I’ve read that the ST60 Rc and the  CL version have different port timing. Will a converted RC version work as well for CL or not recommended? Seems like the RC version is more available which is a little concerning. Ty

     When you talk about ST.60s, you need to be very specific. What some call the "light " or "small case" .60 is the engine that has a one piece crank case with a rear cover. Some versions of it have a 'V" on the left side of the case. They range from early ones with no muffler lugs to the last version that is called by some the "K" version that has full depth muffler mounts and a concaved or dished surface on the head. These were all used for stunt at one time or another and were usually converted from an R/C version by just adding a venturi and a spray bar, usually in a "sprinkler" style set up, or true venturi. Anything else that has a bolt on front main bearing housing is an R/C engine, and I think the vintage R/C pattern guys like those, especially the Blue Head. It is the more recent ST-G.51 that came in two versions, and R/C with carb and the C/L with an aluminum venturi. The only difference between the two is the cylinder liner. The C/L version has a little lower timing. Both are ringed engines. Super Tigre made a .51 back in the 60s also, so don't be confused with that engine. it was a size between the ST.46 and the ST.60, and there was also a .56 for a while. These all had round heads. in the early 90's Super Tigre changes things up and came out with new engine with largeish square heads and cylinder, and this is where the G.51 comes from. They also made a C/L version  of their .34 also, I believe. Dig around on the internet for photos to know what you are looking for. Might only have to search the engine section on this forum for enough to get you familiar.
   Type at you later,
    Dan McEntee

Thisisabout where ital STARTED . Plain Bearing . Ball Race the  bearing housing makes the case otherwise .
these dogs had lapped pistons initailly and overheated . Thus a RINGED , Finned Head , ' 56 ' ( wassa 51 too & 45 )
Plain Bearing ' 56 ' is pretty much what a Kolesnikov KA 9 was , and its double Star 55 clone ? perhaps ? .



Knotte the PLAIN BEARING . for lightyness , Boll Rices give higher r.p.m. with less drag . However . The ST 60 were ALL Ball Race .
unfortunately the plain bearing ( and ball race ) 56 are a differant head bolt p.c.d. to the . 60 . Although the same stroke  .
1 m.m. down on the bore . 23 x 22 Vs, 24 x 22  m.m. .

ANYWAY the ' BIG ISSUE ' onemall is S.P.I. . at Top dead Center , the fore & aft of the piston underside crank clearance cutaway ,
like a early double star ! !  , MEANS A ' TIGHT ' MUFFLER  gives it ' blow back ' into the case . ( the ST C 35 gotaround this with a 20 thou shim under the top sleeve flange , to lift it . )

Thus and therefore , the late 60's may have a angled lower edge front Ex Port ' window ' lower edge ,with piston 9 and backplate ? ? ) mods , to eliminate the s.P.I. . 



      THESE are the FIRST Series 51 , 56 & 60 . With Two Piston rings . Hard Chrome Bore , thinner smaller diameter sleeve ( the 51 has smaller fins ), and Sub Piston Induction .
so want a TUBE MUFFLER . First series was wedge head . Second had the ' Hemi ' with the narrow squish band and big chamber . What was mostly the hot Set Up . running say a .312 venturie ,
cross drilled for a 4 m.m. spraybar . plus 6 or 7 ounce fuel tank .

Next Series , I.D. by Ex Butterfly tapped pivot in vertical bridge at the Ex Stack middle ( center )  THESE have thicker cylinder from then on , are hard chrome , single ring . no muffler lugs .
 Usual to use a tube muffler with one screw ! .

THEN the earlier muffler lug , likely no cylinder chrome .

The same , but P.D.P. , I think thats the angle edge 4 window version . any muffler will do .



TWO ' windows ' Ea. side of devider - the ' bridge ' to stop the ring falling into the port , creates the ' window '
Aledgedly a A B C aftermarket gives beta power as is unbridged , so could flow more . Whereas . . . .

The LAST SERIES had head fins concave on top , and only THREE Windows ! Ex and bypass . AAre said toobee as powerfull , and better economy .
So that about covers it . 

WHAT was the QUESTION .
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Theyre all the bl**dy same , R/C & C/L , as to series . Differ series to series . The First were a nudge lower timed . 8 or ten degrees or sumsuch   . 130 Vs 140ish on the Zorst , Coresponding on Trans .

The MESSAGE is LEAVE THEM STOCK . Clean Thoroughly . Remove Backplate & INSPECT BEARING for rust. Brown Stuff , rot etc .
If Its black inside , Lift the LINER till the Gudgeons Exposed ( no further ) and pull it .      If you can .       

A frozen / gummed wrist pin on anyfing will make it awkward at best , and is rather common on used R/C motos thrown in the draw , unflushed & unoilled .
A weeks soaking and heating should get it started , perhaps .

If a nudge with say a matchstick , starts it Fwd, a hooked end pin might easilly pull it free , out the access hole , But pulling the end cap free with a easy out , is more likely .
C R C , Heat , get it revolving . usually it rock hard castor twixt piston & rod - on the Wrist Pin . So a bucket of patiance will be needed .

THEN clean wrist pin bore , put a wire through it ( or play ' hunt the wrist pin ' ) brush it clean on 600 Wt, and polish it with 800 , sparingly .

Ty both. Good info. I’ll do my homework.
Joe Motta

   And just to add, the internal parts for older .60s don't all interchange, and it can get confusing. There were single ring, and double ring pistons, and differences in the rings I think. I pretty much let Tom Lay handle and engine work I needed or wanted on Super Tigres, and he and Randy Smith would often caution people on this when working on their own engines. Unfortunately, Tom is no longer with us and I'm gonna guess that Randy may be more or less retired, or at least not as active as he used to be. Good luck with it.

   Type at you later,
  Dan McEntee