Engine response at low revs.

**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

Originally Posted by mossy1200

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

Originally Posted by 98tls

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?

Originally Posted by gwigs

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

Originally Posted by sponge

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

Originally Posted by mossy1200

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

Originally Posted by mossy1200

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!

**mossy1200** · 29th July 2009, 23:07

Originally Posted by sponge

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 ?