Ryobi jug    Gallery
View related threads: (in this forum | in all forums)

Logged in as Guest



Users viewing this topic: none
    Search This Thread  
 
Printable Version


TurboHeader Muffler
Seller:  RC Specialties
Details:   $69.95   |  4/28/2013   |  Classified Ad
We will rotate YOUR AD in this spot if you select "Forum Featured" when placing or editing your ad!

All Forums >> Glow Engines, Gas Engines, Fuel & Mfg Support Forums >> Engine Conversions >> Ryobi jug
Page: [1]

Tower Hobbies Get Coupon Codes Brands  
Login
Message << Older Topic   Newer Topic >>
Ryobi jug - 1/16/2004 7:12 AM   
stgrlee



Posts: 97
Score: 100
Joined: 12/31/2002
Last Login: 4/11/2013
From: Overland, MO, USA
Status: offline 		How much can a Ryobi jug be milled and still be dependable?

_____________________________

Old age and trechery will overcome youth and enthusiam every time.

Hide Signatures
       Post #: 1

RE: Ryobi jug - 6/25/2012 2:54 AM  1 votes
APLANEGUY



Posts: 63
Score: 105
Joined: 4/30/2009
Last Login: 5/19/2013
From: Wayland, NY, USA
Status: offline 		Old post but I figured I'd throw my $.02 out there for anyone wanting to know. I read in a conversion article once that the base of the cylinder on a typical 31cc Ryobi can be milled to increase compression. I also read a suggestion that indicated removing the thick base gasket and replacing it with a thinner one or just fuel proof sealer would also help. In doing so you increase compression and also effectively lower the ports which is good on the intake side 'cause it opens the port sooner but bad on the exhaust side 'cause the port opens later. To remedy this it was recommened to either take a bit off the top of the exhaust port or remove a little material from the top outer edge of the piston to maintain good port timing. Not having a machine shop I always opt to use a Dremel tool to remove a bit from the top edge of the piston where it meets the exhaust port. OK, back to the original question. On my first Ryobi conversion I had my brother (a machinist by trade) mill the base of the cylinder .020". When I assembled the engine I also used a VERY thin base gasket (I wanted a little screamer hot rod engine). However, when I screwed the spark plug in and turned the engine by hand I found that the piston was coming up and hitting the plug. Oops. I first considered trying to shim the plug a bit to get it out of the way but it's a tapered seat plug and I really didn't want any sealing issues there and didn't want to mess with a good thing so I left the plug alone. I tried making a little thicker base gasket and there was still contact. Finally I went to a base gasket approximately the thickness of a stock gasket and there was no interference. I assembled the engine that way and finished the conversion. She ran very well like that. That engine ran and ran for hours on the test stand then for approximately 30 flights in an airplane before a servo failure cause a full throttle nose-in and the crank was bent. The cylinder is still on another running engine today. I've done several 31cc Ryobis and I always either have the cylinder milled .020" or go to a really thin gasket to accomplish the same thing. The engines run well and are cheap and easy to convert and a whole lot of fun to work on. My work nets an engine that will turn an 18x8 prop at about 8200rpm on the test stand. I currently have two planes flying with them and a new project that will be a crazy twin with two Ryobi 31s. In my opinion milling .020" (or reducing gasket thickness the same amount) is about the maximum you can go and so far has proven to be very reliable. Compression is really good and my Sullivan starter has all it wants to do to spin one hooked to a 12v lawnmower battery. No signs of detonation or other harmful side effects. I run cheap 87 octane gasoline and keep the fuel mix at 32:1 to make sure things are always lubed well. After seeing what appears to be a rather flimsy connecting rod in these engines I've been rather pleasantly suprised by their longevity. I'll probably eventually blow one up or something but at the low price of replacement it's not really a concern. Especially when I hear stories all the time about purpose built RC engines that don't last and are far more expensive. This has been my very long-winded way of saying the answer to your question is .020"...

