Carburetor issues CBR125RS6

Bezzaboy1234 · 30 Jun 2012 at 14:07

Hi peeps,

So I have been having problems with my carb for the past month now, And thought i'd share my woes with you guys and see if anyone could shed some light on my problem/questions,

So basically my bike was stuttering constantly, at first it wouldnt start but some fiddling of the idle screw and it was working, I was told by a few people it might be the spark plug, I took the old one out and it looked fine to me but I had a spare lying around so I chucked it in, no difference at all,

Took it to the garage and was told it was probably the carb, We stripped it and gave the carb a good clean, the only thing wrong was a screw at the bottom that was stuck in there, wouldn't come out no matter what, So I gave it to a guy I knew who could drill it out for me,

Feeling pretty glum about having to get chauffer driven everywhere I hopped on a well known auction site to see if I could find the screw or possibly a new carb, and managed to grab a new carb for £20,

Now my question(s) are,

1) Do you think I should use the new carb or the old one, the old one was cosmetically looking abit shabby, and this new one appears to be good.
2) What is this screw located in the pic for? this is the screw that would not come out, does anyone know what it actually does? I cannot seem to get it out of the new carb either along with some other stubborn screws :/

Thanks guys

Screw from old carb:

Picture of a random carb, not either of mine, just need to know what this screw does:

Katoom · 30 Jun 2012 at 14:23

Looks like the mixture (air) screw. Usually turn out to lean the mixture, in to richen it.

Bezzaboy1234 · 30 Jun 2012 at 15:01

Ah, Well thats the screw that simply will not budge, Wont move even a tiny bit, I've had enough trying to heat it up and get it out as it just won't move.

Wondering whether I should take it to my local garage and ask them to sort it out =/

thumperslaw · 30 Jun 2012 at 15:11

I would use plus-gas and some heat

After that should move. If not however leave soaking for 24-hours then try again

As for cleaning then sonic bath is great for making them look new again

wazza300 · 30 Jun 2012 at 15:20

just stick the new carb on as it is,i wouldnt mess if you dont need to,it might run fine just boltaing new carb straight on

Bezzaboy1234 · 30 Jun 2012 at 15:23

Don't have any of that, Will have to look around and see if I can get some,

Sonic bath? I Don't think I have access to one of those.

I don't really have anything that can apply Heat, I tried a small hand held chef blow torch thing but it has no gas,

I think I'll leave it for today as the head is starting to get worn and I don't want to completely lose it, May just end up asking the garage to do it as this is just more hassle than its worth. :/

thumperslaw · 30 Jun 2012 at 16:30

Bezzaboy1234 said:
Don't have any of that, Will have to look around and see if I can get some,

Sonic bath? I Don't think I have access to one of those.

I don't really have anything that can apply Heat, I tried a small hand held chef blow torch thing but it has no gas,

I think I'll leave it for today as the head is starting to get worn and I don't want to completely lose it, May just end up asking the garage to do it as this is just more hassle than its worth. :/

Plus-gas can get that off internet
Sonic bath will bring that up spotless and clean the jets etc...

Send it to me i'll get that out for you
just cover p&p

.one. · 30 Jun 2012 at 17:44

Just use the new carb no need to remove the mixture screw all you will be doing is possibly adding a new problem, mixtures can be very awkward even if set to recommended setting as for the previous carb there are many other variables you can address before ******* with the mixture.

Bezzaboy1234 · 30 Jun 2012 at 18:19

Aren't you supposed to be able to adjust the mixture screw? thats what was causing my bike to stutter..

Bezzaboy1234 · 14 Jul 2012 at 17:00

Ok, So quick update, Got the new screw, its the Air Filter screw. Put it in, re-assemble the bike, still the same problem, Tightened up about half way, then proceeded to tighten it, and loosen it, But nothing really changed,

Does anyone know what I can do? Really stuck on whats wrong

famas · 14 Jul 2012 at 17:17

I'd check your fuel line filters to make sure there clean and not clogged up.

the screw you have taken out is the pilot screw, on most carbs there should be a rubber o-ring and washer after the spring as well, do you have a workshop manual to confirm this?

this link might help you set your pilot screw.
http://www.exriders.com/archive/topic/229923-1.html

Katoom · 14 Jul 2012 at 17:17

Try setting it between 1 and 2 turns out from fully seated and go from there.

Even after you set it though, it still might not be the cause of your problem.

wazza300 · 15 Jul 2012 at 17:24

have you been riding it in heavy rain? could be plug cap/lead shorting spray with wd40 inside and out

could try a hotter plug?

Bezzaboy1234 · 15 Jul 2012 at 21:15

famas said:
I'd check your fuel line filters to make sure there clean and not clogged up.

the screw you have taken out is the pilot screw, on most carbs there should be a rubber o-ring and washer after the spring as well, do you have a workshop manual to confirm this?

this link might help you set your pilot screw.
http://www.exriders.com/archive/topic/229923-1.html

Okay, I will try that next,

Yeah It does have a spring and a little washer and o-ring.

Thanks for that link, I will try that too

Bezzaboy1234 · 15 Jul 2012 at 21:16

wazza300 said:
have you been riding it in heavy rain? could be plug cap/lead shorting spray with wd40 inside and out

could try a hotter plug?

No not really, I tend to stay away from the rain, This started happening when it was fairly dry and sunny.

I don't even know what a plug cap/lead is,

Or a hotter plug? could you please explain

atpbx · 16 Jul 2012 at 13:06

Bezzaboy1234 said:
No not really, I tend to stay away from the rain, This started happening when it was fairly dry and sunny.

I don't even know what a plug cap/lead is,

Or a hotter plug? could you please explain

Unscrew the spark plug, take a picture of the end that was in the engine and post it on here.

I suspect we will see its burnt to buggery.

timmy222 · 16 Jul 2012 at 16:32

Thats the air mixture screw

Which effects the first 1/4 of the throttle range.
What you need to do is screw it right in, then screw it out 1 1/2 turns.
Run the bike till it is up to working temp.
Then set the tick over to about 2000rpm with the idler screw.
Move the air mixture screw slowly in and out until you find the spot where the engine starts to run faster - this is the spot to leave the air mixture screw.
Adjust tick over back to level you like.

Bezzaboy1234 · 17 Jul 2012 at 17:18

atpbx said:
Unscrew the spark plug, take a picture of the end that was in the engine and post it on here.

I suspect we will see its burnt to buggery.

When this first started happening I took the spark plug out and it was dirty, Replaced it with a new one the day after.

Bezzaboy1234 · 17 Jul 2012 at 17:21

Quick update:

Everyone has been saying check the airfilter, and I did, It looks like a really dirty bit of cardboard, So I have ordered a replacement filter today, Hopefully that will fix it,

and to Timmy222,

Thanks, I was wondering which screw it was, I tried that and it has been abit more stable, but still juttery, hopefully it is just the air filter, I can pop it in, do some adjustments and hopefully i'll be back after almost a month of no riding

Fingers crossed

.one. · 17 Jul 2012 at 20:02

Bezzaboy1234 said:
Quick update:

Everyone has been saying check the airfilter, and I did, It looks like a really dirty bit of cardboard, So I have ordered a replacement filter today, Hopefully that will fix it,

You do not need to wait for the air filter to arrive just try it with out the filter it will run a little lean but you will notice if the stuttering has stopped or not.