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If a spark plug change and air filter replacement do not have the desired effect on your bikes performance, the three golden steps you need to follow to get your bike running smooth are

- Clean your Carbs
- Set the Float Heights
- Get them Balanced

For Cleaning the carbs

Items needed

1. Aerosol Carb Spray Cleaner
2. Clean Petrol in a Plastic “Squeezy” type bottle
3. compressed air (if available)
4. new screws for the top and bottom carb covers (check for correct length)
5. new fuel filter
6. soft brush and toothbrush


Tools needed

1. Very long (12 inch) Phillips screwdriver
2. Stubby flat and Phillips screwdriver
3. 8,10 and 12 mm spanners (ring preferred), and 2 fixed 10 mm spanners
4. pliers (to undo the clamps holding the fuel pipes)



Getting to the Carbs

1. Disconnect the fuel / vacuum pipes from the tank
2. take off the tank after making sure that the tap is off and place it gently on a discarded car tyre – the edge of the tank will rest on the sidewalls of the tyre while the tap can hang safely in the middle
3. undo the air filter box from the carbs
4. loosen the screws holding the carbs to the manifold – you’ll need the long Phillips head screwdriver for this.
5. pull the carbs out firmly but gently (this is the first hurdle – get ready for some bruised knuckles)
6. undo the accelerator and choke cables with two 10mm fixed spanners and screwdriver (choke cable) making note how they should go back in.
7. the carbs should be free now – wash them from the outside liberally with petrol and a soft brush and toothbrush
8. tap each screw on the top and bottom of the carb gently with a hammer
9. mark the top and bottom of each carb with numbers from 1 to 4 to ensure that you don’t mix the internals / covers up.


Opening Process

1. Open the screws from the bottom of each carb – do this one at a time (this is the second hurdle – have someone experienced at hand and an impact driver if possible) make sure you don’t “round” the heads of the screw.
2. take the cover off and place the screws in it
3. gently slide out and remove the float pin, needle and float and place them in the bowl
4. with the correct ring spanner (8mm I think) and flat screwdriver undo each jet gently !!! the metal is very soft !!! – place it with the respective carb cover
5. repeat this over all 4 carbs
6. turn the carbs over
7. maintain the same sequence – don’t turn it around else you will interchange the order – ie . from left to right (look at your earlier number markings for a confirmation)
8. undo the screws
9. place the top covers with the respective bottom covers
10. remove the diaphram, needle and spring and place each with the respective top cover.
11. wash the carb bodies liberally with petrol, a small paint brush and toothbrush. Spray carb cleaner everywhere very liberally – let them stand for a while – and wash once more with clean petrol
12. wash each jet with carb cleaner and petrol, blow air through them but don’t insert any pins or sharp objects through them – this will damage them.


Closing up


1. fit the jets back and tighten them gently – not too tight (use your brain here – not your muscles)
2. wash the floats, pins, etc with carb cleaner and clean petrol and fit it back on carefully – refer to Shadows manual for specifications if you want to be a perfectionist (I do it just by sight cause I don’t need performance in India)
3. fit the bottom on with new screws and gaskets if possible.
4. wash the carb tops, diaphrams (don’t pierce them by mistake) and springs and fit them back together.
5. its dicey getting the spring back in the MC-17 and 19
6. make sure that the diaphram is not kinked or sticking out of the cover at any place.
7. make a final check to see if all the screws are in – nice and tight.
8. push each slide up gently and release – they should smoothly slide back into place
9. fit the carbs in the manifold – apply a light layer of grease and slide them in after connecting the throttle cables, choke.
10. tighten the clamp clips, connect the fuel pipes with a new filter
11. fit the air filter[hr]

Thanks to RPM's for the write up and pictures

First, some decent pics of the carbs (finally!)
(you may want to set your screen res to 1024x768 or higher for viewing this)

This next pic is of the rear of the carbs, if you could get your head where the rear shock absorber is.
Simply undo the clamps indicated to get the carbs off.
Note I have replaced the crappy screws with torx heads as the heads do not stuff up as easily.
Also I wrapped teflon tape around the threads to make it easier to undo them.


This is basically everything dismantled,
but the intake trumpets and plastic bit in the above photo are not shown.
The perspective is if you had your head where the engine is,
looking back up at the carbs.


This is a pic of the vacuum chamber and all associated parts:


This is a pic of the float chamber and all associated parts.
The carb on the left still has the cover on,
the next one is with all the parts as they will look once you undo the cover,
3rd +4th carb from the right is with the jets taken out:


Last pic is where the two jets + pilot (air/fuel) screw goes.
I noticed the pilot screw and drain screws all had anti-sieze compund on them,
so I assembled them with some more of that stuff...


