Mac 1-70 vs Mac 1-71 Saws

[Tim Exley]

From all the threads I've read it seems the Mac 1-70 saw is the best one for a Mac 10 clone. 
What about the Mac 1-71 saw? According to acresinternet the specs are the same, just one year 
year later 60-61. 
Thx

[David Luciani]

there's a question i haven't seen in a while.
i'm going off memory so i may be a little off anyone seeing a mistake feel free to correct me.

short answer
if you are looking to make a motor indisernable from a mc10 the mc1-71 won't work.


the mc1-70 and 1-80 saw are indeed the correct saw to use for a mc10 clone.
right spec right parts.

the mc1-71 has the correct specs (i think???) but is built differently.
so right specs wrong parts.


what differences?
on the mc 1-71  the flywheel back plate is different as are the points,flywheel and crank.
but i seem to recall does have the 1.5 stroke that's where my memory is fuzzy.

the crank is definitely built in the later style which means its the first version of points near bearing directly off the crank instead of a pushrod.
mc10's and early saws were built with a crank/pushrod operated set of points.the points are conveniently located outside the flywheel area for easy changes.
it also has more parts which in theory could cause trouble.
as the points are external visible it's pretty obvious that the "mc10 clone" made from a MC1-71 isn't really correct.

DOES IT MATTER?
performance wise nope .
i'm pretty sure the mc1-71 has a 1.5 stroke so a really nice mc10 spec'd kart motor can easily be built from a mc1-71.
it won't be a clone mc10 as the flywheel inner flywheel cover points and crank will be different and noticable to a serious mcculloch person.
even if it has the 1.625 stroke it'll make a fine kart motor just not exactly one that was commonly available to racers.
as i recall again memory thing it was a motor we were thinking could be a nice mc20 clone so the stroke may be longer.
as i recall it didn't fit up the mc20 piston as the block is still the slightly shorter one.

if my memory serves my buddy rick chapman was gonna build a mc20 out of one of my mc1-71's but rejected the project when he found the top piston ring (mc20 piston) was going past the bore.
when i got the block back i played around with a mc10 piston instead of the mc20 piston and was certain that fit up.
in the process of assembling i damaged the bearing cup in trhe piston.
(long story about stupid me) so i parked the project still on bench all neatly stored with an inch of dust going on ahem maybe 10 or 15 years now??

anyway with a mc10 piston for the thin rings you should have a good motor.

perhaps in a really close kart show where tiny era correct mistakes mean something you'd be unhappy with the results.
but as a kart motor you'll be happy with either.

if you decide to go forward with build keep thread going .
i might actually get inspired drag out that shelved project and build it.
if it does have a longer stroke you'd be creating a stroked mc10 motor never a bad thing.

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Save

[Tim Exley]

there's a question i haven't seen in a while.
i'm going off memory so i may be a little off anyone seeing a mistake feel free to correct me.

short answer
if you are looking to make a motor indisernable from a mc10 the mc1-71 won't work.


the mc1-70 and 1-80 saw are indeed the correct saw to use for a mc10 clone.
right spec right parts.

the mc1-71 has the correct specs (i think???) but is built differently.
so right specs wrong parts.


what differences?
on the mc 1-71  the flywheel back plate is different as are the points,flywheel and crank.
but i seem to recall does have the 1.5 stroke that's where my memory is fuzzy.

the crank is definitely built in the later style which means its the first version of points near bearing directly off the crank instead of a pushrod.
mc10's and early saws were built with a crank/pushrod operated set of points.the points are conveniently located outside the flywheel area for easy changes.
it also has more parts which in theory could cause trouble.
as the points are external visible it's pretty obvious that the "mc10 clone" made from a MC1-71 isn't really correct.

DOES IT MATTER?
performance wise nope .
i'm pretty sure the mc1-71 has a 1.5 stroke so a really nice mc10 spec'd kart motor can easily be built from a mc1-71.
it won't be a clone mc10 as the flywheel inner flywheel cover points and crank will be different and noticable to a serious mcculloch person.
even if it has the 1.625 stroke it'll make a fine kart motor just not exactly one that was commonly available to racers.
as i recall again memory thing it was a motor we were thinking could be a nice mc20 clone so the stroke may be longer.
as i recall it didn't fit up the mc20 piston as the block is still the slightly shorter one.

if my memory serves my buddy rick chapman was gonna build a mc20 out of one of my mc1-71's but rejected the project when he found the top piston ring (mc20 piston) was going past the bore.
when i got the block back i played around with a mc10 piston instead of the mc20 piston and was certain that fit up.
in the process of assembling i damaged the bearing cup in trhe piston.
(long story about stupid me) so i parked the project still on bench all neatly stored with an inch of dust going on ahem maybe 10 or 15 years now??

anyway with a mc10 piston for the thin rings you should have a good motor.

perhaps in a really close kart show where tiny era correct mistakes mean something you'd be unhappy with the results.
but as a kart motor you'll be happy with either.

if you decide to go forward with build keep thread going .
i might actually get inspired drag out that shelved project and build it.
if it does have a longer stroke you'd be creating a stroked mc10 motor never a bad thing.

Save
Save

Dave, Thanks for the great info. I'd read over all your posts on saw conversions, but had never seen anything on the Mac1-71. Just want to have a Mac 10 spec engine. Have a S44a but not sure if it's any good and then found this 1-71 that looks like it's been used very little. 
Thanks for sharing your knowledge and experience.

[David Luciani]

[quote pid='5263' dateline='1502720490']
veDave, Thanks for the great info. I'd read over all your posts on saw conversions, but had never seen anything on the Mac1-71. Just want to have a Mac 10 spec engine. Have a S44a but not sure if it's any good and then found this 1-71 that looks like it's been used very little. 

Thanks for sharing your knowledge and experience.
[/quote]

TIM,
the s44a is an excellent choice for a mc10 too.
the main difference between them and 1-70 is the s44a and s55a have slightly different blocks and a less balanced crak. but they make excellent mc10's i sent several clones out built with them one to italy and everyone who got one was/is happy.
d

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