'06 Katana 600, won't rev over 6000 rpm

[OkiePokie]

Hi guys, I've been searching the forum and googling the web, and following the suggestions I've found, and referring to the factory service manual, and so far nothing has fixed my problem.

I've got a 2006 Katana 600 that I bought last year that only had 1831 miles on it. Wasn't running and had some carb issues. Tackled the carbs last fall and ran into some problems with them. Bought a pretty clean used set off of ebay. Replaced the float needles and seats and the bike ran great but had no power over about 4000 or 5000 rpm. Cleaned the carbs with carb spray, took out and cleaned all the jets, still wouldn't rev over about 5,000 rpm. Clean the carbs in Chem Dip, at least 12 hours per body, rinsed, blew them out with compressed air, adjusted the floats to 13mm (were set to 14.6 mm when I got them), runs a little better but still won't rev over about 6000 rpm.

If I give it full throttle it acts likes it is out of gas and starts to slow down. Let off the throttle and it's running again. Has good power until a little over 5000 rpm, and on the highway I can coax it gradually up to about 6,000. Sometimes a little more. Seems to run better first thing in the morning before it's fully warmed up. But, warmed up in neutral it'll rev up to 9 or 10K rpm, which is about as far as I'm willing to rev it with no load.

One more thing. I'm only getting 30 mpg. That's from the last two tanks, 180 total miles.

So far I have:

Checked the valve adjustment. Just had a few tight ones. All good now.

Replaced the fuel filter, then ran it without the fuel filter, then drained the tank into a gas can and the fuel is flowing pretty good out of the tank.

Double checked the fuel lines for kinks.

Replaced the spark plugs. Checked the gap.

Tested the coils, primary and secondary ohms and peak voltage: everything good there.

Tested the signal generator, ohms and peak voltage: everything good there.

Replaced the CDI with a used one off of ebay, no change.

Tested the tps, at WOT it's more like 1500 ohms instead of 3800 ohms. Unplugged the tps, no change. I have two tps's (one came with the used carbs I bought), and both test the same. Way under 3800 ohms at WOT and unable to be set to the correct resistance.

I am hoping someone can point me in some direction, maybe see something I'm overlooking. Here are my thoughts:

1. Maybe the CDI I bought off ebay has the same failure as my original one? Anyone near Tulsa, OK have a known good CDI I could try? Or have a good running Katana I could put one of my CDI's on to test it?

2. Is it the TPS? I've seen folks who say the bike will run crappy without it and folks who say it doesn't do a thing. There is a post from Astro4x4 where he had the same issue with his tps not being able to be adjusted correctly. He says he replaced the tps and solved his problem, but doesn't say what his problem was, other than the tps readings.

3. I tested the signal generator at the plug on frame, not at the CDI connector. Probably the next thing I need to check, since the manual says to check it in both places to eliminate an issue with the wiring harness.

3. It's a clean low-mileage bike and the air filter looks good on the outside and I haven't replaced it yet.

4. How about mud dobber nests or dead rodents in the muffler? This bike has spent a lot of time sitting in a garage.

To recap: Right now the bike has a little over 2200 miles on it, starts great, runs great until about 5 or 6K rpm, then stutter's and stumbles. Rev's fine in neutral. Only getting 30 mpg.

[ZukiFred]

Have you checked the air/fuel screw adjustment at the bottom of the carbs?

[Molochnik]

From what I understand regarding the TPS, it simply selects a more or less aggressive advance. The fact that there is anecdotal evidence that the bike will run w/out it supports that. Properly adjusted, maladjusted, or even missing, the black box will just spit out a signal of a given advance which will either provide better response worse response depending on the comparison between RPM and throttle position.

Provided your slide diaphragms all ok and the slides work properly, my guess is that there is still a dirty passage lurking in your carb(s)

Regarding the black box and/or CDI per se, I have seen some fail where the rev limiter starts kicking in sooner and sooner until the bike just doesn't run. I wouldn't say that's a typical failure, but it's happened aside from the CDI simply crapping out. It's certainlt possible you could have two boxes w/ the same issue, but I'd be apprehensive to say it's likely

[OkiePokie]

Air/fuel screw set to 2 1/2 turns, per carbs 102.

Slide diaphragms all look good with no wear marks, holes or tears.

The slides all move up and down smoothly when I push them with my finger.

Since I'm only getting 30 mpg, I'm thinking it's getting plenty of gasoline. Something is definitely acting like a rev limiter.

[Molochnik]

Did you remove and clean the needle jets? The first attempt I'd ever made at carb cleaning was on an old Honda 3-wheeler. A much simpler carb to be sure, but it wouldn't run right until I got the needle jet clean. It's a commonly skipped item by folks new to the carb game, but I'm not making any presumptions on your experience or diligence, I just can't think of anything else specific to check.

If the rev limit "feature" of the black box was kicking in, you'd know it. Unless they've changed a bunch it'll get your attention. My 03 Tuna is the newest bike I have, but I havn't bounced it off the limiter yet.

[OkiePokie]

Are the needle jets the same thing as the "small spacer that the jet rides in" referred to on page 9 of Carbs 102?

