McCulloch 790 build

[slipknot]

Good to see you back at it. Hows that micro grinder..thinkin about getting me one for some of that exotic dental work to ports Mark describes..lol

 

[promac850]

Good to see you back at it. Hows that micro grinder..thinkin about getting me one for some of that exotic dental work to ports Mark describes..lol

Works real nice... not quiet by any means (it screams like an F1 car)

It will cut a lot faster than a dremel at WFO, but can be regulated with the silver air inlet collar switch... variable speed... so if you can't keep up with WFO, dial it down a little.

From the reviews (and my personal experience and expectation after buying it) it should last a few years. Keep it oiled like every other tool and use it... I believe this thing will last at least three years of somewhat regular use.

It is good to be back to work on this old beast... .030" over and ported is gonna make this a hell of a first six cube saw!!

 

[rwoods]

Kyle, check out this port job. McCulloch 101-B Professionally Modified by Comet - Vintage Kart | eBay It looks like real nice work though I don't know how well it functions. Ron

 

[HeRoze]

what's the score in the arbor press v. c-clamp game? it looks like there's a wrist pin in there, so i'm glad it worked out for you.

 

[slipknot]

I cant wait to play with my 790...i got a carb kit from sugar creek supply and got it running then the pull start broke......I really really need a clutch with them starter pawls...I broke one of mine off. Anyone know where to buy a clutch or maybe even a set of starter pawls?

C'mon Kyle your slackin buddy!!!

 

[heimannm]

Slipknot - A clutch from any of the right hand start saws will work, from the D-44 up through the 797.

If you absolutlely cannot find one anywhere contact me in another 10 days when I am back in the country and I'll see what I can find in the attic.

Mark

 

[promac850]

what's the score in the arbor press v. c-clamp game? it looks like there's a wrist pin in there, so i'm glad it worked out for you.

1-0. I'll tell you right now... c-clamps, as useful as a wrist pin removing trick they are, will not remove a Mac wrist pin.

I cant wait to play with my 790...i got a carb kit from sugar creek supply and got it running then the pull start broke......I really really need a clutch with them starter pawls...I broke one of mine off. Anyone know where to buy a clutch or maybe even a set of starter pawls?

C'mon Kyle your slackin buddy!!!

I am slacking, a little.

Having a bit of trouble figuring out how to work the bottom transfers like I did the uppers. Very little room to work with anything. Riffler file set is far too fine for good material removal... heck, I've even gotten to the point of using a narrow 1/4" wide wood chisel to try to scrape a lead in to the ports. Slow going either way.

I can't seem to find any extra long 1/8" shaft cutting bits for the Dremel or mini grinder... 1/4" shaft stuff would be way too big to fit into there. I'd need an 1/8" shaft acorn cutter bit to get some good results... I may have to buy a Dremel acorn cutter from HD and bring it somewhere that knows how to weld on tool steel, and have them weld an extension on, and then grind it smooth.


Not to mention I'm still tripping over the useful crap that I brought home from work last week...


I've got spare one of them clutches... unfortunately, I'm gonna need it on the Super 44A, since that one got all f'd up where the key way is.

I know of a former Mac dealer nearby, I can see if they have one. They supposedly have some NOS parts for Macs and Homelites, and maybe a couple of others.


Ron, thanks for the link... looking at it right after this post...

 

[Warped5]

I know of a former Mac dealer nearby, I can see if they have one. They supposedly have some NOS parts for Macs and Homelites, and maybe a couple of others.

.. might that be Van's Sport Center? I saw them on eBay with some vintage Mac stuff ... was gonna give you a heads up anyway.

 

[promac850]

Kyle, check out this port job. McCulloch 101-B Professionally Modified by Comet - Vintage Kart | eBay It looks like real nice work though I don't know how well it functions. Ron

Wow... that looks like quite the set up... wonder how well that thing would run a bar and chain through an Oak log...


Someone needs to collect that there Comet and build a kart saw that eats other kart saws... that things gotta be capable of 10,000 rpm. Wish I could buy it, but then it'd sit in a plexiglass case on a shelf, protected from grime and dust... It's so shiny...


No idea how well those 'boost' ports below the upper transfer ports would work either... then again, if you are running an engine up towards 10,000 rpm, you need lots of air, and lots of fuel to make the best power...

