Ed

I've got a Brison 3.2 on ignition, and usually on the first start of the day, it will run backwards for 5 - 10 seconds, and then stop. Is this an indication that it's too lean, too rich, or what ? ? ?

Ed

Tired Old Man

My Feedback: (1)

Timing may be off and/or it may need a better prime with a harder flip of the prop, or both.

Ed

I think that you may be on to something old boy, because if I re-prime it again, the same thing my happen again, but after maybe 3 re-primes, it will start running fine.

So ............ My usual procedure is to stop after the first pop, and turn the choke off. Maybe I should flip it a time ot two beyond the first pop while choked ? ? ?

What do you think ?

Ed

Tired Old Man

My Feedback: (1)

Worth a shot but I would have concerns about flooding. You didn't mention mechanical or auto advance ignition, but either one could be advanced too much causing a problem. I'd dowload the degree wheel and instructions for timing at [link]http://www.ch-ignitions.com[/link] and check things out. It's a fairly easy task to perform.

Another item, if the prop diameter is on the small side you may not have enough momentum during the flip to carry through compression properly. Propeller orientation can also have an impact on the carry through. You might still want to try flipping the prop harder.

CK1

My Feedback: (60)

For what its worth , over the years the only time I have experienced this on my Brison 3.2 's is when then low end is a little lean . It usualy only takes about an 1/8 turn richer on the low needle to cure it .

Ed

It is a Brison with the old mechanical timing, but it's tight, and has given me excellent performance at it's present setting for the last 5 years.

I'm going to try both of your suggestions .................
I'm going to richen up the low end some, and flip it harder through TDC.

Thanks gyz.

Ed

Tired Old Man

My Feedback: (1)

Most any of our engines will run backwards. How well they do that is dependant on the timing.

If your advance ring is tight and difficult to move add a couple of drops of 3 in 1 oil or similar to permit free motion. Assure that none of the linkage rods are bent and effecting the position of the ring.

rctom

The only 2 stroke engine design that will NOT run backwards is a rotary valve, like ZDZ, or a shaft-ported design like every glow motor made. Any piston port or reed valve will run in either direction, it does not care at all.

The only thing that is not symmetrical (same either way) is the ignition timing. There are two types of electronically timed ignitions, auto advance and auto retard. Auto advance sets the initial timing around 4 degrees then as engine speed goes up the timing module advances the spark timing to about 28 degrees total. This type of ignition will happily run in either direction, running backwards the total timing is retarded 8 degrees but that's not enough to keep it from running and running pretty well. 3W is an example of an auto-advance ignition.

Auto-retard ignition sets the initial timing at fully advanced, like 28 degrees advanced, and the electronics sens when the engine is turning at a lower speed and retard the timing so it is only at 4 degrees when idling. C&H and Rcexl are examples of this type of ignition. Auto-retard ignitions are less prone to running backwards because going the other way has the ignition retarded almost 60 degrees, and it gets worse as engine speed increases.

I once had a 3w 106 that backfired in the air at the top of a hammerhead and restarted backwards, in flight. It was really ugly trying to control the plane going backwards.

TF

karolh

I have to disagree with you as I've had glow engines run backwards on more than one occasion. I've also had a flooded ST glow engine start without the use of a starting battery.

Karol

Bass1

I've found some of the timing rings (especially on the older Brison engines) don't particularly like cold weather. They seem to get very tight and don't operate freely when they are cold. As Pat suggested a little 3 in 1 oil will help somewhat but try putting a hair dryer (medium heat) to it for a minute and it will be "butter" smooth and resistance free when it's warm. I have one Brison 3.2 (the oldest I have) powered airplane that I don't fly unless the outside temps are over 70 degrees for that reason. However it will loosen up a bit after engine warm up. I was told (by a "spurt") the only real way to alleviate that particular problem was to remove the timing ring and slightly enlarge/ream the center opening of the ring. I haven't tried that yet.

Ed

Sorry to have mislead you all. When I said that it was "tight", I meant that the linkage was snug, and without any slop. The timing ring itself turns very freely.

I have since found, that when I start it at a more fast idle, that it starts more readily, which makes me believe that it's more fuel related.

Does this make sense ?

Ed

rctom

Let me clarify. I'm talking about runing properly. A shaft ported glow engine will run backwards a little, but will never get much above an idle. But look at the old Cox .049 Bebe Bee, it was a reed valve engine and would happily run the same in either direction. But the TeeDee engines, being shaft ported, would not run backwards.

Even a 4 stroke engine will run baclwards a little, I'm talking about running at power.

TF

tkg

My Feedback: (1)

Trey another ignition or send in yours to be updated. A weak spark can cause this.

Ed

A spark, is a spark, is a spark. And if it comes at the correct time, what matters if it's weak or strong ? Please explain ?

Ed

Tired Old Man

My Feedback: (1)

TKG is Terry Grant of CH Ignitions. I won't argue ignitions with him because I'll lose every time. He's the "go to" person for ignitions.

Not all ignitions excite correctly as they age. The spark should be in the area of 20kv when it triggers. If it's weak and a lot less that that you have "weak spark", with perhaps just enough to barely fire the spark plug.

tkg

My Feedback: (1)

It take more "spark" to start an engine than it does to keep it running.
The easy is to swap out the ignition for a know good one, lacking that choice then it needs to come to us for a tune up.
Weak sparks can be a bad/weak coil, bad ht lead, bad plug cap. Some times the ignition needs a power transister changed.

NM2K

My Feedback: (14)

Some of the old Super Tigre front induction engines were famous for starting backwards, but all they would do is run at idle speed or slightly above. The Poster in the article that you are referring to meant run equally well, forwards or backwards - I think.

I had an HB .40 PDP with Perry pump and carb that would start up without glow heat being applied. It eventually bent the crankpin and I just gave up on it. It made a nice display engine. The owner of the engine (me) had ruined the pump diaphragm by using 3 in 1 oil as after run oil and didn't realize that the pump was filling up the engine with fuel. What a dumbass! Some lessons are expensive and the moral isn't really apparent at the time. That's what happens when you buy used accessories with no instruction sheets. How was I to know that petroleum distillates would damage the pump? I didn't figure it out until many years later, when I bought a brand new Perry Pump and read the instructions.

I have three or four of the HB .40 PDP engines now. Not one is of the same series, but they are pretty. All need to spend a night in the antifreeze bin.

Backwards running TOC engines. Wasn't it Chip Hyde that used to reverse his TOC engine's running direction on purpose in order to perform a certain maneuver? I imagine he was running a glow plug instead of spark ignition.


Ed Cregger

Ed

Chris wins ! He wins the Most Knowledgeable Brison Man Of The Year Award.

The low end was simply a little lean. Case solved, no more running backwards.

Thanks Chris. > Ed

CK1

My Feedback: (60)

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