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<  Performance issues  ~  Keihin cr 29 or 31???

pedro750
Posted: Sat Jan 31, 2009 3:07 pm Reply with quote
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Joined: 16 Jan 2006 Posts: 48 Location: Italy
So, I "need" a new carb set, I have 66.5 Henry Abe pistons, stock head, cmc camshaft, lightned alternator, DynaS, dyna 3 Ohm coils.
What do you suggest: Keihin Cr 29 or 31?
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Satanic Mechanic
Posted: Sun Feb 01, 2009 5:03 pm Reply with quote
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Joined: 04 Sep 2005 Posts: 309 Location: Munich, Germany
Ciao Pedro,

with 900cc I would recommend 31s. Don't forget to open the ports for the larger throats.

Cheers,
Axl
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pedro750
Posted: Sun Feb 01, 2009 9:42 pm Reply with quote
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Joined: 16 Jan 2006 Posts: 48 Location: Italy
Grazie Axl,
so I know that a porting work it's necesary, but now I can't. So If I'll install on the stock head, 31mm can I find a decent low-medium torque?
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Satanic Mechanic
Posted: Mon Feb 02, 2009 6:48 am Reply with quote
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Joined: 04 Sep 2005 Posts: 309 Location: Munich, Germany
Well, any of these carbs (29 or 31mm) will take away some of your low end in exchange for top end gain. What seems to be common for both sizes is that if you fully open the throttle below, say, 4k revs, the engine just stalls.

31mm on a stock head won't help you much, performancewise.

Ciao,
Axl
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pedro750
Posted: Mon Feb 02, 2009 9:48 am Reply with quote
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Joined: 16 Jan 2006 Posts: 48 Location: Italy
So, 29 it's better and I think that they will work fine with ported head too.
But the option will be this: buy the 31mm, find a decent set-up for the stock head and when I'll find time I'll port the head to free HP.
What do you think? What's the better...?

P.s.: I'm organizing to by all this with dynoman, we did me a very good offer, now we are in 3, do you need something?
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Satanic Mechanic
Posted: Mon Feb 02, 2009 11:41 am Reply with quote
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Joined: 04 Sep 2005 Posts: 309 Location: Munich, Germany
I would definitely go for the 31s. As long as you have not ported the head, you can run stock carbs (or try the 31s), and once you have the head done, you are ready for the best setup.

Re Dynoman order, I'll send you a PM.
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