It's possible those ports could compromise for running an exhaust with no back pressure... most of the mixture seems to go right out the 'muffler' on these engines... kinda like a drag racing v8... the fuel/air is burned as it exits the engine through the exhaust valves and ports... hence the flames coming out of the pipes as it's hauling mail down the strip. Gives you more power, but uses a lot more fuel...

 

[promac850]

.. might that be Van's Sport Center? I saw them on eBay with some vintage Mac stuff ... was gonna give you a heads up anyway.

SHH!!!

That's where I got my cylinder bored...

 

[HeRoze]

===I can't seem to find any extra long 1/8" shaft cutting bits for the Dremel or mini grinder... ///...

how long does it need to be?

would a flex-shaft do the trick?

 

[promac850]

how long does it need to be?

would a flex-shaft do the trick?

Flex shaft won't do it... too big to fit into the area of the cylinder that I'm working from... my mini die grinder is the same diameter as many flex shafts out there.

It would need to be like this, only in 1/8" size... need a couple more inches of reach... have yet to inquire about one of these in 1/8" size with a .190-.200 diameter ball or acorn cutter on the end at an actual carbide burr and tooling company.

I'm working from the bottom of the cylinder... in other words, looking up the passages to the transfers... not working from the 1/2" holes, which has proved futile so far. Seems like the plugs are there for covering up casting forms and maybe allow for a good cleaning of the cylinder after porting it to ensure chips are not in there.

Sounds like he next time I see my dentist, I'm gonna have to bug him about one of them neat little porting tools that they use on teeth for some strange reason...

 

[slipknot]

Kyle, have you checked out Cutting Edge Tool and supply? Thats where i get my cutters...although the one you posted looks neat..may have to try it. Putting the bevels on to avoid a ring catcher seems to be my weakness...whats your approach? That 350 you did ran like a striped azz ape while it lasted..lol it sits in a box waiting for me to get the cash up for a new cylinder.

 

[promac850]

Kyle, have you checked out Cutting Edge Tool and supply? Thats where i get my cutters...although the one you posted looks neat..may have to try it. Putting the bevels on to avoid a ring catcher seems to be my weakness...whats your approach? That 350 you did ran like a striped azz ape while it lasted..lol it sits in a box waiting for me to get the cash up for a new cylinder.

No, I did not check out CET&S... forgot to check in to see if this thread had anything new in it...

I ended up ordering some burrs through McMaster-Carr. The one I posted is actually a 1/4" shank cutter, I needed 1/8" shank cutters.

I used the egg/oval shaped one, and even with the extra length, had to work from the 1/2" freeze plug holes... the extra length helped a lot even here, since my view wasn't obstructed by my hand/the porting tool... so now the lowers are at least somewhat close to what the uppers are, except they aren't polished like the uppers. Two reasons behind this...

1. No room for a polishing wheel on the porting tool
2. fuel would probably be a little more likely to settle in this area, since it's on the bottom of the saw... so a little turbulence might actually be good.

Pics will come later... right now I gotta try to find pics of teardrops in the cylinder... and figure out how I'm gonna lay those out and how I'm gonna make the cuts... and with what cutter as well...

As for beveling on the 790 cylinder, it isn't necessary since all of the ports are round/oval... and have bridges in between each individual port. Thus the piston actually doesn't have pinned rings...


For something like the Husky cylinder, I made a decent bevel on the exhaust port to where I felt sure the ring wasn't gonna catch... thing is it is possible to overdo it. You only need like 1/16-1/32" for it to work, the ring doesn't pop out all that far... unless your really hogged that sucker out, lol. Like instead of 60% of the bore, say you made it 80%... yeah, you're gonna have problems...



As for your Husky cylinder, look into these... available at places like McMaster-Carr (link) or Fastenal, or other places as well... McMaster-Carr

It might be worth going to the thick or extra thick inserts... though they are only available in SAE thread sizes...

Otherwise get the standard ones if they offer them in metric... it would be better than the thin wall, which would probably pull out just like usual.

Find a keysert with the same inside thread as the muffler bolts, and then drill/tap the holes in the cylinder for the keysert thread size. After seeing these flipping through the fastenal catalog, I immediately thought of that little 350... I imagine a fix with these and a good muffler brace set up will make the saw bulletproof.

Then put a brace on the muffler that attaches it to the cylinder at the top, so it doesn't fall off again. If I had known that little bit of info when I had the saw, it would've been bulletproof.

