Kawi2strokes.com Forum

Hi everyone,

Thanks for having me here, this is my first post.

I have an issue with my S3 400. I’ve been browsing these forums in the hope someone can help me, I’ve run out of ideas.

The bike splutters on ¼ throttle and feels flat. Once past that it flies, revs clean and pulls well.
The bike is completely standard apart from Higgspeed pipes.
Electronic ignition by Boyer Bransden.
Standard airbox, carbs are ultrasonically cleaned, all jets, floats, etc are Mikuni. Floats are new.
Pilots are 25 (used to be 22.5) This made an improvement.
Main jet is 90 (used to be 85). This too improved the issue.
Needle is on number 1 (leanest setting), I find so far that any other setting apart from this, the bike does not run well.
Air screws 1+ 3/4 turns. But I find that 1+3/4+1/8 works better.
I’ve tested for air leaks and found none.
Carbs, slides, cables, etc. have been set up as per manual.

I enclose a Dyno graph for anybody interested. All cylinders were pretty much the same. This engine has been recently rebuilt and seems very healthy, good compression.

I am hoping to improve that middle range low rev performance, but I’m lost and confused!

Many thanks to everyone in advance.

All the best,

Mikel

When it's not running right at 1/4 throttle, push the starter lever and see if it gets better or worse. If it's too lean, it will get better.

This diagram shows what parts affect the mixture at 1/4 throttle. As you can see, at 1/4 throttle it's the pilot circuit, the slide cutaway and the needle jet and needle.

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If it surges, that's normal, upshift.

Keeping the same carb settings, try removing the air filter and see if it helps.

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Answers are here: http://kawatriple.com/

Thank you so much for your answers, they really helped.

Just took it out for a spirited run, works a treat. Tried first riding with choke, but did not like it. Then I tried with no air box, and she flew, totally different bike.

Plugs are still showing good color.

Now the question is... any good suggestions for pods? And should I leave the settings as they are now?

Running worse with the starter lever pushed and running better without the air filter both point to overly rich mixture. mraxl has more experience with the S series air intakes than I do, but pods aren't always the way to go. Let's see what he says.

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If it surges, that's normal, upshift.

You will be better off keeping the air box. The intake shape at the carbs offer a benefit for air flow.
You may need to go up one size on the main jet.... maybe not?

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Answers are here: http://kawatriple.com/

I'm confused.
Without the air filter/box it run better than it has ever run. The miss-fire up to 4000 revs has disappeared. The bike pulled clean from idle. Did you mean running it with an air box but no filter?
The plugs are also showing a good color.
So sorry to be a nuisance.

mraxl can correct me if I'm wrong, but I believe removing the filter was just to test to see if the mixture was too rich. Now that you know it is, you can do something to make the mixture a little leaner at 1/4 throttle.

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If it surges, that's normal, upshift.

Running without the filter is an option.
It has been proven that if the air flow is "bent" prior to entering the carb performance is enhanced. Guys running pod filters are putting PVC elbows between the pod and carb to achieve this. The stock air box setup also does this (maybe to a lesser degree). The effect is most noticeable at midrange.

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Answers are here: http://kawatriple.com/

Since it runs better without the air filter, you may want to look into using a K&N filter in the stock air box. There is a little work involved in making it fit but it is well worth it. This is the only thing that is not stock on my S3 and it runs great!
http://kawatriple.com/tips/s3filter/s3filter.htm

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