trouble with BME 116

Jedijody

Proud father of Soldiers
The #1 biggest problem with BME engines are the users. They typically don't understand that a BME is a high performance engine, it's not a DA or DLE. They don't ensure adequate cooling is provided and don't tune safely. All it takes is a few seconds running too hot and lean to damage set of rings or worse. I suggest you take one of the plugs out, flip the engine over a few times and get a feel for the compression on one cylinder. Take that plug out and put it in the other cylinder and repeat. Any noticeable difference by hand would surely indicate a problem in that cylinder that could easily cause what you're experiencing.

The #2 biggest problem with BME engines is Tom at BME. He is the epitome of anti-customer service, it's almost impossible to trade him hard earned cash for engine parts. My BME116 runs like a watch but it didn't when I got it because the previous owners (yes multiple) didn't understand it. I tried to order some parts for it from Tom but after two attempts with my best Mother Teresa impression he hung up on me twice. He's a complete idiot. I made what I needed by hand and now it's a beast.
 
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closetguy

Well-Known Member
funny you say that about Tom. I fried a 58 due to running it to lean, piston skirt was burnt,,stuck a ring.
called Tom and told him I wanted a new piston and ring and that it was my fault and the condition of the piston.
you know I couldn't get him to send me the parts even when I told him that I would pay for the parts.i thought it was just a customer service thing and he wanted to do it for me.
he repaired everything for free,but the engine never did get the same RPM's that I got before.it doesn't even get the rpm's that I get from a DLE55.
 

skipm

Member
Everything looks clean after over 100 flights. Attached are pics of the piston/ring and bores for both sides. The plugs have 15 flights on them. I was doing some searching and some people having success with 12" headers. Guess I will go in that direction when I get a chance. Again, once the engine warms up and catches, it runs without hesitation, has a nice slow idle and pulls the 30# biplane with authority which was why I wasn't concerned about being over propped.
 

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Jedijody

Proud father of Soldiers
Ummm, if them plugs have 15 flights on them one of them isn't doing squat. Whatever performance you're getting is being heavily carried by one side. Your engine has issues that aren't going to be solved with header length or pictures through the exhaust port. If you really want to know what's going on, put your gloves on, follow good advice, and get to work. Otherwise, leave us alone and run it till it blows.

Yeah I know, everybody knows, I'm an asshole, but just tryin to help.
 
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skipm

Member
No problem. I really would like to figure this out as I have been fighting it from day 1. Looking at the left exhaust port I would say it's too clean as well. This is the side that misses. All jug screws are tight. No obvious cracks in the cylinder. No oil streaks or carbon deposits in strange places. I did remove 1 plug at a time and the right cylinder has much more compression than the left. Guess that means pull the jug and take a look.
 

skipm

Member
Pulled the cylinder. I don't see a smoking gun. 2 rings, both float freely, pin indexed @ 90°. Don't seen any major gouges or cracks. The right cylinder makes and holds a solid compression requiring considerable torque to reach TDC. The left which I have pulled comes up on compression then fades with light force on the crank. You can hear it bubble as the piston reaches TDC. What should I check now? Should I just get a set of Bowman rings? 1 or 2 cylinders?
 

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Tired Old Man

Staff member
Measure the ring end gaps in the weak cylinder. Looks like you know what you're doing but to be safe, carefully remove the rings one at a time and insert them into the cylinder aligned as they would be when on the piston. Get them "square" to the cylinder, just above the exhaust port, an measure the distance between the ring ends with a feeler gauge.

It's starting to sound like you have rings that have never seated or are weak in tension.
 

Jedijody

Proud father of Soldiers
Concur. After visual inspection (we can't see anything well in the pictures) checking the end gap is first. I would also measure the cylinder for out of round and taper if you have that ability. Just because it's a BME doesn't mean a bad jug couldn't slip through the crack.
 

skipm

Member
BINGO! :willynilly: The top ring is missing .125" on one end. Once I got it off the piston I could see the break versus the pin notch. The second has a .022" gap which seems large. Squared rings with piston. Can't believe there is no gouge in wall or skirt. This also explains why the engine had to be very wet to start. And it has been this way out of the box. :banghead: This is my 1st twin and my 1st pipe setup with nothing to compare to. Always assumed it was something with my setup or tuning. Never considered the problem could have been inside the engine. BME Tom was little help blowing me off after I questioned why the carb high speed needle could only be opened 1/2 turn before maxing out making it hard to get rich enough on pipes. After some time with the MVVS I knew something wasn't right and started this thread looking for fresh ideas because I had run out. Just had to take the blinders off.:biggrin: Thanks all.
 

Jedijody

Proud father of Soldiers
I thought I could see something not quite right in that ring in one of the pictures but it wasn't clear enough to be sure. I knew you'd find it if my suspicions were accurate. Not surprised about your experience with Tom at BME. Clean both cylinders with coarse Scotch-Brite, get new rings from Frank Bowman for both cylinders, make whatever gaskets you need from the thinnest gasket material you can get at the auto parts store and start over. Should be good to go now.
 
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Bunky f. knuckle

Cover shot, MA 10/09!!!
Damn!!! Missing .125" on a ring. I looked at the pics just like everyone else, and said to myself, "Self, that one ring looks to be missing a little......"

And sure enough!!

Next step is to get a full set of rings, and reassemble. Don't forget a little oil for reassembly.
 

Tired Old Man

Staff member
You might be able to visit a saw and mower repair shop and look at cylinder gaskets for Echo engines for a couple that will drop right in. BME's are based upon the Echo product line.
 

skipm

Member
I can do that. FYI, Frank Bowman is on vacation until the end of the month so I will be awhile to get back up and running.
 

skipm

Member
Time for an update. Its been a bumpy road. Got a set of rings and put them in. Fired the engine up with no change in performance. After a couple of tanks, did a compression check, no compression on the same cylinder. Pulled the jug, broken ring in the same spot. Put one of the better used rings back in. Few more tanks, same result. Using a magnifier I found a bump at the top of the cylinder wall left by the gap in the original ring. Tried light honing to remove the bump, same result. I then ordered new jug/piston/rings from BME. Engine is now starting and running without issues. Power is coming back to previous levels although I can't say there has been an overall improvement like I expected. The new rings have seated in the old jug. The new side is still seating after 15 tanks. I have also recently tried a Falcon 28x9W prop which livened things up, 6800 rpm vs Fuchs 28x10 @ 6200. Definitely improved the vertical but it rips. Going to try a 29x9W as a compromise. Thanks again for the help.
 
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