90 DEGREE FIRING VS 180

[DRAGBOY]

I'M BUILDING A MOTOR FOR MY 800. I HAVE A 180 FIRING RPC BOX. I'M BEING TOLD BY THE COMPANY WHOSE PORTING MY CYLINDERS THAT ITS MUCH EASIER TO CLUTCH A 90 DEGREE FIRING MOTOR THAN A 180 DEGREE MOTOR. ANYBODY HAVE AN OPINION ON THIS?? HOW MUCH MORE DO YOU GAIN BY GOING TO A 180 ???? ALL I'M DOING IS BUILDING THIS TO DRAG RACE. ITS TRAIL RIDING DAYS ARE LONG GONE!!!

[Skinner]

If you check the classified forum and go to 800 cdi box for sale, I just posted info on that this morning. How many rpms are ya gonna spin? That will have allot to do with how you clutch it. Need any more info, give me a holler

[bufalobob]

180* was a theory. there was never any proof that it was better than 90*. had a 880 vmx4 & changed firing to 180*. motor made no more power than if it was fired @ 90* - just a whole bunch harder to pull start.
no difference clutching either one.
bob

[Busted Max]

the 180 was intended for high rpms.

at 90 degrees the crank developed funky harmonics or a wobble. it would destroy itself if it wasnt set to 180 degrees.

[bufalobob]

bustedmax:
i never heard that one before?? also never heard of it happening. again, it was a theory - never proven. one guy does it & wins a few races so everybody jumps on the band wagon & says it's gospel. however, the crank did need to be welded for durability.
before the 880 @ 180* my vmx4 was a 750 @ 90* with trail port & bender quad pipes. ran @ 9250 rpm for thousands of miles & never had a problem.
bob

[Busted Max]

one problem is probly because one half the crank weighs more than the other. another is at 90 degrees the crank is not symitrical. its really hard to explain.


its only at the higher rpm it does this. im talking 10,000rpm!!

[4with4]

I agree Chris. All the research I've ever done on this mod claimed no more hp at anything under 10,000rpm. Maybe a bit of torque gain. Where this mod was developed was for the 750's running pipes like Crankshops or Hauk Howlers which made crazy amounts of hp at over 10,000rpm. The 750 crank was of different weights from side to side because one center gear fit inside of the other. This did cause problems with high rpms. The problem seemed to be solved by phasing the cranks to 180*.The 800 cranks had different center gears which eliminated the unbalance. I've never heard of an 800 owner who found a difference between the two. Maybe the phasing was just needed for the 750. What we have to remember about the Vmax4 was that by the time the 800s came out with all the changes to the engine and the clutching, it was old news and many aftermarket manufacturing co's were done developing parts for it. This caused many of the differences between the 750 and 800 to go unnoticed.

Ian

[fastmax]

:agree: 750@10000 + rpm has harmonics issues.

[YAMMIEGOD 3:16]

FIRST ANYTHING OVER 10,000 RPM, YOU NEEDED A PERFORMANCE SHOP AFTERMARKET CDI FOR THE VMAX 4!! NOT EVEN THE 800 STUFF REVED OVER 10,000. HOWLERS MADE BY HAUCK RUN AT 10,200. THIS IS WHERE MOST FIRED ENGINE AT 180. WHAT THIS DOSE OR DID IS INCRESED LOW END TORQUE, MADE THIS MOTOR ACTUALLY THINK IT WAS A HUGE TWIN. I DON,T BELIEVE THERE IS HUGE HORSEPOWER ADVANTAGES OVER EITHER BUT FOR 500 F.T. GRASS DRAGS TORQUE GETS YA OUT OF THE HOLE. !! 3:16 (tony)