Rockman

I have reset my needles back to what I beleive are factory settings.
HSN 2 3/4 out from closed
LSN 1 1/2 turns from flush with collar.
It is putting out smoke and runs fine for about 2 to 3 minutes and then cuts off. Temp is about 215.
I am running Monster Brew 20% with A5 OS plug.
New plug was installed.
Any advice?

dcwolf

Typically, if an engine runs great for 2-3 minutes, then dies suddenly, it is because the mixture is too lean or the engine is loosing compression. You may have the mixture set perfectly at the beginning of the tank, but as the engine warms up and fuel empties from the tank, the mixture will lean. I'd recommend going slightly richer on both needles to see if it helps. If not, the engine should checked out and serviced if necessary.

David Wolf, Senior Product Support Supervisor
Great Planes Model Distributors
3002 N. Apollo Dr. Ste. 1 Champaign, IL 61822 USA
Phone: 217 398-8970
Email: [email protected]

Rockman

What service would you recommend? Piston and Sleeve?
Also, David, how far from closed would the LSN be set to start with?

dcwolf

In many cases, replacing the piston and cylinder liner will be the cure. If they are worn, it should be fairly obvious when you look in the engine. There should be little if no scoring on the cylinder liner and the piston should be tight at top dead center when cold. While you have the engine open, its a good idea to check the rest of the engine out. Inspect the head for signs of leaking. Also, check all the gaskets and o-rings. Rotate the bearings to make sure there are no rough spots or excessive wear. Also, the lower connecting rod bushing should be inspected for excessive wear.

The provisional setting for the Mixture Control Valve is:

First rotate the Mixture Control Valve until its slotted head is flush with the ball link outer face. Then screw the valve in exactly 1.5 turns (0.75mm).

David Wolf, Senior Product Support Supervisor
Great Planes Model Distributors
3002 N. Apollo Dr. Ste. 1 Champaign, IL 61822 USA
Phone: 217 398-8970
Email: [email protected]

Rockman

David, I finally received a new piston and sleeve to replace the old one. When I took the head off I noticed some pitting of the pistion and the part of the head that meets the piston. I then noticed the bottom of the con rod had flat spots. So I need to replace that part to.
How much movement should the back bearing have where the crankshaft slids through? It doesn't have rough spots, just seems to have some movement in it side to side. Very slight though.
What would cause the conrod to have some flat spots?

Bax

My Feedback: (11)

Running for a few minutes and the quitting indicates overheating. That means the engine could be too lean from a bad needle setting, dirt getting in, an air leak in the fuel system, and so forth. You'll need to go over the system to see what the difficulty actually is. If the engine winds up with low compression, then it's been severely overheated and replacement of the piston/liner could be indicated.

Another source of problems could be dirt damage. That would cause the piston/liner fit to be a bit loose and as the engine warms up, the fit becomes so bad that the engine no longer gets enough compression to run well. Again, only replacement of the piston/liner assembly would repair the difficulty.

When running your engines, temps will tell you absolutely nothing until you have it properly set up. You have no way of knowing what temps are correct until you have the high-speed needle properly set. You have to set the engine based upon how it sounds and how it performs. Once you have the engine running properly, then temps will tell you if you have something wrong. You cannot use temps, especially temps someone else tells you, to set your engine in the first place. There are just too many variables involved to use temps as a reliable gauge to engine setting.