Topic: 650 sohc nighthawk engine in 550?

[chris801]

I just need a straight yes/no answer please, anyone know if a sohc 650 nighthawk engine will fit in a cb550 frame without mods?
many thanks

[A Grove]

Isn't the 650 engine almost identical to that of the 550?  Talking CB's here...

Nighthawk is probly another story?  Just guessing, interested in this tho.

[KB02]

The Nighthawk is a CB. CB650SC. Just a slightly sportier version. Kind of an off shoot of the F series, really.

Sorry, wwe're already starting to get off track here. Anyone have the answer to help Chris out?

[cb650]

Some one here has done it.  Dont know the details.  The sohc nitehawk is the same engine as the other sohc 650's just black and chrome

[A Grove]

Ahh.. Here I thought the "nighthawk" was a much later model of honda's. 

[fergie]

If it is the same sohc motor used in the cb650 then it should bolt right into a 550 frame or even a 500 frame for that matter. I believe the motor cases are the same bolt pattern/spacing but you will have to run a 650 header pipe as the cylinders are taller. I have also read that clearance between the top of the motor and the tank could be an issue. also there is the wiring updates that will need to be done. but yeah the motor should bolt right in , at least from what I have read here.

[Ecosse]

If it is the same sohc motor used in the cb650 then it should bolt right into a 550 frame or even a 500 frame for that matter. I believe the motor cases are the same bolt pattern/spacing but you will have to run a 650 header pipe as the cylinders are taller. I have also read that clearance between the top of the motor and the tank could be an issue. also there is the wiring updates that will need to be done. but yeah the motor should bolt right in , at least from what I have read here.

I understand the 650 to be the successor to the 550 engine and therefore essentially the same dimensionally speaking. I think you're right fergie about the points you made, plus the tach drive is different. Although I've not heard about top side clearance. Paulage and TT are bound to weigh in. Guys I personally would never doubt.

[chris801]

Thank you all for the responses, i will get it then and see how it goes!
cheers

[kirkn]

Ahh.. Here I thought the "nighthawk" was a much later model of honda's. 

Well, yes and no...

The Nighthawk model was a mix of old and new (for the time) depending on displacement and model year.

The 750 version was equipped with the 'new' DOHC motor.  The first-year ('82) 650 model was equipped with the 'old' SOHC motor.  The '83 650s came with an all-new DOHC 650 motor (which grew into the 700 Nighthawk S a year or two later and eventually, I think, grew into the 750 Nighthawk motor of the '90s).  A 550 DOHC version was available for a year or two in the mid-80s too.  No relation (except displacement) to the earlier SOHC 550/500 motors.

In the early 80s, there was also a 400 & later a 450 Nighthawk twin.

In the 90s & early 00s, there was the above-mentioned 750 Nighthawk and a 250 Nighthawk twin that used the same single-carb motor as the 250 Rebel.

[Ecosse]

Ahh.. Here I thought the "nighthawk" was a much later model of honda's. 

Well, yes and no...

The Nighthawk model was a mix of old and new (for the time) depending on displacement and model year.

The 750 version was equipped with the 'new' DOHC motor.  The first-year ('82) 650 model was equipped with the 'old' SOHC motor.  The '83 650s came with an all-new DOHC 650 motor (which grew into the 700 Nighthawk S a year or two later and eventually, I think, grew into the 750 Nighthawk motor of the '90s).  A 550 DOHC version was available for a year or two in the mid-80s too.  No relation (except displacement) to the earlier SOHC 550/500 motors.

In the early 80s, there was also a 400 & later a 450 Nighthawk twin.

In the 90s & early 00s, there was the above-mentioned 750 Nighthawk and a 250 Nighthawk twin that used the same single-carb motor as the 250 Rebel.

Geez, that's confusing... good to know though!