Engine leaning out...

[nitroholic]

Hello sorry for the newbie question but here goes. I have a new mbx pro with the .26. I am really happy with this buggie I just bash aroundi n the backyard and on the street. I had a rush when it first came out and a rs4, I hated the rush and rs4 was decent. Anyway I have noticed that a big block is a little different then a regular .15. I have just finished about my 8th tank of slowly breaking it in. I have set the needle to what I think is a very ideal setting. When I have a full tank and I come off hard acceleration the motor leans out for a few seconds, at least I think. The motor changes pitch and kind of revs. This makes me feel uneasy as I am trying to take the best care of the this thing I can. In my expierence a full tank always ran rich and thined out towards the end of the tank so this is why this doesn't make sense to me. It stops doing it at 3/4's down. the only thing I can think of is that I am getting a lot of bubbles from high acceleration. Does that make sense? Is this okay and I am over paranoid? Maybe something I can try? Tell me what you all think

Thanks

Joe

 

[El Pirata]

I have found some engines require more than their manufacturers specify of 5 tanks of fuel. I have had an engine take as many as 15 tanks of fuel before it was completely broken in. I would start back on the break in settings and start from scratch leaning as the instructions specify as if it had never been started. One thing I have been doing to my rc's lately when I broke in a new engine was to run 2 - 5 tanks of fuel at idle before I even start adjusting the needles.

 

[FastEddy]

What your describing is a classic case of needing to adjust your Low Speed Needle settings.

When your under power the HSN controls most of the fuel flow. When you let off the trigger and the carb closes, its leaning out due to lack of fuel from the LSN. This can be very dangerous to the health of your engine.

Start by richening your LSN 1/16th of a turn and running as you normally would for 2 or so minutes. Continue this until the issue goes away, then 1/16th more. Don't over do it or you may have flooding issues while trying to get it started.

As your engine breaks in you were running it way on the rich side and there was residual un-burnt fuel still in the engine. As you leaned it out with the HSN for power this fuel is no longer available for the engine to scavenge coming off of a high speed run. Its now time to give it a bit more through the LSN.

Finding the proper marriage between the HSN and the LSN is difficult at best. Fine tuning an engine is an art and is rarely mastered by all but a few.

-Ed

 

[nitroholic]

Thank you for the suggestions. Ed your logic in this matter was right on. I took it out today and turned in the LSN just a very little and presto!!! Still launches like a bat out of hell with a little more smoke too which I like to see. No more lean conditions. I am also not letting the tank run dry like I use too, as this is the same condition that you said is not good for the motor. I think she is ready for some fun if this weather here in illinois ever gets nice:ahem:

Thanks again