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Brillelli 46 Dies on Take Off - HELP

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Brillelli 46 Dies on Take Off - HELP

Old 04-04-2009, 11:11 PM
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propstrike
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Default Brillelli 46 Dies on Take Off - HELP

I have a Brillelli 46 GT that I picked up here on RCU some weeks ago. It's used, but looks to have very low run time. Anyway, on the ground, the thing starts like a champ, idles great, has perfect acceleration and top end performance. I couldn't ask for anything more........until it's time to take off. When I advance the throttle to take off, the engine tries to cut out and die. If I walk over and hold on to the plane, it runs great as I stated before. It does this cutting out thing on take off. If I manage to feather the throttle and nurse it off the ground it eventually picks up and is o.k. as long as I'm doing scale aerobatics like loops, rolls, and such. As soon as I start doing anything real aggresive it dies and I have to deadstick. Any notions as to what's going on?
Old 04-04-2009, 11:27 PM
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w8ye
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Default RE: Brillelli 46 Dies on Take Off - HELP

Sounds like it is too lean. you need to richen the mixture
Old 04-04-2009, 11:48 PM
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propstrike
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Default RE: Brillelli 46 Dies on Take Off - HELP

That's what I thought too, but it doesn't seem to help. I started with about 1-1/2 turns out and kept going out from there. I went out about a 1/4 of a turn at a time until the high end needle was actually loose. Right now, it is adjusted just ever so slightly rich on the top end, and the bottom will idle all day long and accelerate great without fail. That is of course, as long as I am holding onto it!
Old 04-04-2009, 11:51 PM
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Default RE: Brillelli 46 Dies on Take Off - HELP

the low end sounds lean and be sure to take the carb apart to make sure that screen is not filled with junk even though the motor is farly new
Old 04-05-2009, 12:15 AM
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propstrike
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Default RE: Brillelli 46 Dies on Take Off - HELP

W8YE and Krazyc-RCU thanks guys. I'll take the carb apart and look for this screen before I fly again next. I'll also tweak the low and high needles afterwards per your reccomendations. I know it can't be anything serious as this thing runs too good while the plane is being held. I am new to gasoline though so I follow your lead.
Old 04-05-2009, 08:44 AM
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Walt and Sage
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Default RE: Brillelli 46 Dies on Take Off - HELP

My Burelli 46 used to miss badly ONLY on take off then run GREAT...
UNTIL it quite over a vineyard and dead sticked into the vanguard... Shredded the plane....

After trying a new ignition (same problem)
Found that it was a BAD Hall switch..
You might keep this in mind... Walt
Old 04-05-2009, 12:09 PM
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Default RE: Brillelli 46 Dies on Take Off - HELP

If the engine is cowled it could be the carb's pulse acting up during the take off run being exposed to faster moving air.

Karol.
Old 04-05-2009, 12:16 PM
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Default RE: Brillelli 46 Dies on Take Off - HELP

Also check all electrical connections.

Isn't it great when people dump their problems on you in the RCU marketplace. If I EVER sell an engine with problems, I tell them exactly what the problem is, discount it appropriately, and it sells every time. Never have anyone come back unhappy. That's why I'll never buy an engine here unless I know and trust the seller. My buddy bought a DL-50 that mysteriously won't start. And it's not him. So yeah....rant over. [:@]
Old 04-06-2009, 07:16 AM
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propstrike
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Default RE: Brillelli 46 Dies on Take Off - HELP

Good stuff guys. I'll check the items you've mentioned above. It will be later in the week or this weekend before I can get back to the flying field to see how these fixes helped.
Old 04-06-2009, 08:01 AM
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Default RE: Brillelli 46 Dies on Take Off - HELP

If backing out the high speed won't richen... that is a sign of either trash blocking fuel flow or sucking air.
Old 04-06-2009, 08:15 AM
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Default RE: Brillelli 46 Dies on Take Off - HELP

Head to your local lawn mower shop.

Get the number off the carb and get a rebuild kit for the carb.

Rebuild the carb replacing the gaskets and that screen.

It will cost you bout 8 bucks and I'd do it before you go any farther chasing electrical problems.


EDIT: I probably would have done that as a matter of course when buying a used engine with an unknown history.

