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Need help ID ing Mcculloch motor. Mc100? - Printable Version

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Need help ID ing Mcculloch motor. Mc100? - Dean Richards - 03-08-2017

Hey all, just acquired what I think is at least a Mc 100 from a swap meet and I need some help making sure that is what it is.  Found the thread about the difference in engines, but still have some questions and facts about my engine. First of all the bore is 2.265 and stroke is 1.835,  one large exhaust port that appears to be stock, and has the recessed copper head gasket. I am assuming this to be a Mc100 with rebore of .015? since mc 100 bore is normally 2.250 and 101's are 2.280?
 
Does not appear to have a serial/model#. It has a BDC 14 carb and has the chrome flywheel shroud. other then the shroud chrome flaking off, it appears to be in great shape.

Any assistance would be appreciated. Thanks, Dean.


RE: Need help ID ing Mcculloch motor. Mc100? - Sterling Brundick - 03-08-2017

(03-08-2017, 07:48 AM)Dean Richards Wrote: Hey all, just acquired what I think is at least a Mc 100 from a swap meet and I need some help making sure that is what it is.  Found the thread about the difference in engines, but still have some questions and facts about my engine. First of all the bore is 2.265 and stroke is 1.835,  one large exhaust port that appears to be stock, and has the recessed copper head gasket. I am assuming this to be a Mc100 with rebore of .015? since mc 100 bore is normally 2.250 and 101's are 2.280?
 
Does not appear to have a serial/model#. It has a BDC 14 carb and has the chrome flywheel shroud. other then the shroud chrome flaking off, it appears to be in great shape.

Any assistance would be appreciated. Thanks, Dean.
Dean, I am clearly not an engine specialist by any means but if you could post some pictures it would help you immensely.


RE: Need help ID ing Mcculloch motor. Mc100? - Vince Rosanelli - 03-08-2017

Dean,
I'm not sure if this chart from MacBob's is on here somewhere, but just in case, it's a good reference....

http://archive.is/cDV6u

MC75 and MC100 each have the original bore dimensions you outlined above, but according to the chart, neither have the recessed exhaust gasket. The chart indicates the differences between these two are LH vs. RH pto threads and original porting. Post photos when you get a chance, you should hopefully get the real deal expert feedback then from those with tons of experience. Good luck!


RE: Need help ID ing Mcculloch motor. Mc100? - Scott Kneisel - 03-09-2017

(03-08-2017, 07:48 AM)Dean Richards Wrote: Hey all, just acquired what I think is at least a Mc 100 from a swap meet and I need some help making sure that is what it is.  Found the thread about the difference in engines, but still have some questions and facts about my engine. First of all the bore is 2.265 and stroke is 1.835,  one large exhaust port that appears to be stock, and has the recessed copper head gasket. I am assuming this to be a Mc100 with rebore of .015? since mc 100 bore is normally 2.250 and 101's are 2.280?
 
Does not appear to have a serial/model#. It has a BDC 14 carb and has the chrome flywheel shroud. other then the shroud chrome flaking off, it appears to be in great shape.

Any assistance would be appreciated. Thanks, Dean.
Mc100 would have a part number stamped next to the oiler nub on the back side of the crankcase.  The part number for the Mc100  block is 47873B   Some later Mc75 blocks have 47873 stamped but the 100 has the B added.

The block also definitely does NOT have a recessed head gasket unless someone added it and the crank PTO has RH threads and a key slot.  None ever had LH threads which didn't arrive until a few years later with the 101AA.


RE: Need help ID ing Mcculloch motor. Mc100? - ted johnson - 03-09-2017

Scott, I had three 101A/A's, and all had a PTO side keyslot and RH threads. The 101B I bought for a buddy had no keyslot, and had LH threads. Did some A/A's have the LH threads? I bought all three of my A/A's at the same time in '73 from Brown Motorsports in Massachusetts. I had two as duals on my '73 Bug Stinger, and later as B Limited opens. Ted


RE: Need help ID ing Mcculloch motor. Mc100? - Vince Rosanelli - 03-10-2017

I'm certainly not an expert or even close to one, and am trying to learn as much as possible through resources like this forum and others and all the great folks on them. What I see according to the MacBob chart found in the link provided above, is that it suggests the MC75 came with RH PTO threads and beginning in 1966, the newly introduced MC100 came with LH PTO threads? It also states the MC75 came with factory 9 port transfer ports where the MC100 did not. It further indicates the 101, 101A and the 101A/A came available with either RH or LH threading. The 101B, 101C, 101D and the 101MC came available only in LH threaded PTO.


RE: Need help ID ing Mcculloch motor. Mc100? - Paul Hunter - 03-10-2017

My all original mc100 has right hand pto threads with the original crankshaft. 
Paul


RE: Need help ID ing Mcculloch motor. Mc100? - carl haydt - 03-10-2017

Gotta post some pics if you want a correct ID but I can tell ya the Mc100 had a small flatback carb/intake from the factory not the BDC-14 and intake you said yours has.


RE: Need help ID ing Mcculloch motor. Mc100? - Dean Richards - 03-11-2017

Hope these pictures help with the ID. if not let me know and I will post others. I was watching a you tube video the other day on Mac chainsaws and the guy said if you have porting humps under coil it is a 101B and that is what this has. You guys are the experts. Again any help is greatly appreciated. 
 
                                                                        Dean.


RE: Need help ID ing Mcculloch motor. Mc100? - Dean Richards - 03-11-2017

The Crank threads are right hand.