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I recently bought a 1-50 saw engine on ebay for a real good deal. Im on a budget and wanted the experience that comes with converting and learning the engines. I didnt know how much was different on between the engines or even what block the 1-50 matched up to in the kart engines. I will need to cut the fan cover because it has a huge circular thing that when I dismanted the engine it seemed to have no purpose. Anyways a couple of questions for the mac experts. Firstly I am starting my porting with getting rid the wall for the 3rd port and removing the ribs. I also Drilled the 3rd intake out because only 2 were drilled out. The main question I have is about the 3rd port. It has a small hole leading to the cylinder but is well below where the piston would be able to uncover it so it seems to only aid a small amount to the transfers. Do I machine boost ports leading to the 3rd port across from the exhuast? If so should it be at the same level as the transfer ports? Another question is in regard to the clutch. Will the saw clutch work if I find a sprocketed outside from another manufacturer? As you can see I am on a tight budget as I have a young family to feed but also want to finish my 62 hellcat so i can finally ride it. Anyways any input or advice on the saw engine conversion would be appreciated. I have done a lot of research but there are alot of details not mentioned on the web. Thank you

michael

wow,
for a newbe you sure waited a lonnng time to ask advise.
i didn't finish reading you post because there were a ton of sins that may have ruined your block already.
first cool your jets set down the dremel tool and STOP cutting.
wait for some direction.
hopefully the hole you drilled is the right angle and height.
messing with ports with no knowledge is like taking out your cam and just filing away at their lobes.
i am busy right now but will try to help advise you later this weekend.

dave

I am young but have quite a bit of experience. I know porting and have gone through the 2 stroke tuners handbook no less than a dozen times. Firstly, The port angle is correct pointing toward the rear wall and have measured precisely the depth and width and to be sure not to be too close to the exhaust. I started small as to not ruin the block as you have said. Right now all I am doing is removing the ribs and opening up the 3rd port. Before I do anything I do massive amounts of research and have an obsesion with gathering information to better my knowledge. I can tell you though that the block is NOT ruined and thats why I asked for help from some knowledgable people to help me along the way before I just start cutting and hacking at the block.

Hey, Michael. Things to remember... First, no matter what you do to an Mc5, IT'S STILL AN Mc5! The lowliest Mc91 out there will eat your lunch no matter what you do. It's a 50+ year old design. Second, the biggest problems on the Mc5 are the thick ring piston, the restrictive HL-63 carburetor and the 6.5/1 compression ratio. Carefully squaring the exhaust ports will be of more help than messing with the intake ports. More Macs have been ruined by modifying the intakes than anything else, unless you're a true pro. Don't bother 9-porting this engine. Removing the port ribs is a waste of time. A period correct SINGLE carb manifold, such as a Van Tech or Hovey, both of which utilize the third port as Mac intended, along with a 1" bore GAS Tillotson or Mac Flatback carb will give you all you need on a 4.9 C.I. engine. Install a head gasket which will give you about .020 squish to the piston at T.D.C., and an Mc6/Mc20 or Mc49 piston with the thin rings. Using the rod from an Mc91 series is a good move, and a direct replacement. Using the head from an Mc6 will safely raise the compression. I'm building an Mc5 as described right now to install on my '60 Bug Wasp. It'll be quick, but won't explode every time it's run. I'll have it at TBO next year, and there will be other Mc5's there to run with. PLEASE don't think you'll ever run with the Mc91's! The 610 modified West Bends I recently sold would also completely outclass a modified Mac 5. Great engine, and reliable. Gear it carefully.

Unless you have the right crank, you'll have a Mac 5 with an output shaft that may be difficult to put a sprocket, or clutch onto. Correct me if I'm wrong, but your engine has a stepped shaft.

Michael,
I should weigh in on this.

