Karting1.co.uk

[chris watkins]

looking for a bit of advice.
i can only seem to get 1300 revs out my engine???
engine has done about 10hrs time for a rebuild maybe?
even going aggresive with gearing it still wont pull anymore.
its a 09 engine with 09 carb new gears and clutch.

[david7m]

What jet and needle position ?

Plug?

Temperature and pressure ?

Power valve setting?

Dave
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Like everyone else, a Rotax driver - Redspeed

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[chris watkins]

needle position 1
jet i got down to a 160
power valve is set to around 7 turns.
took it testing to a local track just to see if it was a gearing issue and even going stupid with gearing still 1300.

[Alan Reynolds]

Do you really mean 1300 rpm or do you mean 13,000?

[david7m]

This is only a guide, but can't imagine anywhere recently has had a temp high enough and pressure low enough to warrant a 160.

www.superkart.org.au/Documents/rotax_jet_chart.pdf

Dave
_________________
Like everyone else, a Rotax driver - Redspeed

********************************

Amazing quality animal portraits for gifts etc - www.uniquepetportraits.co.uk

********************************

[chris watkins]

sorry i mean13000

[chris watkins]

yeah i have jet software however.
was told by a owner that although it matches with temp and pressure the lower the jet i can use the better performance i will get.

[JocoG]

Exhaust wadding maybe

Or cracks on exhaust...

[ireman]

So you have jetting software and presumably can see the colour of the plug and/or exhaust manifold but still run a leaner mix because someone in the paddock told you that it would be better?

With all due respect I can't understand either your reasoning or logic on that - just doesn't make sense.

[niracka]

Some people tell you to go super lean thaugh and everyone who has told me that has been quick however other quick people have told me different. You dont want it popping on you thaugh surely.

Ollie

[chris watkins]

ireman with all due respect!
it was a very respected team owner trying to help a fellow karter out.
they saw i was having a problem and giving me a diff option to try.
thanks for the other feedback ive replaced the wadding.
im not having a dig at anyones software it was just something to try!
thanks for advice guys.

[Nick]

Chris, you have just given Ireman and myself a huge dose of deja vu having gone through this with someone very recently

Be very careful about jetting too lean, it's worth a try for a session to see if it cures your issue, but not advisable long term, I'll leave you with John Savage's words of wisdom from a very recent thread as it says it all quite frankly.

"Over the years a myth has developed that the weaker you jet your engine the faster you will go which quite frankly is just utter rubbish, weak jetting will cause engine damage and overheating very quickly and is certainly NOT the way to go."

Try another carb if you can.
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Nick

[ireman]

I started karting with an air cooled 100DD years ago and very quickly learnt to respect what I could see from examining the plug and piston crown. If the combustion colour indicated too lean it meant a seize was imminent. That was before software or any other aids so we relied on what we could see and knew about carburation.

A water cooled Rotax does seem to be be more forgiving if run borderline lean but it still gets it's lubrication in the same way so if the plug looks too lean ( and I know that it is difficult to see the piston crown but you can see inside the exhaust ) then it is too lean and is likely to result in damage.

There is an optimum fuel/air ratio at any given time and it changes frequently throughout a day. With a 100DD with a sensible carburetor you could adjust the mixture as you drove it, but Rotax isn't like that and that's why there is software to help.

Regardless of others advice, if the plug/exhaust colour looks right then the jetting won't be too far wrong, so you can discount that and concentrate on other the areas that might be the cause of your problem.

[HectorvS0310]

have you checked all the electrics are wired up properly and is the battery alright, Does it get to 13000 cleanly or does it make a fuss?
on the powervalve 9 turns out is what i have been told to run and is the powervalve(including the bellows) completely clean?
The engine should be fine after 10 hours
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Being second is to be the first of the ones who lose.

[chris watkins]

yeah i havnt run jetting like that all the time. i just tried it for a single session.
it gets to 1300 easy then nothing. almost feels like theres nothing.