Author Topic: dead spot in revs. (Read 6171 times)

Lumpy · « **on:** 26 June 2015, 09:38:28 am »

my less than pristine 98 with only 120 000 miles on has developed a massive dead spot and misfire between 7k and 8k, once through this it's better but not perfect. Most of the use she gets is up to 7k but it's irritating all the same when I do want the extra revs. Carbs are worn to fook of course although it feels electrical. The TPS doesn't affect higher revs does it?

I have some spare coils so may fit them and check connections of course but I have heard many other stories of this dead spot, almost like turning the ignition off, but no resolution other than substitution hoping to hit the cause. The plugs aren't that old but if they were knackered it wouldn't pull through. The problem is worse due to the open 2 port blue flame of course but it never used to be there

any definitive ideas other than the usual clean carbs, change plugs please

Jules-C · « **Reply #1 on:** 26 June 2015, 04:07:29 pm »

Sounds like mine was like a couple of years ago. It was that bad it would throw out puffs of black smoke sometimes when trying to get through the dead spot.

New air filter fixed it even tho old one didn't look to bad.

Fazerider · « **Reply #2 on:** 26 June 2015, 04:39:53 pm »

TPS is a possibility, it shouldn't be doing anything much at those revs with the throttle open, but if there's a knackered spot on the resistive track it could be the problem. As could a dodgy connection/frayed wire anywhere in the ignition system.
But, as you suggest, the carbs are the most likely cause.Rather than cleaning them, I'd ditch the carbs. I never get more than 85,000 out of a set before they start getting rough because the teflon coating on the slides is worn. A set of barely used ones (i.e. 40,000 miles or less) can be had for about £80.

Lumpy · « **Reply #3 on:** 30 June 2015, 10:06:03 am »

Air filter isn't very old I think but I do a fair mileage so may be I guess, the fact it runs though it of sorts makes me think ignition of carbs.Carbs must be shagged by now, I know they are well out of balance. I wondered if a dead spot on the tps would screw with the ECU.

unfazed · « **Reply #4 on:** 30 June 2015, 02:34:25 pm »

Could even be a dodgy Rectifier/Regulator.
Drain the carbs on to white kitchen toweling or tissue to see if there is sediment in the bowls.
Check the fuel filter.
Check the fuel flow from the pump.
Check the Air filter
Check/test plug caps
Check Plugs
Check/test coils
Balance the carbs
Set idle speed
Set TPS
If all check out change the rectifier/regulator

darrsi · « **Reply #5 on:** 30 June 2015, 05:15:53 pm »

Quote from: unfazed on 30 June 2015, 02:34:25 pm

Could even be a dodgy Rectifier/Regulator.
Drain the carbs on to white kitchen toweling or tissue to see if there is sediment in the bowls.
Check the fuel filter.
Check the fuel flow from the pump.
Check the Air filter
Check/test plug caps
Check Plugs
Check/test coils
Balance the carbs
Set idle speed
Set TPS
If all check out change the rectifier/regulator

Is that the short hand version of Red98's old problem, rather than reading a few hundred pages?

unfazed · « **Reply #6 on:** 30 June 2015, 09:24:14 pm »

It probably is and the first time I came across it was on my sons 2003 model 600, I swapped over everything one item at the time from my 600 and when we swapped out the Rectifier/Regulator the problem disappeared.
There was no other symptom and it happened suddenly.
Spoke to a number of mechanics I know and they never came across anything like it. I have come across another one since on a 1999 model 600 and it was the first thing I changed, problem gone.
They are different rectifier, look the same with same connectors, but are very different.

darrsi · « **Reply #7 on:** 01 July 2015, 06:52:12 am »

Quote from: unfazed on 30 June 2015, 09:24:14 pm

It probably is and the first time I came across it was on my sons 2003 model 600, I swapped over everything one item at the time from my 600 and when we swapped out the Rectifier/Regulator the problem disappeared.
There was no other symptom and it happened suddenly.
Spoke to a number of mechanics I know and they never came across anything like it. I have come across another one since on a 1999 model 600 and it was the first thing I changed, problem gone.
They are different rectifier, look the same with same connectors, but are very different.

