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Mac saw engines continued - The versatile model 250
#1
The model 250 chainsaw had a long production run. First introduced in 1962 and ran until 1970. The Super 250 was available thru 1975.

This saw replaced a bulk of the direct drive models. It consolidated the line likely to cut production costs. As previous models were dropped, so were the replacement parts. This new 250 now would replace both the 1-4X, and 1-5X models. A short lived model 200 was available for one year. A lower powered unit than all of the others covered here. Slightly more output than the Mc15 model. But more inline with price of the other variants.

With the 250 in full production, replacement parts were also consolidated. Now if you needed a cylinder block for the 1-41, 1-42, 1-43, 1-45, 1-46, 1-51, 1-61, 1-62, 1-63, and early model 640, this is now the same as a 250.

If your earlier model had been equipped with a removable head, the replacement would now have cylinder head as integral part of the block. Something else about the latest version replacement. It would have all of the intake and exhaust ports drilled. So there is also a slight increase in power output on some of the earlier models.

All of the standard series model 250 powerheads had the conventional ball bearing on the mag side of crank and needle bearing on the pto. The latest part number stamped on block is 61911. But not all of the blocks were stamped. Earlier ones were still identified by the model number. Go figure.

The early model 250 was in production late 1962. Starting a new line in 1963. About mid year the model 200 was introduced using the same block. But was a lesser model. The 200 remained in production for only 11 months. A second version of the 200 came out later in 1963. It now used a different block. This one is now shared with the model Mc15. The remainder of earlier blocks were used up in 250 lineup. You will see these stamped with both models numbers.

If you have a block stamped 200 250, it will be a later model 250 and should have all of the ports drilled including third port induction. If your saw is stamped only 200, will be either the first 250 block 58971, or the Mc 15 block, 52886.  

There are early and late 250 models. Like the 200, not all had been drilled with third port induction. Some of the early models did not have but four of the intakes. On the latest ones, all ports and third port induction became standard.

An interesting change was made is two particular models, the 1-52 and 1-53. They are nearly identical to the Super 250. Including all of the ports and passages utilized. But both of these last 1-5x models now have ball bearings on both sides of crank. Even tho it still uses the direct drive step type crank. But this line was dropped in 1963. The 250 is still using needle bearings for the duration of the standard line.

By 1963 McCulloch had a lot of different models of saws that were nearly identical, in appearance, size, power output and cost. The 250 seemed to be a consolidation of many direct drive models. Or just a newer series of numbers used for them. Parts making up the 250 line could now replace earlier models.

So if you have a model 250, it is like a universal blood donor. Your saw may have only 4 of the intakes drilled and no third port induction. It could have all six of the intakes drilled and no third port induction. If you are really special, then maybe it will have all six intakes drilled and the third port induction utilized.

Here are some known compatible blocks that will interchange or are almost identical to the standard 250. But not all of the ports are drilled on most of these either. 58971, 58528, 52886, 52886A, 48946A, 47661, 61911, 62481. These are all fixed head blocks.

If you notice above the 52886 is for a Mac15 saw motor. The 52886A is for the first model Mc49. It is also used for the later model 200.

The block 47661 is also used for the Mc-2 kart engine for the bushing class. But it is 100cc in displacement. It also shares the same crankshaft as all of the 100cc standard series kart engines. This would be the idea cheater 80cc clone to build.

With a standard 250 in production for so long, there needs to be a Super 250 right? Well McCulloch wasnt going to let you down. What would make it better than the standard 250? Always more power. The Super 250 model has a longer stroke of 1.5 inches. It was manufactured from 1970 thru 1975.

But you ask, what about the model 300? Is it next in line to replace the 250? Well not exactly. Introduced in 1964 and available thru 1966. It is basically the same as the latest model Super 250. This one has ball bearings on both sides of crank. It shares the same block as models 380, 380A and 440. It also has a tapered end pto crank. There was an early and later version like most in this time frame.

[Image: attachment.php?aid=4661]

On left is the early style intake opening of the fixed head models. Depending if equipped with needle or ball bearing on pto can be any of the listed part numbers. On right in the later intake opening. Again depending on pto bearing and stroke as to the part number.

The early model 300 on left is part number 53563A. Later model number on right is 62707. For a Super 250 is 83830.

The above pics for early 250 is 58971 then replaced with 61911. Late model on right is 62481. The 62481 first appeared in 1965. It will be the last major change of the model 250. The Mc49C first appeared mid year in 1968. It shares the same block as this latest model 250 block. The more you dig the more part numbers can be found that have been superseded. Most numbers listed on this page were used between 1962 and 1975.

There are around 6 variations of the 250 series. Some are identical to other models.

Have I confused you yet? I certainly am. 

When the Mc6 came out it had just about the same power on track as a Mc10. Only cheaper to buy. The Mc10 has ball bearings on both sides of crank, and was slightly faster right out of the box. So what do all the speed shops do? They get smart and figure the double ball bearings must be what makes the difference. 

Send me your crankshaft and block and I can convert it over to be just like a Mc10. Only $29.95 plus shipping. Except it didnt make any real difference. But when you are bench racing it was always the better choice or the super series kart engines would not have been built that way. So it has to make a difference, even just a little bit. And everything helps, so send me the money anyway!

Include a check for $29.95 plus return postage to:
Get Faaaaaast Kart Shop
1000 Checkerd Flag Drive
Always somewhere in Southern California 902XX


If you want to bore out any of the removable head standard series blocks for ball bearing on pto side with tapered shaft, these are the later model cranks that fit. Super 250, 380, 380A, 440, 450, and 660 will do the job of converting your wimpy under size wannabe 4.9 Mc6 clone into a thoroughbred 5.3ci Super Mc6.

One important note. If your motor is drilled for third port induction, it will need a different piston than one without. Regardless if your motor is 1 3/8 or 1 1/2 stroke, it will use a piston with longer skirt. The skirt in 0.060" longer for motors utilizing third port induction. Short piston is about 1.535", long 1.595". If your block has been nine ported, or 8 ported if not previously equipped, then just need to make sure the skirt is long enough not to open the exhaust ports when at tdc.

I will be doing a write up sometime in the future covering how to do this great conversion using saw parts to make a Super Mc6. Stay tuned more might follow. Probably later than sooner.

Please feel free to rate this thread if you think it was of some benefit reading.


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#2
Well it took some time digging thru manuals and IPL's. But I have specifics on the 200 and 300 series chainsaw engines. These are all fixed head models. The years covered are 1962 to 1975.

I will be posting the various part numbers for these models, including piston, rod, crank and cylinder. Also the production dates of each. Soon as I come up with a decent format to post here, the info will help you to identify your old saw to the year and even differences in each of them. The model 250 alone has at least 6 variants I am aware of so far over the years. Some big differences in them.
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