with smaller skirts.

Some people even cut out more room in the heads to accommodate.

The std bore on SS barrels is 2.875 but mine will be 50thou over once cleaned up.

I've heard of people using honda pistons ..... so I need to figure out which ones.

Ended up speaking to guys in Melb, Sweeden & sent a message to the virtual indian list "VI" to get the following info

Sport Scout bores

Bore size

2.875 = 73.025 mm

But we need 2.875” +.05 = 2.925” = 74.295 mm

The boys in Melb used Honda XR250 pistons but I don't think they come in 50 over part 13102-Kti-315

Jurgen built his "102" with Yamaha golf cart pistons

Welded up a little mountain in the head – to displace & improve air flow

Part j38-11635-01

Then I wrote to the virtual indian list & got the following comments

Think I'll run with option 1 for $260

Any thoughts wise masters ?

1]

Charlie,

I have NOS Rocky Cycle pistons from the Hap Jones dealership that are used for stroker scouts, they are in +.050 size, if interested contact me off list at rocky@iron wigwam

Stroker pistons to make your scout have 57 ci using chief flywheels. Brand new old stock. avaibable in +.030, +.040, +.050, +.060, +.075 over size. You get a pair of pistons, domed for use with Bonneville heads or stock heads, ewp ins, 4 clips and two complete sets of rings. This special set of pistons allows the rider to increase his engine size without adding stroker plates under the cylinders, which is a sure give way that the engine has beem leaned on or the use of intake port extensions which create intake leaks which are no fun. So with these pistons a builder can keep the stock look on the outside with a stroker on the inside.

2]

Hello Charlie

Go a little further and use One of Rockys Crank pins to suit HD Sportster Rods

and bearings and use Iron Sporster rods. The SS rods are not all that strong . I

am also in the process of building a similar Standard scout motor to you and

fitting to a 101 frame.

There are a few problems to over come.Crankcase clearance for the rods needs

adjustment, I would also fit a top head steady bracket to the frame.

Regards Phil

3]

Our Late Great Guru "Cliff" made up a top motor bracket that attached the rear of the rear head to the s/c loop under the frame. He then joined the 2 cyls with a strap from the forward of the rear head, to the rear of the front head, much like a conventional upper mount goes. But this one was anchored to the 101 frame from the top s/c mount hole. It was just easy, and didn't require a new lug on the frame.

Jus' Sayin' RF.

Cliff did over 106 mph with this 101 in Reno (which is considered high

4]

Charlie,

The old standard piston for this combo is the 2 7/8"Cushman piston. They

are available from Dennis Carpenter Cushman parts fairly quickly. they

have to be relived a tiny bit on the skirt to clear the flywheels and

will require special wrist pin bushes. The pop up is almost exactly a

Bonneville pop up. I looked and don't have any .050s just some .010s.

Dave Clements

Sport Scouts & Antique Electronics

altitude).