What oil are you running?
Old 04-06-2009, 11:47 AM
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Default RE: Brillelli 46 Dies on Take Off - HELP

Scott E. said at some point several 46's left with carb probs. that weren't found out until people started reporting problems like yours. My friend had one that cost him two airframes-did exaclty as you said and no matter how much tweaking was done the engine would just quit at the most inopportune times-later He found out about the carb prob. but he didn't want any part in the engine and sold it ASAP! This is not the only time I have heard of such issues with the 46.
Old 04-06-2009, 12:46 PM
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Default RE: Brillelli 46 Dies on Take Off - HELP

Another thing to try is a velocity stack. That could be causing it too. Air hits the carb inlet and leans it out killing it. That or even going rich. Either one.
Old 04-06-2009, 02:34 PM
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propstrike
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Default RE: Brillelli 46 Dies on Take Off - HELP

As I don't know exactly how much time is on the engine, I'm using non-synthetic oil for a couple of gallons to break it in. It's Briggs and Stratton Ashless 2-cycle oil mixed at 32:1 with 93 octane gas.

Just found a great site for carb parts. I will likely order my rebuild kit from their. It's www.learnsmallenginerepair.com . On the home page there's a link to a comprehensive Walbro carb listing for ordering re-build kits.

Hadn't thought about the velocity stack possibility. I may do that one if the other things don't work.

This sure is a great starting and powerful motor. I'm not going to give up on it very soon. I should know more after I fly it again next weekend.
Old 04-06-2009, 03:35 PM
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Default RE: Brillelli 46 Dies on Take Off - HELP

I did have a fit with mine that I bought used after a bit. A rebuild kit, specifically replacing that tiny screen, fixed it right up.
Old 04-06-2009, 03:35 PM
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Default RE: Brillelli 46 Dies on Take Off - HELP

take carb apart and see what condition the diaphragm is in
Old 04-06-2009, 06:15 PM
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the Wasp
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Default RE: Brillelli 46 Dies on Take Off - HELP

Propstrike,, I don't know anything about your ignition, but I do know on "some" ignitions it could be as simple as needing more ignition battery power, or having the incorrect Spark Plug gap for your ignition's battery,, if your's is a 4 cell you may have to much gap,,

before spending all kinds of money find out if you can run a 5 Cell (6V) pack on the ignition, and make sure you have the correct gap,,


why I say this is my MVVS 35 took 30 or more flips to start, and the power was low at lower RPMs, then I went to a 5 cell ignition pack my problem was solved..

Jim
Old 04-06-2009, 06:57 PM
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Default RE: Brillelli 46 Dies on Take Off - HELP

My money is in the same pile as Karolh. It's the vent hole covering the metering diaphragm.
Old 04-06-2009, 08:00 PM
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Default RE: Brillelli 46 Dies on Take Off - HELP


ORIGINAL: Rcpilot

My money is in the same pile as Karolh. It's the vent hole covering the metering diaphragm.
Rcpilot,
LOL, I don't know what you or Karolh are talking about! Are you guys recommending rebuilding/cleaning the carb because a vent hole is plugged? Am not that knowledgable about these carbs.

This problem seems velocity related which makes me think either the velocity stack or the "equalizing line" that you run into the fusalge isn't installed. Is the equalizing line connected to the vent hole? I am relatively new to gas engines. I have a B46 with about 2 gallons through it - gonna put it on a Fusion 80.
Old 04-06-2009, 08:52 PM
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Default RE: Brillelli 46 Dies on Take Off - HELP

When the model is stationary the carb's diaphram reacts to the air pressure it sees via the pulse hole, but when the model starts moving forward the air pressure changes and the diaphram reacts to that change.

What might be needed is to have a small nipple soldered into the pulse hole in the carb's front cover plate with a length of fuel tubing leading into the fuse via a hole in the firewall to the static air there which is what the diaphram will react to and which will not change wether the plane is stationary or not.

Karol
Old 04-06-2009, 09:32 PM
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Rcpilot
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Default RE: Brillelli 46 Dies on Take Off - HELP


ORIGINAL: Uncas


ORIGINAL: Rcpilot

My money is in the same pile as Karolh. It's the vent hole covering the metering diaphragm.
Rcpilot,
LOL, I don't know what you or Karolh are talking about! Are you guys recommending rebuilding/cleaning the carb because a vent hole is plugged? Am not that knowledgable about these carbs.

This problem seems velocity related which makes me think either the velocity stack or the "equalizing line" that you run into the fusalge isn't installed. Is the equalizing line connected to the vent hole? I am relatively new to gas engines. I have a B46 with about 2 gallons through it - gonna put it on a Fusion 80.

