mpk490p

so i have the 51 running well but having a few issues with the idle mixture i can't get my head around, it had 65F10's in it and ran like poo well rich, so as i didnt have any others at the time i put the idle jets from my 45dcoe in there 60F11's it ran a load better although the idle jet hold is smaller in length, i swap the idle jets into the ida (120) holders and again ran like ****? i have a cheap air fuel gauge (not a wideband) and i was still all the way round on rich so i ordered some 60F9's same thing it will only run on the DCOE holders? still right round on the gauge and my eyes are stinging! lol the idle screws come out 1 - 1.1/2 turns so thats all good and the car runs sweet enough, is it just a crap gauge or should i go smaller on the idle jet?

the carb also has the 3rd progressive hole and the change over seems fine



running 195 mains and 160 airs 40 chokes F11 tubes and that seems good its just the idle mixture

motor is a 13b 4port street port



had another look tonight and took the car for a run, got back put the 48ida 120 holders in with the 65f10's would run if i wound the idle screws out but the gauage was reading normal to lean? so i put some 70F10's in i counted 4 turns out before it would run at all left it a while then it started going lean again, do you think it could be float height? the smaller holders from the 45dcoe seem to work fine the longer 48ida one's don't

j9fd3s

whats your timing set too? stock is fine, or a little advanced, maybe 5 BTDC L.



rotaries are usually happiest idling a little rich, factory is in the low 12's, if you're willing to tolerate a misfire here and there, you can run it leaner, but to get into the 14's is tricky



so the old school way to set the idle mixture on a carb, is to hook up a vacuum gauge up, and adjust it until it pulls the highest vacuum



if you max out on the idle mixture adjustment, then you can step up (or down) a jet or two.

mpk490p

i guessing it would be stock timing i have a few idle jets but it really seems to like the dcoe idle jet?????

would having a 3rd progressive hole mess up the mixture on the idle?

j9fd3s

so i'm looking at mine, just to make sure i have this right.



if you think about the throttle plate, the idle hole is underneath it, so with the throttle closed it can flow fuel. as the throttle opens it uncovers the second and third holes.



since the weber adjusts idle speed by opening and closing the throttle plates, you could have it open enough to uncover all three sets of holes. i think, mine doesnt have the 3rd set.



so it should not be affecting the idle, but it could be



you should verify the timing too



i dunno why it likes one jet over another, just find the best running combo!