Topic: 650 engine in a 550 frame

[blounstation]

I'm looking into putting a 650 engine in my 77 Cb550, Does the 650 have to be a paticular year for the swap or will any 650 motor fit?
will I need to swap out the wiring harness too? Has anyone done this and have some tips? thanks in advance

[bill440cars]

Any 650 will fit (as long as it's an sohc) The 650 will drop right in. The only differnces beween the years are the carbs and head intake spigot spacing. '79-'80 and '81-'82 are the years. You would also need a wiring harness, the 650 has electronic ignition, not points.

           The 650 exhaust will be needed too! It's been said that the exhaust port angles are different (I believe that's the main difference).

           You DO know that you will be minus a kickstarter, with the 650 engine, right? Just checking.

[Ecosse]

Excuse me for butting in; regarding the 550 points vs. 650 elec. ignition, if a 650 wiring harness cannot be obtained can an aftermarket (Dyna, Hondaman system etc...) be used?

[blounstation]

 I have a line on a 83 650 motor and carbs for cheap but it sounds like it's the wrong year. I don't mind not having the kickstarter, it makes your legs stronger when you have to push it down the street and pop the clutch... 

[blounstation]

Actually the motor is from an 82, it has CV carbs on it and I'm not sure how the breather box is set up on the nighthawks, but could I run slide carbs with that motor?

[Hush]

The carbs seem to be the only change I can see between the 79-80 and the later SOHC models of 650.
The early custom should fit, not sure about how they altered the air box and rubbers, after 1980 they repositioned the battery into the centre of the 650 frame as opposed to having it hang out the right side like mine does.
Also repositioned the rectifier and regulator too but that is no biggie if the loom you get is same model.
There's at least 3 different types of stock exhaust pipes though so watch out for that, 2 into 1's 2 into 2's low level 2 into 1's and then you get into the 4 into 1's.
I know I been looking for a 79 set all over the world!!!

[paulages]

I have a line on a 83 650 motor and carbs for cheap but it sounds like it's the wrong year. I don't mind not having the kickstarter, it makes your legs stronger when you have to push it down the street and pop the clutch... 

eric- i have an engine for you if you want it. it's either an '81 or '82. i know of a whole cb650 parts bike too. you don't need an entire 650 wire harness, just parts of it pertaining to the ignition. i have your exact model sitting in my shop with a 650 engine in it if you want to come see the necessary ins and outs.

[paulages]

The early custom should fit, not sure about how they altered the air box and rubbers, after 1980 they repositioned the battery into the centre of the 650 frame as opposed to having it hang out the right side like mine does.

i modified the 550 airbox fairly easily to accept the 650 plenum. just fiberglassed over the old hole, and cut a new one.

[blounstation]

right on! I'm around tomorrow if you've got some time. After riding my bike back from Reno a few weeks ago making a 550 mile trip a 750 mile trip, my bike is seriously on it's last leg. It even has trouble going up HWY26 at full throtle. I planned to ride it into the ground and the grounds getting real close..

[blounstation]

I'm picking up a 550 motor today to swap over as a temporary fix while I look for 650 tid bits. On Monday while riding to work on Hwy 26 towards Beaverton I noticed my right leg getting hotter and hotter, once I stopped and looked down I saw my entire leg covered in oil and a nice steady stream running down my leg and into my shoe  ... The Head gasket went and was spurting oil out the side and the entire right side was covered in a mass of oil. It was kind of funny and not at the same time, but I made it to work. Luckily I had a Penske truck at work with a lift gate so I could get it home. To be continued..