mikenlapaz

Help Just finished first attempt to start new Ryobi.
Engine is short shaft with 5/16-24 thread output shaft.
Alum nut is thru threaded the same. Using bolt thru Alum prop washer, prop into forward face of the long Alum nut.

The hub adapter came unscrew on first rotation (it almost started) throwing prop assembly. Flywheel came off next.
Inspection reveals that the 'molded in' key in flywheel it sheared off, there is no raised portion left.

The majority of sources I have read about adapting these engines have made no mention of a problem with this type of adapters unscrewing so easy.

I have large flats on the alum adapter nut and it was tight to flywheel at start.

Any ideas of what I did wrong or a step that I omitted?

With the 'molded key between the two molded recesses now flush to the taper, is the flywheel trash or is it fixable?

Any thoughts on advisability of drilling the hub nut and flywheel and putting tension pins in to take the torque of starting and the rotation of the prop?

walton

My Feedback: (24)

Maybe it isn't if you can cut another key way 180 degrees from the sheared one and another one on the crank shaft

tkg

My Feedback: (1)

It would take a while, but get a square jewlers file and make a key way for a real key.
OR find a junker at a repair ship and buy it for $5 and use its flywheel.
Sorta sounds like the flywheel was not on the taper tight enough. Cause you can run a lot of the engines with out any key.
These flywheels have a cast in taper and key it might not be true, so no matter how tight the hub the flywheel still wobbles.

bn120

My Feedback: (1)

I have run alot of engines without the keyway it is only there for timing reasons and fast assembly so if you just put it back on with some locktite on the taper , make sure it is still in time and then mostly make sure it is really tight this is why it came off to begin with because once they get loose it just shears off the keyway.you could also locktite the prop hub to crank as well but if you get it tight enough you wont need it.once the motor is run just the slamming of each stroke acts like a impact wrench so it will tighten while it is running if you can just get it tight enough to get it started it will do the rest I guaranty you.

Darin

mikenlapaz

bn120:
Ok, If I understand correctly, we do not really need that key in flywheel and the taper fit with pressure is going to hold the flywheel (FW) from rotation.
A couple of observations and questions.
1) The crank will turn, when putting the factory or hub nut on, long before it even starts to bear on the FW. To stop the crank rotation any suggestions? A piece of hardwood dowel stuck in the plug hole to stop piston compress stroke?

It will be easy enough to find TDC and mark output shaft position on case and flywheel. Does anyone know what the timing degrees are for a Ryobi?
Do the Ryobis, old and new (single vs 2 ring models) all have the same timing?

tgk: I have 3 older junkers that I'm rebuilding, they are all single ring older models. They have a real key and different recess in the flywheel. Plan was to use this new 2 ring engine as a baseline for evaluating the rebuilds when finished.

Search list for the day: locktite and hardwood dowel (and finding the cat, which did not appreciate the prop flying towards her observation post yesterday!) No blood trail, so she will be fine.

bn120

My Feedback: (1)

if you have the magneto ign. I just put a screwdriver flat blade in the flywheel where the magnet is and rotate it to where the coil is and wedge it between the coil and magnet,this will keep it from rotating ,or you could use a dowel just put it in the exhaust port.keep in mind it will tighten once you start to run it so be sure to mark timing marks really good so you can check it after running, the locktite will hold it but I like to check everything a couple times.I have never had one spin on me but I guess if you had a bad enough prop strike it might get off time but I have never had one move on me so this is just speculation. I have piled mine in pretty good with no problems.

