Re: 1978 cb750 carb swap

Posted by Re-run on Apr 18, 2012; 12:40am
URL: http://vintage-and-classic-hondas.81.s1.nabble.com/1978-cb750-carb-swap-tp3911046p3918734.html

Lucky, I know you frequent the other sohc4 site, but obviously you have not been around there long time. I was around there from years back. Now, I am going to tell you this once. Pods will never work better than the airbox will, it just will never happen, even if the motor is bored, for everyday use. You suffer from crosswinds and a host of other things. Honda designed these bikes to work with the stock airbox. Pods CAN be used and, with work, are able to work close to the level of the airbox. There is NO magic bullet for these carbs OR the earlier carbs. Why? Cause every bike is different not to mention a persons location. At sea level, settings will be different than at 1500 ft and that is different from 3000 feet. Therefore it is impossible to come up with 1 setting that will work for everyone. I do not get your desire to get exact settings when that is impossible to do since every bike is different. Why do you think honda gives BASE settings which are then tuned upon?

As for tuning the carbs, I also fail to see why this is hard to understand. It is widely known that the fuel screw is more flexible than the older air screw was. I tossed in a K&N in my box, didn't have to rejet. Ran with NO box or filters and did not have to rejet. I suppose if you are tuning for power, then sure, you might have to rejet. I tune for a balance and as such, I can knock on the door of 50 mpg at 75 mph, even on ethanol fuel and I have sufficient power to get my 220 pounds moving pretty darn quick.

And then you have the accel pump, what a lovely item that truly is. It allows you to have a leaner idle mix and then get a shot of raw fuel when you crack the throttle. This is why the 78 carbs are more responsive than the earlier 76 carbs are.

If you were to ask around, a number of people have bored to 836 and used the stock carbs with no troubles at all. Most of the time, this includes porting the head.

And finally, what benefit do the earlier carbs offer? An idle jet that uscrews? So what, you can get other press in jets, problem solved there. They are simpler? Only difference is no accel pump and really, the accel pump is not that difficult, it either works, or it doesn't.

Lots of people prefer the earlier carbs but I think most of that is because they do not understand the later carbs for whatever reason, I find this prevalent mostly with older riders. I have used both styles and I, by far, prefer the 78 carbs. Anything you can do with the early carbs, I can do with the 78 carbs. Anything.
I know how to tune these carbs and that is why my bike, even at 40 degrees and cold, will start with barely the touch of the starter.

And again, no 1 setting works for every bike and it never will, because no 2 bikes wear their internals exactly the same. If they did, you should be able to line up 10 bikes that used the same filters and fuel and oil and have the same mileage and compression readings should be identical. Guess what, won't happen.
But hey, you don't have to believe me. I am ok with that, after all, more carb parts for me.