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Dynaflite Decathlon/Ryobi 31cc conversion combo?

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Old 10-21-2003, 05:41 PM
  #1
zipnsplat
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Default Dynaflite Decathlon/Ryobi 31cc conversion combo?

Hey guys, I've been doing a lot of research on converting engines and wanted to know if there was anyone out there flying the decathlon with the Ryobi 31cc conversion? plane with engine should be around 17-18lbs. Will this be enough to "have fun with"? Obviously I won't be doing 3d, but want enough power to do stuff other than fly in circles. If the Ryobi won't be enough oomph, then what would you guys reccomend? I'm on a bit of a budget, so cost will play a roll.... I know, I know.... why am I even in this hobby if I have a budget!? isn't that an oxymoron? Thanks for your input.

-Zip
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Old 10-21-2003, 07:06 PM
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Default RE: Dynaflite Decathlon/Ryobi 31cc conversion combo?

I've got a ryobi 31cc jag conversion that I was going to use in a bud nosen citabria. The plane is similar in size, the wingspan is a little longer, than the dynaflite decathlon. Alot will depend on the final weight but this engine should fly the plane scale like. I'd try to keep the airframe as light as possible. I'll probably go with an 16-8 or 18-8 prop with the ryobi. If I was going to spend more money on an engine I'd probably go with the rcs 1.8 or zdz 40B. A zenoah g23 / g26 would also work or even a 3w 24. I chose the ryobi because I had an old string trimmer laying around (BTW ryobi trimmers are junk..I'd only buy another one for the engine) and thought it would make an interesting conversion project. I have yet to get my engine started, I tried starting it by hand and had no luck. I've been told that they will start easily with an electric starter. I thought about converting it to electronic ignition but can't justify the added expense
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Old 10-21-2003, 09:52 PM
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Default RE: Dynaflite Decathlon/Ryobi 31cc conversion combo?

Contact Scott Baldridge at scottbaldridgeconversion.com. He's been converting Ryobi 31cc engines, and has a lot of stats. I'm currently flying one of his 42cc Poulan conversions, and it's awsome.
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Old 10-21-2003, 09:53 PM
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Default RE: Dynaflite Decathlon/Ryobi 31cc conversion combo?

I had the ryobi in the dynaflite fly baby and it was a perfect setup at 13 lbs. I would say go for the poulan 46cc or homelite 45cc.My poulan with magneto ign. and h9 aluminum mounts come out to 4 lbs and the ryobi is just shy of that by 8 oz so for 8 oz. go with the poulan.

Darin
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Old 10-21-2003, 11:21 PM
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Default RE: Dynaflite Decathlon/Ryobi 31cc conversion combo?

You can do a lot to make a Ryobi run better.

I just finished one. I put a CH synchro-spark ignition on it. Total overkill, but they gave me a deal on a used ignition system.

Order a new piston ring from Frank Bowman. It's a lot better than the stock ring.

Take the cylinder off the case and dremel the intake ports a little just to smooth them up. Don't remove alot of material. You just want to smooth the radius' a little to help with fuel transfer.

On the backplate; bend the reed valve stop out as much as you can get it without letting it hit the crank. This will let a lot more gas in.

Get a bigger carb. I've got a McCulloch chainsaw carb on mine. It's a Walbro WT348. It's a perfect fit. Bolts right up. And it's a lot bigger than the stock carb without being TOO big.

Lighten it up. Machine off the mounting lugs where the coil used to bolt up. There are 3 other bolt boss' on the front of the engine. Cut 'em off.

If your still in doubt about the performance on the Ryobi--check my add in the Giant engines forum. I've got a nice Craftsman 38cc conversion engine for sale. It's got a Frank Bowman ring and an electronic ignition.
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Old 10-22-2003, 11:29 AM
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Default RE: Dynaflite Decathlon/Ryobi 31cc conversion combo?

Thanks for all the replies.

