I have two blowers with Homelite 25cc. One is just pumping out smoke so I'm taking it apart tomorrow.
I want to put it in a 1/5th scale clipped wing Cub. Maybe some floats too.
I want the electronic ignition. I have access to a lathe (a very accurate lathe! and CNC mill so just about anything I can draw can be made) so I may make my own hub.
I might have to put in a new ring. I've read av8tor talk about a special piston/pin/ring set.
Here are my questions.
Where do I get an electronic ignition. I saw one at my hobby shop today. for about $80? and about $165? for the one with the hub from CH. Are there better deals out there.

Should I get the upgraded rings/piston/pin setup and where are these found.

Should I use the Walbro 10?

What kind of magnet goes in the hub?

Would it be cheaper to buy a new Zenoah EI than upgrade one of these engines? I have a Saito 1.20 but I prefer gas.


Thanks in advance, Tim

http://www.ch-ignitions.com/

Frank Bowman

1211 N Allen Ave. Farmington, N.M. 87401-3568

505-327-0696 Email: [email protected]

Use a Walbro WA-167 or WT-499

THIS is your best bet ignition wise, it has everything you would need other than the prop hub and a battery.

I used pretty much the same thing on my Mac 32cc engine and it runs good, I would suggest making a hub with a taper in the back and a ring with setscrew for the magnet, it makes for an easy to set up system, looks clean too. For these small engines you don't have to make anything too complicated, they seem to hold the prop fine with just a machined surface, no need to knurl (if you have the tools, go for it, never hurts). for a prop hub, the crank threads are 5/16-24 and I would suggest going 5/16-18 for the prop bolt, easier to find bolts and a little more meat in the threads.

the attached picture is of my mac 32 that I converted to EI to give you an idea of what I did, the homie should convert about the same just with more cutting of the crankcase.

just wanted to note that the ignition I linked to above you would want to specify one of the 14mm spark plug units, it doesn't matter if it's taper or gasket seat these are set up to work with either... when I got my ignition I ended up with the 10mm plug and had to make an adapter (an old spark plug, my lathe and a tap made fine work of it)

Most long shaft engines are 3/8"

good call, I haven't taken apart my homie blower yet, or one of my clutched homie's... I do know that the 7/16" threads on that Mac engine seem monsterous in comparison to the 5/16" or 8mm engines...

Some blowers are left hand rotation and present a problem as a model engine

If you study the blower before you take it apart, you can determine this by looking at the pull start

Thanks guys.
Where's a source for Walbro, or should I use the stock carb?

You very much need a larger carb in the 11mm range.

Look on the internet for them?

You need both low speed and high speed mixture screws for airplane use

Thanks, where do you get them?

I've bought four carbs from these guys but there are many other places to get them. http://www.outdoordistributors.com/

http://www.davesmotors.com/s.nl/c.88...t.A/id.4131/.f

Ok, I've read about the numbering system and I think it's a WT carb. But what is a Walbro 32 and what about the HDA HD carbs?
Thanks, Tim

The little number cast into the venturi? A 32 would be a carb with a 1/2" diameter venturi

You need to look for a Walbro carb with a "27" or "28" in the venturi for a Homelite 25. it could be a WA or WT carb

The HD and HDA carbs are bigger engines

Ok, how do you know if you need a 433, 499, 755, or what ever? Is there a chart somewhere that lists venturi sizes with the model numbers?
Why aren't there stickys in this forum with that info? You guys are a WEALTH of knowledge. My flying buddies were over last night and we're all clueless (and that's saying something for these guys who build UAV's and have been in the hobby a long time).

Thanks, Tim

http://www.prestwich.ndirect.co.uk/walbrocarbs.htm

Here's the plane I'm wanting to put it in. I may have to move the servos to the back.

Here's some photos of a Ryobi I found. I think av8tor was saying this Ryobi isn't the most powerful of the 31 cc engines, maybe someone can say if it is or isn't (because of the bar in the exhaust?). The trimmer that it's on runs poorly and smokes a lot. Do you think the rings are bad? Here's some photos of the cylinder wall too.
The Homelite 25cc engines I have might be better for this size plane. One of those starts fine, acts like it needs a carb rebuild, and the other one smokes like a train. I'll try to get some photos of the one I choose this weekend.

I noticed my Homelites have a metal plate on the front of the engine. Can this be milled off? At least the exhaust on them are on the side and not the back like the Ryobi.

Yes

I did a couple and I sawed them off on a big band saw and finished up with a big half round file rasp

if you are using electronic ignition the whole plate can come off, it doesn't take long with a hack saw, the trick is to make a couple cuts down the side and just break off big pieces with pliers. I wouldn't go all out removing aluminum as all of that on the front is probably 2-3 ounces tops.