sboxer

My Feedback: (1)

I purchased a ryboi 725r from harbor freight last week (http://www.harborfreight.com/cpi/cta...emnumber=51584).
Upon pulling it apart, I'm seeing extra aluminum around the front of the crankcase. The pictures show the front end and back of the engine.
It looks like I am gong to need to hack that stuff off (based on previous threads). Since I don't own a grinder (and would rather not get one) I want to konw if anyone has any good ideas (hack saw / dremmel??). I guess I can buy a cheapo angle gringer for $40 at Sears.

Thanks,
Steve

CrazyHerb

My Feedback: (1)

Ack!! Bummer...you got one of the newer cases....
But that's good in a way...cause you have twin-ring version...all the new cases I've seen have twin ring pistons.

The flange isn't too hard to grind off. I think it's pretty soft metal...But it will make a mess. Sucks that the company went this way...maybe to thwart our conversion attempts?
Or 4 bolts was too expensive to keep using to hold the flange on....

Try the hacksaw...it may cut easy....you may be able to have local machinist "work" it off for really cheap if you tell em what your doing with your old weedeater...local guy here laughs at me and makes good conversation...

Can't tell if that's the long or short version....need a side pic.....I like the long shaft better cause I know my prop is riding on the actual crankshaft instead of threaded hub.
But I have two short shafts too.....work just fine..

Make sure you specify when you order parts which shaft you have.

Good Luck...start grinding!!
CrazyHerb

mikenlapaz

you could just drill a bunch of holes near the desired finished line and then pop off the outer material. A little bit of filing and your done. I'd use the $40 towards some dremel grinding tips and cut-off wheels...

Volfy

My Feedback: (23)

If you have a good size air compressor, you might try one of these:

http://www.harborfreight.com/cpi/cta...emnumber=90114

I've been using one like it to do the rough cutting. It doesn't come out as pretty as one done on a mill, but the engine will fly just the same.

Tmoth4

My Feedback: (1)

The aluminum is gonna load up a grinding bit or wheel. I found the best way to cut away the aluminum is to rough cut it with a hacksaw and then file by hand. The metal is pretty thin and soft so it's not too difficult. Drilling holes helps too.

Jim

sboxer

My Feedback: (1)

Thanks for all the input. I think you guys saved me from buying a grinder that would collect dust.

Crazy Herb- Thanks for all the help on this and 'splaining BIG PINK to me. If I had this kind of help 20 years ago, I would have not stopped flying RC.

BTW, the shaft-I believe- is the long one and thats the conversion kit that I ordered from wackerengines. It was my understanding that all 725r's are the long shaft. Of course, I could have imagined reading that.
Thanks,
SB

Sport_Pilot

I would go with drilling holes, then cut through the holes with a jig saw with a fine tooth blade. Just banging and breaking the flange off might work, but if it doesn't it could crack the case.

But I have never done an engine conversion, but do have some metal shop experiance, so others would could best tell you if that method is safe.

Edwin

My Feedback: (2)

I would use a dremil with a fiberglass cutoff wheel. I do this a lot at work and at home. You can even use it to dress up the jagged edges once you've lightened the load. I even use the cutoff wheel to cut my aluminum spinners since they never fit the props I have. I also used it on the Jag motor mount to get a little extra clearance for the throttle lever.
Edwin

sboxer

My Feedback: (1)

All good tips! Thanks.

As an aside, when I did open up the crankcase, I was surprised that there was a fair amount of tiny plastic chips inside the cylinder. I don't believe that was a result of my work, since I was pretty careful. I guess it is a testament to reliability of the engine...
SB

Edwin

My Feedback: (2)

They are great little engines. The one I'm currently using was wore out with 8 years previous use in the yard. Given to me by a co-worker that didnt want to deal with it when it wouldnt start. All it needed was the carb pump diaphram (sp? must be the gas). I'm pretty sure I hear a con-rod knock but it still runs good so I'll just use it another season and inspect it next summer. (Summer is building season down here) Got 4 more waiting to be used. Be careful, occasionally they like to revert back to their original use and head for the weeds.
Edwin

Rambo-RCU

My Feedback: (1)

Please don't laugh but check to see if Homier tools is having a sale in your area as they sell 4" grinders everyday at $5.95 .They are junk but with a piddle job like that they will do just fine.Later

Flypaper 2

Stick a new hacksaw blade in your saw and it will cut aluminum like butter.

