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sponge
29th July 2009, 22:12
Hey, Im new here so excuse my noobyness.

My bike has a problem, It's responsiveness at low revs is terrible(-3000) . When i say terrible I mean I rev the bike (Fully warm) and i get a chug chug chug and then it tears to life after a couple of seconds. There is a reasonable amout of smoke.
Past 3000 revs the bike is fully responsive, and the exhaust fumes are clear.

What is the problem, I was thinking the mixture was too rich

What do you guys think?

Cheers,

Sponge.

mossy1200
29th July 2009, 22:16
Mixture does very bottom end or the choke is partially on.Could be blocked air jet.Float level could be to high.Idle jets may be to large.
Have you been playing around?
Is headers good condition without leaks.

sponge
29th July 2009, 22:30
Mixture does very bottom end or the choke is partially on.Could be blocked air jet.Float level could be to high.Idle jets may be to large.
Have you been playing around?
Is headers good condition without leaks.

I checked the choke and it is fully off.
I will clean the air jets.
I am unsure about the float level, But ill do a bit of looking around and hopefully work that out tomorrow.
How can i check if the jets are too large, And what can i do about that?
Headers looked okay from the outside, I didn't really want to do much playing around because of fears i would mess something up :)

I have been playing around, At first i thought the throttle cable must be lose, And it wasn't. And then i played with the mixture, And went a half turn either way, Testing as i went and found no difference.

98tls
29th July 2009, 22:34
Have you had the plugs out?if so?Sounds like flooding to me so far.

gwigs
29th July 2009, 22:36
Dont forget to check your air filter, if its blocked it will run rich..

sponge
29th July 2009, 22:40
Have you had the plugs out?if so?Sounds like flooding to me so far.

that's what i thought it was too, Ill take them out tomorrow and have a look.
What am i looking for? :)


Dont forget to check your air filter, if its blocked it will run rich..

I cleaned it and checked all the intake system, I cleaned it and dried it but nothing improved :(

Mumbles
29th July 2009, 22:40
There is a reasonable amout of smoke.
.
What colour is the smoke?
From my ZXR manual

Black smoke could be
Air cleaner clogged - Main jet to large or loose - choke stuck - inlet needle held off needle seat

Brown Smoke
Main jet to small or clogged - fuel flow insufficient - air cleaner poorley sealed or not installed carburetor intake manifolds loose

sponge
29th July 2009, 22:42
The smoke is grey, With a small tinge of blue. Its not very dark.

mossy1200
29th July 2009, 22:47
It seems like if the fualt occurred prior to any fiddling and sudenly that is likely to be float related.perhaps a float needle is no shutting off when the float is up.this will flood a bowl.At higher revs you maybe using gas fast enough for the bowl not to over fill.it would mean maybe a small bit of crap.
if its this i would look at a new fuel filter.
Assume you still have fuel filter and someone hasnt removed it.Older bikes often have rusty inner tank and a fleck of rust can cause float needle worries or blocked air jets.
Did you run very low of gas prior to problems starting or even run out recently.

sponge
29th July 2009, 22:50
It seems like if the fualt occured prior to any fiddling and sudenly that is likely to be float related.perhaps a float needle is no shutting off when the float is up.this will flood a bowl.At higher revs you maybe using gas fast enough for the bowl not to over fill.it would mean maybe a small bit of crap.
if its this i would look at a new fuel filter.
Assume you still have fuel filter and someone hasnt removed it.Older bikes often have rusty inner tank and a fleck of rust can cause float needle worries or blocked air jets.
Did you run very low of gas prior to problems starting or even run out recently.
Yes, I had to switch to reserve fuel just before this started happening, So i need to replace my fuel filter, and clean the float?

98tls
29th July 2009, 22:51
It seems like if the fualt occurred prior to any fiddling and sudenly that is likely to be float related.perhaps a float needle is no shutting off when the float is up.this will flood a bowl.At higher revs you maybe using gas fast enough for the bowl not to over fill.it would mean maybe a small bit of crap.
if its this i would look at a new fuel filter.
Assume you still have fuel filter and someone hasnt removed it.Older bikes often have rusty inner tank and a fleck of rust can cause float needle worries or blocked air jets.
Did you run very low of gas prior to problems starting or even run out recently. Methinks from his prior post youve hit nail on head mate.Well done.

sponge
29th July 2009, 22:56
Cheers everybody, thanks for the help! :D

mossy1200
29th July 2009, 23:07
Yes, I had to switch to reserve fuel just before this started happening, So i need to replace my fuel filter, and clean the float?your float will move a valve upwards.This is what shuts off the incoming fuel.be very carefull not to bend the thin metal that supports the needle as this will adjust the float level which you dont want to do.
Most systems will involve you removing a pin which let the float drop off.
there is normally nothing stopping this pin from coming out but when the bowl is fitted it cant come out.
The needle is normally hex shaped and about 4mm wide.you will be able to see the bottom of it attaching with thin wire arround the float tab.
The top is like a sharp pencil(this is the part you cant see).When you carefully move float up and down you will see how it works as it is just a shut off valve.It is likely to be small amount of crap stuck to the needle or seat(area that it seals against).

