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Post by rocky88 on Jan 28, 2012 20:04:50 GMT -5
anybody out there have any advice about the big valve head's from scrappy..please let me know...thank's.......rocky88
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Post by Rebel on Jan 28, 2012 22:53:44 GMT -5
I'm leaning towards for a street scooter it is a waste of money. Theoretically it will flow more air but I just don't know if it is useable for most riders.
Just an opinion.
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Post by theswede on Jan 29, 2012 5:48:46 GMT -5
I don't recall that installing one made any significant difference on my engine power back when I did it. However once I have swapped out the carb for a larger one it seemed to make a difference, a 22mm carb on a original head would probably have been too large but worked just fine and gave some more power.
If you go for a large valve head you can probably expect to have to replace the carb for it to make any significant difference. If you stay with the original carb you most likely have to upjet.
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Post by Rocketdog on Feb 1, 2012 9:24:16 GMT -5
I agree with Rebel and Theswede. Just the head on a stock 50 won't make any difference. It will take more upgrades for that to be worth your while. I've never personally tried just the head and a larger carb.
RD
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Post by mainepeace on Feb 14, 2012 2:15:11 GMT -5
Even on a 72cc BBK a large valve head is overkill. You just don't the the airflow to take advantage of the flow, and possibly can kill power by slowing down the air velocity.
Greg
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Deleted
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Post by Deleted on Feb 14, 2012 10:47:56 GMT -5
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Post by mainepeace on Feb 16, 2012 19:36:06 GMT -5
The simplest analogy I use is the straw.
A cocktail straw obviously won't flow alot of fluid quickly and it takes quite a bit of sucking to drink through it.
A normal sized straw gives a predictable amount of flow. If it's a small cheap straw from a diner it might impede the flow more than a big straw from McDonald', but think in terms of cyclical pulses. A quick suck may fill up your mouth more with a smaller straw than a larger straw.
A huge straw like they have for the bubble tea obviously can flow the most amount of fluid. But just try to fill up your mouth without getting a glassful of backwash. That's what you get when you go too big and throw on a UNI style filter before you grow the size of your mouth.
Greg
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Post by Rebel on Feb 16, 2012 19:47:38 GMT -5
Terra, people that have a slower scooter after a bbk probably have inadvertidly tuned it for an rpm range they can not really use. Another thing is that a bore and stroke that equal each other is often the most efficient. So if you install a 4 over piston a 4 over crank might be a good idea and give a lot more cubes too.
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Post by terrilee on Feb 16, 2012 20:29:04 GMT -5
BIG HEAD WHAT
OH WAIT........... never mind.
who used the line, 'ahh never mind' in her comedy skits?
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Post by Deleted on Feb 16, 2012 22:14:48 GMT -5
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