Date: 23-10-19  Time: 14:39 PM

Author Topic: CARBURETTOR Problems In Low RPMs  (Read 7666 times)

Dave48

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Re: CARBURETTOR Problems In Low RPMs
« Reply #25 on: 02 August 2016, 04:53:03 PM »
Its a possibility. I think you may need to go back to basics & recheck everything to do with the fuelling,from the supply pipe from pump to the inlet rubbers,item by item. Dont assume anything just work from first principles. Even recheck work you have previously done yourself. You will get there!
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Bretty

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Re: CARBURETTOR Problems In Low RPMs
« Reply #26 on: 02 August 2016, 06:43:31 PM »
So did the bike come to you with these problems, or did they develop while you've had it?
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7uckyDog

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Re: CARBURETTOR Problems In Low RPMs
« Reply #27 on: 02 August 2016, 11:07:44 PM »
2 further thoughts:
1. You did tighten the needle valve seat retaining screws when you changed them?
2.Float height for 2000 on models should be 3.5mm above float chamber mating surface ( Its 4.5mm on earlier models) 2000 on carbs are marked 5DM1 01
Earlier models are 5DM1 00.
Only mention this in case carbs have been replaced by previous owner. I know its a bit of a long shot but in diagnosing faults you cant assume anything. :eek
Dont mean to teach anyone to suck eggs but it seems you have ruled out a lot of the obvious things mentioned by others. Good luck!


1. Of course I did and last time I opened the carbs I took the floats out and checked if the needle valve seats were sitting in it's place properly
2. According to the markings on the side these are the correct carbs but it's true, you can't assume anything when you buy a used bike without any history at all

7uckyDog

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Re: CARBURETTOR Problems In Low RPMs
« Reply #28 on: 03 August 2016, 02:49:11 AM »
So did the bike come to you with these problems, or did they develop while you've had it?



It hasn't been idling very well after a rusty tank incident. Carbs have been cleaned, floats leak tested, O rings replaced, and new needle valves fitted. After a lot of struggle adjusting the fuel level it seems to have changed over a period of few months and sometimes the valves don't seem to be closing properly as the level is randomly too high. The new needle valves have a harder spring, bigger rubber needle and the seats have a bigger hole and are marked 2.0 instead of 1.0 like the old ones. Apart from the obvious differences they seem to be same. My logic thinking tells me that a harder spring would make it easier for the floats to close them but maybe I'm wrong. I did a leak test with the bowls off and not a single drop of fuel was spilled. But when adjusting the fuel level I had to bend the tangs on the floats quite a lot towards the valve to be able to obtain a "useable" fuel level.Does anybody have experience of these aftermarket needle valves? Or any other brand? Here's a link http://www.ebay.co.uk/itm/CARBURETTOR-FLOAT-NEEDLE-VALVE-WITH-SEAT-YAMAHA-FZS600-FZS-600-FAZER-98-03-NEW-/272231399564?hash=item3f6241808c:g:zmEAAOSwqv9V6uV1

His Dudeness

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Re: CARBURETTOR Problems In Low RPMs
« Reply #29 on: 03 August 2016, 06:55:37 PM »
The Fazer carbs really shouldn't need any tweeking. If I was you I'd put everything back to factory settings. Or for the sake of an easy life just get another set of carbs. They aren't very expensive

7uckyDog

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Re: CARBURETTOR Problems In Low RPMs
« Reply #30 on: 03 August 2016, 10:53:44 PM »
The Fazer carbs really shouldn't need any tweeking. If I was you I'd put everything back to factory settings. Or for the sake of an easy life just get another set of carbs. They aren't very expensive


Yeah I've done everything I can because I wanted to find the problem. The bike has been to two shops without good results hence me still working on it. Few weeks ago I thought about a set of second hand carbs and tonight after having set the fuel level almost perfectly and the bike still idling like a retard I've decided to formally give up and get another set of carbs!!!  :'(


I spotted a nice set of 2003 version, they should be compatible with the 2002 bike, right?

darrsi

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Re: CARBURETTOR Problems In Low RPMs
« Reply #31 on: 04 August 2016, 06:19:08 AM »
The Fazer carbs really shouldn't need any tweeking. If I was you I'd put everything back to factory settings. Or for the sake of an easy life just get another set of carbs. They aren't very expensive


Yeah I've done everything I can because I wanted to find the problem. The bike has been to two shops without good results hence me still working on it. Few weeks ago I thought about a set of second hand carbs and tonight after having set the fuel level almost perfectly and the bike still idling like a retard I've decided to formally give up and get another set of carbs!!!  :'(


I spotted a nice set of 2003 version, they should be compatible with the 2002 bike, right?


02/03, same bike.
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7uckyDog

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Re: CARBURETTOR Problems In Low RPMs
« Reply #32 on: 06 October 2016, 05:46:53 PM »
Update and a surprising twist!

So after my last post I got a second hand set of 2002 carbs. They were filthy on the outside and had gunk and cracked o-rings on the inside. Went through the carb fixing process again and slapped them on the bike.