Just be carefull and take your time.Give yourself a clean work area so you dont lose any of the small parts.Dont try improvising with tools.If you dont have the tools get a mate who has good collection come around.
Dont refit the original bowl screws.Take one out and go get allen key replacements.If the screws are stuck i use side cuters pointed down at screw to nip and crack(get them loose)then screwdriver.
Bowl screws are made of butter extract.

Ultrasonic2
10th December 2010, 07:27
i would love to PM Sponge but i don't have the rights

Sponge did you fix this issues cos i think i have the same problem Also did you fix it your self ?

avgas
10th December 2010, 07:33
How the hell do you fuck up a brand new bikes mix?

If it aint broke......

MSTRS
10th December 2010, 07:54
How the hell do you fuck up a brand new bikes mix?

If it aint broke......

2009 post...2010 bike. Do you think OP just might have updated his bike in the interim?:sherlock::hitcher:

avgas
10th December 2010, 08:35
2009 post...2010 bike. Do you think OP just might have updated his bike in the interim?:sherlock::hitcher:
Too True
So what was the original bike?

MSTRS
10th December 2010, 10:47
Pass. I'm not THAT clever...

Flip
10th December 2010, 13:52
Sounds to me like there is a small bit of crap sitting under a neddle valve on a float bowl.

What usually clears this is turning off the petrol and running the bike right out of gas, then turn the gas on the the crap is pushed into the float chamber.

But then WTF would I know.

Ultrasonic2
10th December 2010, 15:05
im not the op but i have a 20 year old bike..

Im gonna have a go at dismantlementing the crabs im sure their will be some blockage in there somewhere. im pretty nervous about the process though. cos if i brake it i can't get to work

MSTRS
10th December 2010, 15:28
im not the op but i have a 20 year old bike..

Im gonna have a go at dismantlementing the crabs im sure their will be some blockage in there somewhere. im pretty nervous about the process though. cos if i brake it i can't get to work

Um - dare I say it? Leave them the fuck alone. Carbs should not be touched if you know nothing about them. That way lies tears.
Someone who does know can surely help you?

avgas
10th December 2010, 15:30
im not the op but i have a 20 year old bike..

Im gonna have a go at dismantlementing the crabs im sure their will be some blockage in there somewhere. im pretty nervous about the process though. cos if i brake it i can't get to work
If your happen to have an ultrasonic (excuse the pun) cleaner.....put (a safe) solvent in it and sit the carb in it.......worth gold

Flip
10th December 2010, 15:53
Also drain the float bowls, some times it works wonders.

Ultrasonic2
10th December 2010, 19:06
Well i have the CARBs of thank god ( Seriously ) . And well i may have already found the problem. One of the slide carb covers only had one of the 4 bolts holding the cover on !

Since i have them out i'll try and keep going to see if there are any blockages which is what i thought the issue. i'm gonna do a little blue printing too.

By the way i have a 1992 ZXR 250

Ultrasonic2
11th December 2010, 13:36
right carbs out and back in again. There were no blockages at all, which i guess is a good thing.

Went for a ride and it seems the issue hasn't be resolved :facepalm:

i also made a mistake reasmbling the throttle so it looks like im gonna spend tomorrow taking it apart again. mybe i can just swap the cables around in the throttle instead.:facepalm:

specter
11th December 2010, 20:58
uhh if hes talking about the ninja chugging it could just be the lack of engine torque.
depends on the type of chugging.. is it full on shaking the bike (carb problem) or just the engine struggling with a 6th gear acceleration at 30-40k's?

Ultrasonic2
12th December 2010, 07:16
uhh if hes talking about the ninja chugging it could just be the lack of engine torque.
depends on the type of chugging.. is it full on shaking the bike (carb problem) or just the engine struggling with a 6th gear acceleration at 30-40k's?

Well mine will chug in first great below 6,000 but not all the time . Also below 10,000 if i pull the throttle open it hesitates.
The problem is wores the hotter the bike gets. Im sure if i run the bike with the choke on the problems isn't as bad. But with the choke out the bike is much slow up high.

I've done a bit more resersh and im gonna loosen the pilot screw to let more fuel in. there was a post saying doing so made a massive difference to their bike ! So im gonna give that a shot . and to be honest a lean condition kinda makes sence so more fuel it is :yes:
Dose anyone know if i add more fuel via the pilot screw withh this alos add more full to the top end 12,000 plus ?

MSTRS
12th December 2010, 09:09
The pilot screw sets the mixture at low revs/idle. Once the throttle is twisted more, the needles clear more of the main jets to increase fueling. You do know that you have 4 carbs? The problem may be in any or all of them.
Sometimes the symptoms you describe can be caused by a coil breaking down under load, esp once warm.
Or even just worn plugs.

racefactory
12th December 2010, 10:08
I am also fucking astounded as to how you do this to a new bike? It is beyond me.

