Some time ago there was a discussion about using LA 25 pistons and cylinders in other engines. As I had a rather tired Thunder Tiger GP 25 lying around, I bought a couple of LA 25 assemblies—just in case.

Last week I replaced the TT piston and liner with the LA 25 assembly—fits were spot on, and there is no boost port. I ran the engine yesterday for a total of 20 minutes. Initial start took some time due to having to find the correct needle setting. Once found, after that, the start routine was finger over the venturi for one turn, flick twice, add power to the glow plug, start second flick.

Configuration for the TT GP 25-LA: Scott Riese venturi—excellent work, thanks Scott—Randy Smith NVA, OS E-2030 muffler.

Good question Andrew. There wasn't a Thunder Tiger source when I bought the LA parts. Thundertiger4you had disappeared but Tower was not supplying at that time.

Tower has them available now—limited stock—and for LA 25 users, they list aluminium backplates for $4.99 and gasket sets—which include the thrust washer—for $2.69.

Here Dick, http://www3.towerhobbies.com/cgi-bin/wti0095p?FVPROFIL=&FVSEARCH=thunder+tiger+gp+25&search=Go 

Tim, the hole in the Thunder Tiger crankcase accepts a 4mm spraybar. The Super Tigre-type NVAs from several sources—including Randy Smith—will fit and that's what's in my rebuilt TT 25. I believe that the Enys NVA is 4mm as well. Again, the only one that I have is in a Randy Smith modified engine so that's where to get the Enya or the PA needle assemblies.

For reference. the venturi is 0.136" ID from Scott Riese and the needle is open about 2 1/4 turns.

No idea, Chris.