Sachs Engine I.D.

[imported_n/a]

I just got Issue No. 18 of Still Keeping Track.  Great issue.  I loved the "Tech Tips" article on John Durrill's 175cc Sachspiner engine.  

The top photo on Page 11 shows different Sachs crankcases.  Engine C is listed as stock Sachs B cases.  I have a used set of cases that look like the cases listed as A.  However, my cases are stamped up on the top rear with the "6" designation for a six-speed trans.  My cases are not the style as John's "C" photo shows, with the reduced crankcase volume.

What engine do my cases belong to?  Is my set of cases a 1251/6A or B?  I can find no part numbers anywhere on the cases.   Any help would be appreciated.

Glenn

 

[john durrill]

Glen i believe they are 6 A cases. all the B and up cases i have seen have the double cut outs where the cylinder slides in .
 we had some early CMF Pentons that had mags and A motors.
 they had the large shifter shaft and key. They used the shifter adjusment like a B motor. you can put a large journal 5 speed or a 6 speed tranny in them.
Hope that helps



Edited by - john durrill on 03/17/2003  6:46:39 PM

[imported_n/a]

John, I love your 175 Sachspiner engine.

Thanks for the info.  What effect would putting a B crank into the A cases have, if much?

Glenn

 

[john durrill]

You would have some change Glenn,
 you would increase your crankcase volume.
 and change the way the charge flows up the transfers. It might be so slight it doesn't matter. but it could change it significantly.
 you might loose some throttle response at low rpm and it would knock some off the top too. you could stuff the cases and reduce the crank case volume. They still do that with the 250 road racers I know. they still are using the old standby Devcon aluminum putty to do it with. or you could make up some aluminum horseshoes and hold them in with screws and epoxy.
 if you have the time and don't mind putting one together more than once I would  try it like it is and see how you like it as an A motor with a B crank. then do the crank stuffing if needed. we looked a long time trying to find a set of case's like you have with no luck. we got ours from Germany finally.
I have never done the a case b crank thing so it would be good to make sure that the two would fit with enough clearance  from side to side.
John & Peter

 

[imported_n/a]

John, I picked the cases up on e-bay, thinking I would use them in case I badly blew up one of my B engines.  

I also have a 1251/5A parts engine, Serial No. 6317205.  Would the 6A cases be compatible with it?

Glenn

 

[john durrill]

yes if the 5A cases have the larger bearing on the clutch side for the counter shaft.
 you have to shim the tranny different and need the 6 speed  stuff including the 6 speed shifter boss.
 we are useing a  large journal 5 speed and can put the 6 speed tranny in if we think it will help.
John

 

[imported_n/a]

Thanks, John.  You've been of great help.

Glenn

 

[imported_n/a]

John, after re-reading your "Still Keeping Track" article on your 175 Sachs, and looking at your set of crank cases you used with the large transfer area, and also picking up Issue No. 14 of VMX, in the article on Scott Wallenberg's Monark GS Pro 125, he mentioned a factory Sachs engine that was built for Marty Smith to race in his Monark for the 1974 nationals, but Marty jumped to Honda, and the bike ended up racing around my area here.  The engine utilized a special four-transfer port barrel, and I'm thinking maybe your cases were from this engine concept, cast to accommodate a four-transfer port cylinder.  I'm guessing on this, but it may be an explanation.

Glenn

 

[Larry Perkins]

The four transfer port Sachs factory cylinder fit the D GS stuffed cases and would also fit any B or later cases.  The sleeve was different and of course the piston was too.  The difference in the piston was the boost holes from boost ports in the back.  I talked about this sleeve before when I had a NOS one.  It is now being put in a nameless AHRMA expert's bike for 125 Classic Nationals.  There was in Europe and a few here a 175 Sachs motor with 6 speeds and those are the cases like John had, I believe.  Dwight Rudder could shed some light on those because he has one of those rare birds.  The trouble with those as opposed to the 175 KTM/Sachs match-up John did is the pistons are about non-existant.  Hope this sheds a little light on my angle of this subject.

 

[imported_n/a]

Larry,

Thanks for the info.  Lots of light was shed.  

How long does a rod (and piston, for that matter) last in a D GS stuffed case engine?

Glenn

 

[Doug Wilford]

Glenn and all;
KTM Penton never used the "D" cases.  Reason: not enough volume of oil reaching the rod bearing.   On and off throttle like MX, okay, but the Penton was built for reliability and to run down the road wide open for long distances, which are death to the rod in a "D" lower end.   Glenn, you cannot use a "B" crank in "A" cases, or vice a versa.

 

[imported_n/a]

Thanks, Doug.  Now I know I've got some Sachs stuff that I can't use, like the Sachs 6A crankcases and 1251/5A parts engine mentioned above.  Once I dig them out of storage, I'll post them here.

Glenn

 

[john durrill]

Doug,
 can you tell us what keeps the D cases from allowing enough oil to the rod? . thats a bit of information i will file away for use another day and would help me understand more about two stroke engines. It seem the longer i live the more things i find out i dont really understand as well as i thought Chuckle , Chuckle
Thanks
John D.

 

[Doug Wilford]

John;  To answer your question, about "D" cases.   I think you have never seen them.   The reason most of the fuel & oil mixture does not get to the rod is because of the design of the crank area.  The "D" cases leave barely enough room for the rod to go up and down.  The transfers still have the holes to lube the main bearings. I took some pictures of this for my seminar at Penton Day at the AMA.  I will send it to you.