Mac 250 kart motor?

[T.Roller]

I was doing alittle reading today and found that a MC91 will fit on a 250 chassis. Is this true? If so is it worth the swap?

 

[psuiewalsh]

@Lee H

 

[T.Roller]

@Lee H

Thank you

 

[awol]

It will with a little work. The greatest advantage of the kart motors is the pyramid reed setup, and that cannot really be incorporated into a 250 build. Just installing a mc91 or mc92 long block will net a good gain though.

 

[T.Roller]

It will with a little work. The greatest advantage of the kart motors is the pyramid reed setup, and that cannot really be incorporated into a 250 build. Just installing a mc91 or mc92 long block will net a good gain though.

So the reed setup on the kart motor cannot be used?

 

[awol]

Not without a LOT of butchering. The oiler tank would have to be moved, and the carb box pretty well gutted. The carb would also be left protruding a long ways above the top of saw.
A way to get around the oil tank issue would be to use a 1-41/d36/1-50 saw body with the oil tank in front of the fuel tank. I have never done one of these builds using a non super series of engine and saw; I'll have to do a little research and get some photos.

 

[T.Roller]

Not without a LOT of butchering. The oiler tank would have to be moved, and the carb box pretty well gutted. The carb would also be left protruding a long ways above the top of saw.
A way to get around the oil tank issue would be to use a 1-41/d36/1-50 saw body with the oil tank in front of the fuel tank. I have never done one of these builds using a non super series of engine and saw; I'll have to do a little research and get some photos.

I'm just looking for a fun project with good gains. I don't want to modify a lot but don't mind alittle. So you say just the long block would net good gains. By long block you mean cylinder, crank, piston, and rod correct? Also would my stock carb do well?

 

[T.Roller]

Also the reason I'm wanting to do a 250 is cause I already have two complete saws

 

[Al Smith]

Dan Henry,aka Dozer Dan--- Dolmar Dan sent me over a smashed Super 44 Mac .My intention ,some day ,if I get time and the motivation to soup the thing up,use a 250 chassis and make an 80 cc vintage hotty .Weather that ever happens or not remains to be seen .

Fun project but I doubt,pipe,big carb whatever if it will ever outrun a more modern saw .You never know until you try .I've done more stupid things before .

 

[Lightning Performance]

These both sound like great builds.

 

[T.Roller]

These both sound like great builds.

If I could come up with a motor than I'd get mine rolling.

 

[Lightning Performance]

Is this going to be a pipe saw or work type saw?

 

[Al Smith]

A regular old stock 250 has a fair amount of torque but it lacks in RPMs .I'm afraid if you get to cranking them up by whatever means the rod and piston would fail .At one time of course about everybody in the kart soup up business made them but they are rare and anyone who has the parts gets a bloody fortune out of them .
I'd rather have a 101 but that is a task just to find one in decent shape that again doesn't cost an arm and leg .Maybe some day ,right place right time .

 

[T.Roller]

A regular old stock 250 has a fair amount of torque but it lacks in RPMs .I'm afraid if you get to cranking them up by whatever means the rod and piston would fail .At one time of course about everybody in the kart soup up business made them but they are rare and anyone who has the parts gets a bloody fortune out of them .
I'd rather have a 101 but that is a task just to find one in decent shape that again doesn't cost an arm and leg .Maybe some day ,right place right time .

I gotcha. Thank you

 

[Chainsaw Jim]

I'm afraid if you get to cranking them up by whatever means the rod and piston would fail.

I'm curious about this. Is it your experience or just something you wouldn't want to do?

 

[Al Smith]

Based on kart engines of the 60's .They were good for about 10-12 races before a rebuild if ran on alcohol .Now thats about 3 to 5 minutes on a 10 lap heat race and 8 to 10 on a 20 lap feature depending on weather it was a tenth mile or eighth mile oval .That's with racing pistons and rods not chainsaw stuff .So you are looking at maybe an hour and a half running time all total .

How they did on enduros and road courses I have no idea,those came long after I was interested in karts .However it didn't make any diff if it was a Mac engine,WestBend ,Power Products they all needed attention .For that matter I have a WestBend 580 I just don't think it's up to the task .

 

[T.Roller]

Based on kart engines of the 60's .They were good for about 10-12 races before a rebuild if ran on alcohol .Now thats about 3 to 5 minutes on a 10 lap heat race and 8 to 10 on a 20 lap feature depending on weather it was a tenth mile or eighth mile oval .That's with racing pistons and rods not chainsaw stuff .So you are looking at maybe an hour and a half running time all total .

How they did on enduros and road courses I have no idea,those came long after I was interested in karts .However it didn't make any diff if it was a Mac engine,WestBend ,Power Products they all needed attention .For that matter I have a WestBend 580 I just don't think it's up to the task .

Thank you for the info

 

[Chainsaw Jim]

Thank you for that info @Al Smith
An hour and a half run time for a racing chainsaw equates to approximately 540 three cut cant races and approximately 350 one cut 14" round races. I was having second thoughts on building a 450 into something fun, but now I think it might be worth the time.

 

[RandyMac]

 

[Al Smith]

I really don't know what would happen if you put the soup to a 250 .It would run for a while for sure the question is how long ? On the other hand they are plentiful .You damned sure aren't going to run it in 540 races .