I pulled them out and they looked pretty clean. What if I put them back in upside down? I just guessed which way was up when I was putting the carbs back together. Seems like the opening on one end kind of flared out a little and the other end didn't.

[Molochnik]

Umm, I'm unable to find a page 9 associated with either carbs 101 or 102, however, needle jets are also referred to as "emulsion tubes" as I saw during a cursory glance at one of the tutorials (101 or 102). That's a very standard alternate name.

Taking a look at the fiche, it appears that Suzuki chose to call the piece you speak of in the latter part of your post, a needle jet. The emulsion tube or needle jet as identified by Mikuni is actually called a "jet holder" in the fiche.

The small silver items that protrude into the carb bore should be installed with the countersunk or flared end looking up at the slide.

The "jet holder" is the item you need to be sure of getting clean, ie,: all the holes need to be clear and no crap sitting inside it.

If you go to the Ron Ayers site and look up your bike's carb fiche, you'll see it's #17 that I'm talking about.
They are calling #27 a needle jet, but perhaps I've gotten institutionalized by old GSXRs and dirt bikes.

[OkiePokie]

It's page 9 in the pdf version I downloaded. The jet holders all got cleaned and blown out. I was able to see through all the little holes, all looked very clean. I think I put the small silver items in with the countersunk end in the bore, but that is something I should check. I've put things in upside down and backwards before.

[Molochnik]

It happens. Take a look; I'm curious to find out what the problem is.

[IanDMacDonald]

It happens. Take a look; I'm curious to find out what the problem is.

Quick question: Do you have pod filters on your bike? Cheap filters (Emgo) have a lip on them that block the intake bell, (air jet), and this has a direct effect on engine rpm's under load.

Second question would be: has the bike been stored? Sometimes mice nest in the exhaust system, causing too much back pressure.

Third question: Is your advance rotating freely?

Fourth question: Do these bikes have pickup coils? And, if so, are your pickup coil wires broken? It would mimic a carb issue, but really is an electrical one.

[Molochnik]

I imagine you're asking Okie, not me. I've been addressing other issues with mine.

Interesting about the filters; gosh, all the tail chasing that lip must have caused...

These bikes do have a pickup on the signal generator plate - good suggestion about the possibility of iffy wiring.

[OkiePokie]

Quick question: Do you have pod filters on your bike? Cheap filters (Emgo) have a lip on them that block the intake bell, (air jet), and this has a direct effect on engine rpm's under load.

Second question would be: has the bike been stored? Sometimes mice nest in the exhaust system, causing too much back pressure.

Third question: Is your advance rotating freely?

Fourth question: Do these bikes have pickup coils? And, if so, are your pickup coil wires broken? It would mimic a carb issue, but really is an electrical one.

Hey, Thanks for the suggestions.

1. OEM paper air filter
2. It's been stored. Should I try running without the muffler? Take the muffler off and see if anything shakes out?
3.Not sure about any rotating advance.
4.I tested the signal generator according to the service manual. checks out okay.

[shpielers]

Have you checked your petcock is functioning properly? Might also be a fuel line kinking.
Sounds like you think it's getting enough fuel, but easy enough to check those things if you haven't already.

[IanDMacDonald]

I imagine you're asking Okie, not me. I've been addressing other issues with mine.

Interesting about the filters; gosh, all the tail chasing that lip must have caused...

These bikes do have a pickup on the signal generator plate - good suggestion about the possibility of iffy wiring.

Yes, sorry. Quoted the wrong person.

Hey, Thanks for the suggestions.

1. OEM paper air filter
2. It's been stored. Should I try running without the muffler? Take the muffler off and see if anything shakes out?
3.Not sure about any rotating advance.
4.I tested the signal generator according to the service manual. checks out okay.

No, I would not run it without the muffler. I would shine a flashlight into the muffler to verify there is no mouse nesting, etc. in there. But, I would definitely try to run it without the airbox for a quick lap. Nothing crazy, and no dirt roads. Gotta isolate the issue. Do you have spark across all four? Are these symptoms that came out of the blue, or were they inherited from a PO? The fact that you are getting full revs in Neutral, but not under load tells me that it is either one of two problems: electrical, or carb. Pull your ignition cover off, and verify your advance is rotating freely. Have you cleaned and greased your advance? Sometimes the weights and springs can get dirty and hang-up. The second thing I'd do is verify that you have the proper voltages coming out of your TCI. Third thing I'd do is give a tug on the pickup coil wires. These wires are not just ordinary wires. They're similar to one's you'd see inside an oven. Heat-resistant insulation, and very expensive to buy. You want to look for stretching in the wire, signifying a break. What happens is, when the advance rotates, sometimes those wires get hung-up on a retainer hook, and end-up snagging. The break won't be obvious. It'll be inside the insulation. A common fix for it would be to use some multimeter lead wire as a temporary fix.

[Molochnik]

These bikes don't have a mechanical advance. Inside the ignition cover you'll just find a plate with a coil and a rotor on the end of the crank. The rotor doesn't have any moving parts; all of the magic for the advance curve happens in the black box.
It is, however, worth ringing the coil wires while giving them a gentle jiggle.