7 flights old BME 102. Not an EVO. In cowl stock mufflers, Aeroworks 33% 330L not the arf. Prop 26-10Menz S. Lawnboy 32-1. Every flight motor sags off and sounds like its running on 1 cylinder. Since 1st flight we put a plate in front of diaphram, changed plugs, sent ignition back to C&H where the coil and plug wire was replaced. Initial start up 6300RPM. Down hill from there. Currently backed off high end to 6000RPM. No change! Great transition, all obvious gone over a dozen times. After flight temps left cylinder 140-right cylinder 185-200. At idle motor shakes and plane is a dog...My old BME-100 will smoke this engine. BY the way its not the needles. Any hints before we sent back motor? Thanks Walt

Send it back, it sounds to me like one cylinder is starving for fuel. May be the bypass ports are not correctly machined or one is stopped up. Have you torn the engine down yet?

The engine has not been disassembled yet. Im hoping that I have overlooked something but It doesnt seem to be the case. I will look into your suggestion. Thanks

Check the fiber reeds in the reed block under the carb. Make sure none are torn.

Now that sounds like a better idea.

I'd also go to 50:1 ashless, though that's a matter of taste. Your temperatures seem okay, but your symptoms point to an overheating issue or ignition timing/performance problem. IF CH replaced parts on your ignition, make SURE you get at least a 1/2" air-gap spark when flipping past TDC with the plugs out. Both sides should be equal.

This is the second post, and third engine (including my own) that seems to be having ignition problems with the CH units. Sagging cn be caused by a weak spark, synchro-spark module not fully advancing the timing or getting hot and degrading its performance, or one cylinder dropping off line.

Keep us posted on what you find.

I had a phone conversation with Keith and he thinks its an ignition problem also. Im going to swap plugs and modules from another engine to try to isolate this problem. Thanks for the responces, Walt

Walt, this is dejavu all over again. I think you tried swapping the plug leads to the other cylinder. What happened to temperature then? If the cold cylinder didn't move with the plug lead, then it's likely something mechanical. Maybe a ring is sticking on one cylinder when hot? Perhaps one cylinder doesn't have adequate piston clearance? I'd pull the cylinders and have a look inside. It's hard to understand how CH would "fix" the bad ignition and it would still be a problem....low probability.

I dont think this problem is mechanical due to the compression after a run. It stays the same or I will say feels the same. This engine has the flat top plugs and module which has been known to break contact. The design has been changed by C&H to a different configuration to eliminate this. Also an ignition which breaks down from heat may be hard to troubleshoot. If another ignition module does not correct this problem then I will do the teardown and have a look. By the way Diablo--get your scale ready!! Walt

In answer to your query, Diablo, it's very possible that an unknown, but later appearing, problem developed with the module.

In my own ignition, it received a new Synchro-spark module, which supposedly "fixed" the problem, but after 5 flights in one day, the ignition refused to work 3 days later. No spark at all at the field. Then, this morning I checked the 'bad" ignition before swapping in a brand new unit, and it worked just fine. Great 1/2" sparks and very strong. Needless to say, I still swapped in the new ignition, and the old unit is on its way back to CH. This is the second time that "bad' ignition pulled the same "heat sensitivity" problem with me, and now it's also the last time.

I would like to say, though, that CH did provide a replacement upon request, which is just the right thing to do in this case. Hopefully, whatever problems that have cropped up will be resolved for all customers which this happens too. Nothing more frustrating than to flip the prop and have nothing happen.

Yes, it's possible the 2nd ignition failed too, but not likely from a probability standpoint. If the failure rate of an ignition is one out of 100 (WAG), then the chance of getting 2 bad ignitions in a row is one out of 10,000. It's possible, but so is me winning the Powerball.

Walt:
You probably already tried this, but it's worth a shot.
Throw in a new ignition battery.
Dereck's ZDZ was acting up, not taking throttle, but would idle and start fine. His battery load tested fine. However, a new battery fixed it. His load tester must not put a big enough load on the battery for a valid test.

SO what did you eventually do to fix your problem???

I initially had an aluminum plate blocking the carb diaphram made out of flashing. I removed the plate and went with a brass tube soldered over the diaphram hole with a piece of fuel tubing to the fuse. All problems vanished. The plate obviously still allowed pressure deviations / turbulance so to speak which created this mess. I have used both systems with great results but this time the old standby did the trick. Regards, Walter

Thanks for the response.
I see that BME has them for sale.
I may get one.

two BME 50 Same thing, they have one flight in them, Good customer service. But the product is junk.
I will never buy anotherone.

After this teething incident this 102 has turned out to be a great engine. Right now its flying an Aeroworks 33% Extra "kit" plane. Its spinning a NX 27-10 at 6200. It makes lots of noise...All the problems we had are gone. Walt