Nice C-51 I just got!

[w30bob]

Hi Guys,

  Here's that C-51 I got that I talked about in my Titan post.  Haven't had a chance to give her a proper clean and polish, but figured you'd like to see it anyway.  As I look closely at the decals.........I think they're not decals at all.  I think they're paint stamps.  Which is really interesting.  To be continued...........but check her out.......she's a pretty girl!  I love finding them with their original bar.....it makes the saw.

;O)
bob

[ronaldt]

That looks to be in very nice original condition. Thanks for sharing!

[edju1958]

Damn! That saw is in unbelievable condition! What do you mean you haven't had a chance to clean her up?What did you do,forget to get out the Turtle Wax?Lol

[sparky]

It may be a pretty girl but she'll bark a song when ya get that bar into some wood.

[tangobravo]

Sounds loud from here-Those stack "mufflers" are something else.

[w30bob]

Oh....is that little metal thing on the side a 'muffler'? I thought it was for lighting cigarettes while sawing! Yeah, I bet she's loud. It's funny that in all the early saw brochures......no one is wearing any type of hearing protection. We've become such wimps.......but can hear past 50!

;O)

[tangobravo]

More like open headers- At least they don't run nitromethane!

[edju1958]

Something to remember about "stack mufflers" - they might sound real cool when you're ruinning the saw,but fact is you lose H.P.when on the saw as opposed to running a real muffler.A member here (night hawk?) did an experiment on a SXL-925 with a stack muffler on vs.a regular stock muffler & his findings were as I stated above.If you want more power,use a regular muffler,if you want it to "sound cool" & lose your hearing,leave the stack on.

[w30bob]

Apr 9, 2022 22:28:53 GMT -5 tangobravo said:

More like open headers- At least they don't run nitromethane!

The competition saws sure run Nitro...10 to 20% with only 5% oil.  Nice cool burning Nitro......man I love that smell!  Actually, gasoline back in the late 60's and early 70's smelt really good too.  I remember as a kid loving going to the gas station with Dad and smelling that gas.  Then the EPA started dicking around with and now it smells like shit.  Oh well.  At least the 2-stroke oil still tastes good!

;O)

[w30bob]

Apr 9, 2022 22:45:53 GMT -5 edju1958 said:

Something to remember about "stack mufflers" - they might sound real cool when you're ruinning the saw,but fact is you lose H.P.when on the saw as opposed to running a real muffler.A member here (night hawk?) did an experiment on a SXL-925 with a stack muffler on vs.a regular stock muffler & his findings were as I stated above.If you want more power,use a regular muffler,if you want it to "sound cool" & lose your hearing,leave the stack on.

That makes sense.  I'd take it one step further and say if you want any saw to make the power it was designed for.......keep the stock muffler in place.  2-strokes are way more sensitive to how their exhaust works than 4-strokes, because the engine's volumetric efficiency (VE) is mostly a function of how well the combustion chamber scavenges, where in a 4-stroke the piston forces scavenging to happen by pushing the burnt gases out of the combustion chamber. So the VE of a 4-stroke is more a function of how restrictive the airflow thru the heads is (how much air/fuel you can get into the combustion chamber).  On a 2-stroke how much you can get in the combustion chamber depends on how much can get out before the exhaust port closes, with nothing physically forcing it to leave other than pressure difference between the combustion chamber and the exhaust outlet.  The transfer port dimensions and timing in a 2-stroke are optimized for the inertia of the air-fuel mixture and how restrictive the exhaust system is.  So messing with one and not the other will always move the saw off design point, and lower power.  2-stroke exhaust is a really interesting subject, and it wasn't really all that well understood until Gordon Jennings published what's become known as the 'Bible' for 2-strokes, his "Two Stroke Tuners Handbook", back in 1973.  If you ever run across a copy give it a read.  It's what allowed 2-strokes to pull so far ahead of 4-strokes in power to weight.....before the EPA cut their balls off.    So.........putting a 'stack' muffler on an SLX-925 in place of it's original muffler SHOULD reduce power, just as putting the 925 muffler on saw that came with a 'stack' muffler would do the same.  Sometimes the OEMs actually did know what they're doing.  Sometimes.  

