how to set up your carbs

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ross46
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how to set up your carbs

Post by ross46 » Wed Jul 31, 2013 10:29 am

Ok, the idea of this post is to show people how to set up their carbs. all the specs i will be using are standard out of the manual, though i will say at what points how to richen or lean out each part of the carb circuit. Please use in conjunction with the manuals http://www.zxrworld.co.uk/zxr400/manual.html and Banners excellent carb cleaning guide viewtopic.php?f=115&t=14018

-This is a guide ONLY! I will not be held responsible for any damage caused to your bike by following this guide. It is intended to show you the basics of how to set up your carbs. if you do not feel confident take them or the bike to a mechanic. I will try to say where there are advisable methods or risk of damage.

Right onto the actual guide-

Tools;
-Flathead screwdriver (may need a couple of sizes to avoid damage, though i did with one)
-Phillips screwdriver (The bolts used on the carbs are JIS, it is advisable to get a JIS screwdriver to avoid damage of the bolts)
-Vernier caliper or ruler
-10mm spanner

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Other parts you may need to change;
-Main jets- The specific size will depend on what is already being used
-M3 washers- these can be used to richen the needles unless you have Dynojet needles which have an E-clip
-you may also need to replace certain seals or the float valve, float valves can be purchased from cradley kawasaki or online. seal kits can be bought off here from maelstrom viewtopic.php?f=115&t=14830 i can vouch for these seals, they are very high quality and i recommend changing the seals if you want your carbs perfect.

i am presuming that you already have the carbs off, disconnected and drained of fuel

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To change the needle height you will need to remove the top black vacuum cover by removing these phillips screws

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once you have removed this cover this is what you should see

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carefully lift out the slide by removing the edge of the rubber out of its groove, being careful not to damage it (there should be a spring resting in here like in the picture below, but i remove the spring first, but you can do it either way)

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once this is removed this is what you should have

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check the rubber for any damage, tears etc.

remove the spring, the plastic bit that covers the needle may come out with it

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you should now have a slide with a needle resting inside it

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now turn it carefully upside down to remove the needle, the needle may have some washers on it as this is used to richen the midrange (by putting on more washers you raise the needle height therefore allowing more fuel through)

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to richen the midrange add an m3 washer, to lean out remove one (if yours has washers to begin with, if not you will have to change the main jet to a smaller size)

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check all of the needles for damage and that they are all set at the same height

to change the pilot circuit you will need to turn this screw using a flathead screwdriver, only do this by 1/8 turn at a time as the pilot circuit is sensitive to changes ( turn in to richen, turn out to lean) standard for L models is between 1 1/2 and 1/3/4 from a fully clockwise seated position (lightly seated!)

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now to get to the floats, main jet and pilot jet you will need to remove the float bowl. to do this you will need to remove these phillips screws

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this is what you should see with the float bowl removed

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this is your main jet, to change simply unscrew with a flathead screwdriver, (be careful when removing the main jet and use the correct size screwdriver to avoid damaging the soft brass) and screw the new one in. the needle jet holder may come out with it, if it does simply use a 10mm spanner to hold it while you unscrew the main jet.

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standard size main jets for L models are 90, with 92, 95, 98 and 100 also used, though anything may be used depending on your bike

to richen top end put in a larger main jet, to lean out, put in a smaller main jet (larger and smaller refer to the numbers on the main jet)

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this is your pilot jet, it is very rare that this will need to be changed though may need to be removed for cleaning. to remove simply unscrew with a flathead screwdriver

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this is what it looks like when removed

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now to check your float height rest the carbs upside down like so

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you want the float to be just resting, gently tap it down with your finger and it should spring back up

now using either a ruler or vernier, measure from the gasket surface to the highest point on the float (as you can see this is around 14mm)

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to change the float height (standard for L models is 11mm +- 2mm) remove this screw (float height can be changed without removal but this allows you to check the condition of the rubber tip for damage, if there is any tears or indentations on the rubber tip then replace)

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then you can remove the assembly

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to change the float height you will need to carefully bend this metal tang, it doesnt need much to change the float height (the float can be used to change the fuelling altough this is not normally required, but just incase, to richen, decrease the height of the float e.g. from 11mm to 10mm and to lean increase the float height e.g. 11mm to 12mm)

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now put the float back in with the float valve spring in its hole and put the phillips screw back in. now re-measure the float height again as outlined before, remeber you are aiming for 11mm for standard settings.

