oceandiv

My Feedback: (1)

I have a Brison 4.2 mounted on an Ohio R/C Giles 300. I am having vibration problems. The vibration doesn't change with different props. or spinner installed or uninstalled. I have had the engine checked & rechecked by Brison. The vibration is so bad that something on the airframe breaks each time I try to fly it. Six flights and six repairs. The engine is solid mounted and I have tried soft mounting it. Soft mounting it made the vibration worse. HELP!!!!!

Albatross

My Feedback: (7)

Is your spinner properly balanced?

oceandiv

My Feedback: (1)

yes the spinner is balanced. vibration happens with or without spinner

BPKlein

My Feedback: (1)

Try leaning the low end mixture just a little. About 1/8 of a turn or so.

Bryan

Albatross

My Feedback: (7)

I have never tried this methode; however I think it could help you. Makes sense to me! take a look at this web site for an alternative way to balance your prop/engine:

http://www.fly-giantrc.org/technical/propbalance.html

oceandiv

My Feedback: (1)

The vibration is close to normal at idle and at 1/4 throttle. Then at 1/2 to FULL it goes wild.

Falcon-RCU

My Feedback: (1)

Maybe the engine has been wrecked and the crankshaft is bent.

oceandiv

My Feedback: (1)

The crank has been checked twice by Brison.

Big_Bird

My Feedback: (1)

I'm not familiar with the Ohio R/C Giles 300. Is the airframe really light? Single cyl engines produce quiet a bit of vibration and a can give a light airframe fits. Have you tried running it on a test stand? I feel sure that Brison checked the timing when they had the engine. Did you have a talk with Gary or Harvey when they checked it? What was their response? Since you are a "local", take it, still mounted on the plane, over to Gary and run it for him so that he can see what you are talking about. He may be able to diagnose the problem better.

I know that I've thrown a lot of questions at you but I'm just trying to help.

Ken

oceandiv

My Feedback: (1)

I have taken the whole plane to Brison and thats when he decided to recheck the engine again. Reinstalled and vibration still just as bad.

Big_Bird

My Feedback: (1)

You've done every thing that I can think of without getting any good results. I'm surprised that we have not heard from many of the Brison 4.2 owners pro or con. Hey guys is this just an unfortunate isolated vibrating engine or what?

Ken

AJF 2

My Feedback: (1)

What kind of prop are you running? I have seen heavy carbon fiber props viberate when wood props run very smooth. However your problem sounds very strange-----

ajcoholic

My Feedback: (10)

Guys,
I bought a used Brison 4.2 off a guy here on RCU, and have it mounted to my own design 26 pound 1/3 scale aerobatic plane. I am running a Bolly 24-10 prop. I have quite a few dozen flights on the engine, and it runs quite nicely. I had it hard mounted first, then tried a soft mount (made things worse) and now am back to hard mounted. I had only some small problems with my tail brace wires breaking, but I strengthened them and it is OK now. I have run only large twins (104, 80cc, 66cc) and cant compare it to them since the twins run so smooth.

I would say the 4.2 shakes LESS than I expected it too, and being hard mounted I am quite happy with it.

What exactly are you breaking? My tail shakes quite a bit at idle but once I transition to above 1/4 throttle it smooths out and I havent had anything else come loose.

Andrew Coholic

oceandiv

My Feedback: (1)

Have tried wood & composite props. with same results.