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Brison 3.2 Throttle Coupled Timing

Old 03-05-2005, 09:58 PM
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Diablo-RCU
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Default Brison 3.2 Throttle Coupled Timing

I decided to check timing on a new-old Brison 3.2 with throttle coupled spark advance. Put a degree wheel on the crank with a pointer. Checked to make sure the throttle opened to full throttle and didn't rotate farther. The engine was set with throttle closed - timing is 8 degrees ATDC. At full throttle, timing is 28 degrees BTDC. The timing seems awfully retarded at idle through mid throttle. I'm going to fix it by drilling another hole on the throttle arm so there is less "mechanical" advance. I can't understand why they built it with 36 degrees of throttle advance. My guess is they're all built that way.
Old 03-05-2005, 10:32 PM
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Default RE: Brison 3.2 Throttle Coupled Timing

Shoot for 28-30 BTDC at wot and 4-6 BTDC at idle.
Old 03-05-2005, 10:46 PM
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Diablo-RCU
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Default RE: Brison 3.2 Throttle Coupled Timing

Thanks TKG. I was thinking about 4-8 degrees at idle. The project is stuck right now, have to buy a 2-56 tap.
Old 03-06-2005, 01:57 AM
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Antique
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Default RE: Brison 3.2 Throttle Coupled Timing

How did you even get it to run timed at 8 ATDC ? Backwards ? Didn't it try to break your hand ?
Looks like Brison copied a little too much from A&M .Some of theirs were 45 BTDC..
Old 03-06-2005, 04:44 AM
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pe reivers
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Default RE: Brison 3.2 Throttle Coupled Timing

Consider it a tribute Ralph.
Maybe they were not aware just what to copy?
Old 03-06-2005, 08:24 AM
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Default RE: Brison 3.2 Throttle Coupled Timing

8 degrees ATDC.
I am suprised that it would idle steady.
If you can shift with wheel/ring you will have 28+12 or around 40 degrees BTDC.
That seems like a lot to me but I am new to these engines.
Old 03-06-2005, 08:29 AM
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Default RE: Brison 3.2 Throttle Coupled Timing

I didn't try to get it to run yet, still finishing up the plane (Double Vision). The reason I decided to check timing was because I sanded down the nylon carb spacer about 1/4 inch so it would narrow the engine enough to put the cowl on. Moving the carb alters the timing, so I figured I'd just have to adjust the length of the 2-56 rod going from the carb to the timing ring.
Old 03-06-2005, 02:39 PM
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Default RE: Brison 3.2 Throttle Coupled Timing

By offsetting the hole on the L-shaped throttle arm, I was able to set it up for 4 degrees advance at idle and 29 degrees advance at full throttle.
Old 03-06-2005, 07:13 PM
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Default RE: Brison 3.2 Throttle Coupled Timing

Is this a normal problem of the engine being this far out of time. I am considering a good 50CC motor and the brison is on my list. I figured it would come set correctly from the factory.
Old 03-06-2005, 10:53 PM
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Default RE: Brison 3.2 Throttle Coupled Timing

I can truthfully state that I have never checked the timing on either of my Brison 3.2's. They both run so well that I have never had the inclination. I have one each in the ignition types. One throttle coupled and one that has the Syncrospark. I prefer the throttle coupled for the smoothest midrange, but the Syncrospark version isn't all that far behind it.

Perhaps I'll check the timing someday, but it works too good now to try to fix it. Diablo, perhaps you got an oddball?
Old 03-06-2005, 11:11 PM
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Default RE: Brison 3.2 Throttle Coupled Timing

I kind of doubt that mine is all that odd. My guess is they machine all the little L-shaped arms the same and drill the holes in the same location. In Brison's defense, I did move the carb in which would have increased the throttle advance because of less angularity on the rod between the carb and the timing wheel. I also noticed on the Brison website that they've changed the location of the ball link on the timing ring on the new engines. Mine has the ball link on the back face of the nylon ring. The new ones have the ball link on the outer circumference of the nylon ring. Perhaps this fixes the problem.
Old 03-07-2005, 10:55 AM
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Default RE: Brison 3.2 Throttle Coupled Timing

After the timing change, did the engine run differently? Mine runs great, but you always look for more. Where do you get the degree wheel?
Old 03-07-2005, 11:19 AM
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Default RE: Brison 3.2 Throttle Coupled Timing

You have to remember that he removed 1/4 inch from the carb block. This would change the timing on any mechanical advance engine. The Brison line of engines are great from the factory and without user modifications.
ORIGINAL: m.gramling

Is this a normal problem of the engine being this far out of time. I am considering a good 50CC motor and the brison is on my list. I figured it would come set correctly from the factory.
Old 03-07-2005, 11:49 AM
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Default RE: Brison 3.2 Throttle Coupled Timing

And you guys wonder why I use DA engines???

DP

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