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PLUGCHOP comes out LEAN, opinions please...

  • Thread starter Thread starter gsBert
  • Start date Start date
G

gsBert

Guest
so i did 3 plug chops in fifth gear (hit the killswitch/clutch after driving 15 seconds at constant throttle and coasted to a stop), here are my results:

closed throttle (no load) : nice and TAN
1/8 to 1/4 throttle (acceleration) : GREY
1/2 throttle (acceleration) : WHITE

so im guessing my mixture screws might be right on?
1/8 might be too small a pilot jet?
1/2 means raise the needles (the clip is at the top position out of five)

i couldnt do a full throttle run because well, i ran out of road, the 1/2 trottle run brought me to 200...

am i right in my assumptions here? any comments/theories/advice?

thanks a million

bert
 
You can't get the bike jetted right without setting the main jet first.
Click to expand...


No, no, no! This is completely back-assward. You need to set the pilot circuit first, then the needles, then the mains. This is because the lower circuits affect the ones above, but not the other way around. If you set the main first, then the needles and pilot, you will need to go back and re-set the main because you screwed it up by adjusting the other circuits. You don't even need a main jet in place to ride! If you don't believe me, try it and see. Your bike will run just fine without main jets in place and will not bog until you get up off the needle circuit, which is hard acceleration or high speeds only. Ask Keith Krause about this one, as well.


Mark
 
yeah, im jetting at idle and needles first because....


if the bike wont idle, how am i supposed to get on the main jet circuit???
and if my needles are way to lean, i can hole a piston or perform other sorts of damage before my slides are even all the way up...

so yeah, while i understand the logic behind jetting the main first, thats the way to jet a bike that's ALREADY RUNNING OKish (mine wasnt running AT ALL), its also the way to jet a drag bike built for WOT operation only.
my bikes rarely see wide open throttle (i actually only ever open the 750 all the way)

by the way, the main jet does meter the amount of fuel getting into the needle circuit, but will not affect it adversely unless the main is way too small (like a 40 instead of a 140), and its true that you can run a bike without a main jet, i did it once without even knowing until i realised i was running waaaay too rich on full throttle and opened up the bowls...

as far as the factory pro site goes, well, theyre into the business of selling stuff, so by default are to be taken with a grain of salt.
the page starts off with:
"it took years to develop and write and is not based on any other previous work by anybody else"

let me translate this into english for you:

it took years... means "we holed a bunch of pistons before getting the mixture right"

not based on any other previous work means "we're doing it backwards, internal combustion engines have been around for well over a century and everyone has been doing it wrong all along"

first you get it to idle then run at part throttle, then full throttle...
still, the site has useful info, IF you know how to read it properly...

but we digress here, what do you think of my diagnostic assessment?

if i get no replies by tomorrow morning im raising the needles 2 notches.
i figure thats the first thing to try as im lagging at the transition from pilot to needlejet.

im keeping in the 36.5 pilots as the other ones i have are 35. (but the 35s have emulsion holes, would that be better? though i think more sensitive to float height, no?)

maybe if im still lean at 1/8 throttle, i'll try to unscrew the mixture screws by another 1/2 turn (im at 2 turns now i think)
 
Give it a try, that's why we have adjustable needles. Should be a piece of cake as long as you don't have those pesty c-clip's....... or do you???
 
i have clips that look like the letter E on my needle, they are rather annoying as they tend to say "plink" a lot when i take them off, and whizzz by my head to land on a gray carpet on which they are completely invisible...

the other problem i have is i keep loosing the o-rings for the vacuum nipple on the diaphragm cover... after taking the !@#!#@ things apart 10,000 times you'd think i remember they stick to the plastic bit and fall when you're not looking at them...

im kind of worried that my emulsion tubes and needles might be too small now (i just woke up in a sweat) im replacing the needles this afternoon, will keep you posted...
 
i have clips that look like the letter E on my needle, they are rather annoying as they tend to say "plink" a lot when i take them off, and whizzz by my head to land on a gray carpet on which they are completely invisible...
Click to expand...

Yup, that sounds about right... :)

What I do is put a clean white rag on the bench (an old t-shirt works great) and put all my small parts on that. That way they don't roll around and are quite visible. To remove the clips, try holding the needle against your vise (or other hard surface) with the open side of the clip against the vise. Now put a finger on the clip and then push the needle towards the vise with your other hand. The needle should pop off the clip with no issues and you should have both pieces nicely in hand. To install the clip, I get it started by hand then push against the rag on my bench to pop it on. That way it usually gets caught on the rag if it slips loose and you have a better chance of finding it again.

I hate that sound of a small part bouncing on the floor on the other side of the garage, knowing I am going to have to crawl around for 30 minutes to find it. Even worse, I once had a shim pop out of the tweezers while doing a valve adjusment on my ZX-9 and fall onto the head. Problem was, it bounced around first and I didn't know if it had fell down the cam chain tunnel or what. I spent two nights with a magnet trying to find it in the nooks and crannies under the little pools of oil and eventually ended up pulling the cams to get it out. Lots of sweating there! :P :P


Mark
 
yeah, im jetting at idle and needles first because....


if the bike wont idle, how am i supposed to get on the main jet circuit???
Click to expand...

Good to hear you are on the right path with your jetting approach. From your description, you need to raise the needles at least one notch and probably two. I prefer to only go one at a time and sneak up on the final settings, but you are way better off too rich than lean. So go two notches and the worst that will happen is you have to pull the carbs and drop the needles one notch afterwards. And step up 2-3 sizes on mains, maybe more. Someone here mentioned that once they have the bottom circuits set, they increase mains until it stops running hard and stop there. Not a bad approach. The perfect settings are (in my opinion, there are others, of course :) ):

Pilot - slightly lean of perfect, for crisp throttle response and good mileage when cruising. There is no danger of seizing on the pilots, because the engine is not making serious power and there is no heat to cause problems.