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put the float bowl back on by re inserting the four Philips screws

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repeat for all 4 carbs and floats

reassemble the carbs and you should have a set of carbs set back to standard or changed to suit your bikes fuelling needs. after this balance the carbs (there is a guide in the workshop section on the main site)

for clearness, standard settings for L model are
main jet- 90 (92, 95, 98 and 100 also used)
needle height- no washers
float height- 11mm +-2mm
pilot jet- 35
pilot screws- 1 1/2-1 3/4 turn from the clockwise seated position

i hope this helps, if you have any questions or suggestions please ask/say

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Re: how to set up your carbs

Post by banner001 » Wed Jul 31, 2013 12:24 pm

good guide, but please put in a warning that ALL the crossheads on these bikes are JIS, not phillips, and if you use a phillips you WILL damage them - you can see that yours are showing cam-out damage.

the best thing you can do to avoid further damage is to replace all the screws with small allen bolts.
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Re: how to set up your carbs

Post by ross46 » Wed Jul 31, 2013 12:44 pm

That's my spare set, in the box for you to take and sonicate there is for the float bowls but I can't find any for the top ones, and it says to use a JIS but most people dont have them so ive advised but it can be done without just very carefully, what do you think of the guide?

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Re: how to set up your carbs

Post by banner001 » Wed Jul 31, 2013 2:27 pm

im buying some small allen bolts for my race bike carbs, ill let you know if they fit - i know the top ones are sleeved, but the tops are pretty secure on their own, i dont think the sleeve is really all that necessary - ill let you know how it goes :D

i would put some washers over the actual needle to show people where to go, other than that, maybe retake a few pictures in focus? :D
UK ZXR400 L3 (1993) - Fully restored and on the roads, my green beast!
JPN ZXR250 A2 (1990) - Revs to 19,200rpm... 'nuff said :smt003

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Re: how to set up your carbs

Post by banner001 » Wed Jul 31, 2013 2:30 pm

edit - mention that to richen the float bend the tang towards you (or away from the carb body), and to lean it bend it away from you (i.e. towards the carb body)
UK ZXR400 L3 (1993) - Fully restored and on the roads, my green beast!
JPN ZXR250 A2 (1990) - Revs to 19,200rpm... 'nuff said :smt003

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Re: how to set up your carbs

Post by CrazyChris » Fri Aug 02, 2013 2:54 pm

Nice write up. One question though. I measure my floats exactly the same but if I set them any less than 17mm fuel leaks out of the overflows. Got new floats, needle and seats and everything. And yes, floats are installed correctly. Any ideas?

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Re: how to set up your carbs

Post by ross46 » Fri Aug 02, 2013 3:46 pm

Have you got the carbs the right way up so that the float is only just resting on the needle? Are the little filters in the carbs blocked? Are the gloats cracked? At 17mm they would almost be touching the bottom, check that the seals are all in good condition

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Re: how to set up your carbs

Post by CrazyChris » Fri Aug 02, 2013 3:55 pm

Just had the carbs off now to double check. Its exactly like your pictures just instead of 11 mine is 18mm. Filters are good. Gave them a good clean just to be sure. Floats are secondhand but checked them as well and the are brilliant.

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Re: how to set up your carbs

Post by banner001 » Fri Aug 02, 2013 7:20 pm

im guessing the zx400 carbs are slightly different to the zxr400?
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Re: how to set up your carbs

Post by CrazyChris » Fri Aug 02, 2013 7:24 pm

Same make and model as the manual. But might be true. Thanks for the advise though

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Re: how to set up your carbs

Post by ross46 » Mon Aug 05, 2013 4:23 pm

Right, your lucky as yesterday I had to be taken to hospital because of my back, so atm im lying in bed, I've been searching and calling around (side note, dynojet mains from them £1.64 each + vat) from what i can find you are running cvk d30 carbs which is the same on the zxr250, float heights are supposed to be 13mm +/- 2mm, hope this helps

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Re: how to set up your carbs

Post by CrazyChris » Mon Aug 05, 2013 4:30 pm

Thank you very much Ross. Highly appreciate it. Hope your back heals up soon. Know that pain myself

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Re: how to set up your carbs

Post by ross46 » Mon Aug 05, 2013 5:19 pm

Been two and a half years, copius amounts of painkillers and having an ambulance called up, fed up of it really

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Re: how to set up your carbs

Post by maelstrom » Wed Aug 07, 2013 12:48 am

Hey Ross, are there some green things missing from these pics? :smt003
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Carb kits in viton
http://litetek.co

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Re: how to set up your carbs

Post by ross46 » Wed Aug 07, 2013 11:01 am

Haha, yes they are, when I got those seals I was so giddy I ripped the carbs off the bike straight away and fitted them, these are my spare set of carbs im doing this on so didn't want to put the green gold on these, but I will be doing a tear down of my bike and they will be in the carbs that are in that as they are amazing quality, and I put 115 thb in your PayPa, im guessing I have permission to use your images? :smt002

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