Topic: Help me rejet for air pods! Everyones favorite posts!

[Shinglejohn]

I picked up a 74 cb750 crate job for a coupl-a hundys this winter. It did not come with an airbox so i decided to go pods with it. The original Jets were 105's. I upped it to 110's and also raised the needle one position( why? I dont know. Because someone in a forum told me to).

The result was better than the 105's but did not have much power and bogged really hard at about three quarter throttle and then shot out of the bog as i continued to roll on the throttle.

Next i upped the jets to 115's and returned the needles to their original poition. I now get very smooth power and excel through the lower gears and a slight loss of power in the upper gears at about 3/4 throttle. The power returns as i roll on toward full throttle. I also have a bit of popping on decel, seemingly from the muffler.

any thoughts?

[scrapvalue]

I picked up a 74 cb750 crate job for a coupl-a hundys this winter. It did not come with an airbox so i decided to go pods with it. The original Jets were 105's. I upped it to 110's and also raised the needle one position( why? I dont know. Because someone in a forum told me to).

The result was better than the 105's but did not have much power and bogged really hard at about three quarter throttle and then shot out of the bog as i continued to roll on the throttle.

Next i upped the jets to 115's and returned the needles to their original poition. I now get very smooth power and excel through the lower gears and a slight loss of power in the upper gears at about 3/4 throttle. The power returns as i roll on toward full throttle. I also have a bit of popping on decel, seemingly from the muffler.

any thoughts?

Are you running a stock exhaust or something else.
It makes a big difference some times.

[sangyo soichiro]

I also have a bit of popping on decel, seemingly from the muffler.

any thoughts?

I got this one:  I believe this is your idle jet screws.  Try progressively turning them out to see if it helps.


As for the mains, you need to figure out what the bike is doing at 3/4 to WOT and adjust the main size from there.  (There are a few ways to do this; checking plugs, playing with the choke, etc.)  The needle position mostly affects the midrange throttle.  Dink with this after you've figured out your mains.  There are a lot of threads dealing with this topic.  I'm sure the process is explained better in those threads than what I could do here.


Or try to find a stock airbox.   

[Shinglejohn]

no its not stock, im not sure what the make is but it is a 4-2 setup.

Ive read every post on th net about jetting, but i like to confer with yins during the proccess. Give me something more to do to avoid swmbo.

[xenoscr]

Let me ask it before anyone else... what do you spark plugs tell you? Do they look like you lean, rich, oil fouled, etc? You're going to have some tinkering ahead of you with pods. I got my 75 cb750 with crappy pods on it and no air box, switched to K&N and played with all sorts of adjustments. The 115 mains are what I'm running now, needle is one notch richer than stock and my idle screws are 1 1/8th turn out. That's what works for me, what works for you depends on how your plugs look. Check out the Carb FAQ if you haven't already, there's a wealth of info out there. If you post some specifics about your plugs you might get some more advice as to what to try next though.

XeNoSCR

Damn soichiro beat me.

[Shinglejohn]

With the 110's the plugs were a very light brown. Now with the 115's they are a fairly dark brown.

[xenoscr]

Light brown sounds better than darker. have you done all the other tune up stuff. Cam chain tension, valve clearance, timing and lastly sync your carbs? Any one of those things not being done could cause the bike to not run correctly.

XeNoSCR

[scottly]

Next i upped the jets to 115's and returned the needles to their original poition. I now get very smooth power and excel through the lower gears and a slight loss of power in the upper gears at about 3/4 throttle. The power returns as i roll on toward full throttle.
any thoughts?

Try moving the needles back up..

[scrapvalue]

My bike was running 110 main jets stock.
All I did to the motor was installed pod filters and the exhaust I built is just 1 1/2" straight pipes.
They are a lot longer then most pipes because I stretched the swingarm 8" and run the exhaust back past the axle bolt.
The stock jets would idle o.k., but as soon as I gave it any gas, it would cut out.
I installed 150 mains and then it would run up to about 1/2 throttle and then cut out again.
I then installed 190 mains and it didn't cut out, but it would stumble and burble,(?),when you tried to cruise.
I then dropped to 170 mains and it runs like a raped ape.
It idles fine, revs very fast and cruises effortlessly.
I know this sounds crazy, but I have put 3750 miles on it and never fouled a plug. Plugs are medium dark brown.
Needle is still in the stock position and slow speed jets are also stock.

But one thing I highly recommend is to install an electronic ignition. Doesn't have to be the real expensive one.
I have one on my stone stock 72 and my modified 74.
Mis adjusted points can act a lot like carb issues.
And carb issues can act a lot like points issues.
Until you are positive you have one of them right, it makes it real hard to get either right.  

Basically, no 2 jetting situations will be the same. It always requires a couple,(or more) tries.  


I know this is the same post as another carb issue, but it is relevant to both.