Hello From Melbourne (Kawasaki F11B)

[tony27]

Generally stuttering would mean too rich.

Moving the clip towards the top groove lowers the needle into the jet further making it leaner

If you're going to try moving it to see what happens then richer first is safer, worst thing that will happen is fouled plug

[Doc]

yep Simon, I agree with Tony, If you are going to err err on the side of rich. The plug colour itself looks in the ballpark. Maybe the new plug correctly gapped will eliminate the stuttering. Riding it around the block isn't an overly accurate way to determine, you will need to go for a decent ride at a fair pace to get any real idea of how it going to be once on the open road. As for the temperature I really have no idea what temp the old aircooled engines run at. Unless the jetting is miles out either far too rich or far too lean 'which it doesn't appear to be' it should remain within normal operating temps. Usually the only time aircooled engines overheat is when you are doing something like riding in deep sand at low speed with the engine under constant load where the air isn't circulating sufficiently. Maybe ask your dad why the clip was changed on the needle when you first looked, he may have the answer you're looking for

[JADERD]

Ok new plug in tonight,

started up bike no worries, drove it around it seems that you can wrap it on fairly nice and smooth in first and second gear and on the flat even third, maybe up to just under 3/4 throttle.

in first and second you can quickly twist it up to 3/4 throttle approx and it will get up the revs and speed with no hiccups.

i took off out of estate and up a steep hill, 2nd gear i think was ok but third gear as i got prob 1/2 to 3/4 throttle it was really pronounced and bad stammering and missing to the point where i had to drop back to 1/3rd throttle or so to keep it going ok...prob around 40kmh max, had to pull over for traffic.

On the flat/slight down hill i had the bike up to 80km approx (after the hill) as i didnt have to wrap it on too far.

Regardless of terrain if i am in 4th or 5th doing say 45kmh is i slowly wrap it on its ok for a while but regardless of speed i try to accelerate it always stammers and misses etc.

5 min in to the ride i revved it fairly hard in 1st 2nd and 3rd, prob just up to 3/4 throttle and pulled out plug it looked fine (same as pic below)

i then continued for maybe another 10 min when i was testing all the above problems and then checked plug (pic below)

Looks to me like its running just fine, nice chocolate brown color no excess oil etc, what do you think ?

Seems that the symptoms are that its too rich at that point, air screw is at exactly 1 & 3/4 turns out.

Would first thing be too drop the needle down one notch and move the circlip to spot 2 which is where it was all its life and i dont remember it ever missing like it is now.  Ill test it tomoz night.  I dont think i ever got bike past 3/4 throttle so im pretty sure that the main jet is fine and not blocked etc.

Is it normal that the problem seems to be exaggerated in gears 3-4-5 ?

Cheers

[Doc]

It is normal for the problem to become exaggerated in the upper gears due to the fact 1st and 2nd are only used for such a short duration. 3rd gear is where the engine starts to stretch it's legs sort of as you hold it in the upper rev range for longer. Plug colour looks pretty good. At around 3/4 throttle the needle will be controlling much of the fuel supply through the main jet. Maybe try dropping the clip 1 notch and see what happens and then try raising it. Bit of a hit and miss method I know but so long as it's only for a short test ride it shouldn't cause any detrimental problem. With this model the main jet is in the bottom of the float bowl so it may pay to drop the bowl and double check it's totally clean. If worst comes to worst I'd be willing to loan you the carb off my bike to fit and find out if it is the carb or a possible electrical issue.

[JADERD]

No worries doc, I'll try dropping needle one first, then drop bowl. If all that fails I may take you up on the carb borrow / test .

Seems crazy how just one little change could fix something but I guess that's how fiddly carve are.

As I only just replaced the bowl gasket would I be able to reuse it id im careful or buy another one ?

Cheers

[Doc]

you should be able to reuse the bowl gasket heaps of time..just don't over tighten the screws. Give me a yell in regards to the carb if you wish to try it

[JADERD]

no prob cheers doc, read some other pieces of info on net, mainly from larger capacity bikes where its seems to commonly be fuel filter, though often happens all of a sudden, in my case i thinks it what we have discussed.

[JADERD]

another person on another forum mentioned at first try removing air filter completely and see how that goes for a ride as he had heard the unifilters with the unifilter oil can hamper smaller 2 strokes.

he also said to hold adjust idle up with idle screw to say 2k, then turn air screw in, then back it out till get the fastest idle and crispest sound....i figured that would only really effect the idle though to which i feel is fine already ?

any thoughts.

im going to go filter first
then move needle
then remove bowl and inspect if necessary.

from all the reading ive done the exact symptoms seem to be the too rich and needle move as ppl have said on here.

is there much need in altering the air screw or i should leave that at factory 1&3/4 out as thats not where my problem is i dont think.

Cheers

[Doc]

Simon, the air screw is usually adjusted at lowest possible idle speed turned in and out slightly until a smooth idle is achieved. Adjusting it at 2000 rpm is not correct as the carb would be starting to run on the primary circuit aka the primary jet. I doubt the airfilter would have the effect when it is simply a replacement of original type/design. You could surely remove it to eliminate the possibilty. You would think if the filter is restrictive it would be creating an overly rich mixture much like having the choke on and your plug would be sooty black when inspected. Your plug looks pretty right so I really don't feel it is a mixture problem. Leaning toward something in the float bowl or blocked main jet, low float level or even the possibility of an electrical issue such as the stop switch on the throttle housing. Try disconnecting the rev counter also since it could be interfering with the plug lead and grounding partially at high rpm somehow.

