Engine problems OS 90FS 4 stroke
 

I got this motor and was supposed to have only 15 min of flight on it and from the looks of it, it is true. But, I have it on a spacewalker (GP I think) and it wont run steady. It will kinda go up and down slightly in rpm while at full throttle and when I come in for a landing it will just die as soon as I let the throttle to idle. I have had lots of 4 strokes but none this bad off. I have put a new fuel tank, fuel line, 2 to 4 new glow plugs or thereabouts, and balanced the prop. But not the nose cone. I caint figure it out. It appears to run fine on the bench but it has been a while since I have ran it on a bench so I caint remember it. Anyone with this same problem? Thanks.

RE: Engine problems OS 90FS 4 stroke
 

Your needle valve(s) are out of adjustment.

Enjoy,

Jim

RE: Engine problems OS 90FS 4 stroke
 

remake all of the setup by sequence

1 start your engine let it warm
2 open your engine at full throttle and set the high end to reach the max rpm and after turn the needle 4 click back to have a little rich high end
3 now try to set your low end and let your engine turning at idle and see wath happen.
try to run it at 2200 rpm
if the transition idle to max rpm is plenty of smoke your low end is to rich turn the screw clockwise

I hope this help you

and let me know wath happen

RE: Engine problems OS 90FS 4 stroke
 

one more thing I forgot to mention, I think the former owner bent the needles. Becouse at different settings it will lean out then richen up then lean back out. It acts weird. I have done all of what you fellers have said. As I have had many engines 4stroke and 2. But this one just stumped me. I think I will check the valves and then buy a new carb. Unless a miricale happens.

RE: Engine problems OS 90FS 4 stroke
 

Your carburator may need a disassembly and thorough cleaning. The slightest bit if material can raise havoc with an engine that is trying to idle, but just can't.

RE: Engine problems OS 90FS 4 stroke
 

Yep. It sounds like you got some gunk in the carb.

RE: Engine problems OS 90FS 4 stroke
 

I will do that then. It seems that I caint get another carb so I hope that will fix it.

RE: Engine problems OS 90FS 4 stroke
 

If you need a new carb let me know I have a brand new carb for an OS FS-90 and no use for it, would be willing to sale or trade.

RE: Engine problems OS 90FS 4 stroke
 

Also I would go ahead and checck the valves as I have had one or two qs four strokes that would not run when throughly warmed up and worked very well when I ajusted the valves.

RE: Engine problems OS 90FS 4 stroke
 

I think I may have figured it out. The seal between the carb and the pipe intake had a sag or whathaveu and I shoe goo'd it and flew it for almost 10min and no bad tendancies. But I might need your carb Maxime, how much do you want or what are you needing in trade?

RE: Engine problems OS 90FS 4 stroke
 

well I went back out and flew it again this evening about 3 times and so far so good. that must had been it. air leak. LOL!

RE: Engine problems OS 90FS 4 stroke
 

shoe goo to the res-cue!!:D