Topic: 64mm bore

[kevleaper]

Hi
I recently bought a 750 frame and engine. The frame's been modded for racing, probably back in the 80s. Looking inside the engine it turns out to be rebuilt but never run with 64mm bores and a 327 cam. Looks really nice inside with ported head, new valves etc, but there's various bits missing like the rockers and shafts, but the barrels have some fin damage. I'm assuming it's impossible to get the fins repaired so it's a case of finding some decent barrels but will I need to liner them or do the standard bores go out to 64mm?
Thanks Kev

[seanbarney41]

Std. Barrels can be bored to 64mm.  Iirc, 65.5mm is the absolute limit.

[seanbarney41]

Also, liners can be removed and swapped between cylinder castings.  So, if your bores are still good, you could save yourself the machining cost by heating the cylinders in an oven until the liners slide right out.

[MRieck]

Fins can be repaired

[kevleaper]

Thanks, the fin damage is a case of replacing missing material, so without knowing how someone could do that, or how they could do that, a secondhand set of barrels and a bore seems to be the way to go. Thanks.

[MRieck]

Thanks, the fin damage is a case of replacing missing material, so without knowing how someone could do that, or how they could do that, a secondhand set of barrels and a bore seems to be the way to go. Thanks.

If you need a cylinder let me know as i have quite a few.

[BPellerine]

327 cam seems huge for that bore,wonder what it was built for?

[754]

Looking at the bike , I say roadracing....
 I saw the pic in introductions.,

 Yes fins can be reoaired, sometimes reasonable , sometimes not.
 We need a pic if the pistons..if they are 12:1 might be bad on the street..

[Don R]

 I have a friend that builds up fins from the edge with tig weld. They clean up nicely.

[seanbarney41]

I recently came up with some 64.5mm Powroll pistons and liners...what displacement does that make?  823?

[newday777]

I recently came up with some 64.5mm Powroll pistons and liners...what displacement does that make?  823?

According to Dynoman 64mm is 811 and 65mm is 836. So 64.5mm should be 823.5, doing the math.

[seanbarney41]

I recently came up with some 64.5mm Powroll pistons and liners...what displacement does that make?  823?

According to Dynoman 64mm is 811 and 65mm is 836. So 64.5mm should be 823.5, doing the math.

I wondered if anyone was ever gonna answer this...I hadn't even thought to do the simple math of figuring the halfway point between 811 and 836...I vaguely remembered seeing that 823 number somewhere,,,can't remember where or how long ago.  Thanks for confirming.

[newday777]

Building up damaged fins(not mine)

[Don R]

 The bored out twin cams often are 823cc.

[Tracksnblades1]

The bored out twin cams often are 823cc.

Ran across this a while back….

[PeWe]

That page has one error, 67.5mm does NOT make 915cc.
Do the math from high school for volumes x number of cylinders (4) and find 901.7cc. (stroke is 63mm) 
900cc a more correct name for that bore

Even CycleX has that error on their piston kit they call 915cc, Wiseco 67.5mm piston

(68mm make 915cc.)
915cc need thicker sleeves, no stepped version as 67 and 67.5mm pistons can use, the latter ends up in thinner sleeves where enter the case than 836 when using the stepped sleeves that can fit case without bore it.

More info when at it:
I noticed that 1975 and 1976 cases needed some massage by grinding off some. An old K2 case not.

That 67.5mm-915cc error can cause problems when ordering gaskets, sleeves, rings and pistons. Always mention the bore diam when order.