well i decided to go fly the modeltech magic today and the st51 just did not want to run good. It starts easy, but has no throttle response, basically one speed, and the high speed needle does not adjust it at all, basically half power throughout any throttle position and runs very rough. this motor has not been ran in over a year, but i let it warm up through a whole tank. compression is not the greatest, if i turn in slow i can feel a lot of blowby, would that explain the problem? i changed the rings about 3 hours of running time ago. any help would be appriciated

G'day Could it be that the engine is a bit "gunked up" with old oil? And as a result, the carby is partly clogged and the ring is stuck in the piston and so not sealing properly? If the engine has been sitting, perhaps what it needs is a good clean out of the carby and possibly the ring needs to be freed up? Bearings too could be clogged up. If it were mine, I think I would start with a good cleanup and even possibly a new ring even though the "old" one is not all that old and possibly even some new bearings. Castor is great stuff if you use an engine often but not so good if it gets to dry out in an engine in storage. I have had little blockages in a carby from castor after only a few weeks storage.

I cleaned the carb and everything before I started it up, and it moves pretty easy, doesnt feel tight at all. Ive never seen a motor run that rough, i thought it was going to shake the rudder off.

Pul the needles out and check the little O-Rings on the needles. I had a new St .40 that has a pinched HS needle O-ring that wouldn't let me tweak it right. I also had older ST .61 and a .45 that the Orings dryed out and started to leak over a long storage. I could get them to run but not reliably.

Pull the needle valve out and put your finger over the muffler outlet and crank it over with a electric starter. That way it will flush out any thing that might be in the carb. When you crank it over you see almost a steady flow of fuel coming out of the needle valve hole. Just a thought.

Please check the carburetor settings. How does the engine run when it's at full throttle and leaned to just rich of peak RPM? It should be able to run nearly a full tank with little change in the mixture setting, or with a slight richening of the needle.

Please see the 'sticky' thread in the SuperTigre Support forum for instructions on adjusting the carburetor. If the low-speed needle's set too rich, or the passage is clogged, you'll get a similar result to what you're getting. If you start over with everything at a rich 'ball park' setting, you should be able to get the engine running well.