31CC weed whacker project
12-01-2004, 07:53 AM
#1
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31CC weed whacker project
Hello all,
I have a 31cc weed whacker project sitting out in the garage that I was thinking about putting in an airframe.
I read an article a year back about a modification that should be performed to the carburetor & was wondering if this is necessary.
The article has you soldiering a brass tube to the fuel pump diaphragm cover weep hole & routing it to the carburetor venturi.
The logic is to keep equal pressure at the fuel pump diaphragm, is this necessary?
I also noticed that some people install HEI ignition systems on these engines, is there a substantial weight savings with this ignition system/performance gain?
What other modifications should be performed to make this motor airworthy?
What size fuel tank should be used?
I have a 31cc weed whacker project sitting out in the garage that I was thinking about putting in an airframe.
I read an article a year back about a modification that should be performed to the carburetor & was wondering if this is necessary.
The article has you soldiering a brass tube to the fuel pump diaphragm cover weep hole & routing it to the carburetor venturi.
The logic is to keep equal pressure at the fuel pump diaphragm, is this necessary?
I also noticed that some people install HEI ignition systems on these engines, is there a substantial weight savings with this ignition system/performance gain?
What other modifications should be performed to make this motor airworthy?
What size fuel tank should be used?
12-01-2004, 03:34 PM
#2
My Feedback: (13)
RE: 31CC weed whacker project
Just trying to be helpful...
Did you know there is an ENTIRE forum here at RCU dedicated to conversion gas engines? It can be found here: http://www.rcuniverse.com/forum/Engi...umid_92/tt.htm
Those guys are the grass roots finatics of WW conversions in this hobby. If it's been done anywhere, it's almost assuredly been discussed and re-discussed in that forum.
Did you know there is an ENTIRE forum here at RCU dedicated to conversion gas engines? It can be found here: http://www.rcuniverse.com/forum/Engi...umid_92/tt.htm
Those guys are the grass roots finatics of WW conversions in this hobby. If it's been done anywhere, it's almost assuredly been discussed and re-discussed in that forum.
12-01-2004, 05:09 PM
#3
My Feedback: (13)
RE: 31CC weed whacker project
Wonderful... some moderator moved the post here (appropriately, albeit) and didn't even bother to leave the redirect in the original forum in which it was posted. (sigh)
Maybe this guy posesses the rare trait on this board being the ability to do a "search" and find it. If he knows how, he's a rare bird on this forum. He'll probably just assume it was deleted and repost it again where it was.
Maybe this guy posesses the rare trait on this board being the ability to do a "search" and find it. If he knows how, he's a rare bird on this forum. He'll probably just assume it was deleted and repost it again where it was.
12-02-2004, 07:33 AM
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RE: 31CC weed whacker project
One of the moderators posted an e-mail informing me that it had been moved.
(sorry about the placement location, did not know about this forum subject)
All is well, but I am still looking for some good information concerning my 31cc conversion
Take care & enjoy the holidays
HO-229
(sorry about the placement location, did not know about this forum subject)
All is well, but I am still looking for some good information concerning my 31cc conversion
Take care & enjoy the holidays
HO-229
12-02-2004, 08:32 AM
#6
My Feedback: (2)
RE: 31CC weed whacker project
HO-229,
Now that you're here, I'll tell you what my experience has been. No, I dont have any problems with pressure differentials. I think that mod is unnecessary. Mine runs fine pretty much stock using Jag parts. I'm doing 2 more conversions right now and will use a larger bore carb from wacker engines. My stock ryobi flies a 14lb plane (82"ws) with pretty good sport performance. Not unlimited verticle but fun flying none the less. I use zinger 18x8 props and get about 6700 rpm on a tired old wornout engine thats been run hard for about 5 years. All of my ryobis have been given to me for free and almost all of them so far have only needed the carb diaphram to fix it. You really cant beat it.
Edwin
Now that you're here, I'll tell you what my experience has been. No, I dont have any problems with pressure differentials. I think that mod is unnecessary. Mine runs fine pretty much stock using Jag parts. I'm doing 2 more conversions right now and will use a larger bore carb from wacker engines. My stock ryobi flies a 14lb plane (82"ws) with pretty good sport performance. Not unlimited verticle but fun flying none the less. I use zinger 18x8 props and get about 6700 rpm on a tired old wornout engine thats been run hard for about 5 years. All of my ryobis have been given to me for free and almost all of them so far have only needed the carb diaphram to fix it. You really cant beat it.
Edwin
12-02-2004, 09:04 AM
#7
RE: 31CC weed whacker project
I had a Homelite that I had to do this mod on because on it's particular carb, the hole faced forward and was being pressurized by the airstream and causing the engine to lean out in flight. (On this one I was unable to just rotate the cover to a new position.) In other cases with cowls, it is sometimes necessary to add a tube and a hose running into the fuselage to sense static air because the air is pressurized in the cowling. (Note that this is not a "weep" hole; it is a air pressure sensing hole for the regulator.)
An uncowled Ryobi would not likely need this mod, as the carb is in the back and not in the airstream.
Good luck,
AV8TOR
An uncowled Ryobi would not likely need this mod, as the carb is in the back and not in the airstream.
Good luck,
AV8TOR
12-02-2004, 09:30 AM
#8
My Feedback: (2)
RE: 31CC weed whacker project
Thats one thing I forgot to mention. Mine is cowled and I did have a big difference with the cowl on verses off. I solved it by drilling carb adjustment holes in the cowl and adjusting the carb with the cowl on. Since then, no problems. I also run a 28:1 oil mix, (klotz). For some lame reason I started my oil mixes at 50:1 and had overheating problems. A mechanic buddy recomended more oil and thats what utimately solved most of my problems. It would run uncowled, but not cowled. I am amazed at how much punishment a ryobi can take and still run. I know I did some damage to it but it starts pretty good and runs reliably thru the entire flight. I set my flight timer for 15 minutes cause I dont want to stand around any longer than that and use about half a 16oz tank. Will definately use a smaller tank next time. There IS one issue that I havent figured out yet. I have to raise the tail of the plane level with the ground to choke the engine. Lower the tail and then it starts. If I dont do that, it wont choke. Hope I dont have that problem on the next ones.
Edwin
Edwin
