Eagle 2 GS Tanaka rebuild

[HeliJoel]

I just took the engine out of my Eagle 2 GS. Last time I flew it was getting a weird engine buzz, so I decided to take a look. When I first got the heli ( used ), there was some light scoring on the piston on the exhaust port side. Didn't worry about it much and it seemed to run fine.

I didn't find anything to explain the buzz, maybe too lean as I was hunting for the sweet spot on a new carb.

I did decide to replace the cylinder and piston and think they are the same as the Tanaka THB-2510. It's near impossible to find info on this engine, but I think I got the parts right. Once I get the parts and confirm, I will post the part number here in case it helps someone else.

[fastflyer20]

Form the picture, the piston is very scored from running too lean, it's good you are replacing it. Running lean and/or the damaged piston could be the cause of the buzz.

[HeliJoel]

I got my piston and cylinder, they look to be correct. The only difference I saw was on the cylinder where this is a mounting boss. On the original it is filled, on the new one it's drilled to be tapped. Does not seem to matter

The Tanaka/Hitachi parts are,

Cylinder 6685446
Piston 6685889

The cylinder had a stippled finish in it, need to find out if I should hone it or not.

Edit; I decide I am going to hone it, just seems wrong not to.

Now that I have taken a closer look, I see the crank bearings are open. I did flush things out, but given the open bearings, I want to split the case and make sure no metal bits are in there. Things turn smooth for now but... I had ordered a case gasket from another supplier when I ordered the cylinder and piston. It has not shown up yet. For now I wait.

[fastflyer20]

Does the cylinder have a cast iron liner or is it hard-coated? If it is cast iron lined, you can hone it. If it is hard-coated, they are not usually honed, the cylinder is replaced.

[HeliJoel]

It is hard coated which is what made me think otherwise. I suppose the stippling will help the rings seat.

[HeliJoel]

So I flip flopped and did not hone the cylinder. Engine is back in the heli and I got a first run on it today. Started without issue and runs well, I'm running with the needles a 1/2 turn more open that before. When I put the engine back in, I also swapped carbs, but even previous carb swaps I've always been 1 1/8 turns on L and H needles ( 5000 feet ), any more open than that, the engine Would not run. Now I am about 11/2 turns out running fine.

Few more runs to fine tune.

[rbort]

Is it the same carb or a different numbered version? Often different versions require a different needle setting to achieve the same mixture to the engine.

What carb number do you have?

-=>Raja.

[HeliJoel]

I did change carb types, went from a wt-990 to a wt-643.

[rbort]

They have different needle settings.

For a 643 use 1 1/4 on L and 1 5/8 on H in general for us here at sea level. You'll have to adjust for your altitude.

Best regards,

-=>Raja.