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| Posted: Wed Aug 15th, 2012 07:40 pm |
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1st Post |
Cam Sweet
Member
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All,
This may be opening a can of worms but I love info. I picked up a '66 Rupp A-Bone a while back, with a MC90 on it. In looking through the boxes of other stuff, I uncovered another cover with a MC90 decal on it and enough parts to complete the engine. Of course my mind went, "twin MC90 A-Bone" hehehe....
My quetion.. I see a lot of info and discussion on 91. 91B1, 92 and 93 Macs. What is the lineage and progression of the McCulloch engine development and what is the differences in the '90?
I'm envious of you guys that raced these things through the period of time when this was all happening..
Too much to discuss??
Thanks a ton!!!
CamLast edited on Wed Aug 15th, 2012 11:06 pm by Cam Sweet
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| Posted: Wed Aug 15th, 2012 08:59 pm |
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2nd Post |
| Posted: Wed Aug 15th, 2012 09:01 pm |
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| Posted: Wed Aug 15th, 2012 09:14 pm |
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4th Post |
Cam Sweet
Member
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So, I've seen Bob's data before and it's great spec's. Why, when you guys refer to MC9X, do you refer to 91's,92's and 93's. What's different about the 90? Are all parts interchangeable between the MC9X's, including the 90's?
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| Posted: Wed Aug 15th, 2012 09:15 pm |
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5th Post |
Cam Sweet
Member
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...and what happened in the natural progression of these motors that mandated the changes?
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| Posted: Thu Aug 16th, 2012 07:51 am |
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6th Post |
SteveO
Member
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Cam,
The Mc 90 model is unique among the 6.05 CI (100cc) "standard series" engines that include the Mc2,5,6,7,8,9,90,91,91A,91B,91B1,92 and 93 models.
It is the only factory "9 ported" version and the only model that was built with a single large exhaust port.
Another feature that makes the 90 unique is that it was supplied with an intake manifold made by REED Eng. and it was called a sloper with a Go Power six petal reed cage... also unique among the standard series models
The 90 was also the first of the 100cc standard series engines to be fitted with the "square" head which replaced the long used round heads that were common on the 9 and earlier models. The 90 is a good solid engine and much more rare than the 91 and later models. Not quite as much power but the differences are pretty small if the same intake and carb are used.
The 90 was only in production for a few months and they didn't sell many.
The 91 was a major design change with the "third port" passage completely removed from the block casting and the introduction of the "9 port" piston as the OEM piston.
Crank, rod, side plate, stuffer are interchangeable with the later models.
Definately good engines to restore for a collector vintage kart... you won't see many 90s, especially a pair on the same kart so I would go for it and set that A-Bone up with twin 90s.... it will be almost as rare as my Gran Prix with twin 100s!
Steve O'Hara
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| Posted: Thu Aug 16th, 2012 01:01 pm |
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| Posted: Thu Aug 16th, 2012 01:26 pm |
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8th Post |
Cam Sweet
Member
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Outstanding Steve!! Thanks!! I love this kind of info and is exactly what I was looking for..
Cam
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| Posted: Thu Aug 16th, 2012 03:46 pm |
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| Posted: Thu Aug 16th, 2012 06:01 pm |
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10th Post |
SteveO
Member
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That is the correct manifold and reed cage for the 90 and 100 models. There is also a generic version of the manifold that does not have the identifying numbers and letters. I don't know if REED made them for McCulloch or if McCulloch did knock offs without the lettering.
I have one of the letter free versions in my collection and it is the only one I have ever seen.
Steve O'Hara
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