Cannot rev engine above 4000 rpm

[jneaves]

Hi,

I have a zzr600 e4 that cannot be revved above approx. 4000rpm (the rev will either go down and if I continue to apply throttle it will cut out).

A week ago I balanced my carbs and ever since I have had this problem. I previously created a message thread regarding only one cylinder firing and was advised to methodically go through what I did (when balancing them) and ensure I put everything back correctly (which I'll do tomorrow).

However, I don't think this will solve the problem (as I did it today) and therefore I was wondering if anyone knew what could possibly cause the revs to die when above 4000rpm so I have an idea of what to look for?

An issue that I think maybe related (but not totally) is that the battery is buggered and so the bike needs to be jump started to get it going. But once this is done it runs perfectly fine at idle speed so I dont see how this is what affects the revs when throttle is applied (and it wasn't a problem before I balanced the carbs and I don't want to waste money on a new battery when I've got the above problem).

Thanks for all of your fourthcoming replies
Jon

[GREENISBEST]

Let's jump right in the deep end and suggest a NEW Battery

~ Why is the Battery Knackered ?
~ Charging system ok ?

My reason for asking is that your ZZR600's Ignition system requires a minimum operating voltage for it to function correctly and if the Ignitor doesn't see this Voltage it won't work properly, this could be your problem if the Battery/Charging system is faulty..It could be that there is only enough juice to run the motor at 4k above that it is trying to pull more than can be supplied..

[elr658]

I agree with green.

[jneaves]

I'll try replacing the battery then!

I'm not sure why the battery is knackered. But basically the bike has become a bit of a project (after I crashed it last september). Since that event, I've removed the battery and left it to charge on a tricle charger (taking it off to run the engine every month or so).

However last month, I did valve clearances (which went ok). But one of the pick-up coil cover bolts had siezed and snapped in the hole. So I took it to a garage to have it removed (as I couldn't get it out). They couldn't get it out either and suggested to just jam the cover on (with lots of gasket sealant). This has worked as there are no leaks. But they held onto the bike for approx. 4 weeks (waiting for the paper gasket that was on back order) and I think they left it outside in the rain as there were signs of corrosion/surface rust that wasnt there before. Plus, the engine was sized as the sparks were not in engine; I expected them to only hold onto the bike for a couple of days AND to keep it inside so didn't bother to put the new ones in. I also kept hold of the battery (on the tricle charger). That all cost £80 (the robbing buggers)

Anyway, I unsiezed the engine and got it running. But it was whilst unsiezing that the battery stopped working and I had to resort to jump starting. I then did carb balancing, the engine would rev fine before I balanced; but straight after, I got the 4000rpm rev problem.

If it was the battery; then wouldn't it work fine when connected to the 12v car battery (through jump leads)?

[GREENISBEST]

Ummm, Battery check then Before replacement might be advisable..

I would suggest you Charge the Battery up, Stick it on the bike, Start her up with a Volt meter across the Battery terminals and read the voltage when the problem occurs and see what it is showing..

Battery voltage should be around 13.5 to 14.5V give or take a couple..

The more info you supply and the more i read..... It does sound like somethings not gone back together right after the carb sync.!!!

Questions then

~ Are you running her up with or without the Airbox on ?
~ Have you TRIPLE checked ALL the Vacuum connections ?
~ Have you made sure no pipes are kinked ?
~ Have you got full throttle movement ?
~ Were the carbs out much when you sync'd them ?
~ Is the choke OFF all the way ? (Check carb end for this)
~ Are both coil connections good ?
~ Can you check pickup coil resistance ?

[jneaves]

The response to your questions:
1. I have run it with and without the airbox. The rev problem occurs on both. The air filter is also new and never used.
2. Yesterday, I re-seated the carburettors and also the tube that balances 2-3 carb (I was told that even with an air leak the engine should still rev, but it would just be rougher. Is this correct?)
3. I don't think they were kinked, but did properly look for this so will have to check.
4. I've got full throttle movement.
5. when I first synced them, they were not out at all. All I did was remove the fuel tank and airbox. I then connected the carb-tune to the vacuum connectors, ran the engine and balanced the carbs using the 3 screws.
6. I checked this and the choke was ok.
7. Both connections are good.
8. I've got a multimeter so should be able to check pick-up coil resistance.

I was thinking it could have something to do with the electric fuel pump. but would this also cause fuel supply problems at low revs?

Anyway, I'm off to check the bits stated above so will get back to you when done.

ta

[GREENISBEST]

2~ Yep more noticable at Idle..

5~ So you sync'd twice then ? Maybe explain in more detail as it sounds like it was ok the 1st time but out the 2nd time you sync'd ?

Normally Fuel pump problems are more apparent when your on the Gas..

Let us know what Volts you get running at 4k..

[jneaves]

I did sync them twice. I synced them last week and that is when I got the rev problem. I did it again this week to check that it wasn't the syncing that caused it.

I couldn't find any kinks.

The pick-up coil resistance was reading 457 ohms and the acceptale range (from the haynes manual of lies) is 380 to 570 ohms. So they are within tolerance.

The battery voltage at idle is 14.5v and it drops to 14v when at 4000rpm.

I did notice a perculier thing this time. The very first time I revved the engine, it went up to 5-6000rpm with no problems. But then I relaxed and when I revved again it reverted back to only going to 4000rpm (max). That was with the jump leads still connected as well.

