Topic: Carb QUESTION

[zekd]

I just got back to college and I brought up my set of carbs. I need to change the needle height and the jet size I believe. Im running a stock air box with a 4 into 1 exhaust with a shorty baffle on the end from DCC. Heres my question, how many need clips should I go up (or down)? And also, should I change my jet size??

[flybox1]

for what bike?
what makes you think you need to change jetting?
poor performance?  plug chop readings?  etc...we need more info to help you determine what will work
did you change exhaust system to your current setup or add the new exhaust can?
any changes to your intake system?
what is your current jetting?

[LesterPiglet]

Try the bike out before you do any jetting changes. Most exhaust changes do not require rejetting.

[zekd]

Try the bike out before you do any jetting changes. Most exhaust changes do not require rejetting.

What should I do about the needle height???

[Black 750K8]

I just got back to college and I brought up my set of carbs. I need to change the needle height and the jet size I believe. Im running a stock air box with a 4 into 1 exhaust with a shorty baffle on the end from DCC. Heres my question, how many need clips should I go up (or down)? And also, should I change my jet size??

What filter in the box?  flybox1  LesterPiglet are right on as usual need more info. on your setup. You did not even tell us if you have a 750 350? What carbs? I guess you may be new at this but you will catch on Lots of understanding people here.

[Black 750K8]

 zekd Wihout knowing any more I would say do a plug chop to see what you have. Just what seems to be the issue?

[zekd]

Sorry. I have a build thread and I just copied and pasted from the build thread to here. Thats why I didnt put what bike I have 

I have a 1974 CB750 with a stock air box with the air filter that originally came with the bike. I have 110 jets on now and the needle clip is up to the second notch from the bottom. the bike runs ok but bogs down when you pull throttle too fast.

Hope this helps you guys help me

[harisuluv]

Your bike doesn't have an accelerator pump, to some extent what your describing is normal. 

[zekd]

But shouldn't I adjust the needle for more air flow?

[Black 750K8]

the air filter that originally came with the bike. I would get a new air filter first even if it looks new they break down over time. You need to know you are getting enough good clean air. Now when you have the new filter time to do a plug chop to see what you need to do. You adjust the carbs by what the plugs tell you not the other way around.

[Davez134]

But shouldn't I adjust the needle for more air flow?

Adjusting needle does nothing to increase airflow, it influences fuel. As everyone pretty much stated, do full tune-up (including new air filter) then do a plug chop to see what they look like. There is a sweet spot in air/fuel ratio and too lean OR too rich can affect power. Raising needle (by lowering clip position) makes the mixture richer lowering it leans mixture out.  Also search the forums, there are quite a few great posts on the effects of too rich or too lean. See if any of your bike's symptoms match.

[flybox1]

correct.  needle height changes the amount of fuel added to the system in the throttle range between the pilot jet fuel flow being maxed out, and the main jet beginning to pull in fuel.
dropping the clip a notch(towards the pointy end) INCREASES fuel supply.  and vice versa.

get a NEW air filter, and do ALL tuneup items BEFORE you make your carb changes.  otherwise you'll be chasing your tail.

question: at what rpm range are you when you pull the throttle 'too fast' and experience the bogging?

if you're at idle, yeah, that bogging is going to happen to most bikes without FI or an accel pump, and to some extent it will happen to accel pump carb'd bikes, too.
if you're up near 6000rpm...all these bikes should respond rather well to a brisk roll-on of the throttle (as you are now drawing fuel through the (larger) main jet.)

[Bankerdanny]

Go into your profile and add the year and model into your signature and that will save you having to type that info into every new topic you create.