Hi Everyone,

I've been stumped for a week with some strange behavior of my new JBA 120 (ringed) engine, and hope I can get some tips from someone on how to resolve my issues. There are a number of symptoms (which are possible related) that I'll try to present in a clear form below:

a) It's difficult to get started...it's pretty tight (compression) at the first start of the day so I use a Sullivan Dynatron starter on 24 volts. Even then though, the engine just spins over for quite a number of tries before I can get it to start (it feels like a bit of a gamble).

b) Once it gets running, it runs pretty well at the bottom 40% of throttle (from idle up to 40%) and at the top 15% (85% throttle to full throttle). Anything in-between it tends to die. I have checked the idle needle setting by pinching the fuel line and it's fine (the engine continues at the same RPM for about 4-5 seconds before quitting without a change in revs). At full throttle I have the needle open about 3 to 3 1/2 turns and there's a healthy level of oil/exhaust smoke coming out of the muffler. It doesn't like anything less than 3 turns (it just won't run above 40% throttle at about 2 turns). It isn't too rich either as it is in a happy "slightly" rich two-cycle note, not four-cycling. Another funny thing is that to get to full throttle I have to leave the glow igniter on and advance the throttle to full pretty quickly, then take it off. It runs happily at full then - but if I lower to half throttle for more than 5 seconds and try to come back up the engine dies on me. When I keep it there just for a second or two, it can come back up okay, but not smoothly (it struggles a little bit inconsistently then clears up). I have tried 2 OS 8 plugs, 1 OS F plug, and 1 cold plug from a brand I can't remember (recommended by someone). This behavior persists whichever plug I use (and the plugs still appear to be in good condition with the exception of the first one I used - figure it's not unusual when breaking in an engine).

c) The most annoying thing is that after I run the engine for a while (about a 1/2 tank to 3/4 tank) and need to restart it, I can't! It's even worse than at the start of the day - it just won't ignite. I do feel the compression is not as tight as at the start of the day, but still at a decent level so I don't think that's an issue.

I'm just about ready to give up on this engine - I feel I'm the unlucky recipient of a poor quality control process - some JBA engines are just fine I'm sure, but there's also a fair amount of troublesome ones I bet. Please help!!!

Thanks,
Ken