Hi all,
I recently bought from ebay this Homelite 30cc conversion, and I’d like to upgrade it. This is the first one for me, so I’ll gladly accept any feedback and advice to help me in the process to learn how to do these things.
Here's the little noise-maker:
I’ve spent several hours searching this forum but despite being a rather common engine, I’ve not seen any clear ideas, numbers or how-to about how to hop up the engine. Well, I got to find some numbers and mods made to a Homie 30 by the modeller AV8TOR.
I’m not looking for radical mods; in fact, all I’ve thought of are even reversible, so if I mess things I can still go a step back. I’ll do a small review of it as well as exposing my doubts and ideas.
The engine is, to my understanding, completely stock. The conversion consists of a machined flywheel, prop hub, mount and home-made muffler (and a painted engine block, if you call that a conversion).
The prop hub, as you see it, is simple and functional, as well as the mount. To bolt the engine to the plane I will just drill four M4 holes on that mount and screw them to the firewall. I first thought of silent blocks, but after reading about them I rejected the idea. It came with a primer bulb, but doesn't seem to belong to this carb. Maybe it's useful to put it anyways to prime the engine, but at least in this carb, I have a choke so it's not that critical.
The exhaust is custom made out of an aluminium box and a machined aluminium tube which is screwed in place. It looks weak, because the thread section in both box and tube are thin and will likely get damaged in the event of a relatively soft hit (i. e. while moving the plane around). There’s a screw in the box; I guess it’s there just to seal a hole the box had from origin, but maybe comes handy if I try to make a smoke system. Now, if the muffler will just make more noise than the stock one or really help moving the gases out, I’ll know when I tach it. I have a 20x8 MA prop, so from what I've read I'll better use a 18x8 or 19x8.
A couple of things I just don’t like are the exhaust hole, which has been poorly made (as clearly seen in the pic - I hope it wont’ affect the engine), as well as the carton gasket. Also, the metal piece from the stock muffler which is still used to bolt the muffler. I haven’t tried yet, but it looks like the screws were too long so that metal piece acts like a spacer (the same happens in the carb).
This pic shows the exhaust port. The original gasket is still there, I’m not sure if I should try to remove or leave it there. But that’s not why I put the pic. When I was turning the engine by hand, I heard a whistling sound. I looked carefully and I saw, right above the exhaust port, a hole. A hole!!! That must be to relief compression, but that’s exactly the opposite I need! How can that be solved? Is it a good idea to tap the hole and put a screw? At least I wouldn’t be wasting that much compression…
The piston has two rings. I could change them in the future (Frank Bowman rings comes to my mind), I don’t know how much wear they have but they don’t look bad. I haven’t opened the engine, but what can be seen on the cylinder walls are very fine horizontal grooves and 1 or 2 fine vertical grooves; the piston looks clean, but also has some very subtle vertical grooves. I guess those few small scratches are the least I could expect from a used engine.
So, I’ve thought to change the usual things:
- Bigger carb. It seems to be one of the easiest and cheaper ways of getting more out of a stock engine. Now it has a Walbro carb with a “22” cast on it (in one of those 4 mould holes). I’m not sure what size or carb id should I look at (WA-167 it's the only reference I've seen). I want more power, but I also want an agile engine, if it transitions slowly or lags a lot due to excess air/fuel, it’s not any good. I will also need a big bore plastic adaptor. I read Carrprecision carried those two items, is that right?
Anyways, if a fellow model has a spare carb and/or adapter I could use and is kind enough to make me an offer for it, I’ll gladly look at it.
- Stuffed backplate. I don’t know how I’m going to do it, but if it’s possible with my means I’ll do it, leaving a good clearance with the piston assembly.
- Electronic ignition. There’s a CDI project here in this forum I found a while ago which looks really good, so it’s another possible mod I make. In that case, I’ll mill the front end of the engine.
- Velocity stack. If I get bored one day and want to try things… then I’ll machine one.
Maybe if there’s a good explanation available I’ll try more difficult stuff on it…
So that's all, I hope it didn't get too long.
I'm open to all kind of ideas and suggestions to make this device make bit more noise and wind!
PS: I've tried to put some thumbnails, but I can't get to either do that right or hotlink the big pics. The best I got was if I put "" at the beggining, still don't know why. If someone knows how, I'll change it.