aj0nr

It is great to see all the other info about the Ryobi.I have torn apart about 20 of them and found alot of differances with them. 1 the lower part with the crank,two differant sizes,some of them have been milled in production and some are cast and cleaned up, also the front seal/bearings are differant on some of them.The outside case,some are wider than others.2The heads,the newer Ryobi's with the "E-Z start "in the title are the ones with the compresion vents that go up the sides for emisions complience.I could go on and on,BUT I have found an older engine that was dated 1978 that had 2 rings on the piston and the rod was forged aluminum and held to the crank with a bolt( name was 'Piston Powered Products model # 99).The other one I have is a Troy built/MDT dated 3/2006 also has two rings on the piston,But this is the new casting I have heard about .The lower crank case has the magneto shield as part of the casting.This will require much more work to convert.

combatpilot

Sorry I dont have video capabillities. Didnt get a chance today as i had to work on other things. responsibility suks. Maybee tommorow.

What was front bearie difference you have seen on the crank seals. What I have seen is on my older engine the seal was after the inner bearing which leaves no way what so ever to lube the front bearing. the latter model has the crank seal out at the end of the shaft next to the flywheel. This allows for good lubrication of the front breaing but it also inscreases the crank case volume which is undesireable. this is a trade off either way. I think i will put the seal next to the inner bearing and use some grease in the outer bearing and see how this changes performance. I will do this in the reducing crank case volume section of the test.

If you look at the pictures you will see that my newer engine had the cast on mag sheild. You can see how i cleaned up mine and it really looks quite nice.

aj0nr

I was able to see the differance in the front seal after I dropped one.oops.It was a long shaft with the seal on the front then bearring.I could see a 1/4- 3/8 " space in there.I have 7 short shafts with the seal first and only one that has the bearring first.Long shafts ,4 with seal first and 6 with bearing first.Some of the motors were Ryan or other type,and the rest are Ryobi.2 large bearrings one far forward and one aft next to the rod/counter weight.

What is everybody doing to replace the mag space when you put on the EI conversion??

combatpilot

I was told that you leave the mag off. I jusst dont see how this will work with the paragon prop hub that i have. I plan on putting my flywheel in a lathe and turning it down to the size that i need. I should be able to acomplish this by removing the crank and putting the flywheel on the crank. then using the prop hub adapter to chuck to to center it all up right. Its gona be a while before I can do this though as i just dont hacve the money. work has suked lattley and i have a lot of chatch up to do

av8tor1977

My Feedback: (6)

It sounds like you have a prop hub for use on a magneto equipped engine. It just takes the place of the nut that holds the magneto on. I have used these before. What you can do is take a hole saw, and carefully cut the center of the magneto out, as large as is practically possible. Then dress it round, preferably with a lathe. You can then use it to "adapt" your prop hub to the crank. Just place the magneto center you made onto the crankshaft, and then screw on your prop hub. If running Gas/Glow, that's all there is to it. If running electronic ignition, then drill either the center piece you made, or the prop hub itself for a magnet to trigger the sensor.

Of course, if you are going to run the magneto ignition, then you must use the mag flywheel. Some people cut off the fins to reduce weight and eliminate the power robbing drag of the impeller blades. Rebalance the flywheel afterwards if you do this.

AV8TOR

combatpilot

Av8tor1977 thats pretty much it in a nutshell. Thats pretty muck what i figured on doing only i was just gona cut it down in a lathe. Any idea where to get the magnet and the shape, size and type?


I got a chance to do some testing today. I think my results are pretty interesting.

Test #1 stock engine no performance mods. Using old 1 ring piston and newer engine with the twin intake runners per side. This should give a good baseline for a starting
reference point.

Recoded RPM 6300

Test #2 Again stock engine and no perfomance mods. Using two ring piston and newer engine.

Recorded RPM 6330 For a net gain of 30 RPM I actually expected it to be a little more than this.

Test #3 Stock engine no performance mods. 2 ring piston and the older and looks to be higher compression combustion chamber design. If you look at the old crank case and
look at the new one the new crankcase is just a modified version of the old crankcase ports. Therfore the ports should match the ports on the old cylinder just fine. Again the purpose of this test is to see if the higher compression help.

