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Discussion Starter #1
My ZR has just covered 8200kms. On Christmas day, it somehow transformed itself. Gone was the buzziness usually associated with this bike. And on the move, the bike feels smoother and 'sedated'. However, at idle, the engine seems to pulsating and sounds a bit like a detuned V-twin. I read in one of the threads in this forum someone claiming after some mileage, the buziness would go away. This has certainly happened. But, is it normal for the engine to pulsate at idle?
 

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Have you changed petrol (eg. standard unleaded to Optimax?)

BTW, I see we are now seven in number.
 

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I rang Cosway Kawasaki and was asked the same question. I did indeed top up the night before I noticed this problem. I top her up at Mobil with regular unleaded as I have always been. Now I might have full tank of sh*t. I put on some mileage the other day, and when it was 1/2 full, I top up with Shell Optimax. I haven't felt the difference yet.
 

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I read somewhere that standard fuel was premium fuel that didn't quite make the grade. In other words, they intend it to be premium but when they test it and it doesn't make it, they just 'change the label'. The upshot of what I read is that standard fuel can indeed be sh*t - not always, but often enough not to use it.

Now, I don't know how true all of this is - nonetheless I'm sticking to Optimax (ie. ultra premium) from now on. In my car I get better mileage with this, so it stands to reason that it should be better in my bike too.

Or not ??

BP seems to have launched an Optimax look-alike too - can't remember what it's called, maybe something like '8000'.
 

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Discussion Starter #5
Since the problem surfaced, I have alreaqdy run through 2 tankful of Shell Optimax. The engine still pulsates at idle. When I twist the throttle, there is a hesitation before the rev catch on. The freeplay of the cable is OK though. Could this be a faulty spark plug? Or, could this be electrical problem?
 

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i suspect a vacuum leak. common symptoms are rough idle but running fine at higer speeds. have you checked for this yet?

scott :)
 

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A spark plug can cause the problem. How many miles on the plugs? Before you pull the plugs out, be sure to clean the area around the plugs with compressed air or vacumm cleaner. I dought its a vacuum leak, I just pulled one of the vacuum hoses off my bike while it was running and it still ran fine even with a small vacuum leak.

Andy
 

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Discussion Starter #9
The bike only has 8900kms on the clock. It had its 6000k service by Kawasaki not long ago. The problem definitely surfaced after a refuel at BP. I hope this is caused by the bad fuel from the pump, and need more than 2 tank to flush it all out.
 

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you can do a few things. the leak is probably near one of the carbs or the intake manifolds.

you can feel around in there for it while the bike is idling but that's not likely to help. don't burn you fingers :)

THIS IS POTNENTIALLY DANGEROUS!!! THINK BEFORE YOU DO IT AND DON'T DO ANYTHING STUPID!!! IN A WELL VENTIALTED AREA you can point the nose of an UNLIT (NO FLAME) propane torch at different points near the manifolds while the bike idles. if you get a sudden rise in the idle the propane has gotten sucked into a leak and been burned in the engine. leak found, problem solved!

lastly, you can get a vacuum gauge at an auto parts store. this is a diagnostic tool. disconnect a vacuum line from each carb, plug the line and connect the vacuum gauge to the carb. at idle there should be a nice steady reading. if it's bouncing around you've got a leak on that cylinder/carb manifold. as you open the throttle slightly you should see the vaccum drop initially and then rise to a steady value again. check each carb individually.

this last option requires the most tools, know how and possibly disassembly and i'm not sure if each carb has an available vacuum line. one of the lines goes to the fuel petcock; if you remove this one you'll need to turn the petcock to prime to keep fuel flowing to the carbs. the petcock is vacuum activated.

hope this helps :)

scott
 

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Hi AP746,

I think if were a vacuum hose that was leaking you would hear it. It would create a sucking sound.

Also the clue is that it all started after you filled up. I don't think its bad gas (never heard of that). That would mean million's of cars would be dying all the time with bad gas syndrome.

To me it sounds like a carburetor problem. Like the pilot screw aka idle mixture screw or pilot jet got clogged. You might of got a load of dirt with the gas when the problem started.

Take a flashlight and look inside the gas tank near the petcock area. It is possible to do even with a full tank of gas. If its not perfectly clean and you see particles then my hunch is correct.

The reason cars don't have this problem is they have a better gas filter.

BTW does the problem exist when you first start it up and using the choke?

Andy
 

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scottmac99 said:
I read somewhere that standard fuel was premium fuel that didn't quite make the grade. In other words, they intend it to be premium but when they test it and it doesn't make it, they just 'change the label'. The upshot of what I read is that standard fuel can indeed be sh*t - not always, but often enough not to use it.

Now, I don't know how true all of this is - nonetheless I'm sticking to Optimax (ie. ultra premium) from now on. In my car I get better mileage with this, so it stands to reason that it should be better in my bike too.

Or not ??

NOT.

Premium gas has more octane added to regular gas to make the fuel burn more slowly. It is only required in high compression engines that would otherwise knock (ping/predetinate). Using premium gas in a stock engine that is designed for regular gas (99% of all engines made after 1975) will have an effect of reducing power and fuel mileage. Not to mention its a waste of money.

Because fewer people use premium gas you also run the risk of getting more dirt/sediment with your gas.

Andy
 

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Discussion Starter #13
The bike is harder to start in the morning with full choke on. It used to start at first go everytime. Now it might take up to 3 hits before the engine fires up. And the first 20 seconds or so the engine would struggle at 2000rpm, then gradually move up to 4000rpm. First I thought it was the choke. But after checking the linkage, I don't think so. I couldn't hear any sucking sound near the carbies either.
 

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Did you check the inside of your gas tank with a flashlight? Look for sediment near the petcock. It should be perfectly clean.

Andy
 

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This is getting complicated ...
http://www.powerplusmrpl.com/techimpure.htm

If higher octane petrol/gas is cleaner (is it? not if it sits around for a long time, as Andy implies), then that's what we should be using, shouldn't we?

I'll dig around some more.
 

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if it's not a vacuum leak andy may be right, you may have gotten some gunk in one of the carbs. particularly in one of the ilde jets. that would explain why it runs fine at higher speeds. seeing some dirt near the petcock would support this but won't fix it. here's something that might:

you'll need to remove the air cleaner to do this but at least you don't have to remove the carbs. remove the air cleaner box so the back sides of the carbs are exposed. start the bike and run it up to about 5000 rpm. then cover one of the carb mouths completely with your hand. hold it for a second or to and then release and let the engine spin back up. repeat several times for each carb.

i used to do this whenever my vw was running a little funny and it sometimes worked. what it does is create some really killer vacuum that can pull though any little bits of crud that have gotten stuck in your carb jets.

have you taken the bike to a mechanic yet? if not you should consider it. unfortunately we don't seem to be making too much headway here :(

scott
 

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AP746,

If the engine is running on 3 cyclinders at idle, you can remove one spark splug wire at a time to determine which cyclinder is not firing.

Once you determine which cyclinder is the one, you can remove the carbs and clean out that one carb.

While your at it be sure to remove the idle mixture plugs and re-adjust the idle mixture screws from 1.75 turns to 2.5 turns.

Andy
 

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Just so long as he doesn't do us another photo to illustrate it ...

:)
 
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