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Discussion Starter #1
HAS ANYONE TRIED THE CRANK SHOP BIG DISC RV CRANKCASE? THEY CLAIM 6-7 HORSE OVER THE STOCK ONE. IF THAT'S TRUE, I THINK MY 670 JUGS FOUND A NEW HOME.
 

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I've never heard of it....tell me more. How is it different from the stock one? What does it cost? How exactly does it put out another 6 HP?
 

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Discussion Starter #3
WITH THE BIG DISC CASE THERE IS LESS RESTRICTION. YOU LOSE YOUR OIL INJECTION, BUT 48MM ROUND SLIDES ARE NOT A PROBLEM. THEY ALSO HAVE A BIG BORE 740 THAT USES ALUMINUM SLEEVES AND NICKICIL PLATING. THEIR STROKER MOTOR IS AN 800CC. I DON'T THINK THE CRANK SHOP HAS A WEB SITE THOUGH.
 

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Discussion Starter #4
THE CASE IS $1200. BUT, THIS WOULD BE THE ULTIMATE TWIN IN MY OPINION. WHY SPEND THE EXTRA MONEY ON A NEW PISTON/REED,WHEN YOU CAN HAVE BETTER TECHNOLOGY UNDER YOUR HOOD FOR ABOUT THE SAME MONEY?
 

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RVR; I made a billet RV cover for my 740. Lost the oil injection but opened up some seious holes. 150-80 timing, 46 mil carbs stock pipes and airbox = 146 hp. It's all over 800 twins and triples.  
 

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Discussion Starter #6
HEY KRUSTY. AREN'T YOU RUNNING A BIG BORE 95 OR 96 MACH 1? DID YOU PUT IN THE BRASS INSERT? I'M ASSUMING YOU BORED .080" OUT OF YOUR 44MM ROUNDSLIDES. DO YOU KNOW ANYONE RUNNING THE CRANK SHOP BIG RV CASE?
 

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Ya, bored 44's in 95 Mach 1. Yes to the brass plate. My motor guy has a big plate but says is isn't worth the hassle to install. If your willing to mix gas, I'm sure you could gain more than 6-7 hp a lot cheaper. Ported case, billet  or shorty RV cover, 46's, 150-80 timing, 13-1 comp. The injection cover is the bottle neck. So was the airbox in my case. Don't know about the S chassis. If your serious about keeping your rotary motor
you should look into the 740. $1200.00 is halfway there. (in Canada anyway)
 

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Discussion Starter #8
KRUSTY- WHAT DO YOU MEAN YOUR MOTOR GUY HAS THE BIG PLATE? DO YOU MEAN THE CRANK SHOP BIG RV CASE? OR DO YOU MEAN THE SHORTY OIL INJECTION ROTARY VALVE COVER? OUR IMPROVED 670 MOTOR USES A HOGGED OUT RV COVER FROM A 76 RV FREE AIR. IT WORKS GREAT. WE OPENED IT UP TO 44MM. THE CARBS SIT NICE AND LEVEL IN THE CHASSIS. THERE'S NO ROOM FOR K&N FILTERS THOUGH. THEY WOULD RUB ON THE TUNNEL. THE JUGS WERE PORTED BY FAST AND WE DID THE TUNNEL PORTING. WE'RE RUNNING FAST TWIN ELIMINATORS AND THEY SPIN ABOUT 8500 R.P.M. BEING A MACHINIST AND A GEARHEAD GO HAND IN HAND.
 

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We have made a big disc from a stock case. You weld both sides of the case and remachine it to a big disc intake. the only thing we got from the Crank Shop was the big RV valve.Those valves are a 1/2" bigger in diameter which allows better tunnel porting.If any one needs more info e-mail me. We also make the intake for this mod.
 

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My motor guy has one sitting on his shelf. The big case. Fabbed it himself. We decided to go billet so I could still use the airbox.
 

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Hey Krusty I have a stock pipe 670 stock bore, 46 mill carbs made 144hp 94ftlb, intrested in clutch set-up's I'm very close to a good trail/lake race set-up now, but intrested in what other guy's are running to doo some comparing.  Thanks
 

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mr 670; I'm now a 740 big bore. I've been dialing in mag arms for the last two seasons. Major pin wieght and soft springs up front. Shallow cams with light tension on th secondary. Alot of testing but once dialed in  
. I can give you multipile mag set ups to try. Let me know.
 
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