I just got my hands on a bunch of weedwhacker engines, most of which are Homies, but there are no marks on the casing that I can find. Is there an easy way to tell what size the engine is?

Two of the engines I got have electric start modules on them and more than that they also have a compression release to allow the engine to spin faster when starting. Neat!
Anyone out there know anything about these engines, for example, their size? They are both Homelite engines but I can't find any information on them.

Here are four of the engines I've torn out of the shell so far. The one on the left is one of the electric start models. All of them need some work but I've got nothing but time to piddle around with them.
I also have four stock Homey mufflers at a dang good price if someone wants them.

....they also have a compression release to allow the engine to spin faster .....
Got any pics of this C release? I'm new to this but it is the first I've heard of CRs.
stick a caliper in the plug hole, measure the stroke(s), pull the heads and measure the bore.
WAG pi radius square x stoke = displacement.

Your WAG is correct. That is the way to calculate displacement.

As far as the compression release, it is a really simple mechanism on the side of the head that is operated when the start button is pushed. Small diameter rod with 1/4" head on it and a spring to keep it closed. I'll try to get some close ups of it and post them.

I thought it was interesting.

JimRoss

Here is a picture of the CR. I was wrong, it is operated by the throttle, Hmmmmmm! Would make going to full throttle somewhat of a problem.

This one is even closer.

:Looks like a coffee table in the background..How did you get your wife to let you put those smelly gas engines in the house ?

Heh Heh, she wasn't home and I spread stuff all over the living room. After all, a fella has to have some place to work while his shop is being finished. I ain't working otuside in the heat.

Ok, let's have some help here.......

I don't have an inside mic so I had to measure the piston diameter and it came out 35 mm. Stroke is real dang close to
28 mm. So, doing the math I come out with 26.9 cc displacement.
pi r squared stroke
^ ^ ^
3.1416 X 17.5 X 17.5 X 28 = 26939.16 cubic millimeters/ 1000=
26.9 cubic centimeters.

Y'all ever seen a 27 cc engine? Or would it be a 25 cc engine?
What's 2 cc among friends unless it's in a syringe?

My measurements could be off slightly, I'm old and my reading glasses don't have long enough arms any more.

Keep us advised on that Compression Release as you continue your disassembly. Got my curiousity up!

well... just from looking at those 4 engines you posted, they look like plain ol 25cc homelites. Never seen a CR on them before though. Here is a shot of some I did once. You can cut most of that aluminum off of the crank.

I just took the head off last night to measure the piston and it looks like just above the intake port there is a small hole that the CR is mounted in. It is above the intake port so there is no doubt as to its function. Shot this pic and I hope it shows up.

Agree with the 25cc. Have one on a new to me blower and it is mark 25cc and a family grp #.
What was attached to this CP on the outside? How do you figure it is activated?
The blower appears to have a hose attached in that area, figured it was just an emissions requirement on newer models.

The only thing attached on the outside is a small cap like head. It is actuated by the throttle going to full position. During Start, the throttle is held and the start button is pushed. This allows the engine to spin up enough to fire and when the start button is released I guess the person driving the weed eater lets off the throttle ???????????

I do know it it operated by the throttle. If you look at the first picture you can see that when the throttle rotates it contacts the CR.

? Once it starts compression may provide enough resistance to close valve and then valve may act as a full throttle stop to prevent butterfly lever from travelling past a full open position??
Would be nice for someone who has converted this particular series to furnish some input.

I agree, it would be nice for someone who has worked with this to speak up but so far no one seems to have any knowledge of it. I thought these guys had seen it all.

Just converted one that was of recent vintage. On mine there was a compression release HOLE above the exhaust port. In a prior posting on conversions someone recomended sealing that hole to increase power.
Looks like on your motor this was handled automatically with the release.

Cassidy:
I was thinking along the lines of using it and being able to start the motor with a regular electric starter. Once it's running cylinder pressure will keep it closed.

Tower catalog show a Fuji twin 86 with CR on both cylinders. I'd keep it until it gives a problem.
Does the moveable part have any type of rotation lock? Might be fun trying to hold it open while running an electric starter!

There is no kind of lock on the mechanism at all. It is strictly operated by the throttle position. At full throttle it is engaged and is released when throttle is reduced any amount off full.

I closed mine because it was a hole in the side of the engine that couldn't be adjusted and was waisting power.
I agree with your intention to keep it in place-hopefully it will make it easy to start.
Keep us posted.

As another check, look down the throat of the carb and see if the butterfly is going past centre when the decompressor is on.