nextofkin

My Feedback: (8)

How do you tell the cc of the Homelite blower engine without taking it apart?
I know it comes in 25cc and 30cc but witch one?
model number 08017G
seral # HSZ961627
BP-250
Thanks
nextofkin

w8ye

My Feedback: (16)

I would think that one is a 25

av8tor1977

My Feedback: (6)

I have found some of the so called 25cc blowers to actually have 30cc engines in them. It only takes a minute.... unbolt the muffler and look inside. If it has a vertical bridge in the exhaust port it is a 25cc. No bridge = 30cc.

AV8TOR

Lnewqban

The BP250 Backpack Blower UT-08017-G can have either engine, 25 cc or 30 cc.

The differences in diameter and piston trajectory is around 2 mm; hence, it is difficult to measure.
You could try measuring the piston trajectory with a pencil inserted thru the plug hole; ~32 mm will correspond to the smaller engine, while the big one will read ~34 mm.

Guessing that the compression rate is around 1 to 9, the combustion chamber of the 25 cc (with the piston located at the top dead center) would take ~2.7 cc of oil (filling it up to the bottom of the plug hole).
The 30 cc would admit ~3.3 cc of oil in the combustion chamber.
(Flip the engine and empty the oil after the test).

Just a couple of suggestions on tests for rough estimates.

av8tor1977

My Feedback: (6)

Well, on the Homeys, I think the bridge in the exhaust port is a lot easier to verify....

If you want to know the diameter of the piston, just stick a wooden dowel with a rounded end into the exhaust port, carefully trying to hit the middle of the cylinder on the opposite side. Then rotate the engine until the piston puts a crimp mark in the dowel by pushing it up against the top of the exhaust port. Then measure from the end of the dowel to the crimp mark.

I measure the stroke with a calipers stuck down through the spark plug hole.

(Bore x bore) x stroke x .7854 = cubic inches, assuming you measured in inches. Divide by .061 to get cc.

You can practice this method on an engine with a known capacity. When I do it, I usually get within one cc of the actual engine size.

AV8TOR

nextofkin

My Feedback: (8)

Thanks for your response, av8tor1977 it did not have a bridge in exhaust port so I dissemble it to cut the extra metal off checked cc and it was a 30cc thanks, it runs good with stock carb. (not a warbo) is there a better carb, and would this engine fly a Great Planes Giant Big Stik with plenty of power like it should and not like a cub I know thay recomend a 25cc to 35cc engine but thay are talking about airplane only engines not conversions.
nextofkin

w8ye

My Feedback: (16)

The best carb on that engine is a Walbro WA-167

Nosedragger

the cr is much lower

Lnewqban

Good to know.

Coincidentally, a friend just gave me an old 25cc Homelite blower that he didn't want anymore.

A couple of general questions:

Are engine conversions something of the past with the newer more powerful airplane gas engines?

If so, I may try to use this Homelite in a bi-plane?

Does anybody knows what size/weight Waco YMF biplane could this baby handle?

Thanks

av8tor1977

My Feedback: (6)

While it is true the weight and power of the newer commercial gasoline airplane engine offerings are very good, and the prices aren't too bad, I continue with the conversions myself. If an airplane flies great and you are happy with it, why bother spending the extra money for just a little bit more performance?

Most of my airplanes will climb vertically out of sight, and cruise around happily at 1/2 throttle or less. Do I need more? Not for my money. Besides, conversions are fun and it is really cool to see the look on people's faces when you tell them the engine came out of a weedeater, leaf blower, chainsaw, etc., and cost you only 10 bucks or whatever.

The Homelites work fine, and I have had many, many happy flights with them. However, the Echo and Stihl engines, while a bit harder to find are much lighter and more powerful. My Echo and Stihl engines are only slightly heavier than the latest gas engine commercial offerings, and the power is fairly close once I've got them hopped up.

As far as weight goes, here's a good example. My 76" wingspan Tiger Moth biplane has a Ryobi 31cc on it, which is known as a heavy engine. The power is more than adequate and I rarely use full throttle. The airplane needed virtually no lead ballast to get the c.g. spot on. So why would I pay all the extra money to buy a lighter commercial engine, and then have to add lead weight to the front of the plane???

AV8TOR

Lnewqban

Thanks, Av8tor.

The extra weight and the relatively low deliverable power are the reasons that made me think of using this engine in a scale Golden Age bi-plane that I have always wanted to build.

What modifications will the engine need to have done to suit this application?

Conversions and giant scale models have never been attempted by me before.

av8tor1977

My Feedback: (6)

The Homelite 25cc is no dog really. It can be modified to turn a 16 x 8 prop at 8700 plus rpms.

I have made a lot of posts about Homelites over the years. You might find "Non machine shop Homelite" interesting, among others. Just do a search for my posts here in the forum.

Here's one: http://www.rcuniverse.com/forum/m_26...tm.htm#2621860

Have fun with it.
AV8TOR

Lnewqban

Thank you very much, Av8tor!!

av8tor1977

My Feedback: (6)

AV8TOR