Author Topic: What is the best RPM??  (Read 4145 times)

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Offline 1031

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What is the best RPM??
« on: January 13, 2007, 01:15:26 am »
Hey Guys,

I am running a Briggs 12.5 flat head.
I have Don's goodies inside. and a little outside. My max rpm is 6500.

My question is at what range does the motor perform at it's best?

Or another way to ask... About what rpm should I be running the motor, not to over rev but still not lug it down?

I ask this to figure out my pulley sizes.  The best way is to try different pulleys at the track I know.
But what I am trying to find out is the Motor "Power Band".

Thanks Guys.

Ron Diebold ~ #1031
President Semow Lawn Racers Inc. 2007
VP Semow Lawn Racers Inc. 2006
Modified Track Champion 2006

Offline allen minaker

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Re: What is the best RPM??
« Reply #1 on: January 13, 2007, 08:34:59 am »
I think Don would be the one to answer your Question , but I know other guys that are running Dons motors and they are turning them to around 7000 on the high side .
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Offline cycloneracer

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Re: What is the best RPM??
« Reply #2 on: January 13, 2007, 09:52:04 am »
Sounds like you have a simmilar set up as I do.  I have a 28 cid, Don's cam, valve work, arc synchro weights, arc rod, small piston, Don's carb work, billet wheel, and my porting.
The sweet spot for my motor is around 6700-6800.
My suggestion is get a digatron with RPM, Cyl head temp, and EGT.  That way you can dial in your carb.
I had the same question for Don last year and he said that they are all different, you just need to experiment and find out what your "sweet spot" is.  You should be able to tell when the motor falls off.
Hope this helps
Paul Krueger

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Offline tory

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Re: What is the best RPM??
« Reply #3 on: January 14, 2007, 01:47:52 pm »
 I am running a simaler  engine,(ARC rod and weights,G-TEAM cam,...)minus the flywheel,and I try to stay below 6,000 rpms.
  The motor feels like it has more,and its week point, compared to the opposed twins that I race against,is below 3500.
  Oddly enough,that seems just about win the twins start to fall off(4.000 rpms)maybe that,and the stock flywheel is why Im a bit conservative.
   If it helps at all,I run 7.5 revelutions moter,to 1 revolution rear tire.And this has worked out best for me at all 4 tracks that Ive raced at.But these are all left turn only tracks on a good hard smooth clay surface.