Did the Carb monster just bite me?

[Giaco]

I bought my '99 Kat 750 at the beggining of the , but due to military regs, i can't "ride" it until i take the advanced safety course at the end of the month. I rode it once to test it before i bought it, and once around the parking lot at my apt, and it has run fine. Today i spent a lovely afternoon working on the brakes and lights, and then took it for a fill up (regular gas). When i got back, i did some practice u-turns, and the bike started sputtering a bit. It will no longer idle, and goes through large fluctuations of rpm when i hold the throttle reletively constant in Neutral. Everything looks, feels, and stinks like a carb problem to me, but im wondering if i just swished some junk up from the bottom of the take when i filled it up and it will pass with some highway rpms, or if i really do need to pull the carbs and clean 'em out.... of course if congress doesn't pass this bill, i may have plenty of time to do that in the next few days....

[Kreylyn]

Did you over heat it? If your only going very slow in a parking lot, it might have gotten too hot. This could cause running issues.

Try again after it's sat for a while... if the problem still exists, look at another issue.

You should have a filter on the fuel line... I doubt it was putting fuel in that caused the problem if it was just regular fuel.

Perhaps while you were doing the work previously... did you remove the tank?

Try it on prime as well to make sure your not having a petock/vacuum issue to the petcock on flowing fuel to the carbs. Also open the tank and make sure it's not building up pressure.

Krey

[Giaco]

i didn't touch the gas tank when i was working on it, just replaced the rear brake rotor and put in an LED rear indicator. I wouldn't say i had it running in the parking lot for more than maybe 5 minutes tops, would it overheat that quickly? After it stalled, i could barely get it started again by holding full throttle for a few seconds, then backing off when i felt it start to fire. I did move the petcock a few times, but it didn't seem to make a difference. it started when running in regular mode. - or perhaps im running into your ethanol issue...

[Kreylyn]

The "ethanol" issues I have talked about would be a long term storage or long term usage of the same fuel. Fresh fuel even with higher levels of ethanol is not going to just up and make the bike not run. It's fresh, and will burn just like non-E mixed fuel.

I really don't think you filling the tank had much to do with how it's running now. I would focus on heat issue, or perhaps fouled plugs. You didn't run it for more than say 30 seconds with the "choke" lever on as an example did you? Also, lots of short starts and stops of the engine can foul the plugs as they never have time to build up enough temp inside the engine to clean the plugs off from the richer starts with the choke.

Krey

[Giaco]

The "ethanol" issues I have talked about would be a long term storage or long term usage of the same fuel. Fresh fuel even with higher levels of ethanol is not going to just up and make the bike not run. It's fresh, and will burn just like non-E mixed fuel.

I really don't think you filling the tank had much to do with how it's running now. I would focus on heat issue, or perhaps fouled plugs. You didn't run it for more than say 30 seconds with the "choke" lever on as an example did you? Also, lots of short starts and stops of the engine can foul the plugs as they never have time to build up enough temp inside the engine to clean the plugs off from the richer starts with the choke.

Krey

No, i had it on maybe 30 seconds max, it didn't need it at that point. it ran great up until i got it back to the parking lot.

[Wild-Bill]

I think Krey got it in that last post. Fouled plugs thanks to running it for short periods of time at low rpms with old gas. You need to loan the bike to a friend and have them run it up and down the highway for 20 minutes or so.

[Giaco]

I think Krey got it in that last post. Fouled plugs thanks to running it for short periods of time at low rpms with old gas. You need to loan the bike to a friend and have them run it up and down the highway for 20 minutes or so.

Replace plugs too, or just run it off?
Thanks Krey and Bill for your help!

[indianboy7]

Replace plugs too, or just run it off?
Thanks Krey and Bill for your help!

I would try burning it off first...ride it at fairly high rpm for at least 10 minutes...keep the bike moving though..don't do it at a standstill

[Wild-Bill]

If the bike will start then you should be able to just burn the plugs clean.

[Giaco]

Well, i got her started today, and had to hold the throttle cracked to prevent it from stalling. The bike was then taken out on the highway for about 5 minutes, running a little bit rough, but held relatively steady at 65 mph at 6000-6500 rpm (it was held in a lower gear to keep the rpms high). After turning off the highway to turn around, the bike immediately stalled, and would not start for a good 5 minutes of fiddling with petcock, throttle and choke settings. After getting it started, it managed to get back on the highway, and rode back with a little hesitation, but no major issues (did get some pops from the carbs when the throttle was rapidly dropped). When pulling into the parking lot, the RPMs were allowed to relax to idle, but the bike immediately stalled. Perhaps the plugs were too gummed up to clear via running, but i'm not sold... any suggestions before i have to bring her in?

[GSXF 600 Guy]

Check for any loose vacuum lines, and also your air filter, it may be clogged. I had a similar issue when I got my Kat. Air filter was pretty dirty & wasn't allowing good air flow. Replaced & problem went away. But, if you haven't done the plugs yet, and have no idea when the p/o did, I'd do them just for peace of mind. I replace my plugs twice a year & filter every other season.

[MylesJr]

I have the same issue right now on my 750. Air filter is good and just did a tune up 2 weeks ago so tomorrow I am going to pull the plugs again and see how they are.

[boomer_95]

i would check the plugs and air filter first. ethinol in gas sucks but it usually takes bout a month to make gas bad... even if left open to the eliments. less you had lots of bad gas in the tank and ran it threw the carbs.. maybe they are just really gummed up and need a good cleanning.. but easiest first... plugs and air filter then go from there....

and Mylesjr could you exlain your "tune up"?? that term can mean a simple oil/filter change to ppl or a full carb clean/ valve adjustment ect.. (i hate the term tune up lol)

[scottynoface]

6500 revs at 65mph isn't going to burn off ****, that's a low load situation. Get out there and flog it a few times, THEN you can say you tried.

[Giaco]

6500 revs at 65mph isn't going to burn off ****, that's a low load situation. Get out there and flog it a few times, THEN you can say you tried.

Moving up from a '81 400 twin... what is "flogging" on a katana then? I will probably pull the plugs tomorrow to take a look. The gas should be pretty darn fresh, but i will fill it up with premium and some fuel system cleaning. Battery is charging tonight as well. Thanks for all the advice!