Rcpilet, your engine looks nice. Too bad I don't have the funds right now or I would buy it. Interested in any trades? I ordered the Ryobi 31cc from harborfreight for $49.99 last night. With your tips, I think I will be able to get this engine running pretty good.

-Zip
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Old 10-22-2003, 01:47 PM
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Default RE: Dynaflite Decathlon/Ryobi 31cc conversion combo?

Quote:
ORIGINAL: zipnsplat

Thanks for all the replies.

Rcpilet, your engine looks nice. Too bad I don't have the funds right now or I would buy it. Interested in any trades? I ordered the Ryobi 31cc from harborfreight for $49.99 last night. With your tips, I think I will be able to get this engine running pretty good.

-Zip
With a Brand New engine-- I think you will be fine. I'd get a Frank Bowman ring right away. Don't even bother with the stock ring. The stock ring has a rounded side to it. It has very little surface contact with the cylinder. This makes the engine break-in fast, but allows for a lot of compression blow-by. Franks' ring is more straight sided, and has very little ring gap. It's a nice fit and will help performance a lot. Frank can send you a ring for around 12--$15. It's easy to replace the ring.

Go to some of the local small engine repair shops and try to get a bigger crab. I know the Walbro WT348 is a drop in replacement for the stock carb-- only bigger. There are probably several carbs that will bolt up. Just make sure they have the pulse hole in the same spot- so it lines up on the intake port when you bolt it to the backplate.

Small engine repair shops and lawnmower shops are a great source for parts. I'd count on spending $15 for a carb rebuild kit if you decide to buy a used carb for it.

As for the trade of my 38cc engine------I would trade it for almost new JR coreless or Digital servos(8101--4131--4721--8231--8411). Not interested in Hitecs or anything else- just JR servos.
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Old 10-23-2003, 11:00 AM
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Default RE: Dynaflite Decathlon/Ryobi 31cc conversion combo?

I also have too much money into my Ryobi. I've had it for 3 years, and can't stop tinkering with it. I've got one of the models without the compression relief slits in the cylinder wall, and I recently swapped in a newer 2 ring piston. I would be suprised if any new ryobi's still come with the single ring piston...
Currently, it has C&H ignition with syncro spark, a free-breathing after market exhaust, and I just swapped on a larger bore carb as well. I picked up one from Ebay whose bore matches the transfer passage in the backlplate. It's a Walbro WT-433 with a 5/8" bore and 11.1 venturi. As noted above, I opened up the reed valve. Current RPM's are 7550 with a 18x8 APC wide prop. This engine just gets better and better. I'm trying to locate a Menz 20x8 but haven't had any luck finding a source.....
You guys who wanted to see a hovering Ryobi might just get your wish!
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Old 10-23-2003, 06:08 PM
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Default RE: Dynaflite Decathlon/Ryobi 31cc conversion combo?

Wow! 7550 with an 18X8. That's pretty good. I plan on upgrading mine bit my bit too. It will be neat to see the upgrade in performance after each mod. I don't know why, but i've gotten hooked on rc conversions. There's just something about them that excites me. In the long run, you end up paying the same amount, if not more than a "r/c" engine, but you have to drop one lump sum, where with conversions, you can do it a little at a time. I think that the Ryobi will be just fine for my decathlon.

-Zip
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Old 12-01-2003, 08:57 PM
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Default RE: Dynaflite Decathlon/<span class=

how do get this ring from frank bowmen
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Old 12-02-2003, 12:33 PM
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Default RE: Dynaflite Decathlon/<span class=

I too am in need of a set of rings for my Ryobi. I've emailed him twice with no response. Does anyone know if he still makes these?

-Zip
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Old 12-02-2003, 01:26 PM
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Default RE: Dynaflite Decathlon/<span class=

Frank Bowman is still in business. Sometimes it takes a few days for Frank to answer his emails. At least that has been my experience.
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Old 12-02-2003, 07:07 PM
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Default RE: Dynaflite Decathlon/<span class=

Emailed him several weeks ago. But, I'll try again and see if I can get a response.
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