Apart from the larger venturi compared to my mc 16 carbs what major differences are there with these mc18 carbs?
what exactly does the "power jet" do and what will i need to do to my mc16 to be able to use these carbs?
my "16" does not have any solonoids will this impair the working of the "18" carbs?

ooohh so many questions!!!

thanks

You can blank the power jets (inside the carbs) and then set them up like a "normal" carb. You wont need any of the air solonoids then. This does mean though you can't use stock MC18 carb settings eg. main jet.

You will also need an MC18 inlet manifold to fit the new carbs.
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If I have to take the carbs off once more...

hi there,
the choke set up on the 16 and 18 are different as well, it's a bit fiddly but you need too change the rod and linkages over, not a big job but make sure you've got some long nose pliers and a good screwdriver.also the two throttle cable end's are different as well if i remember rightly i ended up cutting a washer to fit them over the brackets if not both then certainly one of them(think the top one).the air solenoids just unscrew,and stephenrc45 was right about everything he said.hope it helps
mik.

ok im putting mc21 carbs on not mc18 carbs but i guess the guide lines will be the same but do i start with the standard mc16 jets and put them into the 21 carbs.i know you really dont like quoting jet sizes but as the standard 16 ones are 35 pilots and 110 mains roughly how many sizes do i need to go up? bearing in mind i have done the airbox modification.

no-one will be held accountable for any sizes quoted.

thanks liam

As you arn't running power jets and will be in most cases now be running an MC18 (barrel wise) I would be guessing somewhere between 142-155 main jets and 38 pilots.
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If I have to take the carbs off once more...

Liam how did you get on fitting your mc21 carbs to mc16 with 18 cylinders,i just won some on ebay for £21 .I pm'd Andy for a list of things to do for the mod as a few people are interested in it!

hmmm sore point at the moment as i won mine on ebay too from someone called "nsrhoe" and am still waiting for then too arrive so then the fun can start trying to get it to run properly.

you might get yours done bfore mine yet.

sorry to hear that mate,how is your bike running at the moment,have you got 16 carbs on?

HA good news is they arrived this morning so ill be playing most of today trying to set them up.
bike in standard form runs great now just hoping to get a little more from it with these carbs on.
i'll keep you posted on how it goes.

ok the're on and running but upon test ride it accelarates like mad but seems to give the impression that its running out of fuel under hard prolonged full throttle,is this a float hieght problem or do i still need to jet up further?
currently running 38 pj's 142.5 mj's cant do plug chop as the power dies off.
1st,2nd,3rd gear fine just when we start to power through the higher gears the problem starts


liam

You can do a chop in 3rd - don't run it flat in 3rd for too long though!

I'd be inclined to slap a set of bigger mains in it and see if it gets worse! A bit crude, but it will give you an idea! Sounds like it's running lean.

What have you done with the normal MC21 plumbing? Post a photo of the installation.
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Andy.
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i would post a photo but my camera is goosed so i'll explain what ive done
1, remove tps unit and discard
2,blanked power jets with solder
3,142.5 mj from 128 stanard 38 pilots
4,unplugged pipes from cross piece and left to open breathe normally(should these be linked together)
5,modified mc16 inlet manifold to accept bigger carbs.

i will try to sort out a photo but i would not hold your breath.

cheers

I would imagine it is running dangerously lean at higher RPM then.

You need to meter (i.e. restrict) the air to the pipes where the X-piece was connected.

Also, with the power jets soldered up, would expect you to be more in the mid 180's with the main jets.
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Andy.
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ok iv'e put the bike away in the garage and have ordered a pair of 182.5 and 187.5 main jets and will try again when they arrive as i dont want to kill it.i think it running rich would be a better starting point than dangerously lean!!!!!!!!!lol

thanks

why cant i just leave things alone????????????

What jets are you using? Certainly not genuine Keihin's if they are in 1/2 sizes.

I have it on good authority that mains other than genuine Keihin can have slightly different flow rates, so bear that in mind.
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Andy.
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