Need help with carbs

[ray90813]

I had a problem trying to start a bike I just bought used that was sitting for about two years. Well i got it started after replacing all the o-rings in the carb and giving a thorough cleaning. i replaced the plugs,hoses and such. I think my problem now lies in the carburetor adjustments, i tried syncing them on the bench as best as I could using a couple drill bits, set the float according to the clymer manual I bought, in the manual it says to adjust the idle screws 1 1/4 turn, but I read in here somewhere that it needs to be 3, i own a 95 kat 600. The problem is when I start it with the choke on it revs to about 4000 rpm and just stays there, and when I disengage the choke, it'll idle below 1000 and eventually die, i can give it gas and it'll stay on. i tried the idle adjustment screw on the outside to see if I can get it into a higher rpm, but it doesn't really seem to make much of a difference. So I'm stuck, I've gotten plenty help here when i first took my carbs apart so i'm hoping you guys can get me riding soon.

[The CyberPoet]

Re: Need help with carbs

i tried syncing them on the bench as best as I could using a couple drill bits....

Huh?

To sync carbs, you adjust the screws that sit against the spring inbetween each pair of carbs (which adjust the butterflies compared to the other carbs). Normally, you do this with the carbs on the bike and the engine running around 1800 RPM, using vacuum pull readings to compare the vacuum at each cylinder and making the adjustments to balance all of them so they are pulling the same amount of vacuum.

It sounds like you may have a number of issues:
(A) Did you check the tank for rust? If there is any (usually visible as a orangish paste in the float bowls and as rust in the tank if you shine a flashlight into it), this needs to be addressed before you do anything else.
(B) Disconnect your throttle cables and your choke cable. Set your idle thumbwheel to 1/4 of the way out. Now try to start it. If you can't get it to start at all, recheck the pilot screws (which we talk about in terms of "turns out" and sit at the bottom rear of the carbs, covered by no-access panels the way the carbs originally ship) -- set them to about 2-5/8ths turns out to start and then add a 1/4 turn each time until you get what you expect.
Note: You may still have blockages, or your needles/jets may be worn or corroded.

(C) Once you get it to start, double check for vacuum leaks. Take some WD40 or other flamable oil spray product and spray the junctions at the various air lines -- if the idle changes, then you have a vacuum leak there.

Good Luck!
=-= The CyberPoet

[ray90813]

I took apart my carb again today and rechecked everything, all the jets, and such. I did however find one of my float needles stuck, so i cleaned that out and checked it, once I got it cleaned it worked. So i went about rechecking the float on all the carburetors and set it to about 14.5 mm, then i tried to sync the butterflies as even as possible using some drill bits(until I get it running decent to put some gauges on it). i set my pilot screws to 2 turns out. checked my slide operation, and vaccuum diaphragms. I already cleaned out the tank using the KREEM 3 step process, and the float bowls and ports in carbs(not with the KREEM). I replaced all the orings in the carbs and check all needles and jets. Now heres the problem, when I have it on the bike, with the choke on it revs to about 4000 rpm, when i turn the choke off, it'll idle below 1000, this is with the idle thumbwheel disengaged, when i adjust it in, it jumps to about 3000 rpm, i can't seem to adjust to stay at 1500-2000 rpm, it's either too low or too high.with the choke off and idle wheel off, it'll die. Also if I have the choke about halfway it'll stay about 2000 rpm. So I don't know, hope I can get some help.Sorry for the novel guys but I'm really frustrated, it seems a little harder than it should be you know.

[The CyberPoet]

I'm still confused about the drill bits to sync the carbs... Can you explain that?

Reset your pilots to 2-5/8ths turns outs as the starting point. Remember, this is from a gentle bottoming, not from them screwed in as hard as possible.

You also are going to want to check the choke bar operation at the carbs -- are all four of the little pistons it pulls on hooked into the bar correctly and sliding freely? If not, pull the bar as far out (i.e. - as far right) as possible and clean each one with a toothbrush and some spray carb cleaner.

If it will idle just below 1000 with no choke that's not too bad for a start. Turn the idle thumbwheel about 1/4 turn further (you may want to clean the spring under the wheel and check the cable sheath for the idle thumbwheel), then let the engine warm up -- remember, idle RPM's are set with the engine good and hot (like after several miles of driving or 10 minutes of running in a parking spot), and the idle climbs a bit as the engine heats up. Figure with the engine hot, it should be in the 1250 range for a 98+, 1350 range for a 98+ California model, and I think it should be around 1150 for a pre-98 (I'm not 100% sure on the pre-98 hot idle number).

