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421 cheetah cub 68 bore need exhaust


midospike

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Just got done building my cheetah engine. It is a 68 bore with a 4mm hot rod stroker crank, drag port,lightened flywheel,hinson clutch impellar and noss head with 21cc domes. I was thinking of using my t5's off my old engine. Good? bad? What would be good to use beside my t5. Also one other question. How well will a 2 into 1 carb setup work? Any advice would be great. thanks

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You bought a drag race motor, give it drag race pipes.

take it from me, I tried using stock carbs and T5s on a 421 cub motor...waste of time.

I mean...it's got a drag port on it...why choke it down.

 

If you dune more than drag, get CPI pipes.

If you drag more than dune, get Shearer pipes.

 

I'm not a fan or 2 into 1 carbs for Cheetah or Cub motors. Kind of pointless if you ask me.

If you're gonna keep it on gas, a pair of 35PWKs or Mikunis will do just fine.

 

Do you plan on running race gas or pump fuel?

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Drag pipes 100%, like Dave said, no point in choking the engine, let it breathe! Shearers work well, I'm a fan of GRR pipes but you'd have to find them used. There are several choices to choose from, any drag pipe should work well.

 

Carbs - If you got a drag port then 39's all the way. Get the billet oversized bowls too. Please don't get a 2 into 1 carb unless you just like throwing money down the drain. They're fine for trail riding/duning but not recommended for a drag setup.

 

:beer:

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SIf I am also going to ride around the dunes I am guessing I should get inframe pipes. What is the differ in big bore pipes and small bore? I see a few are for sale in the forums here. Last question. I am planning only running 110 like I did with my old engine.. can I go down to 18 or 19 cc domes for a little more power? Is it worth it? I also have v-force 3's and dyna tech program cdi bo.

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remeber when you build a motor that theres is three parts that need to match up. Carbs, Porting ( both intake and exhaust) and Pipes. If all are not matched to work with one another, then which ever one is more restricivewill determine how much ( or how little) of a power gain your going to get.

 

if your building a drag bike and running 110 you can easily run 18 or 19 domes. get a compression tester and see what your hitting with those domes.

 

21ccc domes are barley smaller then stock head domes are. once you bump that compression some and drop that dyna and reeds on there you will see a huge differance on how that bke runs.

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When I looking to buy a exhaust, should I buy small bore or big bore. The engine is a 421 68mm bore drag port. I was reading somewhere and forgot where that is a small bore? Is that correct. 350 to 439 is small and 440 and up is big? what is the diff from small to large? I would like to stay inframe...

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Hey, look no further, Shearers are the way to go, and Jeremy's got a set show chromed (stock shearer chrome blows), heres the link, pick them up fast, these things will take that motor where it needs to go :biggrin: 475 shipped!

 

http://www.bansheehq.com/forums/index.php?showtopic=82859

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Hey, look no further, Shearers are the way to go, and Jeremy's got a set show chromed (stock shearer chrome blows), heres the link, pick them up fast, these things will take that motor where it needs to go :biggrin: 475 shipped!

 

http://www.bansheehq.com/forums/index.php?showtopic=82859

 

I was going to suggest the same! :biggrin:

 

 

I'm going to run BB CPI's on my 421 cub.

 

I think it will hurt your performance. In my opinion, if you're under 500cc's you need to stick to small bores. 500cc's and bigger, big bores all the way :shrug:

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I was going to suggest the same! :biggrin:

I think it will hurt your performance. In my opinion, if you're under 500cc's you need to stick to small bores. 500cc's and bigger, big bores all the way :shrug:

 

 

That's a hot topic of debate right now, Travis. The old school ways of saying 7mm and bigger go BB and smaller go SB are out the window.

 

Smaller motor guys are finding more performance gains in running BB pipes.

It's all about setup...

 

My 10 mil is only like 465 ccs...and you won't find anybody running small bores on a 10 mil, well...not many anyways...LOL.

 

Mido...if you plan on hitting the strip only, get out of frames. If you plan on duning, get inframes...

Bouncing around dunes, you're gonna break OOF pipes, they'll flap like a bird's wings...

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