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Author Topic: CB750F Big bore and cam  (Read 2317 times)

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Offline garretcb750

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CB750F Big bore and cam
« on: September 08, 2007, 05:38:32 AM »
I need more power.... Love my bike but i really want a few more horses.. What kind of horse power gains can i expect from a Cycle exchange 850 big bore kit and a mid sized cam. stock dis. now and stock cam.  I have a 4 into 1 Header, velocity stacks, jetted carbs, and a Dyna S ignition with 3 ohm coils.
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Offline scondon

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Re: CB750F Big bore and cam
« Reply #1 on: September 08, 2007, 07:30:55 AM »
 I would guess about 70bhp at the rear wheel with just the pistons and cam(25% increase?). Headwork, CR carbs, and exhaust, along with a streetable "hot" cam(Megacycle 125/65 or Webcam 63a) oughta get you in the neighborhood of 80bhp.
Honda claimed 56bhp for the stock cb750.
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Offline garretcb750

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Re: CB750F Big bore and cam
« Reply #2 on: September 08, 2007, 09:44:21 AM »
I would love to get mid 70's HP... that would be just fine in an old bike like that...lol  I am deffinatly doing some port polishing and seating the valves once the head is off.. I got an F2 bottom end and F1 top end.
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Offline scondon

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Re: CB750F Big bore and cam
« Reply #3 on: September 08, 2007, 09:59:10 AM »
Sparty and I both got about 75 with  836 and some porting/cam. Here's Sparty's thread on the subject, can't find my thread at the moment but it's back there.

http://www.sohc4.us/forums/index.php?topic=14307.0
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Offline KB02

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Re: CB750F Big bore and cam
« Reply #4 on: September 08, 2007, 10:57:05 AM »
Quote from: garretcb750 on September 08, 2007, 05:38:32 AM
What kind of horse power gains can i expect from a Cycle exchange 850 big bore kit and a mid sized cam.

I'll let you soon enough... probably next spring. That is exactly my plan right now. I've got Mike doing some head work for me and I plan to get the 850 kit this fall and get the engine all rebuilt over the winter. I talked to Ken at Cycle-X and he suggested a mid-way cam that they use for most of their engine builds, but he didn't give any specifics as for HP.
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Offline mkramer1121

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Re: CB750F Big bore and cam
« Reply #5 on: September 08, 2007, 12:39:09 PM »
Its an F right?  Make sure you get the 836 kit made for F's.  Otherwise your compression will be too low.  Dynoman.net has them.
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Offline MRieck

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Re: CB750F Big bore and cam
« Reply #6 on: September 08, 2007, 01:01:31 PM »
Quote from: mkramer1121 on September 08, 2007, 12:39:09 PM
Its an F right?  Make sure you get the 836 kit made for F's.  Otherwise your compression will be too low.  Dynoman.net has them.
Good point!
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Offline mkramer1121

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Re: CB750F Big bore and cam
« Reply #7 on: September 08, 2007, 01:20:48 PM »
Mike, you can tell I've been doing my research, huh?
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Offline scondon

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Re: CB750F Big bore and cam
« Reply #8 on: September 08, 2007, 04:52:25 PM »
Quote from: MRieck on September 08, 2007, 01:01:31 PM
Quote from: mkramer1121 on September 08, 2007, 12:39:09 PM
Its an F right?  Make sure you get the 836 kit made for F's.  Otherwise your compression will be too low.  Dynoman.net has them.
Good point!

  Thought those pistons were just for the F2's(77-78). I know the F-F1's(75-76) have slightly domed stock pistons but assumed that they used the same 836 pistons as the K bikes. Have I been wrong in this assumption?
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Offline MRieck

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Re: CB750F Big bore and cam
« Reply #9 on: September 08, 2007, 05:05:48 PM »
Quote from: scondon on September 08, 2007, 04:52:25 PM
Quote from: MRieck on September 08, 2007, 01:01:31 PM
Quote from: mkramer1121 on September 08, 2007, 12:39:09 PM
Its an F right?  Make sure you get the 836 kit made for F's.  Otherwise your compression will be too low.  Dynoman.net has them.
Good point!

  Thought those pistons were just for the F2's(77-78). I know the F-F1's(75-76) have slightly domed stock pistons but assumed that they used the same 836 pistons as the K bikes. Have I been wrong in this assumption?
You are absolutely right Sean. Judging by his avatar the bike looks like an F2 thus my comment. ;)
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Offline scondon

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Re: CB750F Big bore and cam
« Reply #10 on: September 08, 2007, 05:14:16 PM »
  Well at least I got something right today ;) ;D  He does state that he's got a F1 top end which is why I spoke up :)
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Offline MRieck

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Re: CB750F Big bore and cam
« Reply #11 on: September 08, 2007, 05:19:08 PM »
Quote from: scondon on September 08, 2007, 05:14:16 PM
  Well at least I got something right today ;) ;D  He does state that he's got a F1 top end which is why I spoke up :)
You are right again Sean....ding...ding....ding....ding. Twice in a day! You win a mackerel. :D :D :D :D ;) ;). I obviously missed that part...good for you for speaking up sir. ;D
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Offline scondon

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Re: CB750F Big bore and cam
« Reply #12 on: September 08, 2007, 05:23:23 PM »
Quote from: MRieck on September 08, 2007, 05:19:08 PM
Quote from: scondon on September 08, 2007, 05:14:16 PM
  Well at least I got something right today ;) ;D  He does state that he's got a F1 top end which is why I spoke up :)
You are right again Sean....ding...ding....ding....ding. Twice in a day! You win a mackerel. :D :D :D :D ;) ;). I obviously missed that part...good for you for speaking up sir. ;D

   I'll be happy to take delivery of that mackerel on the 13th ;) What beer goes good with mackerel ??? ;D
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Offline Sam Green Racing

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Re: CB750F Big bore and cam
« Reply #13 on: September 08, 2007, 05:25:45 PM »
Chimay
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Offline scondon

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Re: CB750F Big bore and cam
« Reply #14 on: September 08, 2007, 05:30:14 PM »
Damn, my friends just returned from Belgium today. Shoulda asked for some :P :)
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