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Cub soupup?

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R-cubed

11-24-2005 08:01:49




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I have a first year Cub that hasn't enough power to pull the slack out of my suspenders. I have the carb off now trying to fix the float valve, etc and noticed the venturi is only .500 diameter, about the size of one on a 2HP Briggs carb. I am thinking about opening it up to say 3/4" to see if it will perform a little better. Anyone ever tried this? I suppose it's natural to be that small since each cylinder puts out only 2.5 HP and they don't all suck at once. Or do I need a turbo? (just kidding about that)

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nunya

12-01-2005 00:02:57




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 Re: Cub soupup? in reply to R-cubed, 11-24-2005 08:01:49  
The cub won't develop enough exhaust pressure to run a turbo with it's high (no load mind you) rev limit of 1600-1800rpms. The engine and fuel/ign needs some attention or perhaps a complete rebuild to get the HP and torque back it had when fresh.



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gene (missouri)

11-24-2005 21:37:38




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 Re: Cub soupup? in reply to R-cubed, 11-24-2005 08:01:49  
You could find an engine out of a later model Cub or an International power plant (combine). I believe they had a few more horses.

Gene



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Peabody

11-24-2005 18:21:43




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 Re: Cub soupup? in reply to R-cubed, 11-24-2005 08:01:49  
I once had a Super Cub Turbo T/A Diesel that tested on the dynamo at 11.5 hp. The belly mower burned the blades off the grass, instead of cutting them.



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Don L C

11-24-2005 15:48:58




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 Re: Cub soupup? in reply to R-cubed, 11-24-2005 08:01:49  
R-cubed---

I might be fun to rebuild the engine with larger pistons.....ported and polished head,milled for more compression....drill out the main jet a little.....now you should have about 18H.P.

Or bring it to my shop we will drop a small block ford in it at about 220H.P.----- -Don



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Don L C

11-24-2005 16:35:36




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 Re: Cub soupup? in reply to Don L C, 11-24-2005 15:48:58  
For got the cam could stand a special grind to allow a little exrta fuel/air charge.....



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George Willer

11-24-2005 09:31:47




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 Re: Cub soupup? in reply to R-cubed, 11-24-2005 08:01:49  
third party image

Changing the venturi diameter is a sure and certain way to destroy an otherwise valuable carburetor. DON"T DO IT! No engineer would pretend he could do it successfully. Maybe you are just expecting your Cub to do too much... or it just needs some repair work.

You may have stumbled on a better idea, one that wouldn't destroy a good carburetor... just put a 2 HP Briggs carb on it. I did it as an experiment and couldn't notice any difference from my 10 other running Cubs.

George Willer

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gene bender

11-24-2005 08:49:22




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 Re: Cub soupup? in reply to R-cubed, 11-24-2005 08:01:49  
Just what do you expect from 60cu in f-head running 1300 rpm putting out 9hp. Sounds like time for some serious hot-rodding if more is wanted.



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Jim Becker

11-24-2005 08:27:40




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 Re: Cub soupup? in reply to R-cubed, 11-24-2005 08:01:49  
Give the engine a decent tune-up and properly adjust the carburetor. If it has good compression, that is about all you are going to get out of it. If it can't do what you want at that point, go buy a Super A. It will be both cheaper and more effective.

Good original Cub carburetors are hard to find. Don't ruin one trying to do something the tractor wasn't designed for in the first place.



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R-cubed

11-24-2005 08:52:43




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 Re: Cub soupup? in reply to Jim Becker, 11-24-2005 08:27:40  
I don't need any collector's item tractors and have several bigger ones but the Cub is a handy utility tractor due to size, etc. Just want a little more zip! 12HP would be nice.



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RN

11-25-2005 00:00:00




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 Re: Cub soupup? in reply to R-cubed, 11-24-2005 08:52:43  
If you're serious about practical increase in HP- check pistons in now compared to late lowboy- compression was about 1+ point higher than 1st production. Governor springs and weights again to later lowboy series- about 200 rpm higher. Just clean carb, no cutting unless to match mounting faces of manifold to carb, block. Milling of block and head-minimal, only enough to make them flat for mating, 'relieving' block from valve seat area to cylinder for slightly better flow, basicly polish down rough metal and sharp edges, no more- you're not working on a Harley K or WR engine. Polish/match intake/exhaust ports to match manifolds and gaskets for uninterupted flow of gas. You said you had early cub- basicly these parts and rebuilding techniques would bring it up to later middle of series production specs- the 12 hp you wanted. RN

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Andy Martin

11-24-2005 17:40:54




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 Re: Cub soupup? in reply to R-cubed, 11-24-2005 08:52:43  
Have you checked the comression?

Old Cubs in good shape put out plenty of power for their size.

As for turbocharging, the flat head would not hold it.

By the way, I think it is called an L head. An F head had the intake in the head and the exhaust in the block.



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Andy Martin

11-24-2005 17:45:19




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 Re: Cub soupup? in reply to Andy Martin, 11-24-2005 17:40:54  
I meant to add, the velocity therough the venturi creates the vacuum to draw gas into the air stream. Opening up the venturi just a little will result in lower velocity and less fuel pulled in, which more than negates any improvement in pressure drop to get more mixture into the engine. Opening the venturi up a lot will stop the carburetor from operating. I guess you could always try to run on the choke, but then you have that pressure loss again.

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lee

11-24-2005 08:23:40




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 Re: Cub soupup? in reply to R-cubed, 11-24-2005 08:01:49  
turbo-cub might be a good way to go. Sure might make a fun development project. I"d think one might be able to get some good results. Suppose a guy developed some hop up bolt-ons for Cubs. I would think he"d be able to sell em. The cub transmission is a weak point.



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R-cubed

11-24-2005 08:58:03




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 Re: Cub weakpoint? in reply to lee, 11-24-2005 08:23:40  
Tranny is the weak point? Didn't later versions have up to 18HP? or were they the ones that shelled the transmissions? If I had 18HP I could run a welding generator off the PTO and life would be so fine! Maybe I should have bought an A but it's too late now. Anyone want to trade an A for a Cub?



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lee

11-24-2005 15:49:34




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 Re: Cub weakpoint? in reply to R-cubed, 11-24-2005 08:58:03  
two cubs lashed together might get you 18.



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R-cubed

11-24-2005 19:12:05




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 Re: Cub weakpoint? in reply to lee, 11-24-2005 15:49:34  
That's a good idea and then I'd have something that wouldn't turn over so easy. But then I'd have $4000 worth of klunker.



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Chris in Washington

11-24-2005 13:19:00




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 Re: Cub weakpoint? in reply to R-cubed, 11-24-2005 08:58:03  
Be aware that the Cub PTO turns in the opposite direction and at twice the speed of a standard PTO.



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Stan(PA)

11-24-2005 10:10:28




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 Re: Cub weakpoint? in reply to R-cubed, 11-24-2005 08:58:03  
In reality, it seems to me that Cub`s bring more money than A`s in the same condition, so the simple answer is yes, there are probably quite a few people that would trade an A for your Cub. Not me though, I use my A :) ....Stan



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