McCulloch Chain Saws

[nstueve]

Porting 101 thread...
http://www.arboristsite.com/chainsaw/108900.htm

Saaaaaaweeeeet!!! I can do that! I know car engines but 2 cycles are kinda new to me so that answers alot of "newbie" questions I probably have rolling around in my head. :msp_biggrin:

As far as bar size goes... Grandpa had 2 new chains sitting with it so I'll run the 16in with it until all three chains are shot and then make up my mind. Hell by that time I might have broken it open for some P&P work and maybe a muf mod... Speaking of which...

Can anyone direct me to Muffler Mod 101??????

 

[Warped5]

Can anyone direct me to Muffler Mod 101??????

Here is a MM thread.

It's so easy, I did a 'quick and dirty' on my blower. It does run a bit better!

Now you're in the market for a Dremel .....

 

[nstueve]

Now you're in the market for a Dremel .....

You must be kidding right????? LOL!

My grandfather left me 5 of them with every attachment ever possible! He built grandfather clocks wooden gears and all! the only thing metal was the hands that told the time and the numbers face plates... Anyhow I have plenty of sanding cartridges, small metal burs, etc to do all of this!

 

[promac850]

You must be kidding right????? LOL!

My grandfather left me 5 of them with every attachment ever possible! He built grandfather clocks wooden gears and all! the only thing metal was the hands that told the time and the numbers face plates... Anyhow I have plenty of sanding cartridges, small metal burs, etc to do all of this!

Well, looks like grandpa planned ahead and saw you porting his little Mac Cat...

Anyone here ever see a big Mac with both RH and LH starters on it? I'm thinking it'd be pretty interesting to see the reaction of people as you pulled out a saw that looks like it needs three people to start it...

 

[nstueve]

Well, looks like grandpa planned ahead and saw you porting his little Mac Cat...

Ok so I just read the MM thread... Not very many pics but from what I read you basiclly hallow out the muffler and drill a second exhaust hole or enlarge the primary exhaust hole.

Sounds like the same principle as hallowing out the cat on your car and adding a cat back system so the exhaust gets out quicker without obstruction...

Correct?

any one have b4 and after pics of their MM?

 

[promac850]

Ok so I just read the MM thread... Not very many pics but from what I read you basiclly hallow out the muffler and drill a second exhaust hole or enlarge the primary exhaust hole.

Sounds like the same principle as hallowing out the cat on your car and adding a cat back system so the exhaust gets out quicker without obstruction...

Correct?

any one have b4 and after pics of their MM?

Yep, just make a hole that increases the overall size of the exhaust port about 80% of the port size (measured at the piston, not the muffler flange)

That saw will wake up after some port work and a bit of muffler work.

Again, just like car exhaust, bigger is not always better... too big and gasses slow down.

In the case of a two stroke, you will not have enough back pressure to keep the air/fuel mix in the cylinder. So if in doubt, use a smaller drill bit.

I do not have a good pic of muff modding.

I'll dig around a little and see what I can find.

 

[nstueve]

Yep, just make a hole that increases the overall size of the exhaust port about 80% of the port size (measured at the piston, not the muffler flange)

That saw will wake up after some port work and a bit of muffler work.

Again, just like car exhaust, bigger is not always better... too big and gasses slow down.

In the case of a two stroke, you will not have enough back pressure to keep the air/fuel mix in the cylinder. So if in doubt, use a smaller drill bit.

I do not have a good pic of muff modding.

I'll dig around a little and see what I can find.

Ok Hypothetically.... If I measure where the exhaust goes out of the cylinder/combustion chamber with a dial caliper and it says .317in I should increase that 80% to .567in... or about 9/16in drill bit size...

 

[promac850]

Ok Hypothetically.... If I measure where the exhaust goes out of the cylinder/combustion chamber with a dial caliper and it says .317in I should increase that 80% to .567in... or about 9/16in drill bit size...

The way to do it is with the total surface area measurement... not just one dimension.

80 or so % of the total exhaust port surface area, as measured from the cylinder.

9/16" would be way too big for a little 32cc's like this Mac Cat.

Eyeballing it works okay.

 

[Warped5]

You must be kidding right????? LOL!

My grandfather left me 5 of them with every attachment ever possible! He built grandfather clocks wooden gears and all! the only thing metal was the hands that told the time and the numbers face plates... Anyhow I have plenty of sanding cartridges, small metal burs, etc to do all of this!

Great! Now you need a speed controller .... s-l-o-w-e-r is better. Sorta one of those 'rules for life' .... LMAO

 

[heimannm]

You want the opening in the muffler to be approximately 80% of the open area of the exhaust port in the cylinder.

There are lots of threads on mufler modification, do a little searching and you will find all kinds of information and opinions.

Regardless of what you do to the muffler and how it sounds after the changes, you will still have a 38 cc McCulloch "Plastic Mac".

Mark

 

[rwoods]

Mark, back to metal MACs for a moment. Do you recall what size bolt fits the tapped holes in the crank cover? 1/4 is too big, #10 is too small and Fastenal looked at me like I was crazy when I asked for a 3/16; said next size down was a #12 which they will have to special order. I told them to go ahead with the SO. Your picture looked like you were using ordinary hex head bolts. Thanks, Ron

 

[nstueve]

Great thanks for the clarification guys. A little practice on MM and P&P work will help me when I want to put my 79cc kit on the 6401.

