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Old 08-02-2009, 09:42 PM   #1
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building a 1970 634 f/c hirth jackshaft puma replica. Wanted to know if there were any mods I could do to it on the way to wake this motor up a little. It has singe HD and stock exhaust. If I run dual carbs would it make much of a difference. What application should I run. someone told me to take off the ringgear for the starter off the flywheeel, would that throw the motor off? Come on CAT GUYS give me a hand.
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Old 08-03-2009, 01:27 PM   #2
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I don't see how removing the ring gear would throw the motor off balance any. Just be careful not to crack anything. I removed the ring gear from one of my kawi twins. Twin carbs might benefit more if the exhaust was more free flowing but it should help some regardless. I don't know horsepower gains for such a procedure but maybe somebody else will chime in. Sounds like a fun project you have going there. Good luck, let us know how it goes. Post a few pics maybe when you get it almost done.
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Old 08-04-2009, 02:31 AM   #3
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Ring gear won't really be doing much by taking it off, you won't notice it thats for sure. Dual carbs would be OK if you did a dual exhaust or like Cheetah said, a free flowing exhaust. If you mod the intake then you must mod the exhaust usually.
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Old 08-04-2009, 03:05 PM   #4
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What would be the best exhaust to go with?
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Old 08-04-2009, 03:15 PM   #5
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For performance a set of tuned pipes would be best, for sound and muscle tone, open megaphone/montana style exhaust pipes.
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Old 08-07-2009, 10:55 PM   #6
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I put a 634 in my 70 puma back in the late 70's.

switched it over to a mikuni carb...can't remember the size anymore and put on a set of montana pipes.

other than the above mods engine was stock. It was one cleat throwing son of a gun... fun to ride.

I wouldn't waste my time on the ring gear.... the little bit of added weight will not affect the engines performance.....the 634 was all about torque not rpm.

Good luck on your transformation.

Mike

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