Hello all,

The OS .46 manual talks about richening the high needle before starting it up and then returning it to the proper spot after it starts. I have never done this in the past....Should I? This is a new engine replacinga new JBA that didnt do so well for me. Just kinda trying to make sure I do this right. Thanks!

I have never had to do that with any of my O.S. engines and they all start and run fine.

I've never had to do that. If the engine is new or you have a sub par tank arrangement or you take the model to another location with a drastic elevation change I might see the point. All my engines of any brand have started just fine at idle at which point the high end needle is useless.

Ok figured so.....I never have done this either but saw it was in the manual.

I believe all they are trying to do is prevent an inadvertent lean high speed run. I've seen guys start up and immediately go to a screaming full power run. I suppose if you were leaned out you might harm the engine so I think they are suggesting you have it a little rich. Or maybe the manual lost something in translation. Anyway, it sounds like you know what you are doing so I wouldn't be too concerned.

+1

Cool, Much appreciated guys!

I was pretty sure nobody that I knew did this method of starting but wanted to see if I was missing out on something.

Justin_92_92

Greetings from South Carolina, in response to your question of what your manual states about setting the High Speed Needle a little rich when starting your engine.

When starting our engines your manual is correct in making this statement.

It is always safer to start with a rich High Speed needle starting point, this aids in cranking as well as preventing our engines from having a lean run.

Thanks
Tom

How does this aid in cranking since everyone I know starts their engines at idle or just slightly above? HS needle has nil effect at this point.

The HS needle is easier to get to and adjust than the LS one.

When you adjust the HS needle you are adjusting the main fuel flow point, which in turn tends to also modify the LS flow.

So if you richen the HS needle, you are also richening the LS flow as well.

That is why you are advised to set the HS first, then work on the LS when first tuning an engine.


I had a couple of engines where I did have to richen the HS out two to three clicks at the beginning of each flying day, to get them started.

Once warm, this was no longer needed.

Interesting, I was never aware of this technique but I will keep it in mind while out at the field for sure! Seems to make sense.

The key here is that it is a new engine. So you are starting the break-in process. Every engine manual I have read recommends starting the engine with the high speed needle quite rich, advancing the throttle to full, and then leaning the high end for a few seconds. After running near peak RPMs for 10 seconds or so, richen the HS needle again to let the engine cool down a bit. Say a minute or so. Then you lean it again for a slightly longer time, then back rich again. Continue running it near peak (just slightly rich) for longer and longer periods, until you finish the tank. At this time most OS engines are about ready to fly, as long as they will idle for 10 or 15 seconds without dying.

By all means follow the break-in instructions in the manual.