There are lots of threads on mufler modification, do a little searching and you will find all kinds of information and opinions.

Regardless of what you do to the muffler and how it sounds after the changes, you will still have a 38 cc McCulloch "Plastic Mac".

Mark

I'll take a look around and see what pops up... If this forum is anything like the Ford Truck forum I'm in it would be more help to get a link from someone becasue the search tool is S*** on there!

As for the "plastic mac" comment... Well that means I won't so much mind using it for P&P and MM practice...

 

[heimannm]

The tapped holes in all the saws I have worked on were definitely 1/4-20. Now remember you are looking for those two in particular, none of the others will be tapped. If your 1/4-20 screw does not go in easily, you may need to clean the threads a bit with a tap.

#10 screws (i.e. 10-24) are in fact 3/16" O.D. more or less

#12 screws are indeed between #10 (3/16") and 1/4" though I am not sure the actual diameter most charts list them as 0.216". Common threads for the #12 screws are 24 threads per inch just like the coarse #10 screw. 12-24 screws can commonly be found on Mini Mac saws to hold the housing to the engine.

Having said that, do not use a 12-24 screw to pull the cover as the holes are in deed 1/4-20 unless the kart engines are completely different from all the saws.

Mark

Tell your Fastenall guys they need to improve their inventory. We have a store in Cedar Falls (IA) and they can have anything I need normally within a day or two if they don't have it on the shelf right now.

 

[rwoods]

Thanks, Mark. I'll run a tap in them. Ron

 

[rwoods]

Cut a little metal but a 1/4 will now thread. Now back to Fastenal for some longer bolts. Thanks again. Ron

 

[Ambull]

10-32's are actually a little bigger than 10-24's at least the drill size is. #12 screws are really odd ball. I don't think I have ever seen them used on anything.

I get all my fasteners from McMaster Carr. They can get almost anything in a day. Great selection of fasteners.

 

[heimannm]

10-24 and 10-32 screws start with the same diameter material, but the 32 threads per inch are finer than the 24 threads per inch so they take that into consideration when recommending the drill size for tapping threads.

#12 just never seemd to catch on, but you will find them on quite a lot of older equipment, sort of like 7/16" nuts and bolts on older farm machinery in particular.

There is a lot to be said for standardization...

McMaster Carr is certainly like having an "Easy" button and is great for small quantities, but can get expensive for anything you use a lot of. I have a pretty good relationship with the local Fastenall and they will try pretty hard to get me what I need and will even work with me when the catalog pricing seems out of line.

Mark

 

[8433jeff]

I'll take a look around and see what pops up... If this forum is anything like the Ford Truck forum I'm in it would be more help to get a link from someone becasue the search tool is S*** on there!

As for the "plastic mac" comment... Well that means I won't so much mind using it for P&P and MM practice...

Yes, but hold on. The muffler isn't all that restrictive, and if you've run it, you know that. Porting? Why? Its not going to be up to cutting redwoods even with a nitrous set-up. A running one in the condition you have it may not be the rarest, but certainly worth keeping. They were not uncommon, but running "good" examples are. Non-running good examples are far easier to find, and the completely hashed out ones are rare, as most didn't make it that far in life, for various reasons. It's your saw, but Grandpa isn't going to leave you another one. Just my $.02.

 

[Eccentric]

Yes, but hold on. The muffler isn't all that restrictive, and if you've run it, you know that. Porting? Why? Its not going to be up to cutting redwoods even with a nitrous set-up. A running one in the condition you have it may not be the rarest, but certainly worth keeping. They were not uncommon, but running "good" examples are. Non-running good examples are far easier to find, and the completely hashed out ones are rare, as most didn't make it that far in life, for various reasons. It's your saw, but Grandpa isn't going to leave you another one. Just my $.02.

I agree Jeff. I have my Dad's PM320. Same basic saw. It needs a new fuel line and a carb kit, and I'm NOT looking forward to that job. However, it is my Dad's saw, and will be a good runner when I finally get motivated enough to crack open that clamshell of frustration. At least mine's old enough that it was made in the USA. It still wears the original 16" sprocket nose and loop of 3/8" power sharp chain. Only 'burried' it once (in pine). It did OK, although the 16" bar is really more for limbing/pruning reach than anything else (as Mark said).

Since Mark can't make it out to the PNW GTG this year, we're gonna have to figure out some other way to get your C5 to you. The McCulloch 200 is still yours too if you want it, and it can wait on the shelf as long as needed.

 

[rwoods]

Crankcase cover is off the kart motor thanks to Mark. Wouldn't you know that I can't bind it now that the crank is unsupported on the flywheel side. Anyway does anyone know a non-eBay source for the splined socket needed to remove the rod cap?

Is $12 and some change a piece too expensive for the crank seals? The inner seal had the lip folded. I might as well fix it right while I have it apart.

I ordered some NOS 125 parts today including: bar plates, spacer plates, clutch, clutch kit (bearing, sprocket and drum), muffler kit (includes muffler) and a muffler . Sorry, guys but they only had one muffler kit and one muffler. My homemade muffler project will just have to wait.

I also brought from an AS member something I do know a little about - a Super Pro 70. Shouldn't be too difficult to put it back together and I should already have in inventory all the parts that are missing or need replacing. Now I'll have a 700 with AV or would it be a 7-10 with AV? According to Acres it is closer in age to a 700.

Ron