Iron cylinder questions

[Mark Annan]

I recently got a 68 Berkshire.  It has a 5A engine with the cast iron cylinder, radial fin head, and aluminum rod. It has been bored to 54.44mm.  I have never worked on one of the iron cylinder engines.  It has transfer slots cut into the cylinder wall that run up the rear (intake side) of the cylinder to the same height as the transfer ports.  Are these slots standard factory items or are they a later addition?  If they are factory what was done about them when the cylinder was bored for the 152cc kits?  It looks like they would be nearly eliminated with a large over bore.

Mark

 

[Doug Wilford]

Mark;
Someone was trying to get a few more ponies out of that cylinder.  I think that was an outside job, I know it wasn't a modification that we would have done at Penton Imports, maybe a race bike experiment.    We had to use 100cc cylinders to modify for the 152 kits the 125s didn't have enough metal around the transfer ports (I think it was the transfer ports??

 

[Paul Danik]

Mark;
  We used to do some porting like you discribed on the later 6B engines.  We referred to it as finger porting the cylinder.  Parts book 002 states that 54.5mm is the first oversize for a 125.  Standard bore is 54.00mm for a 125.  Either this guy ran out of 100 overbores orrrrrr he wanted some real power from his little Berkie!!
Paul
PS  I would be curious to know the width and depth of those slots.

 

[Mark Annan]

Paul,  I will try to describe the grooves to you.  They are approximately 3/8" wide and 1/8" deep in the center.  I would guess that they were made with a die grinder bit about 3/8" in diameter or a little larger.  They have a nice radiused profile when viewed from the end.  They start at the upper rear (intake) corner of where the transfer port opens up at the base of the cylinder.  From there they run up the rear of the cylinder in a shallow S path.  They terminate at the same height as the stock transfer ports and are about centered between the edges of the intake port and the stock transfer ports.  Whoever did the work did a fairly good job of freehand grinding, much better than some of the homegrown port work I have seen.  Interestingly none of the other ports seam to have been altered.  They are still as cast rough except at the very ends where they were deburred.  I am going to try and get a picture of them for you.  The part number cast in the base of the cylinder is 0 613 168 099.  I don't know if this helps identify the cylinder or not, but I wonder if it started out as a 100cc or 125cc cylinder.    

Mark

 

[Larry Perkins]

There are so many things that can be done to the Sachs motor to bring more out.  If finger ports are something you want just copy the 125 KTM finger ports and run a 125 KTM piston or Wiseco copies with the window in the back.  

This will cover that trick but in my opinion that is too much for the bike to be raced in 125 Classic.  It is someting that would probably never get caught but 125 Classic bikes are 1971 technology and older.  The Sachs motored Penton can be a 74 and run in this class because it was behind the times of 1974 and is given a break.  Classic modifications are supposed to be in the spirit of the times.  I believe finger porting is more like mid to late seventies and not 71 and older.  I am not saying it wasn't done then just what is fair considering the break.  It does capture ponies however.

 

[Mark Annan]

Hi Larry,  Glad to hear you guys are doing so well.  Keep it up.

I wasn't planing on actually using the cylinder with the finger ports.  There are easier and better ways of getting a little more power!  I had never been inside one of the old iron cylinders and had never seen any references to the "finger" ports in any of the Penton or Sachs literature I have.  I was just curious about the ports.  I'll be in touch soon about some needed parts.

Mark

 

[john durrill]

Mark they sound like boost ports. I use to do reed conversions for some piston port motors. The Hodaka in particular. It responded very well to the conversion ( use a gem reed valve kit) I did grind two additional ports at the back of the cylinder.
That coupled with a 26 mm carb added a great deal of torque and power to the little 100cc two stroke. Have seen it done on the 175 jack pine and the aluminum cylinder 6 days but with poor results. The ones I rode lost power with the conversion. Might have needed a biger carb to get any benifet from the reed .I think the 54.44 mm is the second over bore. You would be better off if you could to replace the cylinder I think. If your not in love with the iron barrel I would opt for the aluminum and a new radial head. Did that on my 69 Sachs and it worked great.