OS 91 DF Engine
 

I'm having a problem with my OS 91. I am using it with a Ramtec fan and almost everytime I start the engine, it will run backwards. Can someone tell me why this is happening. The engine has never done this until now so whats wrong.

RE: OS 91 DF Engine
 

I have to ask, have you switched airframes and is it a tractor or a pusher setup?

RE: OS 91 DF Engine
 

Could be a little rich on the low end. Are you hand starting or using a starter? BITD, I would flip mine by hand and occasionally it would start up backwards. If it's a little fat, it will kick back alittle harder and run backwards. Try leaning the low end in very small increments.

RE: OS 91 DF Engine
 

the low end is way to rich...try leaning it out a little at a time. my bvm 91 would pop backwards if i let it idle for to long and got back on the throttle.

good luck

RE: OS 91 DF Engine
 

Hi,

If you're not sure whether or not your low-end is rich, let it idle and pinch the fuel line. If it's too rich, it'll cycle way up before it quits. I wouldn't lean it out until I tried that.

RE: OS 91 DF Engine
 

I agree its to rich [:-]

RE: OS 91 DF Engine
 

cross you starter leads so your starter turns the other way.... lol sorry i had to do it....

RE: OS 91 DF Engine
 

thanks to all who replied....I too think the engine is too rich on the low end. the engine is in a Starfire II and is completely enclosed when its ready for flight. On my last attempt to start, I was having trouble removing the starting probe when the engine started and I was thinking that trying to pull the starting probe out was causing the engine to kick and run backwards. I will start leaning out the low in until the response is quick and positive after I make the test recommended by yellowaircraft

donniercjet.......I tried to reverse the starter motor wires but after two starter motors smoked, I guess thats not working....LOL

RE: OS 91 DF Engine
 

You can actually set the low side needle on a .91VRDF with a feeler gauge (.060) or a number drill (#53). Open the throttle barrel all the way (full throttle). Check the gap between the spray bar and the low needle with the feeler gauge or number drill. Set it so you can just slide the gauge in and out of the gap. I have never had to re-adjust a low side needle set this way. I believe this method came from Tom Cook (Jet Model Products).

When flip starting a .91, it will frequently start in the wrong direction. Sometimes a quick blip of the throttle will correct the rotation. I have never had one start in reverse when using an electric starter

RE: OS 91 DF Engine
 

grbaker, That sounds like some good advise and I'll give it a try. I am using an electric starter with a long starter wand and yet the engine will start backwards. I do the quick throttle hit but no help. I also pinch the line until the engine almost dies then let go and sometimes that will work. I will definetly try to set the low end as you recommend.