Cylinder liner

[dkwkid]

I just picked up a 100cc Sachs motor.I want to use the top end. I took it apart and the good news is that someone replaced the liner in the barrel and it is on stock bore like new!However, both intake and the exhaust ports are bridged in the middle! I am thinking that a new liner has the ports bridged to prevent warping when pressing into the barrel.I believe these bridges need to be machined off before it is put into service. I dont want to ruin a good top end so if anyone has some insight to this please let me know.
Thanks,Glenn

[Larry Perkins]

Glenn

The sleeves I have seen for Sachs motor that had bridges were towards the end of "The Day" and they were widened ports compared to stock.  I think the bridge was used to lessen the chance of a ring hanging in the widened port.  Yours might be one of these from memory.  Perhaps others will have confirmation or a different spin.

Larry P

[hrbay]

Glenn you might want to do some research first. There is a golden rule of sorts on port width as a per-cent of bore diameter that should be observed. Don't recall it right off... do a web search on two stroke porting and there will be plenty there. Like L.P. said it may be wide enuf already with the bridges. The bridge keeps the rings from bulging into the port and snagging at high rpm's.

GC

[firstturn]

dkwkid,
  Have you measured the ports (width) compared to that of a stock cylinder?  I agree with Larry in the fact that there was a need to have a bridge if you were going to widen the ports.  Remember that with a 48mm bore you have such small area (diameter) to work with that any additional support for the rings is a plus.

Ron Carbaugh

[dkwkid]

Thanks all,the ports are wider than the aluminum outer barrel.It must be a late model liner.You learn something every day!

[Larry Perkins]

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