Recorded RPM 6570 For a net gain of 240 RPM!!!!!!!! At this point I was not convinced this rpm gain was due to the higher compression and could have been a result of better ports.

Test #4 Takeing the best combination of test 1-3 cylinder and piston combination. Removing the cylinder base gasket and try to increase the compression ratio some more. With the combination of piston and cylinder I have, when the gasket is removed it causes a piston to cylinder contact. I measured the height of the piston in relation to the top of the spark plug hole. If you take a dial caliper and extend it you can use it for a depth gauge at the end of it. If you hold it on the spark plug hole and rotate the crank when the piston comes to the top you will have your reading. Ok so my reading with the gasket was .610 Without the gasket it was .585 and agian there was contact. Ok so i measured the gasket and figured it moved the cylinder down .030 this means that i had a .005 interfereance fit. So i cut a gasket out of carboard stock that measured .010 . When I installed the cylinder with the gasket and remeasured it gave me a reading of .590 so I now have moved the cylinder down .020 and should have .005 clearance between the piston and the flange of the combustion chamber.

Recorded RPM 6,660 For a net gain of 90 RPM now I am convinced the rpm gain of test three is from the higher compression as is this RPM gain is also.

Test #5 This test takes the best results of test 1-4 and uses the crank from the old engine to see if there is a gain as it looks like this crank has more advance in it. Out of pure curiosity i took the ignition coil from the old engine and used it with the new flywheel. It would hardly run in this combination. Likewise on this test i use the old flywheel. In this configuration it runs great with the old coil but like crap with the new coil. On inspection of all these parts there are two manufatures of thses parts. The newer coil and flywheel is made by walbro. the older coil and flywheel is made by phelan. For some reason they are a matched set and cannot be inerchanged in any combination from new to old. The only way to change the flywheel is to change out cranks. Anyhow so the theory is that the older set up has an advanced timming. When the crank was changed out the seal was left on the outside nezt to the flywheel. I will try and put it on the outside of the inner bearing on test # 9 as this should reduce the crankcase volume.

Recorded RPM 6,670 For a net gain of 10 rpm. At this point i am not sure there is any advance in this setup from the other set up. there isnt enough rpm gain to
conclude this. Since there is a difference in the interchange of these part i now feel there is some timming in the coil assemblies themselves. I am not sure how this is accomplised but i am sure it is something electronic. I would like to check the timming but i need to make a degree wheel and fixture for a dial indicator to find TDC. Once this is located i can then make a TDC timming mark on the flywheel and somewhere on the case for a reference. using my timminig light i can tune the light till the timming lines up at TDC. then all i have to do is look at where the knob on the timming light is and I will have my advance number. I will have to check this when I get time. If I can get an electronic ignition all this info wont even matter but it is still worth doing as i hope guys using the stock ignigtion can gain from this information.

Next I will move on to the larger carburetor. I need to do some modifications to the carb so it will fit this application. The carburetor I purchased is a walbro #387. It has a 12.8 mm venturi. The modification i need to make is: Change the throttle shaft as the old shaft has a better arm to it. The fuel pump cover needs to be changed also as it has the correct idle adjustment for this arm. other than that the only other thing that needs to be done is to remove the throttle return spring. I will proceded with this when i get more time.

All in all i have so far achieved a Gross gain in rpm of 370 RPM

av8tor1977

My Feedback: (6)

You have lots of patience. Thanks for posting the results. Classically, the best "weedie" performance gains are from a more free breathing exhaust, and from a larger carb. One won't work well without the other though; with the more open exhaust having an advantage if you are only going to change one thing usually. The next thing is to check the exhaust port timing. Some Ryobis have a really low exhaust timing of around 120 degrees. Bringing them up to about 150 really livens things up.

A good way to check your deck height without all the caliper work is to use a piece of solder. Bend a piece so that when inserted into the spark plug hole, it touches the side of the cylinder. Then turn the engine over a few times. The piston will smash the solder against the head, and then you can measure it for your "deck" or piston/head clearance. .015" is a minimum deck height, with maybe .020" being a bit safer or a good idea for high rpm engines.

AV8TOR

av8tor1977

My Feedback: (6)

Oh, and what prop are you using in your tests?