SilverEagleBW

My Feedback: (1)

Check this gizmo out,right now i am converting 3 Ryobi's and two Homelites.This looks like it could save alot of time,do the job right,and it is only 50 bucks.


http://www.toolpeddler.com/925-6.htm

mikenlapaz

Slade_LoD That does look cool!! Now to find the c/l mount bolt hole requirement.

SilverEagleBW

My Feedback: (1)

Well it does say it is for plastic and wood,but if you take it easy i bet you can do soft aluminum without a hitch.Last night i was milling a Ryobi case on my drill press,had a round stone in it.Was holding the case with a deathgrip...KERPWOIE KIDS!!The case got flung ten feet accross the room.Hurried up to see if i still had all my fingers,LMAO!Yeppers,still all there,went right back to milling,hehe!! I will post some pictures of these engines when i get some done.Going the 'EXTREME' route on them all if i can afford it.I am doing some DEAD SERIOUS GRINDING!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! !!!!!!!!!!!hehe!

sboxer

My Feedback: (1)

The new blade on the hacksaw was the answer for me. It was not quite a hot knife through butter, but about 30 minutes of cutting did the trick. I think I ground down 3 or 4 misc dremel bits trying to clean it up.

So how important it milling the flywheel? And how best to remove the two little mechanism with the springs on the front of the flywheel? Dremel again?

Thanks,
SB

Longaly

sboxer,

If I remember correctly, a punch and a hammer will knock those pins/springs right out.

Rick

mikenlapaz

FWIW Re the milling vise: http://www.toolpeddler.com/925-6.htm
"The vise has 4 mounting slots, each being 3/8" wide by 4-5/8" long. The slots are 5-3/4" apart (measuring centerline). You can use any bolts that will fit through the slot. " per seller

CrazyHerb

My Feedback: (1)

SBoxer,
I wouldn't worry too much about the cooling fins.
I do punch out the centrifical spring clips but I haven't seen a noticable difference in power from the motor with or without the cooling fins...

I think it's 90% cosmetic.

If you can, try dropping it on a prop-balancer, most of mine are stock (off balance) but I've heard you can smooth them up a bit by balancing the flywheel.
Now...how you would go about balancing...I have no idea...but if ya'll have a good way to do it let me know.

Good Luck!

CrazyHerb

ALW Phantom

My Feedback: (2)

Sboxer,
I have a question for you, could you please let me and everyone else in this thread know the exact model and serial number of the trimmer. I have a few Ryobis that I got from a mower shop just waiting for rebuild and I would like to use the double ring piston, if it actually has it. A quick peak in the exhaust opening would verify this. As far as balancing, Im getting all the flywhels machined down that I have and the guy doing it says the are pretty close to balancing from the factory, as long as weight is removed evenly it shouldnt be a problem. Not that I doubt him, I do have the Dubro Tru-Spin Prop Balance (#499) so for laughs and craps (poops and hahas) I will check them to be sure. Im thinking everything you can do to these little engines to improve performance will be a plus. One day when the money flows in, which it never seems to do, I will look into electronic ignition. ALW

sboxer

My Feedback: (1)

the model number is zr725r rev p01
the serial number is 1g074y80016
item: 42bd725g034

ALW Phantom

My Feedback: (2)

Cool, thanks so much, now maybe my 31cc can get the twin rigned piston it wants hahahaha

sboxer

My Feedback: (1)

Damn Pins!
I flipped the flywheel over and used a drill to remove the flashing so I could get at the pins. The top side of the flywheel is supported between two chunks of wood. I've whacked at both of the pins with an 1/8 punch and hammer and they ain't moving. I've probably given each side 50 smart whacks. Any advice would be helpful!
SB

CrazyHerb

My Feedback: (1)

Grind em off!!
Makes lots of sparks...hehehe...

My little 11k rpm Ryobi grinder is awesome....just cut a crankshaft in half in about 15 seconds with the cut off blade.

Now I can chuck it up in my drill press by the cut off crankshaft or take it down to the machine guys here on base and have them true it up nice.

I seem to remember bangin on mine pretty hard too and had no luck...

Hack saw might get to them as well....have to trim into the cooling blades a bit....but if yer gonna do it might as well.

Anyone know if they might be threaded in?

Good Luck!
CrazyHerb

mikenlapaz

They are splined and pressed into the casting. Spray some Liquid Wrench and let them set and try again OR just secure well in drill press and drill them out. I had some that did not want to drive out as well. Even if your not exactly centered it is not a big deal. The pins are about .20", a 13/64 drill will do it.