The 1-50 block is basically the same as and Mc5/6 block except for the missing intake ports and piston port intake (3rd ports). The small hole you see is to provide a bit of lubrication for the piston pin bearings. If you decide to open up the 3rd port intake, don't go any higher than the small hole which is drilled at the same height as the blocks with 3 piston ports. If you decide to machine in boost ports make sure you open up the bottom of the "fingers" into the third port cavity so there will be a path of fuel flow and remove the rib as you said you were. Also be very careful to not have the boost ports exceed the height of the intake ports or you will mess up the port timing and keep the angle of the boost port tops steep so the fuel will be directed up toward the combustion chamber rather than out the exhaust ports. Jeff Campbell has a video on his vintage powersports site showing the boost porting he did by hand on his Mc5 look-alike which was built from a saw block...a 1-51 I think. He installed an Mc6 crank which increases the stroke 1/8", squared the exhaust ports, used a stock manifold with a 3rd port block off plate and a 1" bore Tilly carb and that thing runs great. It turned out to be a very hot little engine. Not an Mc91 by any means but it would give any Mc6-9 a run for the money. Check it out.

Getting an Mc49 crank or an Mc6 crank if you can find one would help your clutch problem a lot but you could use the saw clutch if you can modify the drum by grinding off the chain sprocket and welding on a #35 sprocket. Things would be tight in there though and I don't know if the chain would clear the PTO bearing boss.

You sound innovative, I love turning these old saw engines into something that pushes a kart around, after all, chain saws were our roots!!

Good luck,
Scott

Thank you for all the great information. As far as the clutch goes I was planning on putting the clutch up on the lathe at taking off the saw gear and welding on a sprocket. I am so new to this vintage karting because I just happened my accident to aquire this kart of mine and got very interested in the vintage thing after finding out how old it was and watching some of the videos being posted. I watched the recent post for the saw engined kart another guy, sorry forgot is name, converted over to and MC5 clone and it seemed to go pretty good for 80 some odd CC's and no tuned pipe. Since I dont race and am not a hardcore true to the core enthusiest, I may have a tuned pipe constructed to my own specs for more power. Then if I do take it to an event, since I live in Medford for the duffy invitational I would just put the box muffler back on to be period correct. Again I appreciate the responses and I may post some pics when im done with it to show my results.

Hi mike,
wasn't knocking your skill but with the information you provided at first i was concerned.
with the 1-50 i believe that the rear intake port is also closed.
hopefully it's not and came with all three.
if not you need to bore the inner hole and step the outer one for the weltch plug.
or you can skip that port.

but Ted is right you're better off opening your exhaust first.
square the middle port taking care to not exceed the top or bottom curve.
leave a little bit of the inside corners round so you won't be dealing with cracks later.
on the outer ports just square the inside rib.
the over all shape of the finished exhaust should be oval with two ribs.
with this follow Teds advise and you'll have a decent runner that can go with the mc5's and mc49's.
also it'll start easy and run forever.

if you insist;
for nine porting:
if you have excellent hand skills cutting in the three extra ports is no big deal.
i say this but i was a jewelery model maker for many years working with extreme precision in a scale that makes mcculloch motors seem huge to me.
roll your piston up to the top of your current intake port and mark the wall above the three lower holes with a sharpie.
that's as high as you'll need to go to match the ports you have.
carefully open the ports to that hole in an oval shape bearing in mind that less is more.
be sure to go in increments partially doing all three the same amount each time till you reach the desired port height and size.
i had a junk block i practiced on so that helped my nerves a bit.

one thing if you're using a regular dremel tool be very careful of the nut used to tighten the shaft onto the tool.
as you're working in the slot it'll get very close to the sleeve and can ruin everything in a second.
i often wrap tape around the nut if i'm using one of those.
you'll need to get a tapered cone point shaped diamond bit and a pear shaped bit.
i also have a straight shaft diameter bit that i use to make the first guiding slot so if i need to adjust the angle left or right at first i have room.
buy the good ones they last but figure about 45-75$ for the three at a good jewelery supply house.
the home depot ones are crap.

the order i use is to cut a story slot to top of mark do each port starting with the middle one angle the sides slightly to clear exhaust.
after you're sure the direction is good take the tapered cone point and open all three holes evenly to the top in an oval shape.
when you're happy with that you can dress the inside with the pear shape.
this is when you need to be real careful since you're intent on the bottom where you're working and meanwhile that dang nut will cut above your line and wreck the block.
what you're trying to do is relieve the edges for better flow.
take the walls out of the intake side and ribs as you planned polish smooth and get a manifold plate or appropriate manifold.

