BME 100 tuning

[WRBirch]

My BME 100 idles GREAT, high end is GREAT neither seem to be rich,
low idle is 1,250 rpm. At about 2,000 - 3,000rpm while flying and on the ground the engine gurgles like it is a bit rich,
Do I adjust low end needle leaner or hi end needle???????

[Bat Fastard]

I'm interested in the results that you find about this problem. I can't offer any solutions other than checking the pop-off pressure on the carb. My first response would be to lean out the low-end needle a bit. Your problem lies within the low rpm range which is controlled by the low-end needle.

What prop are you running and what rpm's are you getting from it? This could also be an area of discussion, (if its over loaded or not). A friend of mine has the same engine and it seems a little lame compared the the new 80cc engines available today. I'm curious to see what everyone else says (that runs a BME 100).
Jamie

[bodywerks]

That is right about the RPM that the carb starts taking on fuel from the high needle, so my guess is that it is the high needle. Tune your high needle for max RPM, meaning go 1/8turn lean each run until you notice an rpm drop. From that point, go 3/16-1/4 turn rich. This should get you started.

[bodywerks]

Same method works for the low end, too, except maybe don't richen it up quite as much.

[KrisW]

What I do to tune any engine, but especially all my BME twins, is to get it warmed up, then pullthe throttle back slowly from 3/4 throttle and find out where the burble is. Usually it's at about 1/4-1/3 throttle, the transtsion point low-high.

I then close the high end 1/8 turn and see what happens. If the burble diminishes and only become evident at a lower throttle setting I figure I'm on the right track. If the burble is very low down, at 2-3 clicks off idle, start with the low needle first. Be sure to check your throttle response from idle at WOT to see if it bogs. If not, then keep adjusting.

Be advised, many times it's not possible to get a perfectly clean sounding bottom 1/4 of the throttle, because to do so will lean the top end so badly that you risk overheating the engine. Be ready to live with a hint of a burble at 1/4 throttle. . most engines have this, and it's not a bad thing.

[WRBirch]

Thanks for the help guys, I leaned the hi end first, that made it tooo lean, So I then tryed the low end, well, that was even worse. So I think I'll take Kriss's advice and live with it, it only happens in a very small range, about two clicks throttle area and isn't hurting anything, The engine runs GREAT otherwise, The prop is a JZ Zinger? 26-8 trimmed at the ends to a 25" for ground clearance, The plane is a 33lb Super Stearman 8 ft wing span.
Thanks again guys

[bodywerks]

I found that my timing on my BME 110 was way advanced (33 BTDC), so I retarded it to what Don at Don's hobby Shop recommended (28 BTDC). I was actually hoping it would be the answer to the lack of top-end performance and high CHT problems I have been having with this engine, but it didn't. There was actually not top RPM improvement/drop, but my entire midrange became more responsive and less hesitant. It wouldn't be a bad idea to check your timing , just for kicks - it should be between 28 and 32, typically.

[KrisW]

	Quote: Originally Posted by WRBirch
	Thanks for the help guys, I leaned the hi end first, that made it tooo lean, So I then tryed the low end, well, that was even worse. So I think I'll take Kriss's advice and live with it, it only happens in a very small range, about two clicks throttle area and isn't hurting anything, The engine runs GREAT otherwise, The prop is a JZ Zinger? 26-8 trimmed at the ends to a 25" for ground clearance, The plane is a 33lb Super Stearman 8 ft wing span. Thanks again guys

Bill. .PUHLEASE tell me the PERFECT 5.8 I sold you is NOT the problem. . . . .

Do yourself a favor, if that is a Zinger prop, get rid of it and use a Menz or Menz-clone (BME, Xoar, NX, etc.) style prop instead, You will get more grunt and pull out of it.

[KrisW]

	Quote: Originally Posted by bodywerks
	I found that my timing on my BME 110 was way advanced (33 BTDC), so I retarded it to what Don at Don's hobby Shop recommended (28 BTDC). I was actually hoping it would be the answer to the lack of top-end performance and high CHT problems I have been having with this engine, but it didn't. There was actually not top RPM improvement/drop, but my entire midrange became more responsive and less hesitant. It wouldn't be a bad idea to check your timing , just for kicks - it should be between 28 and 32, typically.

Given your altitude, I don't think ANY engine is going to provide 100% satisfaction .. just a fact of rarified air. As for the high CHT. . try upping the quality of gas to 90-91 octane (premium out there), and be especially attentive to the engine running "raspy" sounding. At 6500 feet your air is some 15% thinner than at Sea Level. Power will suffer accordingly.

[WRBirch]

thanks Kris
It's running a little better with the higher octane. Runs good. As for the props, as soon a I break another one I'll try a good one. lol
Bill

[DStJohn]

My son's BME 95 was doing the same thing when it was new (He has 6 gallons through it now). We had to adjust the idle side to reduce the burble. Now that BME 95 has a TON of power in his 2.3M Comp ARF.
It's even got enough power for Bodywerks, oh yeah, our field is only at 5,074 ft!