Good Luck!
=-= The CyberPoet

[ray90813]

A guy at work told me to use a couple of same size drill bits and use them to hold the butterflies open and adjust them so they all feel the same or have the same amount of drag. I'm going to check what you suggest and hopefully everything works, or at least have a better picture of what the problem may be.

[The CyberPoet]

A guy at work told me to use a couple of same size drill bits and use them to hold the butterflies open and adjust them so they all feel the same or have the same amount of drag. I'm going to check what you suggest and hopefully everything works, or at least have a better picture of what the problem may be.

I've never heard that one before. Interesting... not sure how well it would work. Hmmmm... I guess I'll be thinking about it for a while...

Before I got the sync tool out, while I had the carbs apart, I set all the butterflies so that they all closed right at the same spot (i.e. - one was still 2mm open when the others were shut originally), and started from there.

Cheers
=-= The CyberPoet

[ray90813]

that actually makes alot more sense, okay I have another question. At the initial startup with the choke on, what rpm should the bike idle at. And when you turn the choke off, what rpm should it idle at. I got it to where it'll idle at around 2500 rpm with the choke on,that's with adjusting the thumbwheel in(with the thumbwheel completey disengaged it'll idle I would guess around 800 rpm), but when you disengage the choke it'll die, I know it has something to do with the idle(pilot circuit) probably adjusted too far in, so I'm gonna try adjusting each one out a 1/4 at a time untill it idles and stays on at whatever rpm it should be without the choke. Does that make sense or should I be looking somewhere else.Also I noticed some popping back through the carb towards the intake at times, is that normal. I have some kind of concept about engines but this is the first time I actually worked on a bike, never worked on carbs before, everything I work on is fuel injected, but for two hundred dollars I couldn't pass it up. Hey I appreciate all the help, I'm assuming you use to work on bikes or still do, because you've helped me alot, directly and just by seeing what you posted on other subjects. Hope you can help me throughout the process of rebuilding this bike, thanks.

[ThAzKat]

1000 to 1200 rpm is general idle settings. Cyber has some great info and if he can't answer your questions contact Ivan, KR's Carb Man!!!!

[The CyberPoet]

The initial RPM varies by ambient temp of the bike. If the bike is already hot (200+ degrees), it should be about 1200. If the bike is room-temp, then it could be as low as 800 - 1000. The choke isn't truly a choke -- it's an enrichment circuit which dumps more fuel into the carbs. The idea is to use the choke as little as possible to attain 2000 RPM, and then shut it off within 30 seconds if possible -- and use the throttle if necessary to keep the RPM's up at 2k while the engine heats up.

As for where it will idle with full choke -- again, it depends on the bike and the temp, but 2.5k to start and 4k within 15 seconds isn't uncommon.

When we say thumbwheel, we're not talking about the choke control at the handlebar, but the round idle adjuster at the left side of the carbs, accessible through the hole in the fairing (just so that we're all straight on the terms here). If it idles at 800 with the choke off, turn that thumbwheel a little at a time until it hovers around 1k -1100 idle cold (1100 - 1200 for a California model). You may find that you'll need to turn it down again once the bike it hot, but that's fine and we'll deal with it once the bike runs long and steady enough to get hot in the first place. If turning the thumbwheel (even all the way) won't get it that high or doesn't make any difference, then it's cable is probably broken inside the sheath. If, on the other hand, it simply jumps a big RPM range from a small adjustment, you need to clean the spring under the thumbwheel and maybe lube it a little with some spray oil (WD40, silicone spray, etc).

1000 to 1200 rpm is general idle settings. Cyber has some great info and if he can't answer your questions contact Ivan, KR's Carb Man!!!!

Don't let Thaz fool you -- he's an MMI graduate and professional bike mechanic -- he knows all the answers on such stuff.

Cheers
=-= The CyberPoet

[md86]

But isn't the 600 supposed to idle at 1200-1500 ? I thought the 750's idled at 1200-ish .

[The CyberPoet]

But isn't the 600 supposed to idle at 1200-1500 ? I thought the 750's idled at 1200-ish .

