Pro GS D Motor

[chuck]

Does anythone know what a Pro GS D Motor is? I may be wrong on the name.

Thanks,

Chuck

[Doug Wilford]

What you are asking depends on the brand of bike the engine came in.  The Penton GS "D" engine used a "D" cylinder and head and the same bottom end as a "B" engine.     Some models of Monark use the complete "D" engine which had a very stuffed bottom cases.   There are probably a few other makes that used the complete "D" Sach Engine.   There were many brands of motorcycles that used the 1251 Sachs engine.
Have fun!