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Acceleration is lacking
- Thread starter jlippert
- Start date
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- Tags
- carburetors dohc
amc49
CB750 Guru
Carb work alone often does nothing to fix almost 40 year old bikes.
Compression test....................compression is what opens the CV carb slides.
Compression test....................compression is what opens the CV carb slides.
amc49
CB750 Guru
170 psi is the new engine spec, runs fine but a little slower in increments down to 130.
Accel pump will only be as you increase the throttle, once you have screwed it open and bike still not pulling hard then not pump, as it only works when the throttle IS MOVED. And if the mixture has been richened no need for it at all, it only comes on US spec bikes, the Euro ones do not even have it. Past about 2 full turns on idle mixture you really don't need it if rest of carb working right. It only has effect at low throttle openings.
You can yank the airbox rubbers and using a small mirror look at the carb inlets for the squirt of fuel each has as you open the throttle up. The squirter is that little brass stub you see sticking up on the right that the choke plate has a notch cut in the bottom for. The squirter shoots a small shot of fuel at the needle location when worked.
Accel pump will only be as you increase the throttle, once you have screwed it open and bike still not pulling hard then not pump, as it only works when the throttle IS MOVED. And if the mixture has been richened no need for it at all, it only comes on US spec bikes, the Euro ones do not even have it. Past about 2 full turns on idle mixture you really don't need it if rest of carb working right. It only has effect at low throttle openings.
You can yank the airbox rubbers and using a small mirror look at the carb inlets for the squirt of fuel each has as you open the throttle up. The squirter is that little brass stub you see sticking up on the right that the choke plate has a notch cut in the bottom for. The squirter shoots a small shot of fuel at the needle location when worked.
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Dave
CB750 Junkie
Did it run fine before you cleaned the carbs? If yes, then chances are it's a vacuum leak.
Is this bike new to you? If yes, then you always start with compression. If there's not enough, nothing else will work right.
Is this bike new to you? If yes, then you always start with compression. If there's not enough, nothing else will work right.
amc49
CB750 Guru
Electronic, it pretty much doesn't change, people have to mess with it.
Wasted time with no idea of where the compression is................I used to bank on making money on that because people just don't want to do it. Nobody ever sets the valves because they use shims and how they run like crap. The most common issue with them.
Next most common error is yanking the stock airbox, it kills the carb/engine response too. You gotta do what it takes to make those CVs happy or the bike will always be a dog.
Wasted time with no idea of where the compression is................I used to bank on making money on that because people just don't want to do it. Nobody ever sets the valves because they use shims and how they run like crap. The most common issue with them.
Next most common error is yanking the stock airbox, it kills the carb/engine response too. You gotta do what it takes to make those CVs happy or the bike will always be a dog.