Ultrasonic2
12th December 2010, 11:46
I am also fucking astounded as to how you do this to a new bike? It is beyond me.

As, has been said before the bike is 20 years old not new ?

oh and i was refering to your post here

from here

http://www.kiwibiker.co.nz/forums/showthread.php/120023-Balancing-the-carbs

You will find the trouble is not getting hold of thevacuum gauge, but getting to the fucking adjusting screws!! You need a fucking expensive 90 degree bevel screwdriver for your ZXR250. I suggest you first find one of those!

Another suggestion whilst you are working on the carbs is to adjust the pilot jet screws, it really makes a difference. My bike had an unsteady idle and hanged after blipping throttle, slowly returning down. I suspect a lot of ZXR's are like this... running lean on the pilot circuits. I just used trial and error taking off the carbs, adjusting them, refitting and eventually went from to 2.5 turns out (factory setting) to 3.5 (richer) and its got a nice pulsing idle and the revs drop nicely now!

Ultrasonic2
12th December 2010, 11:49
The pilot screw sets the mixture at low revs/idle. Once the throttle is twisted more, the needles clear more of the main jets to increase fueling. You do know that you have 4 carbs? The problem may be in any or all of them.
Sometimes the symptoms you describe can be caused by a coil breaking down under load, esp once warm.
Or even just worn plugs.

yes i know there are four carbs i've already had them apart .

It really doesn't feel like and ignition issue as i've had that kind of problem before and it feels very different. but is could be an ignition issue all the same.

UPDATE

interstingly the screws were set between 3 and 3-1/4 turns already. i set them to 3.5 anyway. i really want to try them at the stock 2.5 now. arr it never ends

Ultrasonic2
13th December 2010, 07:51
Well fuelling seems better now . that could because of

Replacing the missing slid cover bolts
Increasing the turns on the pilot screws
Changing to 91 from bp 98

The chugging is still there, however im wondering if that issue has nothing to do with the fuelling but to do with the heavily worn chain. ( which will be replaced soon )

MSTRS
13th December 2010, 08:14
Why would a badly worn chain made the engine 'chug'? Smooth rolling and gear changing, yes, but not how the actual motor runs.
No - if the engine is chugging/not running smoothly, then you have one or more cylinders not working to full capacity. That can be fuel, compression or electrics...nothing else.

Ultrasonic2
15th December 2010, 20:25
right after a few days of comuting and well i think really nothing has changed :-(

I took her apart again and changed the pilot screws back to the stock 2.5 turns and well the choke is much less sensatice now which is good but it likes to idle at 3,000 rpm for a while before settling down. i went for a long ride ( not a commute ) and well putting the screws back to 2.5 has REALLY reduced the bottom end power . Chugging hasn't really been effected. But i need to do some comuting before i call anything. At this stage im gonna turn the screws back up . It does make me wounder if it's running lean up high too .. need a dyno and a lamda for that i guess.

MSTRS
16th December 2010, 07:39
... it likes to idle at 3,000 rpm for a while before settling down. ...

That is a sign of either an air leak on the engine side of the carbs ...
OR one or more of the slides is hanging ...
OR one or more of the needles is not seating well...

Ultrasonic2
16th December 2010, 17:09
Yeah man at 2.5 turns the bike really sux. will put back to 3.5 soon

oh and the idle at 3,000 only happend since i changed the turns

MSTRS
16th December 2010, 17:29
How many turns out does the manual say?
See - if 2.5 is right, then you have an air leak. By increasing to 3.5 turns, you are adding fuel. Which somewhat offsets the extra air.

Ultrasonic2
16th December 2010, 17:59
How many turns out does the manual say?
See - if 2.5 is right, then you have an air leak. By increasing to 3.5 turns, you are adding fuel. Which somewhat offsets the extra air.

Manual says 2.5 but the bike is not stock

i pretty much proved Trademe900's comments below to be connect


Another suggestion whilst you are working on the carbs is to adjust the pilot jet screws, it really makes a difference. My bike had an unsteady idle and hanged after blipping throttle, slowly returning down. I suspect a lot of ZXR's are like this... running lean on the pilot circuits. I just used trial and error taking off the carbs, adjusting them, refitting and eventually went from to 2.5 turns out (factory setting) to 3.5 (richer) and its got a nice pulsing idle and the revs drop nicely now!

MSTRS
17th December 2010, 07:39
I will guarantee they didn't come from the factory like that. In what way is your's not stock?

Ultrasonic2
17th December 2010, 10:49
Different headers and muffler and air cleaner

O i have discovered that the chuging only happens around 4,000 rpm .

MSTRS
17th December 2010, 11:59
OK. So you have increased breathing...ie more flow in and out. That necessitates increasing fueling so it doesn't run lean. Adding an extra turn to the pilot screws would sort it for idling. But what about the main jets? Or the needle settings?
Perhaps you could try lifting each needle by one groove? See what happens to that flat spot.