Main Jets and N77S Needle

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U_h0rnet5
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Main Jets and N77S Needle

Post by U_h0rnet5 »

Happy New Year Everyone,

As the weather is absolutely miserable at the moment, I thought that I would strip down some spare carbs and clean them up. I have read up on the forum about everyone's carbs issues and l have a couple of questions to clear up?

1. l have stripped two carbs and on inspection my main jets are 88 and 92!!! Is this strange? As everywhere l read it is generally 98's-105's

2. The needle In one of the carbs is on the second groove from the top (92main jet) the other if I remember rightly has some red needles in it which did not run but found that they had snapped. what would happen if these were adjusted to standard settings on the 6th groove?

3. Also l read about M3 washers being fitted to the needle where and what is this as l an a bit confused?
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banner001
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Re: Main Jets and N77S Needle

Post by banner001 »

88's on the outside two and 92's on the inner two were a common way ot try and cool the midle two cylinders with a bit more fuel (evaporates and removes heat from the cylinders), sometimes you find them the opposite way round as extra heat in the middle two cylinders mean they run with less air, and so need leff fuel to achieve the same air/fuel ratio...easiest thing is to run it, then swap to all 88's or 92's and check it for differences as every engine/carb combination is different.

N77S needles are standard L model needles and should not be grooved, the grooves and more tapered needles are dynojets, though ive never seen any painted red. if this is for a road bike i would try and obtain a full set of 4 N77S needles and try with those in, the dynojet ones are good when always on WOT, but not for everyday riding.

M3 washers are used to raise the height of the standard N77S needles, they have the effect of increasing the richness of the midrange air fuel mixture.
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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U_h0rnet5
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Re: Main Jets and N77S Needle

Post by U_h0rnet5 »

I meant that 1 carb had all 88's in and the other carb had all 92's in. Sorry Banner should have written it more clearly :smt053 lol.

So the needles I have are an after market/dyno jet set??? Would this make the bike faster top end? I have a few more at home so might strip them down and see what they have inside them.

When I last rode my two bikes (ages and ages ago!!) I did notice a difference with them both my race bike felt faster and only did 100 miles to a tank and the road bike I have was a lot smoother through the rev range and done 120 miles to a tank. I take it this could be due to the set up of the carbs?

Ciaran
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