2nd way would be to fill that area with epoxy.
cut in the mc91 finger ports (something that was done back then) and either add window ports to your piston to feed the new ports or overbore the crap outta that motor and install a mc91 piston.

what i would do for now is just follow teds path.
the motor you have will make a great runner.
if you wanna hot rod a motor wait till you have some track time to consider your options.
also there's other saw motors you can buy that'll be easier to hop up.

your biggest problem is the stepped crank.
replacing it with a mc6 crank would be a good fix but they're rare with no saw equivalent.
the tapered cranks with mc6 specs all have ball bearing pto's.
you could also make your saw motor fit these but the machine work is extensive.
if you want the exact work needed i'll post the article that explains this job exactly.
unless you do the work yourself it'll be too much money.

the clutch , you can modify the bell you have if you wreck it send me a p.m. i have a few around.
or find the mcculloch one it fits with the saw clutch though tight.
you might also twist Scotts arm i believe he may know of a guy that can make the shaft extension for your crank.
this person does excellent work and then you can run a regular clutch.

for your next saw to kart motor consider the mc1-62 mc 1-63 or mc250
all have fixed heads i believe but they have the mc5 spec with tapered cranks.
basically a mc49.
also they may have roller bearings i forget but just cross check in the parts c.d. that mcbob has to be sure.

the mc s250 380 300 and 450 have the 1.5 mc6 spec with a ball bearing.
the best one is the mc550 with a 2.165 bore and 1.635 stroke the exact spec as a mc91 but it has ball bearings on both sides and a fixed head.
finally the mc S-550 with a 2.217 bore and a 1.635 stroke a cross between a mc70 bore and a mc91 stroke would also be an excellent saw to kart motor .

Scrap yards are your best source i bought a mc550 that was stuck for 15$ scrap value (75 cents a #) at one.
i was planning on swiping the fan covers only off it.
but when i broke it down only one the ball bearing was rusted but the motor nearly mint inside.
so it'll be a runner, maybe i'll sneak it in to the mc49 class as a little edge for me!!!!.
ONLY KIDDING Dick Teal and company, yeash you'd think i was planning to rob babies or something.

a long letter but a big subject.
if you need help feel free to p.m. me
dave

Now using an MC6 crank with a longer stroke, wouldnt that throw off timing and I would need to modify the ports to compensate. I would think it would leave part of transfers closed on the down stroke?

Micheal,
Below are the videos I made (part 1 & 2) while building my hopped up MC5 look alike motor. This motor is not meant to be an authentic collectible item, but is meant for doing some serious lapping to experience what it was like to drive a modified MC5 back in the day, without tearing up a piece of history.

If the 3rd port holes (3 round holes) are not drilled in your saw block, then you have more options for how to cut boost ports (9 porting it, as it's called, I have no idea where these number names came from LOL, maybe someone else can explain why a boost port is called a 9th port in a motor that doesn't have 9 ports?). In part 1 of my video at the 1:27 mark, you will see the 2 boast ports I cut, they angle up sharply, they should aim towards the center of the head, and cut them the same height as the transfers. If some is starting with a block with a 3rd port drilled in it (those 3 holes), then you will want to at the boost port similar to what was in the MC90 block ... where McCulloch cut slots extending upward, one from each of the three 3rd port holes ... so, you end up with 3 narrow boost ports. Whatever you do, think first before cutting, make sure you aren't going to create any port edges that could snag a piston ring. Also you will probably be using a piston that does not have pinned rings, so you don't want to go cutting out ribs between ports or creating wide ports, those ring ends do not like such things! Just square off the exhaust ports and raise them a tad, watch my video, I did not square off everything, I wanted the ring life to remain long. You don't need to alter the transfer ports, except to add the missing ones. The 3 McCulloch transfer ports on each side of the cylinder pretty much all aim at the same spot.. when adding a missing one, just aim it towards the same point the other ones are pointing at.

As Dave said, be careful not to damage the cylinder wall when cutting on the ports, try to do as much port work as possible from the outside, going inside the cylinder as you will have to do for the boost ports is risky business, one slip of the cutting bit and you can put a deep groove in the cylinder wall that can't be cleaned up with boring / honing. Such marks near to the top of the cylinder are really bad news, but down near the ports you might get away with such a screw up, be careful, use two hands and assume the cutter can jump at any moment. Do all your port work first, then bore / hone the cylinder, and hopefully you will be able to clean up any unintended cylinder marks.

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