[GREENISBEST]

Giving some grief this little Puppy

Have you tried inducing a high flash substance such as carb cleaner into the Inlet Track whilst reving to See if it increases noticeably...If would suggest using Gas but don't want you to get yourself fried on my recommendation

[jneaves]

I havent tried this and I've got some carb cleaner.

But how should I do it? the carb cleaner is in a bottle and is mean't to be poured into the fuel tank so I can't spray it into the carbs inlet track (what about wd40?)

Also, out of curiosity what will this tell me?

[GREENISBEST]

The carb cleaner i use is in Aerosol form so it gets sprayed into the Inlet.
If it's a fueling issue the motor will increase noticeably when it's introduced..

Not sure about the WD40 probably not got a high enough Flash point to work..

[jneaves]

I've placed an order for the rock oil carb kleen. So won't be able to test until friday (I will get back to you when I test).

Just to get my thought process correct. I am to spray this stuff into each of the carb inlet ducts whilst revving the engine. If the engine then revs above 4000rpm it means that it is my fuel supply causing the problem (e.g. faulty electric fuel pump or blockage). If the engine doesn't rev above 4000 rpm then it means it is something else (e.g. cylinder compression problem).

[GREENISBEST]

About right yep..

Comps i would suspect as a last result going on what you have said has been done on the bike..

Plenty of other things you can suspect before you get to an Engine rebuild

[jneaves]

Hi greenisbest (hope you're still there)

Well I did the test (spraying carbkleen into the carb inlet ducts) and the engine revved right up to 8000 rpm (Result!!!). Repeated test and same occurrd again.

So I take it that it is either the carbs (blocked jets); faulty electric fuel pump or a faulty fuel pump relay?

I tested the relay with the multimeter (as it said in the haynes manual). But the results were confusing. I don't fully trust what my multimeter is telling me as its values differed from two other (more expensive) multimeters. But the two more expensive multimeters also concluded that the relay was duff and I couldn't here it click when the ignition button was clicked (although the starter relay was so loud, it may have drowned it out).

Unfortunately the last time I ran it, the starter relay also stopped clicking! I checked its fues, which was ok. So assuming I will have to replace this as well (or could it be something else?).

If both relays are faulty, then I can't help thinking its something related, such as an improperly earthed cable. But I've checked and seen no signs of this.

[jneaves]

ok!

To narrow the search down a bit more; I tested the fuel pump, with the help of a pressure gauge. It was working as it was supposed to (so it's not the fuel pump).

But that still leaves the fuel pump relay, which I'm starting to think is the source of the problem. However, as there is now no response when I press the ignition button (the starter relay is not clicking!), I'm hesitant to just replace the battery and two relays as I don't know why they just failed?

Ta
Jon

[antiq]

Hey Greenie just for your info. WD40 makes the best start spray for cranky two strokes. So yes it can be used to find vaccuum leaks or as additional fuel.

[GREENISBEST]

Originally Posted by antiq

Hey Greenie just for your info. WD40 makes the best start spray for cranky two strokes. So yes it can be used to find vaccuum leaks or as additional fuel.

I stand corrected, Thanks for that

[GREENISBEST]

Originally Posted by jneaves

ok!

To narrow the search down a bit more; I tested the fuel pump, with the help of a pressure gauge. It was working as it was supposed to (so it's not the fuel pump).

But that still leaves the fuel pump relay, which I'm starting to think is the source of the problem. However, as there is now no response when I press the ignition button (the starter relay is not clicking!), I'm hesitant to just replace the battery and two relays as I don't know why they just failed?

Ta
Jon

You need to check the Starter solenoid when you press the starter button and see if she's getting a 12v feed, I would get that sorted then move back to your earlier problem.

[jneaves]

I inadvertently pressed the kill switch (so that's why the starter relay wasn't clicking ;o)

Well that just leaves the fuel pump relay or the carbs that are causing the problem.

[GREENISBEST]

Originally Posted by jneaves

I inadvertently pressed the kill switch (so that's why the starter relay wasn't clicking ;o)

Well that just leaves the fuel pump relay or the carbs that are causing the problem.

Ok lets check the operation of the Relay by working the pump !!

WARNING SPILT FUEL IS DANGERIOUS UNDERTAKE WITH CARE PLEASE.

You need to drain your carbs using the small screws located in the float bowls of each carb (4) try to catch as much Gas as you can cause we want to check for any Water in with the Gas..

Make sure the screws are done up again when the bowls are expended, Not over tight or you'll strip the threads..

Water in the Gas will cause the motor to be WAY down on power..

This will achieve 2 things:-
~ Will work the pump to fill the Bowls back up to float height.
~ Check to see if there's any Water in there.

You need you bike on it's center stand.
Turn the Ignition on and put the bike in First gear, Make sure the Neautral light is out and the back wheel won't turn (Well it will but not much before there is alot of resistance)

Now press the start Button with the Kill Switch in the RUN position (Well i had to say it )

Because the bike is in Gear the Safety lockout system will not engage the starter so all you will get is the Fuel pump working and because the Bowls are empty and you don't have the Fuel tank supply connected the Pump will rattle away trying to fill the Bowls with no supply of Gas..........

If the pump is silent then there's a problem right there

Check with a Meter (Good en) that the relay is getting switched feed when you press the starter button...If it is then trash the relay..