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McCulloch Super 250 for Kart engine?
 Moderated by: Kevin Gagne
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 Posted: Sun Dec 23rd, 2007 04:09 pm
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Darrell Kimball
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Joined: Tue Dec 11th, 2007
Location: Boston, Massachusetts USA
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Mana: 
Hey everybody,

I happened across an immaculate McCulloch Super 250 chanisaw (87cc). I want to strip it down and use it for a kart motor. Am I asking for big trouble?

Thanks,

D

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 Posted: Sun Dec 23rd, 2007 11:36 pm
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Robert Duke
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Mana: 
Hi. I don't know much about vintage karts, just what I read,  so I can't answer all your questions. There was a thread about the Mac 250 at the rear site http://www.rearenginekarts.com but  I think its gone since they got the new message board. I've got a pic from that thread that shows a 250 mounted on a stand I can send you.  I think it said the saw engine is similar to the kart engines, but some have stepped cranks.  This site http://64.224.15.40/mcculloch_main.htm has a lot of Mac info and shows the stepped crank adaptor(look under "Information Articles). I remember that some guys that posted in that thread did't think that one 250 engine would have enough power- might take two. Here's another site with some Mac info http://www.users.bigpond.com/ozflea/saws.html

If the experts don't answer your post remember this..... I've learned form reading the vintage kart forums that if your not talking about true "Vintage Racing Kart" equipment, sometimes the experts won't respond to your post. So maybe I've helped you some.

Attachment: 250 saw engine-2.jpg (Downloaded 320 times)

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 Posted: Tue Dec 25th, 2007 12:29 pm
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Mark L Havery
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Mana: 
Hi Darrell,

 The MC Super 250 saw engine can make an excellent kart engine that pretty much

turns out to be a McCulloch 49 after some work. I plan to use 2 on my McCulloch R1

kart. To make the conversion work out best and most convenient you should replace

the crankshaft with one from a MC49, Hanson Duncan has these. You can use a MC

49 intake manifold to replace the saw version, or a small carb 100cc manifold after

market type that uses the pyramid reeds for increased performance. Later in the

production of the MC49 included a version of this. Also the saw pistons had the

thicker rings, but I have been told not all. It would be your choice to replace the

piston or not if it is in good shape, but if it needs replacement now would be the the

time to replace it with a thin ring piston. During the conversion on the engine would

be the perfect time to replace the gaskets and crankshaft seals.

 I know  this covers just the basics, but at least I gave you a little info on your saw

to kart engine project. Forgot to mention some Super 250's had the extra port

opened up and some did not. Good luck with your project.

Mark

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 Posted: Sat Dec 29th, 2007 03:11 am
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Mike Morrall
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Mana: 
Mark,

I have a motor that I was told was a 49, however it most likely began life as a saw engine (has the thicker rings). The crankshaft is now a straight 5/8" shaft so someone has replaced it. How can I tell what saw motor it is? The number on the block is 52886A but I can't find it in any books. Any idea?

Thanks.

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 Posted: Sat Dec 29th, 2007 07:11 am
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Mark L Havery
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Mike,

 I really have no way to tell you what saw block you have.

Mark

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 Posted: Sun Dec 30th, 2007 05:00 am
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Ray Kelley
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Joined: Tue May 2nd, 2006
Location: Chino, California USA
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Mana: 
Hi Mark,

That number points to a Mac 15 saw, definately a lo po motor as it has some of the ports blanked off. You are correct though regarding it LOOKING like a 49, everything bolts up and works well. I am including a photo of my saw powered Bug Wasp, '61 model. I run an Mc450 saw engine, thick rings and all baby :)   You can see that even this 5.5cu motor looks alot like your 15, and all the kart stuff bolts on.

write me @ kelley4four@msn.com, I like to talk :)

best wishes,

Ray Kelley

Attachment: 100_1160 copy2.jpg (Downloaded 257 times)

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 Posted: Sun Dec 30th, 2007 07:27 am
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Mark L Havery
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Mana: 
Ray,

 That is great info. I plan to run a pair of Super 250's on my McCulloch R1 and in fact

do an article on the build up of one, what parts are required and a track test with the

engine on a Fox Flyweight. This will be in the VKA newsletter sometime this year.

 I think these engines are perfect for the young drivers of vintage karts. They have

some poop but are not as powerful as the 100cc Mac kart engines, especially when

the driver is young and light.

Mark

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 Posted: Mon Dec 31st, 2007 01:04 am
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Paul Booth
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Location: Beardstown, Illinois USA
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Mana: 
Hi Mike

   The block was for a Mac 15 chain saw. The saw was an early 60's Manufactured by Mcculloch as the first United States chain saw to retail for under $100.00. Sorry to say it did not have enough power to turn the chain let alone cut wood. The early versions did not have all the ports drilled so it would make for an under powered kart motor. If all the ports are drilled it would be same as Mc49 block. The Mac 15 saw had the gas and oil tank located above the power unit as it had a gravity flow single diaphragm carb. It was fed through the stuffer area and not the normal intake area.

                                    Paul

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 Posted: Mon Dec 31st, 2007 03:15 am
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Mike Morrall
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Mana: 
Thanks Paul/Ray/and Mark.

I opened it up and the ports have been drilled out and the exhaust ports have been raised. Looks like someone spent some time and did a pretty good job. I picked it up pretty cheap so it was worth the chance. If nothing else, it will be good for my son to use on the Dart. Thanks for the help!

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 Posted: Wed Jan 2nd, 2008 03:12 pm
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Scott Kneisel
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Joined: Fri Aug 17th, 2007
Location: Farmington, New York USA
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Mana: 
I have several saw engines that I have been converting to kart engines for my grandson. I have stripped and readied a Mac300, (very similar to a super 250), 2ea MAC450's and a Mac 740. The 300 & 450's have a nice 1.5" stroke crank with dual ball bearings. The shaft is also tapered and keyed with a RH thread. The 300 has a small bore like the Mc49 but the  450  has a 2.164bore which is standard for the 100cc kart engines. The 2.164 bore and 1.5 stroke makes it about 90cc which is a nice size for a vintage kart and a young person. Kart pistons could probably be used but I am sticking with the thick rings for durability. The 740 is a 100cc super engine with a nice MC20,30,40,45 crank.  All have intergal heads.

None of these are 9port engines so just about any vintage manifold and carb can be used. I plan on using the standard McCulloch manifold and large bore carb from an MC91. If that is too much carb, I will go to the small mac carbs and an older manifold design.

 

My only concern with these saw engines is piston to cylinder clearance. According to the McCulloch documents, the saw engines specify 0.003-0.004 clearance,  the kart engines specify 0.005-0.006 clearance. I don't know if I need to get them honed for more clearance.  Any opinions here??

I also have a question about replacing the rod bolts for the re-biuild which I will put in a seperate post.

 

I am gaining a lot of knowledge about the saw engines and experience will help me some more I am sure. I am really having fun with this.

emails for knowledge sharing are welcome. chuckie72us@yahoo.com

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