Racinrc14

My Feedback: (7)

AV8TOR, I read that thread some time ago and figured I was okay since I have a large crankcase engine with the long shaft. How did you go about checking the balance? I'm not intimidated by adding or subtracting weight, I just don't have a good plan on where to start. I suppose I could weigh the piston assembly, and somehow isolate the counterweight and weigh it, they should be the same yes?

av8tor1977

My Feedback: (6)

I just forwarded an e-mail to you with balancing instructions. On the post I referred you to, if your crank looks like the crank on the right hand side in the picture of cranks and crankcases, it probably is ok. If it looks like the one on the left hand side, it would need to run with a matching flywheel that is balanced for that crank.

Anyway, I checked the balance on my Ryobi using the method I just e-mailed you, and it came out perfect without modifications and the engine runs very smooth. Any two stroke will shake on a rich idle when it is four-stroking, but what you described seems much more than just that.

AV8TOR

Racinrc14

My Feedback: (7)

Thanks a ton. My crank and crankcase are as pictured on the right. I also posted pics of what I have on Combats' Ryobi mod thread.

av8tor1977

My Feedback: (6)

Ok, then maybe your balance is ok, but it wouldn't hurt to check. The other possibility is that your mounting was a bit loose to begin with. A loose or weak mounting can exacerbate vibration.

Check the engine and prop balance, bolt her up tight, and try again.

AV8TOR

Racinrc14

My Feedback: (7)

Thanks AV8TOR, that was very helpful. I didn't find anything out of balance, but it was a good idea to check it out anyway. I did find that I hadn't balanced my prop accurately the first time, so I rebalanced it and all should be better now. As soon as I get the new backplate gasket the testing will continue.

av8tor1977

My Feedback: (6)

I make almost all my gaskets. I use the covers from spiral notebooks, beer cartons, file folders, etc. Doesn't take long to make them with an sharp exacto knife. I finally bought a set of gasket hole punches from Harbor Freight and that makes it super easy to make gaskets.

AV8TOR

Racinrc14

My Feedback: (7)

Hmm, I'll try that next time, since the silly backplate gasket is over $6. We just happen to have a harbor freight here in town.....

combatpilot

$6 for a backplate gasket? man there a rip off I was getting them fere for under 2 dollars and i think its closer to one but i cant remeber.

Racinrc14

My Feedback: (7)

7150RPM !!!!!!! Just got done running it, and it finally runs really good, except for an annoying severe vibration at around 6000rpm. The Walbro carb did the trick. So, here is my current setup:

Big Crankcase, non-recessed reed mount, two-ring piston with stock rings (very small end gap), pressed connecting rod without the reinforcing flanges (connecting rod originally attache to old sigle ring piston, used for balance purposes), gutted muffler, Walbro Wt-312 carb (9.5mm), Master Airscrew 18-8 Classic, electronic ignition set at 28'.

I'm going to further investigate the internal balance issue, because the vibration is pretty severe until the motor goes either above or below around 6000rpm. And the MA prop was pretty heavy on one side of the hub, so it took drilling some holes on the backside of the hub to get the prop to balance. But I think she'll run decent enough for my Midwest G-202.

Racinrc14

My Feedback: (7)

Forgot to mention that the jug is an older one, with the wide, single transfer ports that have not been modified and no 'decompression' slits. I'll measure the timing and include that info. in a little bit.

Racinrc14

My Feedback: (7)

Measured the timing and it seems to be around 135'-140', perhaps I'll do a little grinding to get the timing to 150 or so.

captinjohn

This G38 Zenoah made my Midwst 202 weigh to much. I got to put a real lite engine on it that still has good power. What all up weight do you think you will end up with on your Midwest Giles 202? Thanks Capt,n

combatpilot

Hey racin did you ever figure out the prop with the zama carb? if so what was it. I did see you changed to the walbro and it ran like it should right? I wonder what the difference is.

Racinrc14

My Feedback: (7)

I never got the Zama to run right. It would ALWAYS richen the mixture (as evidenced by the 'four stroking' and the increase in exhaust smoke) above around 5200 or so. I even put a light prop on it to see if I could in fact get the rpm over 5500 (APC 18-6) and no deal. I believe that particular Zama carb is built that way to provide a safety cusion to prevent over-zealous homeowners from over-revving their weedie when the line runs out. Just my thought. And I still can't figure out how exactly it does it. And I don't care, frankly, since it runs good with the Walbro. It has about a half gallon run through it now, and last I checked, MA 18-8 Classic 7200rpm.

Sorry Captin, somehow I missed your post. I am aiming for a rtf weight under 13lbs. I am under no delusions that this Ryobi will be the powerplant for it. I may be in the market for an OS 1.60 or similar. I'm going to continue working with the Ryobi, though.

Racinrc14

My Feedback: (7)

By the way, it still vibrates like a madman at around 6000. I have balanced the prop, tried other props, balanced the recip. assembly several times as per several other posts, balanced the prop hub, even checked the balance on the prop washer, and still it vibrates. I'm afraid to put it in a plane for fear of foaming up the gas or worse, shaking the radio apart. I had to heli-coil the backplate mounting holes because the dam thing vibrated the bolts loose and bunged up the threads. Seems a little better mounted on a wood bench, as opposed to the steel plate and vice like in the video.

Hmmm, after proof reading the above info., seems like I should probably measure the crank runout to make sure it isn't bent. I'll get to that at a later date. I had ACL reconstruction on my right knee 2 weeks ago, so getting around is a bit painful right now.

Racinrc14

My Feedback: (7)

Finally got the Giles done and it weighs 10lbs 3oz. I did not put the Ryobi on it and installed a Saito 1.80 instead (got a very good deal on it). Haven't fown it yet, but as soon as it warms up a bit.

I gave up on My Ryobi. It seemed to run okay, but the vibration threatened to shake apart my 10 months of love and care.

AA5BY

Tommy, I've been following the thread and agree that sometimes it's best to listen to the wiser inner self and avoid what we sense might be destructive. I say that from a little bit similar situation with a Ryobi but no doubt different. On the bench, mine had a serious vibration only when down throttling too fast. I'd not unhooked the spring from the throttle yet and if I let it snap to low throttle, it shook terrible... far too much to consider putting it on a plane. If throttled back at a reasonable duration as a servo would, it however seemed fine but just knowing that the motor was capable of such vibration has kept me from using it.