Very long...<br><br>The process depends on what carb you have, but if it is a 4160 (elec. choke, vac secondaries) I have the process down pretty well...<br><br>Here goes..<br><br>Go buy a spare float bowl gasket.<br><br>Next, take off the fuel line (it will probably spray a little so have a rag handy).<br><br>Now lay the rag under the float bowl, loosen the 4 bolts holding it on, gas will drain once the seal is cracked. If you take off the bowl with care you probably will save the gasket and can re-use it. You will be taking the bowl off several times so be patient.<br><br>Take out a jet with a regular screwdriver read the number on the side of the jet, if you can't find them, I'd say you are already in over your head. It is probably a #65 or so if it is a stock 650CFM carb.<br><br>This is where I depart from the owners manual.. I buy a jet that is about 10-12 sizes smaller, I'll explain.. A Holley jet #65 means the hole is .065" or 65 mils. I assume most people have a good set of drill bits in an indexed case.. if not now is a good time.<br><br>For mine I bought a #53 jet to replace my #65. I put the 53 in, and started it up, it takes a few seconds of cranking to fill the bowl back up. I first set the idle in the ballpark once the engine was warm (choke open and timing is already set of course). Hook a vacuum gage to the manifold and adjust the air mixture screw to obtain max manifold vacuum at idle. (or max rpm, I think vac is a more precise reading) set the screw on both sides the same number of turns and re-check vacuum reading, you can read more about this process lots of places online.<br><br>Drive around for several minutes, (after bolting stuff back together of course) if you are like me, the engine will probably fall on its face at about 1/3 to 1/2 throttle because the jet is too small.., take a look at the first couple spark plug threads (the ones that stick into the engine) and you can tell if there is excess fuel or not. The first couple threads should have a light coating of fuel, if not it is too dry. I never could reliably read the ceramic, I have raced a 4-stroke MX'er for a while now and the threads tell a much better story I think.<br><br>Now go back and repeat the bowl removal, now take that #53 jet and drill it out to the next drill size you have, I think .055 or so was my next size, (I used letter sizes which are about 2.5 mils apart, some machinist probably has them memorized and is thinking .056842 you idiot), very carefully I drilled out the jet on a small drill press and blew off the brass chips, leaving the square edge on each end of the hole the way stock ones are.<br><br>Reset the air mixture and try again unitl you are satisfied with power and plugs.<br><br>I ended up going to a .059, it was responsive to full throttle stabs and the plugs looked just on the damp side of dry. I didn't go bigger because I can't undrill a hole. you could try to go up a size and see if you have a touch more power. Max power is just on the rich side of stoich. It is pretty tough to tell a small change without using a stopwatch though. If you think you are rich enough and still stumbling at throttle bursts, check the accelerator pump lever clearance. You can adjust at what linkage position the pump begins to spray.<br><br>Now go and buy the jet you need to match your best drill size if you went over or are worried about the spray pattern. I haven't though. Jets around here are about $6 each. I only bought one this way rather than a few.<br><br>Lastly.. the stupid high idle setting is on the bottom of the carb. A holley has a plastic cam that holds the throttle part open until the choke closes (choke side, not linkage side). The adjustment for this is a screw that you can get at only with the carb unbolted. It is a PITA if you don't guess right the first try. That is how you set the cold idle though.<br><br>We went from about 11mpg to 14mpg with this couple hours of work. (actually my brothers Bronco) now I finally don't smell exhaust!<br><br>If you screw something up using these instructions don't blame me, but let me know - it might be funny.<br><br>-Jon