[JADERD]

hmm sounds good all nice easy tests really.

i left air screw at stock setting.

i moved jet to position 2, took it for a ride and was a fair bit better, still stammers but better, enough to say that you could almost safely ride it on the road as third gear you can wind a fair way before anything.  i think its def between 1/4 and 3/4, if i wrap it on to full throttle it does the stuttering at a massive level thus cant get it to WOT to see how main jet is etc.

i then came home, took out air filter did same 2km ride and no difference at all, so rules out that.

took plug out 3-4 times nearly all after hard revving in 3rd then clutch and bike off.

Plug basically identical to yesterdays photos, todays pic is below. if anything from my little knowledge it could still be classified as rich, the other factor that may be a big bulb for you guys with knowledge if i even put the choke on the tiniest bit it does the exact symptom - rich ?

the choke can only push 2/3rds of its slider on handlebar before its fully on, which made me think is it permenently on a little, the adjusters at each end were already wound right in, i undid choke at handlebar and reinstalled and could feel that it seems to have free play at the off position which is good so maybe not that.

I almost feel that if i dropped to position 1 on clip it may be spot on....but dont want it too lean of course....

Any diff ideas i should try with this new info...choke even slightly on while riding replicates identical symptoms.

cheers in advance for everyones input.

[JADERD]

advice from another forum below

"The problem coming back with the choke on gives you the clue - it's running rich.
 
Needles are adjustable for this very reason. If it runs better with the needle right down, then move it there."

what do you think ?

that would have been my next step, first i will do the removal of tacho wires and test.

im thinking to drop to position 1 and if feels perfect were good to go ?

or do you believe i should inspect carb first (main jet / bowl) ?

im guessing that the bike ran fine on position 2 but at the same time was gunked up maybe aiding in it not running rich and had a filthy air box and no filter just a stocking on the cage.  Now everything is clean, new filter with oil etc.  Just curious i guess, how many ppl have their bikes on the stock settings or is it not uncommon to drop to position 1 on needle ?

My other dilemma is even though i might get the bike running fine i would like it looked at by someone with experience.

Through VJMC i got onto Gassit motorcylces in melb, explained situation and that i want it running best it can etc, asked about approx costs and got the usual, $90 ph might take one, might take 4.....im like yeah no prob mate.

What i want is a sat, sunday  tune up session where i can meet some ppl with the knowledge, learn at the same time, buy them a slab and a feed or something, that way i would get more knowledge out of it etc., anyone experts on here keen ?, i could prob putt the bike to any melb based location safely.

another reply from other forum below

"That's quite possible. Is it a cable operated choke or a lever? Either way, make sure the plunger is returning all the way and shutting the choke off"

My response below

its a cable operated choke, im 99% sure in the past i would push the lever on the bars and it would use the entire "track" it has, since rebuild i can only push it 2/3rds or so which had me thinking it is slightly on, i checked and appeared not but i think this needs further investigation, it might be that i need to slide the entire unit further up bar to give more slack etc as from checking the adjustment on both ends of cable are on longest setting.


The other reason why i think this could still be the issue is like you said it starts too easy, choke off after a few seconds and its ok, and the fact that just pushing choke on 2-3mm and it replicates the issue severely while riding along in any gear.  Would also explain why idles so well (rich) and the overall richness caused by the choke over the whole rev range would be noticed most when getting towards 3/4 and WOT im guessing ?


def my first test i think before i remove needle and alter that....

[JADERD]

Bit of an update.

Fiddled with Choke, seems to have got it some more "length" so i am sure the plunger sits tight in the off position, didnt have effect on stammer.

disconnected the tacho from vapor dash, didnt effect stammer, even with no wire connected the unit still senses revs ?...wierd.

wired my throttle grip on as just glue wasnt enough.

checked plug, looks really good, whole centre piece a nice caramel brown etc.

tomorrow im just going to put the needle on clip 1...most lean and see what that does.

if that does nothing ill pull carby to bits again, then after that i think ill have to drop bike off somewhere.

Cheers

[JADERD]

Went to clip one on needle, no real difference, maybe slightly better but still stammers, the slightly better feeling is cos it will be taking slightly longer to get to the crap stammering point due to needle dropping, so clip 2 and 1 seemed to slightly improve due to this.

Next step is take carby out drop bowl and inspect things esp main jet, could be some crap there etc.

Will do that tomorrow night, surprisingly im not getting pissed off with things as atleast i have been able to have the bike out etc....trial and error as everyone has mentioned

[tony27]

When you've had the carb apart before have you removed the needle jet?
They push out from the bottom & is another place to check

[JADERD]

Hi Tony,

yeah i think that may be the one thing i did not remove, looking online at pics etc.  Looking forward to getting it apart this week and inspecting.

VJMC melbourne branch rep called me last night, chatted for a while basically saying good work, dont give up on it yet is lending me his ultrasonic cleaner that i will pick up tonight and then see how i go.  Also he mentioned he will be able to line me up with a mate of his who is a tuning guru / bring afew ppl out to my house to get it all sorted.  Really appreciated the call was great so even if i get it sorted the next step of getting a more experienced person to check its tuned fine is being lined up.

Very glad i joined VJMC as my permit club and in general, great bunch of guys willing to give advice....just like OZVMX