Starter Jets?????????

[SFerinTEXAS]

what are the starter jets? the choke plungers? my 78-79 clymers gives starter jet sizes as 78E = 40 79 F and SF = 32.5 . I'm a little unclear what exactly are the jets. do they effect the idle mixture (pilot circuit) or only the choke? and what effect would it have if different ones were mixed on the carbs?

[pggg]

Starter jets, pressed in, can't mix them, they're in the fuel bowl rim, don't affect anything but cold start, when chokes off, they're sealed

[SFerinTEXAS]

pggg

Alrighty then,, Thanks. Not really my present issue then but if bowls from an E model were mixed with the F probably no big deal anyway except during the first few miles running on half choke while it warms up. You think thats enough to affect the pipe coloring on two cylinders? Or could it be the emulsion tubes? I put the ones with less holes in 2 and 3, ten as I recall and 1 and 4 had 16 holes. When I took the carbs that came on the bike apart they were opposite but I know someone had been in them before.

[pggg]

SF, well, after cold starting, the motor should tick over with the choke shut within a minute or so, if the idle mix screws are set leanish, it'll take a bit longer to idle smoothly, but the mixed emulsion tubes will be bad news, giving uneven fuel ratios, unless the jets and needles are mixed to compensate too, but what a hassle tryin' to sort an uneven mix of components with basically guesswork, far easier to have everything identical and set the same. The 'normal' 78-79 emulsion tubes are stamped 266-X2 with 16 breather holes, the starter jet size differences are negligible.

[SFerinTEXAS]

TUBES

For some reason the sf special came with that set up apparently to provide more cooling for the inside cylinders (more rich). It's discussed elsewhere on this site. I think I'll pull them soon and check the inside carbs pilot jets, passages, diaphrams and change the tubes to all the same. If you look at yamaha's parts list it shows the SF inner tubes as 3h3 part numbers and the outter ones as 2h7, same as the E and F all across. She's running pretty good as is but when I set the idle mixtures screws there is very little rpm variation on those inner two compared to the outter's. I'll get back to this after I check it all out. On the later years they put larger main jets in the center carbs with the same tubes all four.

[pggg]

Yeah SF I don't know why they dicked around with that, some theory was the rubber air intakes from the airbox are shorter than the outer ones, whether that's true or not on an XS I haven't bothered to look, and the temp difference between inner and outer cylinders wouldn't be 2/10ths of bugger all, if it's that big a deal, why didn't they just run cooler plugs,BP7's or 8's in there