idle jump while stopped?

[Chimpin07]

yesterday when i was riding i was stopped at a red light and my bikes rpms was like jumping from 1k to 2k just non stop while i was stopped. what could be the cause of this? its on a 97 750 katana

[Kreylyn]

yesterday when i was riding i was stopped at a red light and my bikes rpms was like jumping from 1k to 2k just non stop while i was stopped. what could be the cause of this? its on a 97 750 katana

Bouncy or jumpy idle is most often an air/vacuum leak associated with the carbs. Boots on the airbox not fully mounted on is a common location, but certainly not the only place.

Pull the tank off and start testing/looking for leaks.

Krey

[Chimpin07]

For the last week I've had the tank off and could not find any leaks or anything and I just put the tank back on today and it's still doing it and I can't figure out where an why? I think I might have to take it to the shop ( which that's the last thing I want to do) but I can still ride it. Just annoying.

[Kreylyn]

For the last week I've had the tank off and could not find any leaks or anything and I just put the tank back on today and it's still doing it and I can't figure out where an why? I think I might have to take it to the shop ( which that's the last thing I want to do) but I can still ride it. Just annoying.

When was the last time the orings for the engine to carb boots were replaced?

I would pull the tank bracket, pull the carbs out, pull those boots (only when the engine is dead cold of the bolts will be a major pain to remove) and inspect them. Replace if they show any signs of cracking. Replace the orings on the back of them. About $12 for the OEM orings.

Put the boots on, then go to the carbs. Remove the airbox and pull the airfilter out of the airbox.

Inspect the carbs, make sure the rubber caps on the sync ports are there, in good shape, no holes. Inspect the airbox boots. Make sure they are in good shape, no holes, and seal well to the airbox. If they are not sealed well, or the old glue is cracking/flaking out... get some gasket sealer from the auto store (about $6 or so) and use it to put them back on and sealed well.

Put the airbox on the carbs first. You can push from the inside with the airfilter out to make sure each one is seated all the way down on the carb for proper sealing. Once the airbox is on, put the filter in, put the carbs back on the bike, and put the tank bracket back on.

Make sure the petcock vacuum line is attatched correctly to the side of #4 carb, and that it also does not have any holes in it, and the petcock is not leaking through the diaphram and in proper working condition.

Then run it to see if it is still doing it.

Krey

[Chimpin07]

awesome im going to do that on the weekend and ill keep you updated.

[hinow41]

Just noticed this today on my bike.
Thanks Kreylyn for the answer and Chimpin for asking.

[Chimpin07]

so i was testing it and the only thing i could really find was a slight gash on one of the airbox boots would that cause it? and does the airbox need like clamps around the boots to tighten onto the carbs?

[MikeyZ]

so i was testing it and the only thing i could really find was a slight gash on one of the airbox boots would that cause it? and does the airbox need like clamps around the boots to tighten onto the carbs?

Yes that could definitely be it. You have to replace that boot. Might as well replace them all. And yes their should be clamps that clamp onto the carbs.

[Chimpin07]

oh okay. and i meant like the boots on the air box do they have to have clamps? i know from the motor to the carbs it has clamps to hold it in place.

[KAT TOY]

on my post the boots have a groove that fits into the airbox. they were a little loose so i sealed them with silicone sealer[rtv].