Hi First off i am new ,.. i run a track rgv250 and have since purchased a MC18 that i am building up for a period racer as well.

I have done a few searches and no luck on finding topics on modifiying mc18 carbs. So i have a few questions and hope you guys can help.

The carbs are a U shape inlet running back to a roundshape, the diameter measures 36.5mm. They look like quite a nice little carb ,.. but the section that holds the slides has an awfull mismatch,.. the back part that supports the slide is the part that i would like to clean up it protrudes out a fair way to support the rear of the slide,..cleaning this up would get a smooth transition throught the carb is this ok to preform? I can't see no reason why not?

I was looking at maybe getting PJ38 but after seeing these i think i can make them work rather well?? comments welcome

Thanks
Jamie

Most people run them stock.

Andy has some bored ones but I dont think hes ever run them.

Mine produces best power on stock shape/sized carbs even though I've run it on PJ38's and PWK39's. The stock carb is hard to beat.

If you want to mod them clean the bell mouth side up a little and fill the air corrector cut outs (they have small brass plugs in them, cut into the bell mouth) up with resin and smooth back.
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If I have to take the carbs off once more...

Thanks for the Feed back ,.. that is what i wanted to hear ,.. sounds like they are nice little carbs then.

Jaffa

The MC18 and MC21 TAxx carbs are spot on for 99% of applications. The MC28 TBxx carbs so I've heard, flow extremely well and maybe eveb better than the earlier ones, but they are a twat to work on!

The MC16 has similar TA carbs to the MC18/21, but are only 28mm and have no power jets.

The later FIII carbs are based on 32mm TA bodies, and they consistently out perform PJ38 and PWK39 equipped bikes (and bikes on standard "kitted" carbs) which I put down the higher velocity of the smaller venturii.

My MC16FIII will probably run PJ38's just because of the noise, and the fact it's not going to be any kind of daily ride, but it will be interesting to see just what the difference is between HRC 28mm carbs and PJ38's on the dyno one day. The HRC book says the MC16 should make 68hp in "standard" F3 trim. That's without porting or any other major internal surgery... just slapping the F3 bits on out of the box.
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Andy.
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I really, really want to replace the PJ38's on an RS250 NF5 with a set of HRC F3 NSR carbs one day. I bet 50p they are better or at least don't loose any power.
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If I have to take the carbs off once more...

Make it 50p and a Mars bar, and I reckon Tom will let you!

I've got a couple sets he can borrow for the day if you don't have any more at the moment?
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Andy.
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I've got a set here with a manifold waiting but first we need to get his RS to make as much power as the NSR
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If I have to take the carbs off once more...

Guy's something funny going on here,.. the carbs are measuring 36.5mm at the throat ,.. i see them listed as 32mm for a mc18 ,.. does anybody know what a stock mc18 measures? i am wondering if these ones have been tinkered with?

Thanks

You can't bore 32mm carbs much past 33mm. You are either measuring the airbox side, or they are not NSR carbs!

32mm is across the engine side of the carb.
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Andy.
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Thanks Andy ,... hmmm they are definatley 36.5mm and i am measuring the throat size,.. Engine Side ,.. I Will have to look into it some more.

Has anybody got some pic's of the stock carbs?

Thanks

Have taken a picture of these for attempting identification ,.. would anybody like to have a look? they look like originals with the bike and not modified.

can email

Thanks any help much appreciated

Why don't you upload the image to photobucket or imageshack, and then just post the link?!
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Andy.
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MC18 Race bike project..
MC21 Race bike..

OK Done first time for everything.

Glen thanks for the pics mate ,.. definatley different to them in inlet size but bodies looks similar.

Verniers measure 36.5mm as shown in pic ,.. well 36.36 in pic it was hard to hold them in place and take pic.





Let me know what you think

Thanks

Well, your not measuring the smallest part of the throat are you

They are stock 32mm jobs.

The carbs Glen posted are 28mm MC16 carbs. Thats why they look different.
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If I have to take the carbs off once more...