I have recently bought a many owner but low kms 2002 XT600E {10000 KM}
Once warmed up {10to 15 mins }running the engine runs quitely .The bike runs cleanly in the first 3 gears gets to 4th and wont rev out cleanly {about 110 km on the speedo ,5500 to 6000 rpm}and just about makes 140 kms after a good run up in top gear .I was expecting around 150 km flat out .
Am i expecting too much .i have cleaned the air filter and done the valve clearances and fitted a new plug .{which showed the bike mixture to be pretty good .Would a k&n filter allow the bike to flow some more air to allow me that extra 1000 rpm in 4th .I would like to add I live out in the desert 30C to 40c Plus at 1500 feet ,I noticed a slight improvement at sea level

Any help appreciated .

are you with knobbles or street tires? Second question, check teeth number of sprocket and rear, maybe previous owners replaced them to have better acceleration. Sprocket should be 15, not sure about rear.

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Had exactly the same symptoms as you, here in England. The air filter is definitely way to go. But don't need to buy an aftermarket one if your existing filter is a genuine 4PT one. This should have little metal tabs that hold on a wire mesh cover. Once cover removed, cut out the paper element and push fit in it's place a suitable piece of material and refit mesh cover. I use a thick nylon scouring pad as my filter; but then i don't live in the desert and have to worry about sand getting everywhere!!!!!

Thanks for the reply ,I have standard tyres and 15/45 SPROCKETS. The bikes not been touched on that side {still standard }er ,I`m waiting for a K&n at the moment ,hopefully will allow engine to rev above 5500 in top gear .

Thanks ,bit hard to get bits out here ,have managed to get a K&N ordered as sand is a real headache out here !!

I use Pipercross foam and the engine breathes better than with the Yamaha filter. I noticed even response through the rev range once i fitted an 'Arrow Paris-Dakar' exhaust. I don't know how fast my XT600E will go: i tend to treat it gently prior to going on my 1/2 RTW this summer.

I have stock 15/45. My understanding is that only the rear should be changed because of stress on the engine with 14t and being too close to the 'engine' with the 16t.

Mike

If you fit a 14T sprocket on the front, the extra strain is on the chain, not the engine. Each link has to turn through a greater angle when the chain passes around the cog, and in the long run this will reduce chain life. I can't see any way that this would stress the engine unduly.

(And it's the better option IMO, as it's cheaper, and the reduced chain life is irrelevant, as most chains will be replaced as part of a C&S change long before they are worn out.)

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2006 XT660R daily ride, 1994 XT600E about to be reborn, Blog: http://goingfastgettingnowhere.blogspot.com/

I definitely would not be fitting a K&N air filter if you are in the desert.
They are very good for air flow, but not good at filtering in dusty conditions.
Don't just take my word for it, do some research.
I would recommend the standard paper air filter or a foam one with a pre-filter for desert conditions.

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Remember that Assumption is the mother of all f**k-ups.

I agree that K&N's are NOT good for dusty sandy conditions, don't do it!

Have a look here. I have just fitted one to my 1999 mint condition XT6E.

Yamaha*XT600E Pipercross air filter

Pipercross air filters for motorcycle and motocross

Moulded Panel Filter MPX048 A lifetime performance replacement for the restrictive OE filter. Improved air flow gives additional bhp, and the multilaminate foam construction ensures the filter outperforms rival filters, even when dirty!

Manufactured from multiple layers of patented open-cell polyurethane foam, Pipercross motorcycle filters are a direct replacement for your restrictive paper air filter element.

• 30% more airflow
• Lifetime filter - easy to clean and reuse
• The latest applications
• Increased dust capacity
• All filters available from stock
• As used and recommended by many race teams

Pipercross filters allow air to flow long after other air filters have reached their maximum dirt capacity.

As far as I'm aware they are suited for use in sandy/desert conditions.

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Triumph Bonneville 800 (2004), Yamaha XT600E (1999), Honda XBR500 (1986).

More helpful info about Pipercross -

Why a Pipercross Air Filter?
Pipercross have been making high performance air filters for the motorsport and domestic market for over 25 years and are situated amongst some of the biggest names in motorsport engine design and manufacturing in the world.
Over the last 25 years, Pipercross performance air filters have helped many race teams win major championships on the British, European and World stage. The development work carried out with these teams and constructors have enabled us to produce some of the most technically advanced filters on the market.
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No other performance air filter manufacturer can boast such a wide ranging application list and dedication to the development of new kits for road and competition.

Why use a foam air filter?
Pipercross air filters consistently outperform paper and cotton-gauze rivals to supply air to the engine - even when dirty! This is thanks to the multilaminate construction used in every Pipercross performance air filter. Layers of varying porosity foam all work together to trap different sized particles.

Race Specification Air Filters
Unique to Pipercross, we offer a range of race use only motorcycle air filters with a specification designed to maximise airflow and performance. Fuelling modifications are necessary to take advantage of the increased airflow and to prevent damage to the engine.

Performance Benefits

Designed to provide a dramatic increase in airflow over a standard paper air filter whilst still retaining the highest level of engine protection, a Pipercross motorcycle air filter is the last air filter you will need to buy for your bike.
Pipercross motorcycle air filters have been repeatedly tested on many different motorcycle configurations and the results speak for themselves. An increase in both power and torque without the need to modify fuelling, all by simply replacing the air filter unit.

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Through extensive research and testing using the SAE J726c air cleaner test, we have developed the perfect combination of filter density and thickness for each layer within the air filter.
Where Pipercross filters are impregnated with the dirt retention additive, the filtration performance is greater enhanced as the additive helps the foam to swell, opening the cells whilst providing a "sticky" layer to hold more dirt. This greater dirt capactiy translates to longer service intervals, saving you time and money.
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Triumph Bonneville 800 (2004), Yamaha XT600E (1999), Honda XBR500 (1986).