I've been having a heck of a time with the running of my bike lately. It's getting a little colder but i'm having to use choke now to start the bike, unless i want to crank it for a little bit without. I've developed a hesitation/lean spot off the bottom, although it smells rich from the pipe. When cold it is not very driveable and even when warm it isn't perfect with a little stumble off the bottom. I'm thinking that i may have a clog somewhere and i'll probably be doing a session with some carb clean and compressed air. i checked for leaks, none to be found. the carb still responds to the fuel mixture screw. Some other symptoms are 5mph less up top as well as a powerband that has spikes in a few places. also, it likes the dynojet 170 main the best which makes me think i have a lean condition somewhere in the circuits and i'm covering it up by using the really big jet for the stock exhaust. plugs look ok with the big jet but with the dj160 they are lean.

Any of you guys have any similar experiences?

Just got done readjusting the valves back to the tight side of the range and the bike sounds and feels smoother because of it. Also drilled the slide and it does make a difference in how the bike runs, it picks up quicker for sure.

are you running hotter plugs? I stopped trying to read my plugs just adds to confusion. I run stock plugs dynojet 160 and needle 5th from the top drilled slide cut .5" off slide return spring,airbox mod, notoil filter, fmf power core,1400 miles and have no need to or have not adjusted valves. @ 700ft low temps in the high50's highs in the 80's. the bike runs on the rich side, and changes will lean out to perfect from time to time but is sensitive to filter oil, and temp on how rich or lean it runs. does much better with high flow filter. just my base line for ya Brian, other than that I can't help much, from the other post you have good grasp on the basics. Go back to basic lean circuits and bump one at a time till its there. remember the head does a bit of breathing and the exhaust port is small so you will enter a pivot point on a rich to lean or vice versa.

The only stuff I can offeer is the fact that a 160 jet should be right for the stock exhaust, and also, I have heard of people drilling-out a second hole in the slide (maybe too big?), and the slide then raises TOO quick, causing a lean condition (and a bog hesitation) most of the time when hitting on the throttle hard, but acts normal when the slide is at the bottom, at an idle, sorta like you are reporting.
Maybe you could try a temporary plug in the second slide hole, and see if that fixes things?

I drilled the slide last night, and i like the way it reacts, it allows the bike to pick up steam quicker, like the slide was wd40'ed. The bike was running good, but lately the low end has started to act funny, feels lean. I went back to stock pilot, stock float level, have the factory pro kit needle and slide spring, and i've had to go to the 170dj main to try and get the power band filled in and smoother. i think i may have a clog somewhere because of the suddenness of the symptoms. Also, my intake boot at the head is showing signs of fuel puddling so my float and/or it's o-rings may be taking a dive.


thanks for the words gents

hvae you tried a laxative? mayhbe it will flush the poo out?

lol,poo bike..that just aint right.

tsispyder said:

A little off the subject, but I've seen several times people talking about cutting .5" off the slide return spring. What exactly does that do to how the carb and bike runs?

kkdesigns said:

Supposed to let the slide respond quicker to throttle opening vacuum chnages -- but, like I said above, *sometimes* it may open too quickly at low rpm's, and cause a lean condition bog -- in other words, act like over-carburation -- especially on motors with over-size carbs, if you open the throttle too quick, too soon, before the revs can make enough vacuum to handle it, you can get a bog, and in extreme instances, the motor can even cut out and stop running. In cars with big 4-barrel carbs, with mechanical (race) linkage on the secondaries, they call it "quad-bog" -- you stomp it too soon, and it just dies. On race bikes with BIG race carbs, you can do the same thing, if your revs aren't up coming out of a corner. Been there, done that.

With it getting cooler the bike is sucking in a larger mass of air (cooler air is more dense). If you were on the ragged edge of a good mixture setting when it was warm it's quite possible it's now too lean by a hair.

You must be pretty sensitive to this as it's not usually a big change. I know I can feel stuff like that but then I'm a fussy bugger... :D

I've been ignoring an obvious slight leaness in the slide needle setting at in town cruise speeds waiting until I have the tank off to do the valves again. But with it getting cooler these days it's worse now. Good thing it's time to do the valves...

OldDualsporter, i get that problem. I think i drilled my slide too big, and now i get a stumble just off idle when i crack the throttle, or if i blip the throttle with the clutch in, sometimes i get a loud POP and the bike just cuts out.

Vash, it's an easy fix to close up part of the hole with some epoxy and see if that fixes the problem.

Hey, are you the same Vash that hangs out at the Riderforums Z1000 site?

vash said:

What I learned when racing, if revs were low, was to roll the throttle on gradually, over the space of a full second or even two, from closed to full -- kept down the bogs, and wheelspin, both, and didn't slow me down, either. I always was aware of my revs, so if they were high enough, and already up "on the cam or pipe" I could slam it open if I needed to, with no bog then.
Of course, the other choice was to blast out of a corner by fanning the clutch, the revs go way up, and induced wheelspin kept me from wheelying -- only do this on dirt, though, unless you know for sure you can break your tire loose on the hard stuff, too. This is sometimes quicker than another downshift. So, if throttle control becomes automatic, you may be able to adjust to a bog situation, without having to think about it anymore. Besides, smooth is faster, anyway -- bike is more controllable.

Vash, you've had problems with the popping since you installed the staintune, right? maybe you should consider going to a 45 pilot. Something to think about since you've got a larger header.

How big was the hole in your slide? I drilled one the same size and the one that was in there and it seems to work fine. Try epoxie like JB weld and put in a smaller hole. The bottom end will need to be a little richer to help with acceleration. Usually opening the pilot screw with do the trick that and raising the needle.

Perry

i still haven't pulled apart the carb for a cleaning on my bike. my problem was before i drilled the slide so it's good. i either have a clog or possibly leaking o-ring for float assembly.

I was thinking about going a bigger pilot jet. I'm at 3 turns out and its the only way it will idle smoothly. Jesse's recommended 1.5 turns out and it starves for fuel and idles terribly.

definitely get yourslef the bigger pilot, 45, if you're that many turns out. You have a different set of circumstances than the rest of us with standard headers. When i use the bigger pilot, it gives a big hit down low, much better than the 42.5 pilot, but my mixture is less than a turn out, it's pretty much all the way in. so i'm back at the stock pilot.

Thanks brian. Is 45 a standard size? or is it different between brands like the main jets?

the stock is a 42.5 mikuni and the next step up is the 45 mikuni. You have to be careful when ordering as mikuni makes a lot of different styles of pilot jet and i first bought one for a two stroke thinking they were all the same and the bike was fouling plugs like crazy. Sudco website has them.

I'm not exactly sure what you're asking about it being a standard size, mine came in the factory pro jet kit. No one had any pilots for this carb in town here.

vash, as long as it's a mikuni jet and it's the correct jet for the bike/carb then yes i guess you could consider it "standard" :D