Frank Bowman rings low compression

[thurmma]

Hey everyone,

Just installed Frank's rings in my 3w 106. Was flipping it over last night and noticed that there is very low compression. I haven't ran the engine yet. The cylinders were immaculate and the original rings had good compression. I am wondering if I just need to fire it up and let it run for a bit to get them to conform to the cylinders.

Any ideas or suggestions?

 

[Terryscustom]

I think there is an instruction sheet in there (at least used to be) that suggested to install the rings in the cylinder and push in with the piston top to get square and measure the gap.

 

[pawnshopmike]

Just curious and thinking out load here...
But why install the Bowman rings if the cylinders were immaculate and the stock rings had good compression?

 

[flycanic]

Correct ring gap is very important in any engine when installing new rings. If your ring gap is within spec you will need to run the engine so the new rings will seat in the cylinder's I made a cylinder honing device to do a cross hatch in the cylinders before installing new rings. I try do get a nice 30 to 45 degree cross hatch pattern with emery cloth of different grits of 300 to 600 FWIW
and as pawnshopmike asked Why? Unless there were a problem, I would have left it alone. 3W cylinder walls are very hard and even when new took at least 10 gallons of run time before they were at 100 % and rings seated properly

 

[stangflyer]

Correct ring gap is very important in any engine when installing new rings. If your ring gap is within spec you will need to run the engine so the new rings will seat in the cylinder's I made a cylinder honing device to do a cross hatch in the cylinders before installing new rings. I try do get a nice 30 to 45 degree cross hatch pattern with emery cloth of different grits of 300 to 600 FWIW
and as pawnshopmike asked Why? Unless there were a problem, I would have left it alone. 3W cylinder walls are very hard and even when new took at least 10 gallons of run time before they were at 100 % and rings seated properly

Very good input. Although Franks rings are awesome on some other lesser quality engines, typically there is no advantage when installing them in a 3W. As stated, 3dub cylinders are very hard and even the stock rings take quite some time to get them to seat in. I will say though Mark, if you have them in the 3w, don't worry too much. And I am "ONLY" speaking from my experience. Initially the DLE 111 had good compression before putting Bowman rings in it. Mind you, it was a brand new never started motor. Upon installing the rings into it, it had very little compression. After doing the first run, the compression went through the roof. Gobbs of compression and I expect it is going to get better. You can always put the stock rings back in.

 

[thurmma]

The ring gap was spot on. The reason I put the rings in was because the engine just didn't seem to have the power I thought it should. Yes the compression was enough for it to run, but just didn't seem like it was all there. The engine has about 9 gallons through it and I was putting the aluminum reed block and carb mount on, so I figured no time like the present to get it done

 

[stangflyer]

Ah well, that would 'splain it then.

 

[Bunky.F.Knuckle]

The ring gap was spot on. The reason I put the rings in was because the engine just didn't seem to have the power I thought it should. Yes the compression was enough for it to run, but just didn't seem like it was all there. The engine has about 9 gallons through it and I was putting the aluminum reed block and carb mount on, so I figured no time like the present to get it done

Tell us a bit more about engine set up? Prop, etc.... Needle settings really don't matter, as they vary with location. Has 9 hrs on it? Its hardly broken in. What year was the motor built? When you had the cylinders off, did you look inside them at the combustion chamber? How did they look, and the piston tops look the same?

If anything, the 3W rings are pretty spot on with ring gap. I've flown many 100/106 3W engines, and never once have changed rings in them. I think it boils down to tuning and prop selection.

I flew a Xoar laminate 27x10 on my 106 when I flew in the '09 XFC. That engine ripped that prop HARD! I have since set that engine aside for when my EME 120 decides to lunch itself. Then I found a 106 that was made into a twin spark. Im installing that engine on the Carden cover model (see avitar).

 

[thurmma]

The engine has 9 gallons of fuel through it probably close to 15 to 17 hours of run time. The engine is about 5 years old. A standard 106ib2. The cylinders still had a very small amount of cross hatch in places other than that they were perfect. Pistons had some carbon build up on the tops, which I took off easily with a soft wire brush. A few spots were tougher than others, but for the most part easy to clean. Combustion chambers were spotless. The plugs were evenly colored, but very dark brown, not lighter like my 3w 150. Tillitson carb which has been finicky to say the least, but I think the carb and reed blocks may cure that. Had almost a 2mm warp between the reed block and carb mount so I am suspecting a minor air leak.

 

[Bunky.F.Knuckle]

That air leak will cause all sorts of issues. Poor top end, erratic idle, wont shut down with throttle trim. I blew a cylinder base gasket on my QS 150 a couple years back. I instantly lost some power, and I knew something was wrong. Went up for a dead stick landing (intentional), engine wouldnt die.

At minimum, go with the aluminum carb mount. Ive ran 3Ws with the Ryton blocks and carb mounts for years and not have a problem. When they start having problems is when people who dont know what they are doing when taking the blocks off, and then reinstalling them, they will warp and crack.

The Tillitson cards are great carbs. That is the only carb I use on my 3Ws. My QS 150 has a Walbro on it.....