What d'ya mean "they are different"?
Different in comparison to what?

unfazed · « **Reply #8 on:** 01 July 2015, 07:52:59 am »

The 2002-2003 has a higher charging rate from the alternator and it is better able to control the higher output.
There would be little point of swapping a working older one with the newer one as the alternator does not have the higher output, but if an older one fails the 2002- 2003 will work fine as a replacement or a one from the 2001 to 2006 FZS1000.

The 2001 to 2005 FZS1000 one is the same model as the 2002 to 2003 FZS600, but the wires are longer on the 1000 one.

darrsi · « **Reply #9 on:** 01 July 2015, 01:25:27 pm »

Quote from: unfazed on 01 July 2015, 07:52:59 am

The 2002-2003 has a higher charging rate from the alternator and it is better able to control the higher output.
There would be little point of swapping a working older one with the newer one as the alternator does not have the higher output, but if an older one fails the 2002- 2003 will work fine as a replacement or a one from the 2001 to 2006 FZS1000.

The 2001 to 2005 FZS1000 one is the same model as the 2002 to 2003 FZS600, but the wires are longer on the 1000 one.

So if my 2000 model failed for instance I would need that year or above, or it wouldn't really matter either way?

unfazed · « **Reply #10 on:** 01 July 2015, 05:28:24 pm »

Yes, backward compatible only

Lumpy · « **Reply #11 on:** 03 July 2015, 07:45:33 am »

cheers guys. Odd it will clearish when it pulls through the dead spot. Need to set the tps to start with. I reckon if the air filter was to blame it wouldn't pull through? I think she needs newer carbs but it does feel electrical.

Lumpy · « **Reply #12 on:** 05 July 2015, 09:54:06 am »

tps setting makes no difference. Air filter on order

Jules-C · « **Reply #13 on:** 06 July 2015, 03:44:06 pm »

The carb is changing over from one set of jets to another at that rev range point and it only takes very slight pressure change from dirty air filter to mess it up totally. Once you get the revs higher it will be running slightly rich but not enough to give misfires or significant power loss

Lumpy · « **Reply #14 on:** 06 July 2015, 03:50:13 pm »

Quote from: Jules-C on 06 July 2015, 03:44:06 pm

The carb is changing over from one set of jets to another at that rev range point and it only takes very slight pressure change from dirty air filter to mess it up totally. Once you get the revs higher it will be running slightly rich but not enough to give misfires or significant power loss

it's definitely not happy and if the air filter doesn't help matters I shall swap it for another TPS I know is okay. I may try the iridium plugs I swapped out last time for normal 9Es too. I know NGK state 8Es but some recommended 9s

maxzer1500 · « **Reply #15 on:** 06 July 2015, 06:15:28 pm »

Agree with Darsi the air filter is one of the first things to check, you'd think 9 plugs would be ok esp as our general temperatures are probably higher than when yamaha made the recommendation. The tps on mine won't adjust but seems to pull cleanly right through the revs? One of my high mileage bikes responded well to a carb swap after similar symptoms to yours. I think next time i get a bike that don't run evenly am going to invest in a laser thermometer to get an accurate idea of the eveness of cylinder ( exhaust ) temperatures, not definative i know but might save some grief/money.

Lumpy · « **Reply #16 on:** 14 July 2015, 07:47:36 am »

I have a laser thermometer so that's handy, but only falters under load but is definitely a useful bit of kit, especially for tyre temperatures on the track. Got air filter now, just need to fit. I would be pleasantly surprised if it was. The only similar effect I had was on a kwak. Drilled the airbox as it was restrictive. Revved to 5k and that was that, no more. Oh well. Filled holes back in and fine. Obviously needed the plenum effect

Lumpy · « **Reply #17 on:** 21 July 2015, 01:16:48 pm »

well it was with a certain lack of confidence in changing the air filter doing the trick that it was changed. I have never had an air filter have that effect. Modifying an ER5 air box caused it to rev to 5k, no more in any gear or neutral so I guess it could be.

Amazing result, flat spot completely gone, amazing. Thanks.

Jules-C · « **Reply #18 on:** 21 July 2015, 02:33:50 pm »

Good you got it sorted.

HarryHornby · « **Reply #19 on:** 21 July 2015, 02:50:21 pm »

hmmmmmmm, mine seems to have the odd dead spot since I've fitted the K and N that I got off of RMT on here.

The bike is due a carb balance, which I've not done since fitting a blue flame exhaust and K and N. I wonder if those have changed things significantly.

Might change the filter back this eve though and see if it makes a difference.