Calling all McCulloch gurus

Addicted 2 Minis

Well-Known Member
#1
I have been contemplating running a McCulloch for a future build, thing is, I know next to nothing about Mac's. What is the best Mac I should look for to build, by best I mean easiest to get parts for, make good power and not break the bank.

Thanks in advance,
A2M
 

Addicted 2 Minis

Well-Known Member
#2
Ooops!, I forgot to also ad, is there certain chainsaws or other power equipment I should keep an eye out for?. Is there any cheap/free power secrets like using cranks from one model to another to make a stroker?. Any and all info will be greatly appreciated, I promise, if you tell me your power secrets, I won't share them!, Hahahaha.

-A2M
 

JTG

Active Member
#5
It doesn’t matter which Mac you decide to use it will be a costly investment.
Mac-91 rebuilt approx. $500.00.
Engine mount $130.00
Clutch $250.00
Exhaust $100.00
Throttle Mounting: $50.00
Air Cleaner: $25.00
Gas Tank: $100.00
Recoil starter $115.00
--------------------------------------
Subtotal $ 1,270.00
To avoid burning up your clutch, your bike needs a jackshaft.
Hope this info helps. I have several mini's with Mac's.
 

Addicted 2 Minis

Well-Known Member
#6
It doesn’t matter which Mac you decide to use it will be a costly investment.
Mac-91 rebuilt approx. $500.00.
Engine mount $130.00
Clutch $250.00
Exhaust $100.00
Throttle Mounting: $50.00
Air Cleaner: $25.00
Gas Tank: $100.00
Recoil starter $115.00
--------------------------------------
Subtotal $ 1,270.00
To avoid burning up your clutch, your bike needs a jackshaft.
Hope this info helps. I have several mini's with Mac's.
Upon my limited research I have found Mac 6,7,8,9's, 70's, 91's,101's and then I see others listed as 10-10. Is there any power equipment that use the same powerheads as the kart engines?. I would like to find something somewhat fresh, race engines usually aren't listed for sale if they have any good life left or haven't been wrongfully modified by somebody. I know I'll have about a grand into one, by cheap I mean finding a chainsaw or something that uses the same powerhead and swapping parts from other engine models to increase performance rather than sending it out for machine work, Thanks for the info.
 

Addicted 2 Minis

Well-Known Member
#8
After about a week of hardcore research, I found my answer and the answer is YES!, you can use a chainsaw powerhead for a kart engine. The McCulloch 250, Super 250 and 300 powerhead can be used to make a MC49 clone. Others may be able to be used as well but what information I did find only covered these three models. Essentially you just have to remove all the stuff that makes it a chainsaw, put a kart intake and carburetor on it along with a kart stuffer and there ya go. Some cranks are different and for that they make an adapter, finding one that has a tapered crank is hit and miss. The biggest thing is that some chainsaw blocks don't have all the intake/exhaust ports drilled and therefore you'll have to find a block that does. The next thing is, some of the cranks have a 1.375" stroke while others have a 1.5" which will bring your 80cc MC49 up to 87cc. All three use the same piston but using one designed for karting is recommended. So, what you want to look for is a McCulloch 250 or Super 250 block that has all the ports drilled, preferably a tapered crank and if you want 87cc then you'll want a tapered crank with a 1.5" stroke. Some saws have the stuffer cast into the tank but not all so you may or may not need a stuffer. Then get an intake and carburetor and you have an MC49 clone. There are some other differences in saws over the years so it's kind of hit or miss getting exactly what you want but if you like to tinker and perhaps save some money, this would be a good way to go. Below are pictures of two McCulloch 250 chainsaw blocks, one with 2 ports drilled and the other with 3.

2 port holes.jpg

3 port holes.jpg
 
#10
I have since found that you can make a MC-101 clone from a McCulloch SP125 chainsaw, the only thing about doing this is a decent SP125 cost about the same as an MC-101.
Great point about cost .I`am a Kart Racer and McCulloch expert from the mid 60`s Being a Tool & Die Maker, I carefully measure all engine components, and being a competitor myself know what works and what does not My engines held sprint track records all over California, as well as conversions to Mini Bikes A clone may look similar on the outside but it is not correct internally The product castings are different. True duplication would be far too expensive.
Take Care,
Kerry Davis
 
#11
I have since found that you can make a MC-101 clone from a McCulloch SP125 chainsaw, the only thing about doing this is a decent SP125 cost about the same as an MC-101.
Some McCulloch dealers were taking the SP-125 and SP-797 and coverting the engine to the 101B. Some custom fabrication was required for them to fit. These 2 chainsaws with or without the 101B are at the top of a collectors list and are worth a fortune.
 
#12
Some McCulloch dealers were taking the SP-125 and SP-797 and coverting the engine to the 101B. Some custom fabrication was required for them to fit. These 2 chainsaws with or without the 101B are at the top of a collectors list and are worth a fortune.
Here is a performance tip about the Mac 101 series Kart Engines. They absolutely Make the most power with a stroker crankshaft bringing the stock bore engine up to 125 CC`s; Raising Compression up to 16 to 1 and adding V-12 Reed cage with twin Double Pumper HL Tillotson Alky Modified Carbs. That was the good old days running in B-limited class sprint racing and sending the Italian B-Bomb Karts a Packing.
 
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