79 carbs on an 80 , match float height to year of bike ?

[TDodge7]

ok , so tuning is not my strong point , but i've been thinking about it and this seems to make sense to me . since having the air box bottom on makes everything run so rich then i'm going to have to tune around that . i know that my mid range is rich , and i can't make it to wide open to see how that is . so i should start by leaning out the needle . if that fixes the mid range i can then test wide open and see if any main jet changes are needed . and for idle i can just play with the mixture screws , i think there's probably enough adjustment for them so that i won't have to change pilot jets .


...this kerker must really breathe

[Crazcnuk]

Actually, for many of us, the first step, to lean out the entire range is to lower the floats about 2mm.

This leans out the low and mid range ( high end too but then we tune for your mods) then rejet the main for your modifications.

Before you do this though, have you adjusted your idle mixture screws?

People seem allergic to touchjing these screws, yet they are the simplest adjustment on the carbs.

If you can (or have already) adjust these, then let us know the results (ie: nothing, or how many turns in or out) it gives us a much better idea of what else may be going on.

[TDodge7]

ok , i'll set the floats to 27.7 then ? and i'll work from there . while i have the carbs open is it worth it to steal the plastic floats out of my 80sg carbs , or should i leave the proper 79 brass floats in there , the brass ones are all good , but if it's worth it to change them out while i have it apart then i'll do it . and i'll get those mixture screws tuned in .

[TDodge7]

tho won't the mixture be affected by lowering the floats ? shouldn't i do the floats before adjusting the mixture screws ?

[DGXSER]

If it were me, I'd try the screws first. I'd turn them in a half turn and try then. IMHO, that mixture screw effects the entire circuit of the carb. Others will probably correct me, but I look at it as additive not switching out of the circuits. Starts with pilot idle jet circuit and mixture screw, as the throttle opens the needle joins in, then finally the main jumps into the mix to give total fuel mix. But I do not think the idle jet circuit stops contributing when the needle kicks in, or the needle no longer effects things when the main kicks in.

I agree, change one thing at a time, then you know what did what.

[Crazcnuk]

Yes. Technically, you shouldn't be changing your floats or your needles until all the regular adjustments have been tried.

This is why knowing what your mixture screws do helps us determine which internal adjustments need to be made.

For example, if your screws all want to be closed or near closed to idle the best, then we would say your mixture is too rich for the mixture screws to compensate for, and would recommend lowering the floats 2mm. (assuming you have stock or larger pilot jet)

If your screws want to be at, say, 4 turns out, we would say, that if your floats are at stock height, then you need to go down a pilot size, etc.

Each of these changes gives us a little more information as to what is happening in your carbs.

For most it seems that all the stock settings and lowering the floats 2mm seems to cover the most amount of issues. Then rejetting for aftermarket mods can begin.

For your setup many would say to go up 2 main jet sizes (142.5) Pilots should be fine. However, this only affects the top 1/4 of your throttle range. So you can play with that once you get the initial setup done.

Incidentally, changing your needle height actually only affects throttle position. It changes where you have to turn the throttle to get the same reaction. Lowering the needle only affects lean/rich at fully closed or fully open, since everywhere in between is position dependant.

[TDodge7]

and i take it i should try all of this with the air box bottom on .

[TDodge7]

ok , well i just tried to do the mixture screws (airbox bottom and filter on ) . it seems all of them wanted 2 turns out except for carb #2 which only wanted 1 - 1 1/4 turns out for some reason . i'm not sure why one would need any less turns than the others ,and if anything i thought it would be carb #4 since i had to dig a stuck mixture screw tip out of that one . it's still hot so i haven't pulled a plug yet , but i turned each screw out till the engine would rev as high as it would go , adjusted past that and turned back to find the sweet spot , so it should be pretty close . the throttle response is nice and crisp , and it seems to accelerate up to 5500 with a nice boost in power at 3k . once it hits 5500 it starts gurgling , i can wide open past it to about 7k or so but it's gurgling the whole way . and when i took it down the street it stalled at a stop sign , not sure what thats all about .

[Crazcnuk]

That is the correct procedure. The screws do not have to be all the same, there are minor differences in every carb.

You will have to take it out now for a cruise and run at 5500-7000 for a minute or so then do a 'chop' test to see what the plugs look like. If they are black you're rich, if white, then you are lean.

The chop test just means run at the range you wish to test for a minute or so then pull in the clutch, kill the motor and roll to a stop at the side of the road (pick a good spot) and then pull the plugs to see what they look like

[DGXSER]

Yep, Most bikes I have seen have the mixture screws different for each cylinder somewhat. Diff in compression for that cylinder will change the carb requirements, along with the valve condition and spacing. If you had most at 2 turns and one at 1/4 (besides the one you drilled out) I would suspect something not the same in the carbs, yours sound fine.

What your describing now sounds like a main jet oversize issue. Canuk is right though to do the chop test first to see the condition is for sure.

[TDodge7]

well i'll have to get a new battery , this jump starting it mess every time it stalls out is getting old . i just looked at the plugs , they were pretty sooty before , now they're still sooty around the outside but they're starting to go from a chocolatey brown to a tan closest to the tip . i may buy a new set of plugs and double check my mixture . i didn't drill out the broken off tip , i froze the carbs and it came out , but i did widen the hole a little trying to get it out before i tried the freezer . tho really when i was adjusting the mixture it didn't seem to react any differently from the other carbs so i guess i didn't widen the hole too much . the bike isn't street legal right right now , so i'll have to zip up the street i guess to test wide open . 10 or more seconds of wide open and then clucth and kill it right ?

[petejw]

Hey Dodge,
Id try lowering the slide needle to make the mid range run leaner,
I was running pods and a 4 into 1 exhaust and still had the needle on the leaner setting which ran real sweet.

Id also be changing plugs, its hard to clean a really sooty fouled plug.

[TDodge7]

i wonder if i can clean plugs in an ultrasonic cleaner .... i keep finding all sorts of uses for that thing . at least the low end is sorted out for the most part now .

[petejw]

I clean mine up with the wire wheel,
spray carb cleaner in the guts of it
and blow it all out with compressed air, has never given me any problems,
couldnt see y the ultrasonic cleaner wouldnt wrk.

[Crazcnuk]

I buy new ones. Cheap ones to be sure, until everything is tuned. Then I put in the Iridiums.

I wouldn't play with the needles, yet. Do one thing at a time.