Hi there gents, can anyone help, I have a brand new homelite 25cc which I have converted and installed on an 81" span model it has a 16x8 prop fitted but just doesn't seem to be giving enough power, I haven't been able to check the RPM, do I need to put a pipe on the breather, are there any things I can check or change to get more power, I have a home made silencer fited which seems to work well (is there a set size I should work to ?) any info would be greatly appreciated. Thanks, Joe

Joe i havent had a chance to work on the homelite engines yet. I have a pretty extensive thread on the ryobi 31 cc engines. http://www.rcuniverse.com/forum/m_8479610/tm.htm

Some of the information on there may not apply to your engine but much of it will as we found the most important factors in making more power on a stock unmodified engine anyhow are.

#1 Get the best ring to cylinder seal you can possibly get. measure your ring gap and see what it is. a frank bowman ring may be a very good investment. the best way to tell what your cylinder seal is is with a leakdown testor. If your cylinder has large scores its gona have a poor seal no matter what you put in it. see all the info i put in the thread on leakdown testing. anyhow ring seal is very important.

#2 upping your compresion ratio by decreasing or removing your base cylinder gasket. be very carefull not to get piston to head interferance. there are methods for checking this on the ryobi motors that will work for yours to.

#3 fitting a carburetor that has a larger venturi size. the stock carbs are so puny.

#4 A good free flowing muffler. to large a opening dosent seem to make a problem at least on the ryobis.

#5 check your exhaust port timming. some guys got good results increasing there port timming to 150 degrees. this is all explained on the thread. I didnt have any usefull affect from this mod but i was working on a different cylinder than the other guys were. they say they did and i belive them as there test data proves it. I have my suspicions as to why mine made no diff but i havent had time to prove it out.

Anyhow all of this is pretty easy to do and dosent require any great special modifications. you can make your own leakdown tester for pretty cheap. under 20 bucks i would say or maybee less depending on your ability to scrounge parts.

You really need to get a tach so you can do a before and after analisys to see what worked and what didnt and by how much.

keep us updated on your progress and please lots of pics.

The stock Homelite doesn't like going more than 7000.

Use a 16-10 prop on a completely stock Homelite 25

Makes 8.68 pounds of static thrust and 57 mph

I have been running a converted 25cc Homelite on a Balsa USA Phaeton 90 biplane for 9 years. The engine is not a powerhouse, but it is reliable. 16" props don't work all that well, as the rpms aren't there to develope the thrust. a 16" prop needs to turn at 8000 or better, and that is about the most optimistic you can sometimes get out of the Homie. I have had best results with an ASP 17X8N (narrow) prop. The ASP 18X8N also works well, but it is so butt ugly, I can't stand looking at it, so I went to the 17" prop. Much better!

You didn't say what plane you have, but 81" WS is pretty large (unless it is a Telemaster, or such).

Here's some Homelite 25cc info:

http://www.rcuniverse.com/forum/m_26...tm.htm#5736440

Post number one.

Also, I agree; if your 81" span model is aerobatic, the 25cc is too small. An airplane of that size would normally use a 30+ to 50cc engine depending on its use.

AV8TOR

Thanks for the comments guys, I probably already knew I was attempting to power too big a model but did not want to admit it cos this is my first conversion, I think I will have to convert another engine as it is easier than building another model, Thank you all for your comments as always of great help, Cheers guys, Joe

Joe,

I'd verify the operation on the EOM muffler.

Also, you state the engine is brand new. Aside from potentinally being underpowered for the size aircraft and duty, is it possible it is not yet broken in?

Jack

Heres a few engines that would be easy to convert,parts are availible,and they would power a model your size.
Echo-CS4400chainsawsame thing as BME-44
EchoPB450Blower motor-45cc-im doing one now.
Poulan 46-chainsaw
Homelit 33ccchainsawsmaller but would be doable.-not much for 3-D
Homelite 45ccchainsaw
Im going to send ya a PM also.

I ran a 18-8 prop on a Homelite 25 but the engine had a larger 11mm carb

I have a stock except for larger carb Homelite 30 on a Bridi Stick and it has all kinds of power for this plane.
http://www.bridiairplanes.com/hangar/bridistick.html

I Like the look of that model, I may just look up the cost of having one shipped over to the UK, keep it coming guys this is great info, Thanks, Joe