Carb dissassembly

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banner001
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Carb dissassembly

Post by banner001 »

Hi guys, bought myself a set of UK L5 32mm carbs so i can learn how to work on them - never took any apart before.

I have taken off the 4 black plastic covers (i think its a vacuum cover) and removed the jet needle. I have also removed the back of the fuel bowl and removed the main jet and the needle jet holder, i will remove the pilot jet tomorrow when i have got a thinner screwdriver.

My main questions are...
1. can you remove the main air jet and pilot air jet like on the H-model? I dont think you can, but if you could what would changing the sizes achieve?

2. can i now clean the carb assembly in a sonicator? i was going to use acetone/carb cleaner, but i dont know if the bits of plastic (like the fuel "rail" etc... will survive acetone/carb cleaner? I have not split the carb bank into individual carbs because i have been told it wil be very difficult to put them back together, is this correct and would they clean better if fully dissassembled.

3. do i need to remove anything else (like the pilot screw) to fully clean all parts of the carb?

4. the main jets have '116' stamped on them, i assume this is the size (i.e. L manual says #95installed at factory), but how do you know what size the a) 'jet needle' b) 'pilot jet' and c) 'needle jet holder' are? i dont seem to have any markings on mine.

5. my jet needle had a small clip on the 3rd indent from the tip of the needle, and had 3 shims on top, what should the stock settings be, cant find them in the manual/microfiche?

6. any other hints/tips you can give me?

7. thanks :smt003
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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banner001
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Re: Carb dissassembly

Post by banner001 »

managed to get the pilot jets out, they have the Kehnin 'K' and 35, so i guess they are the stock ones, but i still dont know about hte jet needle and the jet needle holder, i know that you can change the jet needles, not sure about the holder...but how can i ID mine, or is it a case of buying a new set so i know whats fitted, and go from there?
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: Carb dissassembly

Post by R P Corse »

will try and answer best as i can - carb's arent my strongest point, but then i got a bit confused with your questions - they are clear, im just thick! lol

1. yes you can, changing the sizes of the jets will increase/decrease fuel/air ratio.

2. honestly have no idea, but i dont see why not - worth asking people who work with the sonicator and see what they recommend?

3. if you want a full deep clean - YES

4a. jet needle - are you referring to whats on the slide? if it is stock needle then it should say in the manual

4b. pilot jet is air/fuel mixture screw (if im wrong please correct me!) this doesn't have a size but you do need to turn it out 2 and a half turns out - its what "emulsifies" the air and fuel to make it bubble up in the carbs and able to spray into the cylinder head.

4c. needle jet holder?

5. the clip is there for throttle response? I THINK! different positions of the clip plays a part on the response of the throttle/fuelling, middle i think is stock setting.

6. dynojet my friend

7. anytime broham, sorry if its not the best/most accurate info, as i said, carbs arent really my strongest point, more of a chassis person and fuel injection!
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Re: Carb dissassembly

Post by banner001 »

yeah, got some rubber hose on my pliers and removed the fuel filters from the carbs, sonicated the brass/metal bits in acetone, sonicated the carb body in distilled water as i wasnt sure what acetone would do to the fuel divider line thing...then i sprayed 100% ethanol over everything to dry out the last few water drops. evaporated all the ethanol with dry 100% nitrogen and they look fantastic!

"jet needle holder" is what its called in the manual, its what the main jet screws into.

also as for the pilor air screw, the one that you screw out, i guess that if i want to lean out the pilot mixture (mine is currently rich) i screw it further out...OR is it a case that fuel and air goes through there, in which case it will need screwing in a bit?? thanks.

it was really quite simple to clean up the carbs, the worst bit was sonicating the body. ill post a pic later of the finished assembly, these were more to test my ability to dissassemble mine when i need to, but i look to have done a decent job so might stick them back up on ebay...we will see. ive got a fortnight off coming up soon, might have to take mine out then and give them a good clean.

one thing though, where can i buy kehnin mains and pilots from? i dont seem to be able to find the correct parts numbers on allens-performance website?
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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R P Corse
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Re: Carb dissassembly

Post by R P Corse »

i'll have a look at the manual in a mo :smt012

pretty much spot on with the pilot screw, i set mine a little lean - runs a bit hotter but get a touch more MPG, though looking at an exhaust system im getting, im gona run her a bit richer to keep her cool - system is a DIC thats made from alloy/alu, bloody light but scared it might melt lol

please do send a pic! would love to see how clean it has come out!

as for the mains and pilots, have a look on keihin website, that said im sure an MX dealership - OR CRADLEY - may be able to get them in
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Re: Carb dissassembly

Post by banner001 »

sorry, so do i screw pilot air screw in or out to lean the pilot mixture?

if it only flows air then it will be out...
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: Carb dissassembly

Post by R P Corse »

sorry misread it lol

turning it in richens the mixture... turning it out leans it
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banner001
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Re: Carb dissassembly

Post by banner001 »

cheers!
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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R P Corse
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Re: Carb dissassembly

Post by R P Corse »

Should be getting my exhaust next week so will be having a play around with my carbs! Let me know how you get on with yours mate
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banner001
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Re: Carb dissassembly

Post by banner001 »

have to say, i found then a doddle to work on, ill re-strip one carb tonight (currently on kitchen table), take some more pics and post them up as a guide.
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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R P Corse
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Re: Carb dissassembly

Post by R P Corse »

Awesome mate, some of my jets look a little chewed to be honest, previous owner taking them out etc... Ideally should replace them! Can't wait for pay day tomorrow lol
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