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MotoMacGyver
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Discussion Starter #1
Ok. Really weird. My bike will run for about 20 minutes or so, then start losing power and missing and sputtering. Then it stops. I wait 2 minutes, and it runs again for another 20 or so minutes. It's not the fuel valve (tried normal and Reserve), and it's not the plugs or wires (runs fine when running). Could it be the ignition module (or whatever the equivelant is?) I've heard of faulty/old coils and ignition modules on cars that get overheated, then quit. When it cools a little bit, they fire up again. However, I don't see how 2 minutes is enough to cool anything down.

I've checked hoses and plumbing and I don't have any blockage (thought maybe a vent line was clogged and it prevented fuel from being sucked in).

It only started doing this today. I don't think it's related to the whole needle/shim fiasco, but all these problems arose after that whole debacle.

Any suggestions?


Emrah
 

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Wheelie for Safety
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1,550 Posts
Hi Emrah,

An engine only needs three things to run. Compression, spark and fuel.

Right off we can eliminate compression from your symptom.

Next we will try to eliminate spark. When it starts to mis-fire and stops running, grab an extra spark plug and put one of the wires on it. When you try to start it (and it won't start) if you get a good spark then you can eliminate that.

Last and most likely... fuel. Let it run until she dies, then pull off the fuel hose from the pet-**** and see if fuel is still flowing. Be careful to not allow gas to spill on your hot engine.

From your symptom, I would think its the pet-****. May need cleaning etc.

Andy
 

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West Coast Moderator
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12,996 Posts
What kind of engine speed are talking about? When's the last time you changed your oil? DOes it die out like lack of fire (spark) or lack of fuel (cough & sputter). There's line that goes in between carbs 2&3 that lets the equalize. When I was experimenting with mine. I had plugged that hose off (inadvertantly) and it made it sputter and die.
 

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MotoMacGyver
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2,546 Posts
Discussion Starter #4
I'm going to try the petcock thing. I didn't take the tank off or anything to check all those lines underneath (all my tools are at work).

What I can't figure out is, if it IS the fuel, how come it fires up after 2 or so minutes? If something's plugged up, it should stay plugged. It will be going fine, then it will start to lose power (like running out of gas or before you switch to Reserve), and no matter how you play with the choke (thought it might be too rich or something) or the petcock, it just keeps dying until it stops. I let it sit for a few minutes, then bingo, I'm on the road again. It does this approx. every 10-20 minutes at a time.

I'll try and check the hoses and stuff this week. This is the last thing I need to worry about right now. :mad:

Emrah
 

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Silver Member
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881 Posts
I had this happen on my old bike. It turned out to be water in the float bowels. Try draining them and see if any gunk comes out.

:)
 

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Wheelie for Safety
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1,550 Posts
Emrah,

There could be a partial amount of fuel entering the carbs. When you run it for 20 minutes you use up all the fuel. Then when it sits for two minutes the bowls fill up again.

On each carb float bowl (on the right side) there is a little allen screw. When it dies, try loosening the one on the right carb. Place a bowl under the carb to catch the fuel. Gas should stream out of the the fitting on the bottom of the bowl. If no fuel or very little comes out then it is a fuel problem.

Andy
 

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45 Posts
Hi emrah
Just my thoughts on your problem. It sounds like a fuel starvation problem caused by a partial vacuum in the fuel tank. This could be caused by a blocked/kinked vent hose somewhere.
I would check it out by putting the spare key in the fuel cap and go for a ride. When the power loss/sputtering kicks in open the fuel cap while still riding and if it recovers (by relieving the vacuum in the tank) then I would check the venting of the tank. If it doesn't work at least you have eliminated one possibility.
Obviously keep the bike upright with the tank open and shut the cap down again after a few seconds.
Hope this helps - Good luck.
 

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GlennDarragh said:
Hi emrah
Just my thoughts on your problem. It sounds like a fuel starvation problem caused by a partial vacuum in the fuel tank. This could be caused by a blocked/kinked vent hose somewhere.
I would check it out by putting the spare key in the fuel cap and go for a ride. When the power loss/sputtering kicks in open the fuel cap while still riding and if it recovers (by relieving the vacuum in the tank) then I would check the venting of the tank. If it doesn't work at least you have eliminated one possibility.
Obviously keep the bike upright with the tank open and shut the cap down again after a few seconds.
Hope this helps - Good luck.

I'm with Glenn.
This is 99% what the problem is. You probably bent-twitched or something the vent tube that runs under the tank whan you removed it.

