1974 CB750 K4 - problems bogging down around 4-5000K

[Creative Film Cars]

Hey everybody,

I have a 1974 CB750 K4 with Hooker 4 to 1s and have just started having problems bogging down around 4-5K rpm.

I have had the bike for a few years and don't get to ride as much as I would like, but I usually get a 100-150 mile run in every month or so.

At the end of May 2008, I went for a good 150 mile ride and the bike was running great with no problems.

The bike sat for about a month, and I took off the stock air box and put some air pods on.  I took the bike for a few short rides, but it would bog down around 4-5000 rpm.  I could twist through it and it would start running smooth again around 7000 rpm.
I took the bike for a longer ride last weekend, figuring that I had some varnish to blow out, but the problem got worse and the bike ran hot.  

I have changed the points and timed them to spec and the problem remains.  Are there any suggestions of what I can do short of a carb rebuild?

If a carb rebuild is my next step, do you guys have any suggestions for a good shop in the New York City area?  I was hoping to ride out to the mid-Ohio AMA Vintage days next Thursday, so would really like to find a reputable shop that can do the work properly and get it done in time.

Thanks for your help!
Donald

[CCCP916]

the reason it is bogging out is because the bike is not getting the right air 2 fuel mixture. when you take out the box and free up the air intake you have to rejet the carbs to make up for the difference. i have the same pods but waiting to buy the jets bfore i can put them on

[pena750f]

I would also say your fuel mix is lean. If this is your prob or turns out to be something else, could you post your results as a lot of cb750 owners like to "free" their exhaust and "open" their air intake. If you look for new jets, bikebandit.com has sets for our bikes. They come in a mixed size set, so you will need to buy for sets.