Homelite 30cc- Muffler Middle Hole
10-09-2017, 08:12 PM
#1
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Homelite 30cc- Muffler Middle Hole
When rotating the prop on the 30cc Homelite, air is leaking out of the middle hole near the opening for the muffler.
What is the purpose of that opening, and is there a set screw that should be inserted?
If so what size? The set screw in the photo is too large.
Thanks.
What is the purpose of that opening, and is there a set screw that should be inserted?
If so what size? The set screw in the photo is too large.
Thanks.
10-10-2017, 10:30 AM
#4
It's been debated what that darn hole is for, but the truth is we just don't know. Some say a form of compression release for easier pull starting, some say a poor mans EGR. (Exhaust gas recirculation, for smog)
In any case, we definitely don't want a hole bleeding off cylinder pressure, and it should be plugged. It is the perfect size to accept a tap, but I'm sorry I don't remember the size. 10 x 32 maybe? Tap the hole only deep enough to accept a short set screw installed with red Loctite. You don't want to tap all the way because doing so would possibly damage the chrome bore of the cylinder, and would definitely raise a burr in the cylinder. Plus, if the hole is not tapped all the way, your set screw plug could never find its way into the cylinder. You're not going to want to hear this, but I don't recommend doing this with the engine assembled.
I usually grind the muffler flat, braze the hole shut, then surface the muffler flat again.
AV8TOR
In any case, we definitely don't want a hole bleeding off cylinder pressure, and it should be plugged. It is the perfect size to accept a tap, but I'm sorry I don't remember the size. 10 x 32 maybe? Tap the hole only deep enough to accept a short set screw installed with red Loctite. You don't want to tap all the way because doing so would possibly damage the chrome bore of the cylinder, and would definitely raise a burr in the cylinder. Plus, if the hole is not tapped all the way, your set screw plug could never find its way into the cylinder. You're not going to want to hear this, but I don't recommend doing this with the engine assembled.
I usually grind the muffler flat, braze the hole shut, then surface the muffler flat again.
AV8TOR
10-10-2017, 10:38 AM
#5
AV8TOR
Last edited by av8tor1977; 10-10-2017 at 10:52 AM.
10-10-2017, 12:08 PM
#7
I've heard of those electric start Homelites, but never seen nor gotten my hands on one. Do you happen to have any pics of one? Or do you have a model and/or UTC code so I can look one up? The perpetual "gearhead" in me is just curious about how it was designed. I have a Chinese 49cc electric start engine off of a mini-bike in my "someday" stash, but the starter part probably weighs 1.5 lbs. or more!!
AV8TOR
AV8TOR
10-10-2017, 07:23 PM
#8
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Certainly the right way is to disassemble the engine to avoid causing damage.
Nonetheless after some careful measuring, remeasuring, measuring and remeasuring again, the tapping was done with the engine assembled.
Last edited by Rooster353; 10-10-2017 at 09:30 PM.
10-11-2017, 11:02 AM
#9
You're likely going to notice slightly easier hand starting, (more force required but easier starts), possibly a bit more power, and maybe, maybe, more consistent mixture adjustments. Hard to say for sure; I've never done a before and after comparison, but logic dictates that for best performance you don't want to be bleeding off cylinder pressure nor contaminating it with exhaust gasses.
The "science" behind EGR: High combustion temps can cause formation of oxides of nitrogen, a component in smog. Some genious discovered that contaminating the air fuel charge with exhaust gasses could eliminate some oxygen, and lower combustion temps, thus mitigating the formation of oxides of nitrogen, or NOX. Of course, this obviously comes at the expense of reducing the engines efficiency and performance.
AV8TOR
The "science" behind EGR: High combustion temps can cause formation of oxides of nitrogen, a component in smog. Some genious discovered that contaminating the air fuel charge with exhaust gasses could eliminate some oxygen, and lower combustion temps, thus mitigating the formation of oxides of nitrogen, or NOX. Of course, this obviously comes at the expense of reducing the engines efficiency and performance.
AV8TOR