Aris
 

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Wheelie for Safety
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1,550 Posts
The gas tank draws air in through the gas cap. So to have a vacuum problem the gas cap would have to be clogged or partially clogged. You can blow on the inside of the cap to determine if that is the problem.

Emrah, did you turn the gas tank on its side when you had it off?

All the emission hoses and parts do is prevent the gasoline vapors inside the gas tank from being vented to the atmosphere.

Andy
 

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i think you're confusing cali and non-cali models andy. on regular models the tank is vented throught the cap. on cali models the cap vent is sealed up (with a rubber plug if i remember right) and the venting is done through the charcoal canister. there's a separate circuit that catches liquid overflow, channels the vapors to the canister and sends the liquid back to the tank.

so if you kink the emissions lines you might have a problem with carb bowl and/or tank venting.

emrah, do you have the service manual? if you don't i'll scan and send you some of the relavent pages. let me know :)

scott :)
 

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Wheelie for Safety
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1,550 Posts
Hi Scott,

You may be correct. However, when I filled my tank up a little too much, the gas was coming out of the cap. So I think it is still vented through the cap on the California models.

Andy
 

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Silver Member
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Hi, Emrah
I remember you asked about california emissions system removal. Did you remove it? I'd do what Glenn suggested, than if it'll appeared to be a vacuum problem, I'd check emissions hoses.
 

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Wheelie for Safety
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I put a peice of duct tape over the two holes under the gas cap. I went for a 45 minute ride without any problem. So it doesn't sound like a gas cap problem.

Andy
 

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Wheelie for Safety
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1,550 Posts
Hi Shuo,

I only taped the two holes. Now that I looked at it a little closer, there is a third hole under the seal. You can only see it when you push down on the seal.

I guess thats why on my test ride I didn't have any problem.

I see no good way of sealing the gas cap to simulate the problem Emrah might have.

Andy
 

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Silver Member
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479 Posts
Hi, Andy
If you mean the holes in the rubber seal, these are wrong holes. Tank is vetilated through the small hole in the center of the back side of the cap. This hole connected to the small nose on the right side of the cap. On california models this nose goes to rubber fitting when cap is closed. Rubber fitting connected to one of the hoses which go from under the tank, to the hose with blue dot. This hose goes to the separator. There is a discussion about emission system removal with description of all this hoses: http://www.nutndun.com/zr-7/showthread.php?s=&threadid=376&

The hole under the seal it's a rain water drain hole. On non-california bikes it's also ovefill drain hole, and probably, tank ventilation hole. The hose goes from rear right side of the bottom of the tank to the clamp on the swingarm near of the right footpeg.
 

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MotoMacGyver
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2,546 Posts
Discussion Starter #17
I thought it might be a venting problem as well, but why would it do this now? I'd been riding the thing for an entire week (every day) until last Sunday. It was at least a week and a half since I returned all my mixture screws and needles back to stock. I've run though a whole tank of gas since then. The problem should have shown up in a week right? I also tried to listen to a "whoosh" by opening the gas cap the first time I did it, and heard nothing.

Like I said, I haven't even touched the bike since I limped it home on Sunday morning. No time. Been working till 8 or 9 every night, so the bike's been sitting at home (driving the Jeep). I'll look at it this weekend if I'm off; maybe.

Still appreciate all the responses though. I'll update a post here when I get around to messing with the thing and maybe figure it out. Might be a week or two though.

Thanks anyway,

Emrah
 

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emrah, to determine if it's a tank venting problem you could do this: run it until it stalls. then stop immediately, pop open the gas cap and see it it starts and runs. (don't ride like this for obvious reasons.) if it does then something is keeping the tank from letting air in at the proper rate.

scott :)
 

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Wheelie for Safety
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1,550 Posts
Scott and Shuo,

You guys are correct. It does not vent through the gas cap. The blue hose that goes from the gas tank to the Liquid/Vapor Separator is the breather hose.

Emrah, you could try removing the Blue Hose (92191) at the Liquid/Vapor Separator (16165). Then try blowing through it, there should be no blockage when the gas cap is open.



Andy
 

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andy, if you check page 2-2 in the manual there is a part at the top of the page that is cali only. i think this is a rubber plug that plugs the vent hole used on the 49 state bikes. can't be sure since my bike is not here right now. this is what i was talking about earlier. i think someone who did a canister-ectomy removed the plug and plugged some other lines.

scott
 
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