;O)

[edju1958]

I like what you had to say Bob,but I find it kinda contradictory that the folks at Homelite gave us an option as to what type of muffler we wanted on our saws.We could get a stack muffler or a regular muffler on the C series saws.The only saws I know of that had that option (I may be wrong).

[ronaldt]

Apr 10, 2022 20:39:29 GMT -5 edju1958 said:

I like what you had to say Bob,but I find it kinda contradictory that the folks at Homelite gave us an option as to what type of muffler we wanted on our saws.We could get a stack muffler or a regular muffler on the C series saws.The only saws I know of that had that option (I may be wrong).

I guess I always assumed that the stack came on the C series as standard equipment and a muffler was optional.

[edju1958]

I'm not sure how it worked when buying a saw,but I was under the impression that the saws could be bought 2 different ways.One way was to buy the saw the was it was right off the shelf as it came from the factory.The other way was to have options added on,such as automatic oiling on a SXL,or the regular muffler on a C series.Although the muffler could be added on in a matter of 5 minutes.There were other options too,like the style of handle you wanted,which carb you wanted, & I'm sure there were many others.

[sparky]

So what does porting effect in a 2-stroke? I was around drag racing for awhile and smoothing and blending chambers allowed an engine to breathe as I was told.

[w30bob]

Hi Sparky,

Porting for a 2-stroke is a pretty big deal. That's because it's the 4-stroke equivalent of both cylinder head work AND changing the camshaft. The piston in a 2-stroke functions like the valves in a 4-stroke, opening and closing the intake and exhaust pathways, just without all the valvetrain hardware and parasitic drag. The port dimensions act as the camshaft, determining where in the piston's stroke things open and close to move air/fuel and exhaust thru the engine. So modifying port heights in a 2-stroke changes what would be considered the effective "valve timing" on a 4-stroke, and modifying port width in a 2-stroke is like smoothing and blending chambers, allowing more airflow for a given number of crank degrees. I'm oversimplifying, but you get the idea. There's limitations, of course, as ports are areas in the cylinder wall that don't support the piston ring, so making them very wide invites a ring to get hung up on a top or bottom port edge, and once you take metal away in a cylinder...you can't put it back (easily). Porting is also used to shift where in the RPM band the saw makes the most power. Horsepower is calculated, not measured, so you're really talking about torque, and how much and where it's made. There's no free lunch, so you can typically make more low end power at the expense of top end, and vice versa. Just depends if you want a lugger or a screamer. Porting in and of itself doesn't make more power unless scavenging is improved or more fuel and air can be crammed into the combustion chamber before the exhaust port closes. So raising the height of the roof of the exhaust port, for example, will allow more of the spent combustion gases out (better scavenging), but will also let out more of the fresh fuel/air charge that just came up thru the transfer ports. So it's a real balancing act, and there are some real artists out there that know their shit. Transfer port mods typically focus on adding swirl to the combustion chamber, to get better mixing and a more rapid flame front once the plug fires. Again, lots to consider before one picks up the grinder. And porting changes the compression ratio as well, since the piston doesn't start to compress the air/fuel mixture until the exhaust port is fully covered. So you can see that touching one thing affects many.

As for the muffler as an option on saws, have you noticed the saw manufacturers very quickly stopped quoting horsepower numbers. They only used them early on thru the late 50's as a way to one-up the competition, but dropped that stuff pretty quickly. They also don't claim anywhere that I've seen that adding an optional muffler to a saw wouldn't reduce power, if even by a little. I mean look......if you can add a muffler to any engine out there and make MORE power.....you'd be the richest guy alive......and every race track in the world would be beating a path to your door. Now there's a HUGE difference between a muffler and an expansion chamber, so don't confuse those two, although a properly designed expansion chamber can reduce noise to some degree.

Porting is a really interesting subject, and there's more to it than meets the eye. I remember as a kid Yamaha would post tech bulletins for their motocrossers and enduro bikes describing how to port their cylinders for more top end scream. But they wouldn't do it in production, as increasing top end power and speed obviously reduced the engine's lifespan....and no one wanted a reputation for putting engines out there that wouldn't last one racing season. Wouldn't it have been cool if Homelite had done the same?

;O)
bob