Topic: cb750 motor build need some help

[tscat01]

im interested in building my motor a little bit but dont know if my ideas will pan out, my thoughts are to knife edge the crank and put a cam in, looking into (.360 lift 260 degree @ .50") APE cam, my concerns are jetting of the carbs, can i use the stock carbs, what jets would i put it, other supporting mods i would need to do any information helps thanks

[ekpent]

Cam might be a waste of money if you don't have a little work done on the head flow,stock is not the best.Are you changing compression,like maybe a piston kit also?

[tscat01]

head work is a possibility i guess im just exploring my options and trying to get recommendations from people that have already built their motors

[MCRider]

head work is a possibility i guess im just exploring my options and trying to get recommendations from people that have already built their motors

Personally, after doing several engines and sevaeral observations of others engines... the headwork would come first. Porting and a decent fineline valve job.

Everything else will complement that, IMO. jetting is simple and yes you can use the stock carbs. You wouldn't want to use other carbs unless... the head was ported. See?

Everything adds to the headwork. Without it, youre just bolting parts onto a slug.

I'm one of the few if only who ever had a ported head on an otherwise stock, 736cc, bike, with a 4-1 tripleAAA header. It was by accident, we built a bike for me out of parts at a shop I worked at. We had a ported head laying around that had all the fins shaved off of it. Owner (of the bike) thought he was making it faster drag bike by lightening it up. Owner (of the shop) gave me the head for my rat as he figured he'd never sell it or otherwise use it.

Man was that a sweet motor. Taught me the head was the key.

I had a 750cc roadracer. Yoshimura East ported it. Cam, carbs, and a pipe.  I built it for the 750cc class, but ran it in open for the track time.  Could keep up with the Kaw 1000cc Superbikes. Head was the key. Made a lot of HP. Thought I could get by with stock rods, but ended up bending one. Not bad for a 750, though.

If all i had was $XX, I'd still do the head first, and put it together as a 736cc. You can add the other stuff later. Everyone's got an opinion, that's mine.   

[tscat01]

MCrider thanks for your input your onto exactly what i want, i want to make some power out of the stock displacement

 i do want to do all the work at once i think since its a project of mine and i have the time to do it,

just for example i kept the stock bore did the head work and added a cam, would i then neeed to upgrade my carbs or can i just jet the stock ones to accept the work i do i would also be doing rods and machining the crank like i said earlier im not looking to race it but it may see a track day here  thanks again for all the input

[MCRider]

MCrider thanks for your input your onto exactly what i want, i want to make some power out of the stock displacement

 i do want to do all the work at once i think since its a project of mine and i have the time to do it,

just for example i kept the stock bore did the head work and added a cam, would i then neeed to upgrade my carbs or can i just jet the stock ones to accept the work i do i would also be doing rods and machining the crank like i said earlier im not looking to race it but it may see a track day here  thanks again for all the input

You don't "need" the carbs. It will run fine with the stockers. Jetting is easy, cross that bridge when you get to it.

But as an add on now or later, carbs would be nice.

[tscat01]

ah i see i just want to know im not biting off more than i can chew you know...any recommendations on parts or links to other builds or anything

[ekpent]

There is the Hi-Performance section on the Forum that is loaded with speed Gurus-engine builders with great advice and leads,a few would be even happy to help you unload a little of that extra cash 

[Hinomaru]

ah i see i just want to know im not biting off more than i can chew you know...any recommendations on parts or links to other builds or anything

Action Fours is no longer around, but this cam install article just might come in handy:

http://www.hondachopper.com/garage/articles/cam_install/page1.html

[youn6372]

My 2 cents:

I agree head work is vital and stock carbs cleaned and jetted work great.

If you are going through all the effort of taking the motor out, why not a first over?  Freshen up the motor bore it out .25, Cycle Xchange sells pistons rings and clips for $200.  Its good for 5-7 Hp, almost a 10% gain on stock.  Plus you going to want to replace the lower gasket anyways.  I guess the down side is sending the head out, I dont do honeing myself.