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Help, 4 mil 421 Cub buildup


Viktor

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My Banshee blew up a few weeks back.

 

Im really close to buying some parts to get my shee running again.

 

Im looking at

421 Drag ported Cheeta Cub Cylinders

4 mil Crank

Weisco Pistons

 

My Concerns are, will my Stock Carbs Run this motor? (I know they arent optimal)

Can I use my Toomey t5's with the Cub?

What else "Must" I have in order to run a 421 Cub in my shee?

 

Thanks

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The cubs were designed to use all the stock parts, but you are going to be choking the hell out of it with the stock carbs. I am using my T-5's when I get mine up and running and, only because I can't afford to go out and buy new pipes right now. You should get on the phone and contact Jeff at FAST and he will explain everything that you need. There is a lot more to it than just throwing a set of new cylenders on there............. :thumbsup:

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i built a 420 cub last year like that. he never ran a "fast" banshee before. we kept the stock carbs it ran just fine pulled hard all the way through and had a nice overrev. i also cleaned and matched the porting in the cylinder. there is a lot of "flashing and mismatch in there.. the t-5's will work good also the motor will run harder than you stock cylinders ever did.. just put it together and see what you think! if you want to go to bigger carbs thats an easy change.. i would definately have the crank welded and a tz drive bearing to fight drive bearing thrust and a billet clutch basket new clutch componets, and make sure your shift shaft and shifting parts are ok. you are going to add a lot of hp and tq to the motor anything else inthe bottom end thats weak or about to go bad will show up very quick..

Edited by camatv
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Somewhere I have a video of my 4mil cub when I had 33's and my T5's. That thing was a lot of fun with that setup. Retarded power in the midrange with the T5's and smaller carbs. Good for duning, but not drag racing at all.

 

I will look for the video fo ryou.

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i have never run stock carbs on my cub.the only thing i be worried about if i was running stock carbs,is starving the motor when drag racing.get a pingel as well. :banghead: :banghead: :banghead:

 

You don't need a pingel for gas. Stock carbs and T-5's will work fine, but you will be losing out on as much as 20 HP give or take.

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i built a 420 cub last year like that. he never ran a "fast" banshee before. we kept the stock carbs it ran just fine pulled hard all the way through and had a nice overrev. i also cleaned and matched the porting in the cylinder. there is a lot of "flashing and mismatch in there.. the t-5's will work good also the motor will run harder than you stock cylinders ever did.. just put it together and see what you think! if you want to go to bigger carbs thats an easy change.. i would definately have the crank welded and a tz drive bearing to fight drive bearing thrust and a billet clutch basket new clutch componets, and make sure your shift shaft and shifting parts are ok. you are going to add a lot of hp and tq to the motor anything else inthe bottom end thats weak or about to go bad will show up very quick..

 

Hey...cam. Good to see you here over on the HQ...

Wealth of knowledge from this guy...boys and girls.

 

I agree. I put mine together with T5s and stock carbs...on a budget...and it did run hard. My stock carbs liked to stick a little however, and they were clean as the dickens. I think it's just because of all the more velocity/vacuum created by these cylinders, bigger stroke and bigger pistons.

 

Even with good shifting components, adjusted properly, and a new billet basket, inner and outer and 6 HD springs, it still shifted like shit. I know it costs even more money, but you're eventually going to want a dunable override and a lockup as well. YOu're making serious power from a cub....and as said, the weaker links will surface soon.

 

I ran my 421 cub on a stock petcock and 35PWks...never ran out of gas...

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just for info , when i m buy my trinity cheeta 400 , with porting . i run pwk 33 and t-5 , is run great , when at the day i change the carb for a pwk 35 , is run better . and after i change my t-5 for a set of rocket pipe , kawabonga the motor have a new life , the t-5 choke the motor and not rev higher like a good set of high rev pipe ......

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Good luck on the build... I'm in the same boat!

 

I bougt a lot of stuff to make this thing work... I figured seals, gaskets, o rings, over ride, and clutch were a must so I got those things, traded up to 39mm PWK's, and a whole bunch of crap...

 

The money keeps going out, and parts keep coming in!

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My Banshee blew up a few weeks back.

 

Im really close to buying some parts to get my shee running again.

 

Im looking at

421 Drag ported Cheeta Cub Cylinders

4 mil Crank

Weisco Pistons

 

My Concerns are, will my Stock Carbs Run this motor? (I know they arent optimal)

Can I use my Toomey t5's with the Cub?

What else "Must" I have in order to run a 421 Cub in my shee?

 

Thanks

 

Just wondering but what would the 421 Drag ported Cheeta Cub Cylinders, 4 mil Crank, Weisco Pistons approximately run for? How much coin?

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Don't waste your money on a "Drag Ported" cub....just get it cleaned up, that's all you need.

 

Call Jeff @FAST...he normally stocks it all.

 

There are a few things you need to consider if buying a cub.

 

Stud Extenders for the rear studs

Water Jacket Plugs

Properly cut domes for the larger stroke/bore

Getting the crank Re-Welded properly

A good maxload or TZ bearing on the PTO side of the crank

New Crank Seals...big bore base gaskets...etc.

 

There are a ton of little items you'll need....Jeff will go over all these in detail with you on the phone...

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You really need to call and talk to Jeff. There is nothing worse than getting a high Hp motor that everyone raves about and then not put the right parts in it to strengthen it up a bit. Because if you don't prep the motor for the extra horsies, the weak points are going to make themselves known. There is nothing worse than starting a weekend of riding out really good then break something that could have been easily fixed. Or fixing this then breaking that and then fixing that and then break something else...........

 

Do yourself a favor and at least call and talk to Jeff he is very knowledgable and helpful, customer service and prices are hard to beat............. :thumbsup:

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