[br]Okay, I did this, I'm a defintite noob, here's what to avoid:
As mentioned previously, all the vaccum slide things got mixed up (what are they called anyway? the four black things that look like female contraceptives[?]), as I couldn't write on them. [B)]

Somehow, I managed to mix up the float bowl covers too,
despite the fact that they were all numbered properly.[:I]
Someone was talking to me when I assembled the carbs.
The worst part is I only figured this out when all the carbs were back on the bike, and the accelerator + choke cables were attached (and that took a while[B)]).
I peered into the bike and saw that all the float bowl drain screws were all pointing inwards!! "Oh fer chrize-sake" was my first thought.
I'm leaving it that way until I have to take them off again for whatever reason.[B)][B)] *shrugs*

EDIT: Oh yeah at about this point, a good jet of carby cleaner spray ricochet(ed) off the carbs and DIRECTLY INTO MY EYE![B)]
Fuck! You shut your eyelid really tightly by instinct & it feels like your eyeball is vaporising from the inside out. Run to the tap, flush my eye... omg I can still see![hyp]

The bad/good news is that there was one sticking vacuum slide thing
-- turned out to be a very tiny raised bur (sp?).
I fixed that myself with a bit of 1000 emery paper in less than a minute.[HB]

It took 4 to 5 attempts to get the hang of balancing the carbs.
This was because the 3rd balancing screw works the opposite way to the other two.[B)]

I spilled a load of mercury (three times) from the stoopid gauge trying to get rid of the "bubbles", and once the toxic shite ended up in my shoe of all places - and I only deduced that it ended up there after the entire bike was put back together, and I thought "Geez where'd all that mercury from the second spill go?
Kinda went near my trouser leg. Let's have a look in my shoe".
Sure enough it was in my foot for at least half an hour.[xx(]

I thought I did a good job of balancing the fourth or fifth time...
I go up the street and there appears to be a flat spot at roughly 6-8k.
I'm not too sure about this though, as I could only ride in peak hour and it was difficult to tell.
As soon as I hit the powerband the acceleration was decent enough.[^][:S] It idles better than before, but I think it could be even better.

EDIT: more photos of carbs here:
http://witchxx.hp.infoseek.co.jp/cbr250rr/cab02-10/sagyo3.htm
Dunno why his floats are so white...[:S]

 

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Sir K916!!! Im sure you'll get mad at me again! OMIT THE SIR! hehehe!!!

Thanks for this, Im now carefully studying the idling of my CB-1 which is similar to cbr400's engine.
 

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And with that,
MMmMM Carburettor... also I'm shit scared I'm going to break it..

Also when i do open it up, within the next 20-30 mins... does anyone want any newer reference photos of particular things because I can take high quality ones.
 

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Yep - can never have enough good images
 

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Discussion Starter #11
Shadow said:
K916 said:
................. refer to Shadow's manual for specifications ..................
Wow, that's still kicking arround...
And I thought It'd be forgotten...


-------------------------------------------------------------
Castrol 250rr
Never buddy - "you are always on my mind" :blush:
 

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anyone have 2 1/2 turns on all their pilot screws? i found mine to have 1 1/2 for the outer carbs, but 2 1/2 for the inners
 

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need to do this on the weekend... on the DRZ, so itll be 4x easyer :p
 

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Hey guys, I'm following through the tutorial and get stuck removing the carbs from the manifold. I have loosened 4 screws, but the diagram show loosening 8. Is that correct, cause the other 4 screws are impossible to get to as they are on the opposite site :(
 

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You just need to undo four, the ones that connect the boots to the manifold. When you pull the carbs off, the boots come with them.

As for getting the carbs/boots off, it takes a bit of man-handling; wiggle/rock the carbs back and forth, don't be afraid of some muscle, and they'll come off.
 

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you have to loosen 6 screws from the lhs and 2 from the right i think
or maybe its 3 and 1
you can't undo them all from one side

also +1 to what ride2fast said
they can be a bitch to take out just wiggle and pull
putting them back on is easy if you use rubber grease
 

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Hmmm, I think I have all the screws, probably just hasn't been removed in about 10 years. I guess I'll keep trying tomorrow :(
 

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OMG I think I just about gave myself a hernia trying to remove it. I have to sit on the bike to stop it from lifting off the ground :(

I have tried gently prying the rubber boot from the manifold and it gives a little (have only reach the outer ones so far). Is there something else I can try to get this off? It feels like the amount of force I am applying is going to damage something.
 

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I managed to get the bike started with the airbox off, and then oil started spraying out of the engine tube and went into the carbs. I have a feeling that was the problem all along. Checked the oil level and it's over the maximum... A bit confused because I was there when the guy changed the oil and I'm pretty sure he put the right amount in.
 
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