Santa's workshop

[Four Paws]

I'm playing Santa this year and building my dad a saw for Christmas. He doesn't think so, but he needs a 50cc saw. Since he already runs Shindaiwa saws, I thought a 488 will fit in nicely. I managed to pull enough parts together to make him something I think he'll be able to put to good use.

Stock, the 488 is a reliable saw, with a stuffy muffler.



First order of business is a muffler mod. Remove the outlet cover and spark screen.



Use a thin wheel on your dremel tool to cut out the outlet tube. It is tack welded on the flywheel side of the muffler. Grab and twist it with some pliers a few times to break it off. You can also see I modified the outlet cover.



Looking in the muffler, you can see the center baffle - it has plenty of holes, symmetric on top and bottom. I left it alone.



Much better now, and not very loud. Looks pretty stealth, too.



Now on to the cylinder. I measured twice and cut once. Dialed in at .020" with a gasket.



On to the port work. Stock exhaust was pretty high - guessing that is because the muffler is so stopped up. After I adjusted the squish, the exhaust was sitting at 103. I was happy with that, so I widened the port and reshaped it. The intake was sitting at 73. I squared it up and added a little width. I spent the most time on the transfers. The lower transfers are really big stock, so I shaped them and smoothed them up . The uppers are tiny and quite low. I raised them up to 122, squared the corners and brought them back a bit on the intake side.







I didn't touch the combustion chamber. The piston doesn't have adequate skirt length to drop the jug anymore than I did.

 

[Four Paws]

Now, to put it all together.







And go test it out...



Saw ran great. There is still more power to be had. I think it could use a little more intake duration. I tuned it at 13,800 and it held 11,500-12,000 in the cut letting it self feed. I pushed it harder than a normal person would through a few cuts and knocked it down in the 10,000 rpm range, the saw just pulled like a tractor.

After it cooled, I pulled a compression reading. Just shy of 185 psi at 5000 feet. That should be about 210 at sea level.

 

[Stihl 041S]

He'll be a happy man.
Good for you.

 

[HTTR]

Awesome work! What a great gift.

 

[David Young]

Nice work Josh,
nice looking port work and saw.
what size walbro is that did you mess with it at all?
what were the stock numbers?
That black thing on the intake looks like trouble
have you ever played with ignition timing on it?

 

[David Young]

I bet a muffler mod alone on that saw would have made a huge difference!

 

[blsnelling]

Nice work!

 

[David Young]

Brad have you ever messed with a shinny? Solid built equipment.

 

[redfin]

Dang fine nice work Josh!

 

[rburg]

Every Dad should have a son like you. That is a nice light 50cc model and I am sure he will appreciate it.

 

[Four Paws]

Thanks everyone for the kind comments.

Nice work Josh,
nice looking port work and saw.
what size walbro is that did you mess with it at all?
what were the stock numbers?
That black thing on the intake looks like trouble
have you ever played with ignition timing on it?

David, to answer your questions.

I did not mess with the carb at all. It's a Walbro HDA 79A. The intake horn can be removed, but it helps hold the filter.

Factory Squish was .047". Dropping it to .020 adjusted the timing numbers by about 2 degrees...factory exhaust wasn't quite 102, intake not quite 71. Stock transfers were angled higher on intake side. They opened about 24 degrees after the exhaust.

I haven't advanced the timing on the 488s. Although it would be easy enough.

 

[blsnelling]

Brad have you ever messed with a shinny? Solid built equipment.

I ported a 377 once. Very well built little saw!