And when you get her back together, I'd like to see a video.

 

[promac850]

Went out to study the cylinder some more to try to figure out what the teardrops are going to look like, and still haven't actually gone in and ground anything else away yet.


However, I did finish the exhaust flange for the muffler or megaphone or whatever I decide to put on it... I wanted to use three little pieces of stainless steel pipes, but when you mock it up, they are in the way of the bolt holes... might have to do something else, or figure out a different way to make the pipes work...

Seriously, who wouldn't like three shiny stainless pipes about 1/2" in diameter (which turns out to be just a little smaller than the ports are) spitting flames and blowing a trench through piles of chips?

I think it'd be quite something...

 

[rwoods]

Went out to study the cylinder some more to try to figure out what the teardrops are going to look like, and still haven't actually gone in and ground anything else away yet.


However, I did finish the exhaust flange for the muffler or megaphone or whatever I decide to put on it... I wanted to use three little pieces of stainless steel pipes, but when you mock it up, they are in the way of the bolt holes... might have to do something else, or figure out a different way to make the pipes work...


Seriously, who wouldn't like three shiny stainless pipes about 1/2" in diameter (which turns out to be just a little smaller than the ports are) spitting flames and blowing a trench through piles of chips?

I think it'd be quite something...

Like maybe a fire starter. Or a choke. Do something else that will be just as cool. Ron

 

[slipknot]

Nah exhaust stingers are cool in my book...i put them on everything!!

 

[promac850]

Like maybe a fire starter. Or a choke. Do something else that will be just as cool. Ron

Yeah... fire, baby!

[video=youtube_share;zcLfi1Pq14s]http://youtu.be/zcLfi1Pq14s[/video]

Brought to you by Rammstein and their fire masks...

I do have another exhaust set up I can do... and am considering... it'd be wide open, unless I put some kind of little deflector/cover on it, or a screen over it...

Nah exhaust stingers are cool in my book...i put them on everything!!

lol... set any trees on fire lately?


Chances are, the first running and cuts of the 790 will be with the original muffler... maybe I'll still follow through with the pipes or the wide open megaphone for those special occasions...

I just had to get something done that's related to this project... maybe tomorrow will be the day where I can finally get over this blasted cold and spend some time making the port teardrops on the inside of the cylinder. Last thing I want is a huge drip coming off of my nose and causing me to lose concentration... I can't afford to screw up the cylinder bore.


Maybe I should go to HF and get me a 50 lb bag of armex soda blast material... I still got some parts to blast yet. And while I'm there, I'd better remember to get that stuff that I keep forgetting to get. I can't remember what it was now... blasted memory.

 

[promac850]

Alright folks, back onto the 790 project...

Got me a 50 lb bag of medium grade blasting soda from HF, which worked a fair bit faster but still quite gently to remove old paint and light corrosion than the normal box store baking soda.

Here's the air filter cover after it was blasted, primed with three or four coats of primer, and four coats on the outside (top part that is actually outside the saw when installed) and two on the inside... satin black from Rustoleum. Looks and feels very nice, has a very subtle 'wrinkle' look, and highlights some features from the days past... like the #1 and scribbled out 3...

The 'McCulloch' font will be highlighted with yellow at a later date... as for clear coat, forget it. They didn't use it back then, so I ain't gonna use it now. If some paint gets worn away, so what. This saw will earn new 'battle' scars... I'll find me a tree big enough to really make this beast work... someday.

This time, I'll follow through when I say I'm gonna post the pics of the porting results... be back in a few... (God forbid me ADHD get in the way again of this simple task like the last couple times I said I'd get you some pics...)

 

[promac850]

Here are the pics of the cylinder ports... it might be a bit difficult to see, but they are teardropped, the drops point upward towards the cylinder wall above the third ports. Notice I did not raise the ports in any way with the teardrops... they are at the same level as the rest of the port hole.

Also got some pics of the parts that do have primer on them... gonna have to figure out a way to paint these with the yellow paint that I have sitting around waiting to be used. Farm implement paint... done right, it should be even harder to remove than the original paint (which some of the original paint will still live under the new paint on some of the parts)

How am I doing?


edit: dangitall, if forgot to ask the dentist about one of them fancy porting tools that they use on teeth... was just there for the routine cleaning a week ago...