98+ 600 is 1100 - 1300 hot idle according to my owner's manual (pg 54). Same manual says 1200-1400 for the California model). Suzuki's info is a little on the low side, IMHO, for EPA pollution reasons, but 1250 is what I aim for warm and should be fine. The higher the state of mods or the colder the ambient weather, usually the higher idle gets set for reliability sake and ease of starting.

Cheers
=-= The CyberPoet

[ray90813]

Good news, I finally got the bike to idle and stabilize, not at 1200 but I'd say close to 1000 maybe 900, and i actually have throttle response without it dying. I'm pretty sure I just need to go in and do the fine tuning on it. I actually took it around the block. More questions though, is it normal for it do stall instantaneously with the clutch, or should it move with a little clutch engagement and then stall as you don't give it gas. Mine's stall as soon as you let out the clutch(in gear). Another thing, it stumbles a little at about 1/4 of throttle movement then stabilizes as I give it more, does that mean i need to sync my butterflies cause they might not all be opening at the same time. Oh and i have a hard time getting into neutral, it's either in first or second, I have to almost finesse it in just right, is that normal too.

[The CyberPoet]

Good news, I finally got the bike to idle and stabilize, not at 1200 but I'd say close to 1000 maybe 900, and i actually have throttle response without it dying. I'm pretty sure I just need to go in and do the fine tuning on it.

Without a doubt. And probably run some fuel-system cleaner through it. But if you got it to idle at 900 - 1k, you should be able to adjust that upwards with the idle adjustment thumbwheel...

I actually took it around the block. More questions though, is it normal for it do stall instantaneously with the clutch, or should it move with a little clutch engagement and then stall as you don't give it gas.

At 900 RPM, it may readily stall at idle if you release the clutch -- the engine isn't quite where it needs to be in terms of power output. At 1250 RPM, if you are very slow on clutch release, you should be able to do it without stalling it out. Most riders get some pattern memorized by muscle memory where they bring the RPM's up as they release the clutch, thus doing a balancing act.

Mine's stall as soon as you let out the clutch(in gear).

Does it do this on the center-stand? If not, it may have other problems. If it does this on the center-stand (i.e. - no load on the wheel), then you probably have a bad safety-interconnect switch at the sidestand -- there are three safety-interconnect switches: a neutral switch at the tranny, a sidestand switch at the sidestand, and a clutch sense at the clutch lever pivot. If the sidestand switch isn't engaged (engages in the up position), and you put the bike in gear, the electronics kill the engine. If the neutral switch and/and the clutch pivot switch isn't functioning correctly, the bike won't activate the starter.

Another thing, it stumbles a little at about 1/4 of throttle movement then stabilizes as I give it more, does that mean i need to sync my butterflies cause they might not all be opening at the same time. Oh and i have a hard time getting into neutral, it's either in first or second, I have to almost finesse it in just right, is that normal too.

Could be a sync issue, but is probably a tuning issue, because that is the point that the slides should start moving up to provide more fuel and a sticky slide may be hampering that.

You may find that once you get it running, it would be wise to take it to a shop that has an exhaust analyzer and a dyno to have the carbs fine-tuned (i.e. - get the fuel-air ratios set correctly across the board).

Cheers
=-= The CyberPoet

[ray90813]

no it doesn't stall on the stand, that works correctly, but what I did notice was that, if I adjust the thumbwheel in to get it to idle higher, or at around 1500 rpm, and hit the throttle it'll almost want to stay at whatever rpm it jumped to, and slowly decelerate, but if I adjust it to idle back down to about 900 I have pretty good throttle response, it'll go up with the throttle and come down as it snaps closed. Correct me if I'm wrong but the idle thumbwheel actually allows more air in right, in theory if I adjusted it in at idle the butterflies wouldn't be completely closed, therefore it tends to want to stay at a higher rpm even when the throttle is snapped closed, so I was thinking maybe my butterflies aren't closed all the way at idle with the thumbwheel adjusted all the way out. Does that make sense, and what's the average price range for the service you suggested, kind of low on funds, got a new addition coming into the family next month, and trying to do as much as possible before then.

[The CyberPoet]

The hanging idle issue you're getting at higher RPM's is almost assuredly dried fuel residues. Run some techron through with the tank load and it'll slowly disappear over a few days or a few tankfuls...

Cheers
=-= The CyberPoet