Rochester carb with flat spot

Ok all you carb guys, I need to pick some brains. I just completed the frame off restoration on my 70 cj5 with the 225 dauntless and rochester carb. All went well. I did a complete overhaul on the motor and rebuilt the original 2 barrel rochester carb. It starts and runs great, except for a little flat spot in the carb right as you open the throttle. So on every shift it kinda sputters a little but then takes off and runs great. If I ease into the throttle, it doesn't do it, but it's not always easy to ease into it with an old jeep. I've talked to some old carb guys and the accelerator pump was mentioned. There was some play in the rod connecting to the accelerator pump so I adjusted it so the pump would open as soon as the throttle is opened.
Any thoughts? I've played with the idle mixtures some too but I'm still not satisfied. How do you know if the accelerator pump is bad?

 

look down the carb and mash the gas should have a nice even stream of gas from the pump. is there more than one hole to hook the rod on the pump to ? on the 4 bbl i used to move the rod out to get more squirt...

 

With the 2 barrel you will have two solid streams of gas when you pump the throttle.

 

There's only one hole but I bent the rod a little to make it longer and that took the play out of the linkage. I have looked down the throat of the carb while opening the throttle and there is a squirt but it seems to be a little inconsistent. I'll play with it some tomorrow. Thanks all.

 

Lots of folks with the dauntless and the rochester seem to be struggling with that- some type of hesitation. A few months ago someone posted some a thread about an accelerator pump for the carb that was designed to withstand the effects of ethanol, which our carbs were not designed to use. I couldn't find the thread, but I believe he said he got it from quadratech, and it was design to work in the rochester 2g to solve the ethanol problem.

I haven't gotten those parts yet myself but it is on my list to do. in the mean time I am running my idle speed at about 850-900 rather than the factory setting of 650-700 and it seems to help.

Also- i added this later: I found that running pure gas works much better if it is available in your area.

 

Higher idle makes sense. I like the sound of the headers and 14" glass packs at 700 rpm tho. I'll keep messin' with it and let you all know what it takes. May help someone else down the road. Didn't expect everything to be perfect right out of the box after a complete frame off anyway. Gives me something to piddle with.

 

You may want to change the size of the squirter opening. Maybe open it up a tad.

 

My Dauntless went from running good after the rebuild to having a serious hesitation problem. I installed a new ethanol resistant accelerator pump from Quadratec about a month ago and acceleration has been smooth ever since. FWIW

 

I had the same problem a few years back on my 70/225/2g. It was driving me crazy and I thought I was chasing a vacuum leak problem but couldn't find one. After awhile the problem went away on it's own. Never did figure it out. We don't have ethanol gas up here but I'll keep that accel pump idea in mind for future reference. Rob - if ya figure it out please post.

 

I solved the problem of the hesitation under acceleration on my 71 CJ 225 with 2g Rochester. After replacing the accelerator pump, another good cleaning of the carb, checking timing, advance, and everything else I could think of, I purchased a rebuilt carburetor from Carburetor Exchange in El Monte, California. The website is www.carb-x.com. The completely rebuild their carbs, then engine test and pre-set all adjustments before shipping. Took about a week to get it, and they sent a return label to send in my old core. I bolted it on yesterday and it fired right up, runs like a new one, no hesitation, no adjusting at all. So I guess I took the easy way out, but I probably never would have solved the problem with my carb. It probably had something clogged, bad power valve, who knows? Very happy with the new carb though.

 

Thanks for posting. I think it helps to know that yes, it was a carb problem.

I bumped in to The Carburator Shop web site while surfing the web recently. There's a write up on "Bog, Hesitation, Stumble" in their troubleshooting section.

Check it out. http://www.thecarburetorshop.com/Troubleshooting.htm

 

recently I had a problem with my 71 cj5 with 225 and the rochester carb. I rebuilt the carb but in the end the problem was the points. Went to HEI problem resolved. But before I figured out that the problem was points I spent a lot of time on rebuilding the carb. One of my mistakes was with the the ball bearings (check balls) ... the small aluminum one goes underneath the accelerator pump and the larger steel one goes under the "t" by the main jets. Also make sure you get your drop on the float correct. I got my parts at: http://www.hotrodcarbs.com/ He also has main jets. and most anything else you need to rebuild your carb. He also carries the "good" accelerator pump.