Quick question
I'm going to try to "fix" my BME 115 based on some of the posts I've read hear on RCU. Same Mid-range and 'inverted' problems as pretty much everyone else running the 'stock' set-up. Currently running the 'mod 2' carb with the "fix" performed by Keith (brass tube on the high passage to delay the onset of the high needle fuel flow).

I'm going to fit a Walbro SDC-80 carb on the engine, and 'stuff' the reed cage. The question is - how much do the reeds on an engine of this size open? What kind of clearance should be allowed for adequate clearance for the reeds before the edges of the 'stuffing'?

Guess that's just a general interest question too - how much do reeds actually open?

Thanks

BJH

have u sent BME 6.00 to cover the shipping for the reed spacer?

I would spend the $6 for the carb block mod and try that first. I do not think you will be happy with the sdc80.
After "stuffing" the reed block the burble should be gone unless you are to rich on the high needle. Most if not all of the burble is coming from the high needle, not the low as most would expect, but be careful when leaning the high and go very slowly.

My first mod was to put a SDC 80 type carb on it. It will not draw enough fuel with that carb and I caution against it. Here's what I did.
*Origional WGA carb but I moved the pump pulse line to be centered over the diaphram for a stronger pump action.
*Put the choke on a servo to force it to draw max fuel at max rpm. I run the choke to be slightly closed so it draws max fuel at WOT.
*Carved some pieces of aluminum to fit into the reed cage and create a better fuel flow. There's 2.25 oz of aluminum in there. The two larger pieces ride on the crank case and cannot drop into the crank path. The side wedges are locked in by the two larger ones. They clear the crank by about .010"
*The blocks almost touch the reeds at the base and flair to about 1/4" away from where they open. Any closer and power drops from lack of flow volume size.
* Retard the spark about 4 degrees on CH or 2mm with the Falcon. Don't ask me why it works but it does. The CH gives about 150 more rpm, again don't know why.
* 3" drop headers made from AI SS parts. KS KS86 canns at 8 3/4" length from flange to start of cann body, and also Bud Bottle muffs. The Bud bottles are good for 100 more rpm.
*7200+ rpm on a 27x10 Xoar. With absolutely 0 issues.
*It takes about a day and a half to carve the reed block stuffers and worth every minute.
* Fuel consumption went up from 12oz per 14 minute flight to 18 oz per 12 minute flight. I can run it rich enough to 4 cycle all around the sky without a burble. But of course it's tuned to run normaly. 4 cycle on down lines, clean in level flight.
*Also I tossed the head gasket to get the lower ring to ride higher in the jug. (Hope the new owners fix that little problem eventualy, ( the back intake port is too high)).

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A lot easier and faster to send BME the 6 bucks to accomplish the same thing

Depends on how good theirs is. I sent my $6 about 3 weeks ago.

sounds like you understand the "issues"
The retarded timing makes sense.
once you really FILL" the cylinder with a fuel charge the effective compression is raised .
On a really complet tuned exhaust on my ZDZ stuff - I have to rtard the timing a we bit - same reason-
tuned systems pull in more charg from the crankcase .
That's what it's all about. and more power , is more fuel at work. It also makes for more heat -so a little more power needs a fair amount MORE fuel
Some may still believe in the tooth fairy and more power with more fuel economy - good luck

Dick,

Agreed, that can't happen. Nice note about increased heat generation.

Altavillan,

I'm still awaiting a reply to an e-mail to the same location....

Thanks for the replies. I've been trying to keep up on the various posts on the 115, but I must have missed some of the more recent ones.... what's the deal the the "$6".... apparently there's a new reed block of some sort available? Or some sort of modification to the existing unit? What's that supposed to do?

Thanks again for all the info.... going to get this thing running right yet!

BJH

The original 115's had an induction issue that was frequently noted by some in knife edge and inverted flight. Some had it, others didn't. There have been several people working at home to develop a consistent fix, with some being more effective than others. The new BME owners took a look at some of them and appear to have gone with a design that takes care of the early engine issue.

Those that already had a 115 from the original manufacturer are being provided the fix for a cost of $6.00 to cover the shipping. The new engines incorporate the fix. I don't know specifically what the fix is. I'm still waiting for a reply from BME about a question on the subject.