Topic: paulages CB650 head....

[MRieck]

I figured he would like to see the intake ports .

[bill440cars]

                        Whoaa! Fantastic job there Mike! THAT ought to be one free breathing motor. Can't
                wait to see and hear more.

                                                               Later on, Bill

[MRieck]

Thanks Bill. The 650 intake port is much better than the 750's. It has a nice flat to start with. The valves are 5.5mm stems which are much better than the 750's 6.5 (or 6.6 to be exact).

[paulages]

 

you're right, mike: i think i'll be very very happy. nice job...can't wait to run it!

Wykydtron-- it's going on 650 cylinders (bored out to 718cc), fitted on 550 cases and transmission.

[Pinhead]

Makes me want to pull the head off my 650 and get my dremel going.

What year 650 is that from?

[paulages]

1979

[Pinhead]

Neat-o. That's the same year as mine1 Wonder what hp potential porting the head has...

How much of an improvement is this over stock??

[paulages]

it'll be hard to say with all the other mods i'm doing, but i bet mike could give you a good answer...

remember, if you look into the history of the 650, most of the performance increase from the 550 was in head and cylinder design to begin with (better ports, hemi combustion chamber, etc).

[aptech77]

From what I have learned.......polishing the intake is a NO...NO
You want a smooth, but NOT polished port.
This will inhibit in proper fuel atomization.

[physician]

look great! now i want to di the same thing on my spare 550 head...

what sizes of 550 and 650 valves?

[MRieck]

From what I have learned.......polishing the intake is a NO...NO
You want a smooth, but NOT polished port.
This will inhibit in proper fuel atomization.

The port isn't polished. It may look it but it isn't. As I have said before....there are many theory's out there. Look at the ports on the new ZX-6 or 10....very smooth. To be honest most atomization doesn't take place until the last 20 degrees or so of the compression stroke.

[MRieck]

Could you explain to those of us who are less tuning literate (myself included) exactly what you did there?  It looks like you polished the entire intake port but then you added that v shaped cutout.  I'm assuming the shape of that cutout helps to vaporize the gas better to make it burn more efficiently.  Does it increase the venturi effect or something too to increase flow?  Could you explain how all that works?  I remember paulages saying he was doing a 550/650 hybrid motor.  This head is going on a 550?

the flat floor is good as it aids in increasing low lift flow (which occurs 2 times...as the valve just opens and closes. The streamlining of the guide boss & enlargement of the bowl give more volume. the streamling of the guide boss also adds velocity.

[MRieck]

awesome job,
how many hours did you spend on the head,&was it hard to make it exact on the other 3 intake ports?

It can take about 6 hours for that work. As far as getting them the same ...that's a good question. I've done a few so it's not to hard. Check your work frequently.