So, I put a set of carbs off of 83 vf750f (completely cleaned and rebuilt) on my 85 vf700f. I am getting good performance up to 1/2 of the throttle (better than I had with my original carbs), however, it feels very flat after that (1/2-full throttle range). So, it gotta be the main jet, right? Since I am putting carbs from bigger engine I assume I should get a too lean condition if anything, right? This is what puzzles me: 83/750 carbs have much bigger main jets (its 132 vs. 110/112 if I remember correctly). I could not detect any differences in carb bodies, they look (and measure) completely identical to me). So, how can it run leaner than my stock carbs? One thing I can think of is float levels. I had to adjust them for the 83/750 set and it is possible I made it too low resulting in overly lean condition. However, my gut feeling tells me that this is something else... Any ideas?
To rich a mixture and you loose as much if not more than lean. Besides if the A/F was correct on one it should be close if not same on the other. Remember jets and needles are sized together. So the jet size between the carbs may not be that much different overall for a correct A/F ratio. There is some variance you can work with. You may want to try and raise the needles if it's a lean condition. To do so, use a set of dial calipers and get some .020 small washers to raise the needles. Make sure they are all the same thickness. Then see what the result is. You can get drill bits in thousandths and drill your jets out if you can't buy the next size up or down. What do your plugs look like? Do you know the proper way to do a plug check? If not don't even waste you time reading plugs for accuracy. That will only tell you about WOT mixture which what you want to begin with. May be a general look might tell you a little if your way off one way or the other. You sure all the slides are working properly at heavy throttle and WOT? Did you have a factory manual to set the carbs up? Are all the throttle springs in between the carbs? Low floats would give a lean condition. Just some guesses for now.
