Some of you guys recommended a JBA 56 when I posted looking for a good value and good power in an inexpensive engine. Well, I got one the other day and on the bench it looked really promising. I strapped it in a plane and flew the stink out of it today. Very impressive! It's basicly a half priced OS 55AX! The carburetion was excellent, transitioning very smoothly at any throttle opening. The only small problem is on shut-down(or not shutting down actually!). It will continue to idle super slow with the throttle barrel fully closed. Someone tested out this engine in another post and reported the same thing, but said it got much better after a gallon or so. All in all, a very impressive engine that I would recommend as a really good value. Thanks guys for the good advice!

If the engine desn't shut down means that there is an air leak somewhere...most likely in the carb...make sure the carb o-ring is ok and fully seat the carb! you should push down hardly the carb against the throat to get it sealed. It is a common problem with carbs that are locked by the method your engine is, as Tower engines, GMS, and many others...don't know exacltly the term.

If it doesn't get better try looking for a leak in the backplate...

Note that if the engine is not shutting down doesn't have anything to do with breaking in time, if the engine is newer it will have unstable idle instead...

Hope this helps,

Jorge

Glad you're happy with your JBA .56, scott17! Hopefully you can tweak the engine a bit more to produce a reliable throttle kill.

May I ask from where did you purchase it? Kangke?

Don't go doing anything drastic until you have a gallon of fuel through your JBA. I have 3 SK engines (2 .91 & a .50) and a JBA .56, plus I broke in and flew a JBA .56 for a friend. Chinese engines do not have tolerances that are as closely controlled as an OS, and I have 2 .55s and 4 .46s. My Chinese engines have usually needed a gallon through them before they really idled well and shut down. I'd fly it until you have a gallon or a gallon and a half through the engine before I started tearing is apart looking for air leaks.

I have some GMS engines and they were the same way, took longer to break-in and wouldn't shut down for a while.

People who take any of these engines, run a tank or two through them in a slightly rich 2-cycle and claim they are broken in are just kidding themselves. It's going to take some running on the less expensive, Chinese engines.

Well put, Ed. I've been trying to convey this same message for well over a decade. The Sanye series of engines also continue to break-in for quite a while. Judging them on just a few tanks of fuel is doing oneself a disservice.


Ed Cregger