My typical engine mods:
-Mill the cylinder .020"
-Cut/grind the crankcase flanges off (remove anything that made it a trimmer engine)
-Larger carburetor
-Cut away extra plastic from reed valve plate leaving just a rear crankcase cover with reed valve
-If possible use a two ring piston but one works ok too
-Bend the reed valve retainer a little to let it open more
-Grind a bit off the top of the piston to maintain port timing
-Aluminum aftermarket muffler (much lighter... I get mine from wackerengines.com)
-Disgard the flywheel and magneto in favor of a CDI unit (on short shaft engines I cut the center out of the flywheel to use as a hub and put the ignition trigger magnet in it)
 

Hide Signatures

(in reply to stgrlee)
       Post #: 2

RE: Ryobi jug - 6/25/2012 6:02 AM  1 votes
av8tor1977



Posts: 5459
Score: 665
Joined: 5/4/2003
Last Login: 5/19/2013
From: Lukeville, AZ, USA
Status: offline 		Look here; tons of info: http://www.rcuniverse.com/forum/m_8479610/mpage_1/key_/tm.htm

I have lowered the cylinder considerably more than .020" many times. And it is best to raise the exhaust port instead of cutting the piston, which just lowers the compression again. You can use a gasketed spark plug in place of the tapered seat plug. (Many engines are interchangeable in this respect.)

There is no piston ported intake port to worry about when lowering the cylinder, it is a rear intake reed valve setup.

Keep the static revs to 7500 if you want the weak stock rod to live.

AV8TOR

_____________________________

If it is not SCARY, it is NO WHERE NEAR powerful enough!!

Hide Signatures

(in reply to APLANEGUY)
       Post #: 3

RE: Ryobi jug - 6/25/2012 1:19 PM   
w8ye



Posts: 36435
Score: 318
Joined: 12/11/2001
Last Login: 5/19/2013
From: Shelby, OH, USA
Status: offline 		I've used the gasketed and tapered seat plugs interchangeably in both the Homelite and Ryobi engines


_____________________________

Attended the CutFinger Institute of DirtNap University for years but never did graduate....
Recipient, Mangledhand award August 2008
Club Saito Member #7
Original AMA #31261

Hide Signatures

(in reply to av8tor1977)
       Post #: 4

RE: Ryobi jug - 6/25/2012 11:13 PM   
APLANEGUY



Posts: 63
Score: 105
Joined: 4/30/2009
Last Login: 5/19/2013
From: Wayland, NY, USA
Status: offline 		Interesting. I wonder now why I had issues with interference. Next one I do I'm gonna have to make some close measurements and look at things again. Maybe it was just a fluke or something. Maybe it was machined more than I asked for. Who knows?...

Hide Signatures

(in reply to w8ye)
       Post #: 5

RE: Ryobi jug - 6/26/2012 6:20 PM   
w8ye



Posts: 36435
Score: 318
Joined: 12/11/2001
Last Login: 5/19/2013
From: Shelby, OH, USA
Status: offline 		If the plug electrode was hitting, you could use an equivalent non extended tip spark plug.

I have a lot of chainsaws and almost all have the extended tip, resistor  NGK BPMR7A spark plug. But some have had non extended tip plugs when I got them used. They seemed to run just fine.

I bought a nice looking chainsaw that had a non extended tip spark plug when I bought it. When I went to change the spark plug, I noticed a mark (dent) on the piston. It was where someone had used a metal piston stop in the engine spark plug hole to change the clutch or something.


_____________________________

Attended the CutFinger Institute of DirtNap University for years but never did graduate....
Recipient, Mangledhand award August 2008
Club Saito Member #7
Original AMA #31261

Hide Signatures

(in reply to APLANEGUY)
       Post #: 6

RE: Ryobi jug - 6/26/2012 7:43 PM   
av8tor1977



Posts: 5459
Score: 665
Joined: 5/4/2003
Last Login: 5/19/2013
From: Lukeville, AZ, USA
Status: offline 		Yeah, those metal piston stops scare me. I would never use one for fear I would poke a hole right through a piston. I use a positive stop tool I made to find TDC for timing and porting and such, but there is never any force put on it.

And W8ye is right, (as usual), you can use a normal instead of an extended nose plug. www.sparkplugs.com has tons of info....

AV8TOR

_____________________________

If it is not SCARY, it is NO WHERE NEAR powerful enough!!

Hide Signatures

(in reply to w8ye)
       Post #: 7

Page:   [1]
All Forums >> Glow Engines, Gas Engines, Fuel &amp; Mfg Support Forums >> Engine Conversions >> Ryobi jug
Page: [1]





Jump to:


 
Google 



Search | Marketplace | Event Calendar | Local Clubs | Magazine | Product Ratings | New Products | Discussion Forums

Photo Gallery | Instructor Search | Field|Track|Marina Search

Advertisers | Hobby Vendor Resources | Rate Manufacturers | Sign In/Sign Up

SITE MAP!   : :   FORUM RULES

RC Universe is a service of Internet Brands, Inc. Copyright © 2001-2013.

Charities we support that also need your help
Yorkie Rescue | Humane Society | ASPCA | Crohn's-Colitis America


1.125RCU1