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DZR400S upgrade vs aftermarket carb/exhaust

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I just bought a 2003 DZR400S and took an offer to have fitted an FMF Powercore4 exhaust and powerbomb header plus Mikuni flat slide carb. These came off another bike the dealer had for sale.

I have the option to revert to the stock carb and exhaust if I dont like the aftermarket ones.

Question 1

How do the benefits of the FMF/mikuni flat slide combo stack up against the DRZ upgrade

eg 3x3 airbox mod, dynojet stage 1 kit, cutout exhaust rear (smaller) restrictor with holesaw

Question 2

Do I need to do the 3x3 mod on my airbox to allow the FMF/mikuni setup to work properly

The FMF powercore4 is a loud exhaust but I haven't heard much positive feedback about it.

Most people mention the Yosh exhaust with FCR carb as the way to go

Basically I dont really need the extra power and accepted the aftermarket stuff because it was a freebie

Perhaps there's a reason it was free ?

I am thinking I might be better off running stock or stock upgrade rather than second rate aftermarket?

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I don't know what size Mikuni.

Other than Mikuni "racing" written on it, i cant see any other markings while its in situ

The bike is in Cambodia and the dealers knowledge is also very limited.

The bikes for sale here are imported from Japan so the mods were done over there.

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I will try to arrange a digital camera and post a picture.

Couldnt find any model numbers on it.

Has a Mikuni sticker on the float bowl saying for racing use only.

Will get back with more details

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The Mikuni carb is the TM series

It fitted straight on to the existing manifold rubber so I assume its 36mm

The bike runs very well mid range to high speed.

Low speed offroad not so good

I took it to a quarry for some putting around going up and down steep slopes at low speed.

Engine tended to stall / flood whilst on a steep incline

Adjusted fuel screw and idle speed and found best position for fuel screw to be 2.5 turns.

Less than 2.5 turns caused hanging idle, and above 2.5 turns increased engine stalling on steep inclines

Got the engine hot enough during testing to make the fan kick in so it was a fairly decent test.

Cannot find any air leaks on the FMF exhaust and Carb manifolds are sealing OK. No external leaks on Carb

Now I'm wondering what problems inside the carb might be leading to the low rpm problems

Worst case/ most expensive scenario would be a worn out slide and/or slide housing ??

Plus the question still stands about this setup vs stock carb/exhaust upgrade mentioned at the start of the thread

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