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thinking 421


slowblueshee2

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Hey guys, I have been heavily contemplating stepping up to the cub cylinders. The few people I have talked say they are light switch power obviously because of the high exhaust port timing. Just curious what people are doing to counter this. I would like to have a broad power band, well as broad as you can make a cub. Anyone here of maybe taking stock stroke cubs and trying them with the 4 mill crank to lower the exhaust. Or is there some reason you can't. Thanks!

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What I do is lower the exhaust down and then bring the transfers back up to where I want them. It seems to work well with the ones we have done. You will pay for the work that needs to be done and its not cheap.

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  • 2 weeks later...
Hey guys, I have been heavily contemplating stepping up to the cub cylinders. The few people I have talked say they are light switch power obviously because of the high exhaust port timing. Just curious what people are doing to counter this. I would like to have a broad power band, well as broad as you can make a cub. Anyone here of maybe taking stock stroke cubs and trying them with the 4 mill crank to lower the exhaust. Or is there some reason you can't. Thanks!

A 4 mil crank and a stock stroke cub would do just the opposite. It would raise the exhaust and transfer duration of what you had. If it were me I'd get a good "play" port from Jeff at Fast with either a stock or a 4 mil crank or just get a 4 mill cub and enjoy.

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explain to me how a longer stroke that rises higher and a longer rod that raises higher would raise the exhaust. I have a ported motor and I took out the base gaskets to bring the exhaust down a little. Kevin Herr said the transfers are unattainable with the stock stroke cub on a 4mill. But my future plans will be to deck the cases or the bottoms of the cylinders.

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I dune my 421 cub with no problems, granted it takes a little more getting used to i straight fly threw some shit :happy: why not consider the powervalve'd cylinders?? its going to cost ya round the same money getting a cub dialed in for that as just going with a prooven setup, just a thought.

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I dune my 421 cub with no problems, granted it takes a little more getting used to i straight fly threw some shit :happy: why not consider the powervalve'd cylinders?? its going to cost ya round the same money getting a cub dialed in for that as just going with a prooven setup, just a thought.

 

 

I agree with jharader. In wide open big dunes, i love my cub. In tight winding trails like some of the stuff in oregon, not so much love. LOL I would be thinking 421 or bigger powervalve cheetah instead of cub if you are wanting the extra bottom end.

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  • 6 months later...

Powervalve cheetah!!!!! I absolutely love mine and will probably never get away from them again!! You may lose a little on top, but the mid and bottom end are amazing!! By this statement, I am in no way trashing the topend of the cheetah, mine pulls harder on top than anything I have ever rode. But, in talking to my builder, he said that he can get more topend out of a cub vs a cheetah!! It is kinda hard to believe you are even on a banshee, the first time you ride with the cheetah cylinders! Just my .02!! My riding buddy has a 421 cub and the first time he rode my 421 Cheetah, I almost had to pry his lil smiling ass off of it!! Do some research and check into a Cheetah!!

 

Z

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you can run a really thin base gasket to lower the port timing and then get resessed cut dome.

 

cubs dont really have high port timing its more tripples and more area why they have so much top end.

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i have a 421 cub. like rubberneck said''not so much love in tight trails'' its a whole dif bike in some wide open shit and it takes getting used to. mine likes to be ran wide open and likes high rpm's but like jharader said(lol) it will straight f'n fly threw some shit man. the power is rediculous on the top end. if i was you i'd spend the money to build what i wanted it to perform like and just go all the way so your not spending extra time and money trying to get it to run like you wanted it to. but i love mine man. it just doesnt like any putting around at all. but some smooth wide open dunes would be awesome. these man made duky dunes in mississippi aint even big enough to open my baby up all the way man.

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  • 4 weeks later...

a box stock 421 cub is around 198* exhaust timing thats hi for trails riding. the other ting to consider is its not that they are a light switch its that the hp comes on soo strong and is so much higher than what your used to. a 420 cheeta or a 485 cheeta 4 mill crank with PV's is a SWEET dune motor. you just need someone that knows how to port for the powervalves or they can mess them up. its easy to overport the exhaust and end up blowing by the valves. the chetta will still overrev like a cub but just have too much intake ( i believe) to really flow hard enough on top.. if money isn't really a factor id say definatelly do a cheeta pv motor for trail/ play draggin.. they are a LOT of fun you will need some arm or detune it quite a bit..

 

i would like to build a 4 mill cub and purposely try and smooth out the power delivery some day.. i know it can be done but then again why not just a 10 mill cub? if your going that direction?

 

on the other hand a properly set up stocker 350cc bansxhee in the dunes is a lot of fun.. 70ish hp with smooth delivery is not unreal..

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