Author Topic: Expectations for CB550 hp & ft lbs?  (Read 2299 times)

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Offline bambuhiphop

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Expectations for CB550 hp & ft lbs?
« on: May 01, 2018, 09:25:29 PM »
So, as I (hopefully) approach my first attempt at starting my motor I am trying to better gauge what numbers I should be seeing out of this thing. I've been trying to track down some dyno numbers but a lot of the images are no longer working. I am hoping for 50 rwhp and 30 ft lbs.

I'm not looking for gospel but are my expectations in the ballpark or should I reset those expectations before it gets to the dyno???

Motor (complete rebuild)
- Crank lightened and balanced by APE
- New primary chain
- Transmission undercut by Fast by Gast
- HD studs
- Cylinders bored to 592cc and leveled -0.006
- Dynoman DP592/61s pistons (10.5:1, 61mm)
- Rods shot peened and balanced with 750 bolts and nuts
- Stage 3 head from mrieck (milled, serdi valve job, valve guide hone and r/r, OS valves) with kibblewhite valves and guides, o-rings, and spring kit with ti retainers
- Intakes backcut to match head
- CR26 carbs from Powerbarn
- MotoGPwerks 4into1 exhaust
- Yoshi Isle of Mann TT B grind cam
- 520 conversion
- C5 ignition
 
If there is a thread I can read that I missed please feel free to send me there! Thanks All
75' CB550K -- Still in pieces but it rolls again!!!!

Offline flatlander

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Re: Expectations for CB550 hp & ft lbs?
« Reply #1 on: May 01, 2018, 10:16:52 PM »
i have different configuration, details here: http://forums.sohc4.net/index.php/topic,171686.msg1999344.html#msg1999344
that gives me 44.6Nm, 53.9hp.
will be interesting to see what comes out of yours.

Online PeWe

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CB750 K6-76  970cc (Earlier 1005cc JMR Billet block on the shelf waiting for a comeback)
CB750 K2-75 Parts assembled to a stock K2

Updates of the CB750 K6 -1976
http://forums.sohc4.net/index.php/topic,180468.msg2092136.html#msg2092136
The billet block build thread
http://forums.sohc4.net/index.php/topic,49438.msg1863571.html#msg1863571
CB750 K2 -1975  build thread
http://forums.sohc4.net/index.php/topic,168243.msg1948381.html#msg1948381
K2 engine build thread. For a complete CB750 -75
http://forums.sohc4.net/index.php/topic,180088.msg2088008.html#msg2088008
Carb jetting, a long story Mikuni TMR32
http://forums.sohc4.net/index.php/topic,179479.msg2104967.html#msg2104967

Offline turboguzzi

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Re: Expectations for CB550 hp & ft lbs?
« Reply #3 on: May 02, 2018, 04:24:49 AM »
pewe, dont pull his leg, that's a full on race bike done by pros...
with 10.5 CR, would say 50-55. to get into 60s youd need to go 12:1, not recommended for the street IMHO
but no motor HP is a sum of what you bolt on it, the magic is in making it all work together.
just playing with ignition timing could change end result drastically, not to mention stuff like squish, match of pipe an dcam, etc.
deffo spend time on the dyno

Offline bambuhiphop

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Re: Expectations for CB550 hp & ft lbs?
« Reply #4 on: May 02, 2018, 09:44:49 AM »
i have different configuration, details here: http://forums.sohc4.net/index.php/topic,171686.msg1999344.html#msg1999344
that gives me 44.6Nm, 53.9hp.
will be interesting to see what comes out of yours.

Awesome, thanks for the reference. I'm interested to see what I get too!

Look here
http://forums.sohc4.net/index.php/topic,171869.0.html

haha! I was just reading that yesterday. Not expecting those number by any stretch of the imagination.

pewe, dont pull his leg, that's a full on race bike done by pros...
with 10.5 CR, would say 50-55. to get into 60s youd need to go 12:1, not recommended for the street IMHO
but no motor HP is a sum of what you bolt on it, the magic is in making it all work together.
just playing with ignition timing could change end result drastically, not to mention stuff like squish, match of pipe an dcam, etc.
deffo spend time on the dyno


Thanks man. Appreciate the notes on compression. Looks like I'm in the ballpark with 50 hp and 30 ft lbs. Nice to have a frame of reference when dialing in to know how much fiddling around needs to be done.
75' CB550K -- Still in pieces but it rolls again!!!!

Online PeWe

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Re: Expectations for CB550 hp & ft lbs?
« Reply #5 on: May 03, 2018, 02:52:48 AM »
pewe, dont pull his leg, that's a full on race bike done by pros...
with 10.5 CR, would say 50-55. to get into 60s youd need to go 12:1, not recommended for the street IMHO
but no motor HP is a sum of what you bolt on it, the magic is in making it all work together.
just playing with ignition timing could change end result drastically, not to mention stuff like squish, match of pipe an dcam, etc.
deffo spend time on the dyno

Thanks to this forum we amateurs on street bikes can make great improvements.  ;D  This thanks to the Pro's writing how to do and with what.
I should not know anything about Mikes Billet Block, APE's Ultra Crank, new cush rubbers in primary hub, HD primary chains and other modifications I have without reading here. ;D
Just do as the Pro's!   They write the recipe like baking a cake... just open the wallet and do the same. 8)
Russ Collins was the front guy for many years ago. Thanks to him (RC295) and Mike Rieck's block my bike runs really well and strong  ;)

Last ride gave me a big smile and I could forget the pain in my wallet 8)
CB750 K6-76  970cc (Earlier 1005cc JMR Billet block on the shelf waiting for a comeback)
CB750 K2-75 Parts assembled to a stock K2

Updates of the CB750 K6 -1976
http://forums.sohc4.net/index.php/topic,180468.msg2092136.html#msg2092136
The billet block build thread
http://forums.sohc4.net/index.php/topic,49438.msg1863571.html#msg1863571
CB750 K2 -1975  build thread
http://forums.sohc4.net/index.php/topic,168243.msg1948381.html#msg1948381
K2 engine build thread. For a complete CB750 -75
http://forums.sohc4.net/index.php/topic,180088.msg2088008.html#msg2088008
Carb jetting, a long story Mikuni TMR32
http://forums.sohc4.net/index.php/topic,179479.msg2104967.html#msg2104967

Offline turboguzzi

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Re: Expectations for CB550 hp & ft lbs?
« Reply #6 on: May 04, 2018, 07:13:07 AM »
bamboo, is it  a hot street bike or a road racer?
it's the 10.5 CR that made me think the first
not sure how you are going to like the stage 3 port and IOM cam on the street, but maybe with the 600 kit it will be livable with
if it's a race bike, then deffo increase your CR....

Offline bambuhiphop

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Re: Expectations for CB550 hp & ft lbs?
« Reply #7 on: May 04, 2018, 12:48:53 PM »
bamboo, is it  a hot street bike or a road racer?
Very hot street. This is mainly going to be a weekend rider. I'd like to say I am going to ride during the week but that almost never happens at the moment. I had worked through the overall config with Mike and the feeling was this should work out. But who knows! Maybe I get the 592/MDR's if I run into issues. Or I'll go big bore with Carrillo rods!! For now I want to get it running and see what I like and don't like and then I'll go from there.
75' CB550K -- Still in pieces but it rolls again!!!!

Offline MRieck

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Re: Expectations for CB550 hp & ft lbs?
« Reply #8 on: May 04, 2018, 02:34:07 PM »
The engine build reads like a nice combination.....I think you will be happy (for now). ;D ;D
Owner of the "Million Dollar CB"