Balancing a Seagull Engine

[The Tinker]

Anyone out there tried to balance the crankshaft and flywheel of a seagull. It is done in motor cycles to remove the vibration.

[Rex NZ]

Interesting

I've thought about the same.

Was thinking of modifying a flywheel with a series of steel plugs to adjust the balance

The problem I envisage is achieving a meaningful measuring system

Rex

[The Tinker]

With single cylinder engines you can not get perfect balance. You just move the vibration to a different rev range. The research I have done suggests that 65% balance is about the best that can be achieved. This is the difference between the power stroke and compression stroke. I am tiring to find out how to do the calculation. Static balancing seems to be the best way to go.

[Charles uk]

Andy I've played with the balance in some of my higher revving motors, they're never going to run smooth, with luck you can move it to a point where the boat doesn't resonate enough to loosen your fillings.
I always do the flywheel so that it's completely neutral, as the thought of one of those shaking itself to bits at 5000+ revs right by my ear makes me watertight below the belt.

[The Tinker]

So what you are saying Charles is that the flywheel is balanced on its own. The flywheels seem to be very out of balance so might be a good place to start.

[Charles uk]

Andy here's some pictures of the bar I use for flywheels, it fits all of them from the Marston to the Seagull Sport.

Sorry I take such a dreadfull pic all it is is a high tensile threaded bar with turned down ends with 2 threaded cones to centralise & hold the flywheel.

[Chilli Dog]

then there is the prop , both static and dynamic balance need to be attended too .