Also be aware that changes in temperature, and to a lesser extent, barometric pressure and humidity will affect your results from test to test when things are close.

AV8TOR

combatpilot

Yea i know that will all effect it. and it will change from day to day. Unfortunatly i have no control of this. all the test so far were done in a 4 hour period and so the weather conditions should be pretty close.

I am using an 18-8 prop.

I do plan on checking the port timming i think i have that in test #11

As far as checking the deck height it really isnt that hard to do it with the calliper.

You got to admit it is pretty interesting that the older cylinder is the better performer. I had a suspicion this would be the case as it does have a higher compression ratio.

I dont know if my muffler is beter breating or not. i have never tried a stock one and the one i have now it the paragon muffler. it has two giant outlets. Some back pressure is desireable in 2 strokes though. it is possible to go to far and reduce performance.

Even with only 370 rpm gain the power output gain is pretty noticeable.

At this point i am inclined to say find an older engine with the single intake runner per side and the higher compression ratio and add a two ring piston to it. the two intake runners per side may be just fine but this cylinder has a much lower compression ratio.

combatpilot

Ya know something that keeps bugging me about this engine is everyone says what a weak rod it has. Has anyone acctually seen one of these rods fail? I dont know why you cant run it like a regular aircraft engine where you only use the full power at take off or when doing a manuver and reduce the power at cruise. Regular aircraft engines wont take or not supposed to have full power applied for long periods either.

av8tor1977

My Feedback: (6)

Yeah, I have heard of a number of them blowing up, but only when pushed well past the recommended static rpms of 7500.

Throttle back? What's that? Well, I use the throttle stick, but many of the flyers I see fly just push that stick all the way up and leave it there.... (My brother is one of them.)

AV8TOR

andrew66

actually one of the guys that taught me to fly told me not to worry too much about throttle. The other guy that taught me stressed it alot. It actually helps alot when flying. I think that people who use the throttle, even if its just a little bit, make better flyers. I usually like the ratchet on my throttle stick to be very loose.
Well, to get more on topic, were supposed to have nice weather (nice for being outside not for flying) so i might get energetic and finish my mount, so i can test my ryobi. Like i said before, i dont have a tach, so wont have any numbers. I just want to see if the engine will run and last with the area between the transfers removed.

combatpilot

I had some more time today so I performed test #6

Test #6 I took the best results of test 1-5 and used a 12.8 mm venturi carburetor that ws purchased on ebay for 15bucks. After making the necassary modifications to the carburetor which pretty much just consisted of swaping stock parts from other carbs to make the configuration that worked best for my application I test ran the engine and had my biggest gain yet.

Recorded RPM 7170 thats a net gain of 500 RPM !!!!!!!!!!!!!!

Ok so far just using the best stock parts from different engines and a 12.8 mm carb venturi from ebay with no special mods other than a thinner base gasket I have acchieved a gross RPM gain of 870 RPM !!!!!!!!

I was a bit dissiponted in the flywheel and crank swap. I was sure this was going to yeid some increase from advanced timming. This just was not the case due to the fact that I am thin king the timming is set within the ignition coil electronics as the coils could not be interchange with the other flywheels.

I am debating weither to do the electronic ignition first or do the backplate mods first. I probably will do the backplate first as i dont have any money to but the ignigtion yet.

It would be nice to see someone follow the same process I am doing to see if they get simmilar results. All in all I think we are starting to see a map of what changes or mods will yield what gains in power.

rangerfredbob

My Feedback: (13)

you can still advance the timing with the stock flywheel, remove the key from the crank and put a little loctite on the taper, that should hold it in place

Racinrc14

My Feedback: (7)

Here is my take on the prop hub issue. All I need now is the Hobbyking CDI unit w/hall pickup and a magnet.

av8tor1977

My Feedback: (6)

Looks great. Did you make it from scratch, or use the old "cut the center out of the flywheel" trick? Can't tell for sure from the pics what I'm looking at. Also, what carb is that with the nice looking finned cover?

