[monocoupe]

O.K. you engine experts.....

I just picked up a pair of 31cc Ryobi's for a scale twin project, and I'd like to run one of them in the opposite direction.
Since it's a reed valve engine the intake timing isn't an issue, but the ignition timing is.
I'm thinking that if a new keyway was cut in the flywheel in the correct position, the engine should run backwards....yes?

If I am correct in my assumption, I'd sure be happy if one of you engine experts could tell me where to cut the new keyway.....and even happier if one of you has the capability do do the work for me!

Seriously, if one of you guys have the equipment and knowhow I'd be happy to pay you to machine down the cooling vanes on both flywheels and re-key the one.

Any takers?

Cheers, Nigel

[Vulcan1]

Nigel,
I have the same problem and was on another post about it. I am thinking of using my degree wheel and making a back plate mount for the coil and swinging it over to the other side. I haven't calculated it yet but in my own mind it should be no problem. If measured at 20deg. BTDC you would have to swing it 40 deg. to the right which would still be on the jug and would not have to change anything else. If you have any comments on this it would be appreciatted.
John

[monocoupe]

John,
I never thought about moving the coil. I'll give that some thought.

I've just discovered that on these two engines that I have, there is no keyway for in the flywheel in the traditional way. The flywheel bore is machined to fit into the keyway on the crank.
That would be fine, except it's a lousy fit, and the flywheel is allowed to rotate several degrees on the crank, which of course changes the timing.
I'm not certain how much difference this will make, but I suppose I could try running the engine with the flywheel rotated to the clockwise side of the slop, and again to the counter clockwise side, and see if there is any difference in RPM.

Cheers, Nigel

[Vulcan1]

Nigel,
Having the slop to me is a no-no. Anytime it has a chance to rotate and maybe come off I think is a disaster looking for a place to happen. I would use some JB or something on it to tighten it up. put some vaseline or wax on the shaft and apply the jb to the flywheel after it is degreased. Tighten it up and let it set. I don't think there is a lock on the wheel so if the key shears it might come off. I know somebody is going to come back and say the nut will tighten but I would not take a chance. Let me know how you make out.
John

[monocoupe]

John,

I spoke with Dave Carr at Carr precision today, and he is familiar with these flywheels. He says to simply set the flywheel to the most counter clockwise, (or most advanced) position, prior to tightening the prop hub, and it'll be fine.

Cheers, Nigel

[Vulcan1]

Nigel,
Fast answer and I think it would also be okay.
John

[Vulcan1]

Still on the reverse rotation I have a question for the electronically minded. The coil has 2 poles and one is through the coil and the other is out on the side. If I move the coil over say 40deg. would the coil fire the plug in the right time. My thinking is that the outside pole starts to build up a charge and fires it at the centre pole. I am not sure if my assumption is correct. Does anybody have an idea on this?
John

[monocoupe]

John,
Being an electrical idiot, I can't help you there! But here's something else to consider...

There might be problems keeping the prop hub on the engine with the reverse rotation due to the shaft thread direction.

Cheers, Nigel

[nony]

Is that cub flying yet, Nigel ?

[monocoupe]

Originally Posted by nony

Is that cub flying yet, Nigel ?

Hi Wayne!

Well, no.....but the good news is that the Vega is almost finished!

Cheers, Nigel