Topic: Can a CB650 engine be made to pump-out decent power ?

[grcamna2]

Has anyone done a CB650 high performance build?
Can it be built to push output to 70-75+ rwhp in a reliable street engine using pump fuel ?

[PeWe]

Turbo?
As CX650

[newday777]

Has anyone done a CB650 high performance build?
Can it be built to push output to 70-75+ rwhp in a reliable street engine using pump fuel ?

I've talked to Kurt Jordan, Jordan Engineering, builder and tuner, down in Oceanside CA at his shop(highly respected business, Russ Collins Jr is using him in the rebuilds of his dad's motors) where he is still building race motors, he worked for Action Fours back in the 70s, and raced too.
He knows how to make the CB650 scream out horsepower has all his notes still of all his builds he has done(hand written by himself).

[bwaller]

My 572cc race engine makes a reliable 75hp at the wheel. I had planned to build a short stroke 650 and figured on 85 minimum.

So yes a 75hp 650 would be possible and reliable.

[slikwilli420]

My 572cc race engine makes a reliable 75hp at the wheel. I had planned to build a short stroke 650 and figured on 85 minimum.

So yes a 75hp 650 would be possible and reliable.

Kevin Rammer is very successfully campaigning his CB650 in Vintage Superbike Middleweight, and I believe he is making 70+ right now with not a huge amount of internal work done either.

[grcamna2]

My 572cc race engine makes a reliable 75hp at the wheel. I had planned to build a short stroke 650 and figured on 85 minimum.

So yes a 75hp 650 would be possible and reliable.

Excellent 
I would bet aftermarket carbs also.

[grcamna2]

Turbo?
As CX650

No,I mean the sohc4 CB650 engine 

[Ramrod_Racing]

I last dyno'd mine at 77 with some meat left on the bone. Kurt told me his old race bike put out "an honest 90hp" on his dyno.


So yes, it can be done.

[grcamna2]

I last dyno'd mine at 77 with some meat left on the bone. Kurt told me his old race bike put out "an honest 90hp" on his dyno.


So yes, it can be done.

What mods have you done to your engine ?

[seanbarney41]

Depending on what you consider "pumping out decent power"...do you consider a stock cb750 to have decent power?  Cuz last summer a quickie cb650 flipper project fell in my lap.  I got the ugly duckling running well enough to realize that even a stocker runs as good or better than a cb750.

[grcamna2]

Depending on what you consider "pumping out decent power"...do you consider a stock cb750 to have decent power?  Cuz last summer a quickie cb650 flipper project fell in my lap.  I got the ugly duckling running well enough to realize that even a stocker runs as good or better than a cb750.

Hey Sean,yeah I do appreciate knowing that 
Yes,CB750 power out of a CB650 is what I want.
I've subscribed to a few different threads where the members did some rebuild and mild to extensive performance work to the CB650 engine before they installed it into their CB550 frame.
I was also reading that certain CB650 OEM parts like cam chain slipper/tensioners are difficult to source.

[pekingduck]

Here's a little chart as a reminder that the early CB750s may not have been the fastest.
Most by the same magazine with the same rider (Cook Nielsen). 
Top end trap speeds are a better indicator of HP than times.

[seanbarney41]

damn Peking Duck!  that chart kinda blows away some of these K0, K1 750 tall tales and confirms my findings.

Yeah Camna...no engine mods necessary for a 650 to go as fast as a 750.  When I tested my 82 cb650, it really was not even running right...leaky carb boots, old dirty clogged air filter that would not rev out without airbox cover removal etc.  I sold it before ever really getting it dialed in.