AV8TOR

hackinboy

Combatpilot,
After changing to a larger carb in test 6 did you notice a difference in the idle? Each time I've tried to put a larger carb on a stock Ryobi my idle was terrible and the rpm needed to get a smooth idle was way too high to be useable. Interestingly I got about a 500 rpm increase also. thanks for posting your results, i have a slew of Ryobis but not the patience.............mark

combatpilot

Hackinboy I first want to start by saying that pueblo west is an awsome place. I spent many hours at pueblo resivoir. Best bass fishing I have ever seen. I am a colorado native now transplanted in missouri.

Ok now on the idle it does seem a little high. I am using a 12.8 mm carb and most guys on here seem to use the 11 mm carb. Mine may actually be a little to big. I think the reason for this is the fact that when you go with bigger carbs and bigger ports you sacrifice the velocity of the air gas mixture. Sure you can move a lot of air but at a snails pace. With this larger carb I think velocity suffers to the point that at idle the air is moving way to slow all be it is more air. I think a stock reed valve will also affect this as the air is moving way to slow for this set up. I have read that bellmouthing the reed valve port outlet will help. As i understand it if you bellmouth the outlet it decrases the area that the reed valve contacts to seal. the less this area there is the less resistance to flow. I intend to try this along with a thinner reed valve to see if it will improve this. if there is less resistence to flow at this area it should increase the velocity to a more usefull point.

Racinrc thats some mighty fine machine work. Looks real good to me. I would also take a die grinder and remove the mounting lugs on the front of the crank case and get rid if the mounting lugs for the ignition coil as these are no longer needed. I know it may not be that much wieght but it sure looks nice when your done.

I did find a magnet place but they want a 50 mag min order on the size i want. I hate to spend 10 bucks for 1 magnet and end up with 49 more im never gona use.

this seems to be a better place. I think im gona order tonight

http://www.magnet4less.com/index.php?cPath=1_11

Racinrc14

My Feedback: (7)

Looks like C-H ignitions may sell individual magnets.

I machined everything from scratch. I was going to use the flywheel cut-out method, but I think this setup looks way better than anything I could cut off my flywheel. Besides, I didn't have the right dia. pilot to use with the holesaw.

AV8TOR that is the sock small dia. carb that came on my Ryobi weed trimmer. When it was still a trimmer, it idled well, but was seriously lacking in power (compared to my Dad's Poulan). I'm trying to find a chep 11mm or so carb for it. The one on there is a Zama, and the venturi measures just shy of 8mm.

I am hopeful that you can get the idle back where it needs to be with the reed mod. What if we made reeds out of carbon? Motocrossers use these with good results.

combatpilot

Interesting I have never heard of carbon fiber reed valves.

As far as carbs go I found mine on e-bay and it was less than $15 with shipping. you can go to this site and look up the numbers and it will give you a parts exploded view and the venturi size along with some other info

http://web.archive.org/web/200501161...ro/family2.asp

Racinrc14

My Feedback: (7)

Yeah, I used to ride 4-wheelers and I had a Yamaha Banshee. It's a two-stroke twin of 350cc's. Probably the meanest one I ever rode. A company by the name of Boyeson makes aftermarket reeds, cages, and such. I had a set of their carbon reeds on the Banshee. The difference between those reeds and the stock ones was huge, especially with an exhaust upgrade. I may try to find some thin carbon sheet and mill out a reed to see what it does (after I finish the conversion).

combatpilot

that sounds like a great idea. I would be interested to see what you come up with. I was going to try and make a more flexible one out of shim stock that is thinner than the original reed valve.

I am gona order my ignition here in a minute lol

Racinrc14

My Feedback: (7)

OK so the better half gave me the go-ahead and I ordered the ignition. $40.35 shipped for the box and the sensor.

AV8TOR does it matter what type of magnet I use? Like do I really need a rare earth magnet to trigger the pulse switch?

combatpilot

Cool deal mine should cost about the same. Same town different state anyhow lol. I have the same question on the magnet. I think im gona get my magnets from here as i can get small quantites here.

http://www.magnet4less.com/index.php?cPath=1_11

av8tor1977

My Feedback: (6)

Like I said, I often steal mine out of those small, cheap, "give away" screw drivers and they work fine. It is not necessary to have a high dollar magnet, though a better magnet would be smaller, lighter, etc. Don't sweat it, use whatever you can find. www.ch-ignitions.com has them for a buck I think. Doesn't get any easier or cheaper than that....

AV8TOR