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421 cheetah cub


McFlerry

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Better value wise to spend the money on a cub when you look at what it costs dollar per hp. But if you already got good stock cyls, you may be better off going that route unless you trying to get a motor to a specific point. Stock cyls can perform well. I have 2 stock 4 mil motors that make 80 and 105 hp.


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Any motor will run hot regardless of it isn't set up right. A cub can run on a stock radiator. As far as a straight swap, I've no clue in your situation.

Many parts can be used from a stock motor. I've no idea what you mean by "your motor blew". That's like saying "it has had the balls run off of it". It gives no details. Is the crank good? Are the cylinders good? Cases good? Pistons good? Etc etc.


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So it would possibly need pistons, rings for sure, maybe a crank, and the cylinders are probably fine after honing and possibly a bore to the next size. Would have a lot cheaper to repair that then to change to a cub. Assuming stock stroke (details) so a stock stroke cub would be a direct swap.


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For a cub to run "right" it needs

much bigger carbs ( that means intakes too)

stock reeds are going to choke it

 it breathes much better so pipes are a good idea

and a cool head with large bore domes.

 

 

To do it right will not be cheap.

looking at a 4mm serval build myself. Luckily I already have the crank, intakes and carbs

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You can run 87 if the compression is set right.

figure out who is going to be your "builder" even if you assemble it.

ask the builder what he recommends, then do it. If you are totally honest with what you want out of it, the builder will do his best to get you what you want.

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2 strokes are stupid simple to assemble. If you have done any 4 stroke builds a banshee will be a piece of cake to assemble. 

 

A cub is a peaky engine to build, what do you plan on doing with it? trails and just fun riding with a little drag racing thrown in, a serval would be better.

on the pipe all the time? Cub is the a much better fit for that riding.

 

Getting close to winter project time for me, My bike will be torn down rather soon, debating on whether to rebuild the engine that is in the chassis, or go with the spare bottom end.

Going to build both eventually, since my wife has a banshee as well and the engine has not been open in 14 years....

64.25mm bore no porting stock original crank t-5's and boysen rad valves, uncut fenders (really nice ones at that)

 

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Carb size will be dependent on motor set up, porting, etc. you keep just talking cub but that is generic. You can do a stock stroke cheetah cub to a large stroke super cub and cc range from less than 400 to over 600. So many things with change depending on what you build and how you set it up. I have 2 4m stock cyl motors. One runs 35mm carbs and the other runs 39mm carbs. Set ups are completely different. Motors almost identical.


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