Needle - transition from slightly lean as the needle circuit takes over from the pilot, to slightly rich when fully onto the needles. This is to make full power under hard acceleration and prevent seizure due to leaness.

Mains - As rich as the motor can stand. Makes the most power and prevents seizure, as well as helping with overheating. Mileage is worse this way, but you shouldn't be concerned with mileage if you are running on the mains.


Mark
 
yup mark, my approach exactly...
i went up 2 notches on the needles, am about to go try it...
will let you know tonight
 
gsBert said:
yup mark, my approach exactly...
i went up 2 notches on the needles, am about to go try it...
will let you know tonight
Click to expand...
Sorry I came in late. Stupid modem problem.
What were your mods again? 4-1 pipe/pods/bore kit? What brand of pods?
If so, reading back at your plug reads, that's exactly what I'd try next. Raising the jet needles two positions.
 
so i went up 2 notches on the needle, the clip is now in the stock position (center groove out of five)

i didnt try a wot chop, the bike feels the same at wot or at 1/2 throttle. (ill possibly install a bigger main when i get to burn that bridge, as i suspect its starving for fuel at that throttle opening)

so i now get a light tan on 1/8 throttle and a light grey on 1/2 throttle.
oh, that lag at the transition from pilot to needlejet is gone, but tonight it was colder and it was back a bit... (proof that im still tooo lean i guess, as if i didnt know how to read plugs)

ill raise the needle to the richest position tomorrow morning (hopefully that'll start it running rich, else ill have to add washers, but ill remove my main jets first to make sure im not restricted in there. might also be my needle jet is meant for a 400cc bike)

funny thing is i had to raise my idle speed this morning, bike idled rough and at 500 rpm instead of the 1000 i had set it at before, weird, the only change i made was raise the needles 2 notches. oh well, they're going up another 2 notches tomorrow...
 
Just got a chance to read this thread better and catch up.
You say you had the jet needles at their lowest position. This was obviously too lean. Your latest test was at the factory (3rd) position. Still too lean. Do you have any exhaust/intake mods? If so, I'm not sure why you bothered to try those two previous needle positions. Please describe mods, including any mixture screw and float level adjustments.
 
there you go keith:
i am running a stock 1150 motor in a 1100 frame
the carbs are off bob-knows what bike... look like gsxr slingshots.
the needles i had originally were not matched to the needle jets and letting tons of fuel past...

i yanked emulsion tubes off another set of carbs and they work with those needles (same diameter)

the slides on the carbs had one of the 2 vacuum holes epoxied shut, i opened them.

the bike wouldnt run with the stock exhaust, so i hammered on the 4:1 i had on my 750 (not a straight through muffler, but very unrestrictive and loud) ill install the supertrapp header and muffler this winter after i have some adapters machined...

the filters are k&n pods (2 carbs per pod, i know they wont work with individual filters)

mixture screws are 2 turns out and the float level is 17mm, but ill have to adjust that because the carbs have a downdraft to them in the application they're designed for (gsxr) and my float bowls are not horizontal on this bike as the engien isnt tilted forward as much as in the gixxer.

i tried super lean to begin with because it always ran super rich, impossibly rich, it would flood, foul plugs and clog mufflers. this is the first time i actually get the bike to run without stalling because it fouled the plugs after 1 minute of running... (performed 3 oil changes, removed about as much gas as oil, lol)

i think my mains are 140... but im not worried about those yet

on the plus side the bike lights up the rear tire really nicely on takeoff if you accelerate hard (1/2 throttle) with just a bit of clutch slip... im gonna have to get used to that and train my sense of balance....
 
Those carbs and who knows what jetting changes have been done to them, could be a headache. Not only the typical main/needle/pilot jet adjustments to think about, but the needle jets, air jets, float levels...
I'd mark the throttle and take the wide open, 1/3 and low speed/minimal throttle opening tests and do what the plugs say.
Back to basics.
 
thats what i've been doing keith...

i have to go to work now, but i just got back from the basement, i raised the needles as far as they'll go, hopefully i see tan plugs now...

ill try it out tomorrow and post the results...

im ok on the idle circuit, pilot might be a bit lean, but the needles definitely were... my friend is looking for bigger pilot jets in his box... i have a 36.5
more to follow....
 
ok, here's what happened...

with the needles all the way up i was still running lean.

so i tried someting.

by the way, ftgret deserves some sort of apology here...

it seems my 140 mains were too restrictive. im gonna put in some 147.5

what i did was removed the main jet out of carb 1 and 4

did a 1/2 throttel plug chop, and sure enough, 1 and 4 were rich while 2 and 3 were lean...

hehe! found the gremlin, am on the right path, will have a working bike next summer (winters coming here so the seasons over unfortunately)
 
ok, so ive tried 147.5 jets in therre but that was useless my plugs were black anyways so i couldnt have seen sweed quack-all....

im installing a new plug in cyl #1 after warming it up and do a chop on this one...(i only have 4 new ones and would like to run multiple tests, all 4 carbs are jetted the same and should run similarly)

im gonna lower my needles back to the middle clip position, as that's wehre the bike behaved at its best (albeit too lean, but i now know that was due to too small a main jet), and install 155 main jets.

with luck ill have time to re-jet before i have to go to werk, and tomorrow morning will be nice enough that i can do the testing (i have to drive about 8 km to get to my nice flat empty road)...
 
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