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Searched for this specific question no luck.... Looking for some feedback/experience with jetting changes after a similar engine rebuild to mine. I am getting close to assembling my 1216 rebuild and I want to have the jetting as close as possible to 'acceptable' for the initial start-up and break-in, especially for that first half-hour of run-time. I've done some reading on the affects of increased displacement, increased head-flow, and increased compression ratio and all three indicate a decrease in richness, which I admit, was opposite to what I would have guessed. So smaller main jet and leaner needle position are likely needed. Rather than specific jet sizes, or needle position, which is going to be individual based on exact engine specifics and altitude, and other variables, etc. I'm hoping to hear some feedback on just how much of a change I should be looking for. ie 1-2-3-4 jet sizes smaller? I realize I will have to go through the usual steps of dialing in the jetting as I normally do. IE full throttle runs to find best main-jet, followed by needle-jet clip position, float height etc. But just wondering if anyone has any first hand examples of how many main jet sizes they had to change, or how many clip positions etc, with a similar engine rebuild as mine. I have BST38SS carbs nicely set up before the rebuild. I have the Factory Pro 38 mikuni jet kit installed. Think I have a 152.5 main, and needle at top(leanest), or possibly second from top clip position. I live at 1100 meter altitude which leans things out too. The following are the engine changes: -1216 JE kit -11:1 -Head ported by experienced oil cooled head porter -30/26 valves -stock cams Any experiences or feedback is much appreciated!

Evening all. Can't seem to get my. carbs set correctly under 4000rpm. I've had the bike on the dyno and it's reading rich and a flat spot until 4000rpm? After 4K it's spot on! Idle mixture screws seem to be best set at 2 turns out. Any help would be grately apprieciatd!

To keep it short, my bike won't start after (apparently) going by the book when installing stage 3 Dynojet kit in my 38 cv Mikunis. I checked the plugs and they look like they might be fouled, could I give them a clean to save them? Anyway, the bike is a 1990 gsxr 750, with the bst38 mikunis. Stock headers, made link pipe and free flow end can. Dyna coils and k&n dual pod filters. I had the bike back from a mechanic who put some "K" 140 main jets in. Had the bike running....ok (could be a lot better), but he forgot the fuel tap filter that goes in the tank... Result was clogged fuel tap that barely got me home on prime after about 50-60klms. So I got the carbs 100% clean, had new o-rings in already. Got my fuel tap modified for on/off and a new filter. I decided to take a good look at the stage 3 Dynojet sheet, and do what it says myself. I left the same "140" main jets, and plugged the main air jets, which were not until then. I plugged them with zero jets and not the DJ "plugs". So basically I had the DJ stage 3 kit in, EXCEPT the float bowl plugs (to deactivate the powerjet). Also the K140 instead of the DJ 160 main jet. The bike started very easily cold, idled perfectly, and throttle response was like I've never seen !! The problem was #1 and 2 carbs were leaking and I think idle was getting rough after warming. Replaced #1 and #2 carb float bowls with the large cap to replace main jet, with some others I had extra. Result was not so smooth idle but still ok. Probably better than when I got it back from the mechanic. After some more research I read the article here about the powerjet and how it doesn't work without the airbox. So I plugged the float bowls which were open without any jets (!) and installed the DJ155 mains instead of the 160s because I don't have them any more... After that, it won't start!! Probably fouled the spark plugs in the process... Now what? Could it be "overfueled"? I check float height each time I put them back together, fuel is flowing from the tap. Floats are floating. I gave it another try, I wiped and blew the spark plugs and turned the pilot screws from dynojet's 2,5 turns out back to 2 turns. I had a little "gurgle" but no start.... Some of my pics for reference: