Author Topic: CARB PROBLEMS/JETTING ISSUE  (Read 347 times)

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Offline Randy Nevrotski

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« on: November 14, 2019, 04:12:38 pm »
1976 CB750A Hondamadic .  When I first got bike I did carbs. it ran perfect I took it to the shore and back over 200 miles then after a week or too I started having problems. the new points and condenser went bad. fixed them .working on bike my 4into1 pipes the back piece didn't have bolts so I took it off. it has rusted holes on bottom so I cleaned it up cutting rust out make in holes a little bit bigger. when I road bike it wasn't 100%. when on highway Half Throttle or a little more then cranked throttle WIDE OPEN , it stumbled then started going like it should. I have PD44A carbs with 102 jets. I put 112.5 jets in carbs. I didn't notice a difference  but it still did the sane thing. after researching for a week or so. saying to myself and others that I'm missing something not doing something right. I been a mechanic for over 20 years . reading the Formes thanks for the guy who post a pic of carbs that pointed out the slow jet saying that they are pressed in. the shop manual doesn't even say anything about the slow jets. they where clogged up. what a difference but not 100%. what size jets should I try next. it has stock air box ,stock 4into1 pipe. all 4x spark plugs are clean . I was going to try 120 jets .                                                                                                                                Another question the hose from top of motor go to a little box behind air box mine had water in the bottom of it in foam filter    why would that be

Offline raymond10078

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« Reply #1 on: November 15, 2019, 08:16:12 am »
In reading your post, what symptom are you trying to fix?

The stumble when going to wide-open? 

If so, I'd first check the accelerator pump function and adjustment.  The pump is in carb 2, includes a check valve, and then is piped to the other three carbs, each with a spray nozzle.

With the airbox removed, you could check for spray in each carb, after the adjustment is checked.
1978 CB750A (upgrading very, very slowly)

Past bikes - Honda: SL350, CX650C, CB900C, CB1000C, CM450A; Kawasaki: several 1972 750 H2's; Suzuki: TC90J.

Bikes I want: CX650ED, a mid-sized japanese V-twin with ABS.

Offline Randy Nevrotski

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« Reply #2 on: November 29, 2019, 07:30:35 am »
now only a little hesitation. I'm going to put a slip on pipe. I don't want to but have to for safety reasons . 2 weeks ago when I was riding around in N.E. PHILADELPHIA. I had a guy come over in my lane. he said he didn't see me. 2 nights ago it was 60 degrees out I took another ride . same thing happen again. putting a pipe on so everyone can HEAR me.   pd44 carbs with 102jets slow jets #38.  I put 112.5 jets in it runs good but needs more. now I'm going to put pipe on. what jets should I try next 120-125 jets what size slow jets should I try. I know you have to try different sizes I would like to know a round about size.

Offline Jerry Rxman Griffin aka MuthaF'er

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« Reply #3 on: November 29, 2019, 07:52:58 am »
The water issue is likely just condensation. Should drain out into the lower tube if it accumulates enough
As of today 3/13/2012 my original owner 75 CB750F has made it through 3 wives, er EX-wives. Free at last.  ;-)