The engine idles much better! I was so happy! Went for a ride and discovered that now I have a problem in the high RPMs, WTF!?!

It behaves like a ignition retardation when trying to overtake quickly. The engine sputters and looses power of the throttle is twisted quickly. But if I ease it in slowly then I can get through the whole range. I've swapped the TPS sensor (but they're both used) and there's no change. There are new plugs, new caps and the spark looks good.

What's going on!?! Has anyone had any issues with the ECU?

Fazerider

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Re: CARBURETTOR Problems In Low RPMs
« Reply #33 on: 06 October 2016, 06:24:25 PM »
It behaves like a ignition retardation when trying to overtake quickly. The engine sputters and looses power of the throttle is twisted quickly. But if I ease it in slowly then I can get through the whole range.
I'd guess that's one or more of the carb slides jamming because of the sudden large pressure difference, rather than rising smoothly.
You may be able to feel that if you try raising them one at a time by hand, though obviously that's a carbs-out job.

7uckyDog

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Re: CARBURETTOR Problems In Low RPMs
« Reply #34 on: 06 October 2016, 06:39:42 PM »
Well I checked the slides, the membranes and anything else just in case before putting the "new" carbs in.

But it would be an easy job to swap them for the older ones to rule it out I guess.

I'm inclined to try another ECU, does anyone know if I could use with ease from the same model and if it has to be the same year?

BBROWN1664

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Re: CARBURETTOR Problems In Low RPMs
« Reply #35 on: 06 October 2016, 06:45:35 PM »
Sounds like a fuel related problem.
Everything is fine unless you open the throttle too quickly.

I would have a look at the sizes of the jets in the original carbs (assume they are standard) and the new carbs. I suspect you have got a set someone has re-jetted. The ECU would not cause that sort of problem.
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bikemad

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Re: CARBURETTOR Problems In Low RPMs
« Reply #36 on: 06 October 2016, 11:07:47 PM »
On my bike I had carb problems blocked green/brown crust after cleaning them still not starting or firing ?
Found out O rings knakerd thus flooding tried a 2nd set that was on donor bike it ran but not brilliant but it ran,so I took them apart but not the best condition the screws only just came out of the float bowls ! so as my originals are clean I swapped the seats & O rings.


Bike started ran but died after warming up ? I realised too rich pilot screws set at OEM so two & three quarters of a turn out it runs ok now don't need choke to start either bike has a K & N filter.
I still get a slight hesitation around 2000rpm otherwise it pulls like a train I'm considering a dyno jet kit
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oberonspacefruit

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Re: CARBURETTOR Problems In Low RPMs
« Reply #37 on: 07 October 2016, 02:27:24 PM »
If you do end up getting the ngk spark plug ends, dont get the angled ones as theyre not long enough to comfortably pop out of the top of the rocker cover so you hace to turn them sideways, which is hard if youve clipped some off your leads. go for the straight ones, they will fit better.

darrsi

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Re: CARBURETTOR Problems In Low RPMs
« Reply #38 on: 07 October 2016, 05:04:23 PM »
On my bike I had carb problems blocked green/brown crust after cleaning them still not starting or firing ?
Found out O rings knakerd thus flooding tried a 2nd set that was on donor bike it ran but not brilliant but it ran,so I took them apart but not the best condition the screws only just came out of the float bowls ! so as my originals are clean I swapped the seats & O rings.


Bike started ran but died after warming up ? I realised too rich pilot screws set at OEM so two & three quarters of a turn out it runs ok now don't need choke to start either bike has a K & N filter.
I still get a slight hesitation around 2000rpm otherwise it pulls like a train I'm considering a dyno jet kit

They don't need a dyno jet kit.
Been there, done that, had to change back to OEM for it to run right again.
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bikemad

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Re: CARBURETTOR Problems In Low RPMs
« Reply #39 on: 08 October 2016, 12:21:42 AM »
They don't need a dyno jet kit.
Been there, done that, had to change back to OEM for it to run right again.


Ok thanks I'll forget that then
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darrsi

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Re: CARBURETTOR Problems In Low RPMs
« Reply #40 on: 08 October 2016, 08:28:14 AM »
They don't need a dyno jet kit.
Been there, done that, had to change back to OEM for it to run right again.


Ok thanks I'll forget that then


Wasn't just on a whim, it was done properly at a Dyno Tuning place, but the bike just didn't feel great at all, so took it back and he put OEM jets in and all was fine again after that.
These bikes run rich with petrol as the norm anyway, so what they actually like is a bit more air which is why the K&N air filter is a simple but very effective mod to do.
Don't expect miracles or bundles of extra BHP, but what you will get is a much sharper throttle response and a better general all round feel to the bike.
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Paul

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Re: CARBURETTOR Problems In Low RPMs
« Reply #41 on: 08 October 2016, 10:52:53 AM »

Just a thought: Is your fuel tank breather partially blocked?