No man. Not recommending a rebuild. You and me and karolh are all talking about the same thing.

There's a hole in the side cover plate over the metering diaphragm. That hole is in there so the diaphragm will see the air pressure (actually atmospheric pressure) from outside. Weather you're at 100' above sea level or 10,000' above sea level. That little hole allows the diaphragm underneath to see atmospheric pressure. This causes the diaphragm to lay in a neutral position. No pressure under it and no pressure on top of it. Just flat and neutral. As the fuel is pulled from under the diaphragm and sent to the venturi, it sucks the diaphragm down and that causes it to open the jet.

Whats happening (I think) is it runs fine on the bench when the airplane isn't moving. The carb can be adjusted to run perfectly under this static load. The prop is pushing air into the cowl and pressurizing the inside of the cowl to some extent. We don't know if it's high pressure or medium pressure. (anybody got a monometer? ) The point is the cowl is pressurized with a bit of air from the prop blast. Regardless, the carb can be adjusted to run great. Once it gets to full throttle, there is a given pressure inside the cowl. Some air is getting out his cooling holes and some is staying inside where it equalizes. You adjust the carb to run perfect and all seams well.

Then you begin to taxi and gain speed. Now the air pressure inside the cowl is changing. It's no longer static. It's now dynamic. The air is going to move THROUGH the cowl more so than when the plane is stationary. As the air pressure inside the cowl changes, it causes the metering diaphragm to see a completely different amount of air pressure. The diaphragm does it's job and reacts to the air pressure around it. It just stinks that it's reacting in a negative way and causing the engine to flame out. []

The cure is simple and there are several methods or versions. Simple and dirty is just cut a Coke or Pepsi can into a small 2" square. Bend and shape, punch a few holes, install it on top of the carb cover plate so it blocks direct air pressure or vacuum from hitting the hole. More complicated is to solder a brass tube in the hole and hook some fuel line up to it. Run it back inside the fuse where it will see the same air pressure all the time. There's a couple other fixes.

There's only a 50/50 chance this is the right answer. Several other guys have mentioned bad Hall switches and ignition systems. It's going to take a bit of tinkering to find the problem. Sure would be nice if there was a spare ignition lying around to test the engine. I don't envy the original poster. He's going to have to sort through some more deadsticks to find the problem. [:'(]
Old 04-06-2009, 09:46 PM
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propstrike
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Default RE: Brillelli 46 Dies on Take Off - HELP

There is a nipple soldered on the plate and it's going into the fuselage as recommended.

Here's the latest. I just took the carb apart and the screen was a bit dirty. I wouldn't say clogged necessarily, but it did have a significant amount of debris in it. I put it in my ultrasonic jewelry cleaner (bought it at a flea market this weekend for $2 and it actually worked) and it looks much better.

A couple things though, the carb has two spacers between it and the head. There is a removeable resin spacer next to the carb and permanent spacer next to the head. There is a gasket on either side of the resin spacer. The gasket between the resin spacer and carb is supposed to have a large hole and a small hole in it. I don't know what either is supposed to do, but the small hole was deformed and probably not letting air or whatever get through. I wallowed or bored this out a bit. Also, the gasket between the resin spacer and metal spacer was split along one edge. This could have happened upon disassembly, but I don't think so. I had some gasket material lying around so I made a new one.

I will take the plane out in the yard tomorrow evening to see if I can still get it to start. Of course I still won't know if I have the problems on take-off until this weekend at the field, but I just want to make sure I didn't mess anything up. Sometimes I make things worse when I tinker, so wish me luck.

Oh yeah, I have a new NGK coming to the auto parts store tomorrow. I'll put this on too. I'll set the gap to .020" or so. I am running a 1450 nimh 4.8v pack.
Old 04-06-2009, 09:50 PM
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Default RE: Brillelli 46 Dies on Take Off - HELP

Explained much better than I ever could have [sm=thumbs_up.gif]

Karol
Old 04-06-2009, 09:55 PM
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the Wasp
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Default RE: Brillelli 46 Dies on Take Off - HELP

funny how my MVVS with the carb setting up-front doesn't have this problem ..

Jim
Old 04-06-2009, 09:55 PM
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propstrike
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Default RE: Brillelli 46 Dies on Take Off - HELP

Wow you guys rock!

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