Darin

mikenlapaz

bn120,
"I just put a screwdriver flat blade in the flywheel where the magnet is and rotate it to where the coil is and wedge it between the coil and magnet,this will keep it from rotating ,or you could use a dowel just put it in the exhaust port"

The screwdriver is just the extra hand for alignment? The main problem, I think, is stopping the crank/output shaft from rotating while tightening the nut and keeping the FW and shaft in alignment.

mikenlapaz

tkg

My Feedback: (1)

Mike
You have to stop two parts from moving.
A piston stop will stop the crank. A big vice will hold the flywheel. These engines are cheap and sticking something , even wood, in the exhaust port can damage the cylinder
An old 14mm long reach spark plug makes a good piston stop. Just knock out the porcelain and put a bit of wood dowel in the end.
Make some alinement marks and see how the look after its all tight. Might take a couple of tries.
Of course now you have the chance to play with the timing for more power. Moving the flywheel CCW will advance the timing.

captinjohn

This may work also. Clean taper on crank and inside taper on flywheel real good. Aply locktite and install flywheel in correct timing you want....and tap flyweel on crankshaft. Let the locktite set overnite, then install nut. This way you should not loose the timing. I heard about half of the keyway width may advance your timing just right. Good Luck Captinjohn

mikenlapaz

The bug really bit me! I have a second new engine and took the flywheel off it and installed with locktite on taper and threads of both ends of the 'adapter nut'

Got rid of all air in the main fuel supply line. I have the primer bulb set-up installed for present time. The engine spins fine with the Tower HD starter, but will not fire! Turning it CCW facing front of engine.

Magneto gap is .010" (business card) ; plug gap is .020"; primer bulb has fuel dripping out of carb.

I have a new single pole kill switch wired to 'tab' on magneto coil with the other end connected to Alum test stand. Good conductivity to engine.
Switch functions properly. It is my understanding that for engine TO RUN SWITCH SHOULD BE OPEN; TO KILL SWITCH SHOULD BE CLOSED (completing a ground connection)

There is no electrical isolation between the 'pick-ups' (for lack of proper termilogy) and the head.

I have searched and read but I'm confused!
The wire tab on the coil has 0 resistance to the coil attachment bolts to cylinder head. The switch does not seem to serve any function, as there is conductivity to engine case without the switch. It seems that it is in continual kill no run status.!



Can anyone help clarify or figure out the problem? Should that tab have 0 resistance?

Data from some other posts:

A kill switch on a magneto engine shorts out the mag..... rcign

http://www.rcuniverse.com/showthread...to+kill+switch
It is easy enough to check the kill switch. You can either test it with a continuity tester (ohm meter), or unplug it from the coil and try it without.

If that does not work, check the magneto to flywheel clearance. this should be .015", or about the thickness of a business card.

Having watched these forums for a while, I understand that the coils rarely go bad, but it can happen..

mikenlapaz

bn120
A 1 3/4" x 3/8" piece of wood will wedge between back of flywheel and the head where one of the mounting brackets is cast. No load on the screws and magneto which could affect the clearance.

tkg

My Feedback: (1)

Remove the kill switch completly. Remove the spark plug form the engine and connect it to the coil like its supposed to be, lay it on cylinder. Crank the engine with electric starter and see if you have spark. A junk spark plug with a wide gap works good to check the magneto
If you have spark then it may have been flooded. No spark swap out the coil with another and try again.

RJH

The best piston stop is to remove the sparkplug and turn the engine so the piston is 1/2 way up and then feed in as much small soft rope into the sparkplug hole as it will hold.

Antique

My Feedback: (4)

An old spark plug with the porcelain knocked out and threaded for a 3/8-24 bolt makes a good piston stop..Round off the end of the bolt where it hits the piston..Use at least 2024 aluminum for the nut, 6061 strips too easily....OR..Use Loctite on the taper, use a steel nut to tighten the flywheel on the taper, let set up overnight, take off the steel nut, replace with aluminum nut and more Loctite...Green 680 shaft and bearing mount is the strongest.......
If the crank turns before the nut tightens the flywheel on the taper the threads are screwed up..Run a tap thru the nut and a die on the crank..

mikenlapaz

rcign1: [/QUOTE]If the crank turns before the nut tightens the flywheel on the taper the threads are screwed up.

Both new short shafts engines have nut combo square cable drive that behave just as you describe above. I'll chase the threads. I just figured the nut had a special tapered thread to assure it stayed on / in a tip of rotating shaft.

Thanks for insight.