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6/7/2008
Location
Flower Mound, TX
US
Older vet rider, never owned a 4 stroke, but bought a new one yesterday.
Can I run synthetic oil in the transmission? or stick with conventional?
I currently run a leaded high octane fuel in my 2 strokes because of milled heads & porting work and jetted carbs.
What race fuel can I run in a new KX250? Do I have to run unleaded? Can I run Oxygenated without mapping issues?
What about break in? 3 heat cycles?
Thanks and I'll have more questions on this bike in the future
Can I run synthetic oil in the transmission? or stick with conventional?
I currently run a leaded high octane fuel in my 2 strokes because of milled heads & porting work and jetted carbs.
What race fuel can I run in a new KX250? Do I have to run unleaded? Can I run Oxygenated without mapping issues?
What about break in? 3 heat cycles?
Thanks and I'll have more questions on this bike in the future
The better the oil, the better it carries particles to your filter. Motorex Crosspower is a Class 4 oil, meaning it is best in class at keeping particles suspended and carrying them to the filter. I buy it by the 4 x 1gallon case.
Beware, starting an oil thread is like just asking to get picked on. Or you just trolled me.
I am still definitely unclear on whether I can run a leaded race fuel safely, or oxygenated race fuel and the stock mapping options will work. I've never had a modern 4 stroke mx bike. Perspective from people who have been riding them for over 10-15 years is ok, right?
The Shop
I would start with premium pump gas (non-oxygenated).
Modern 4-strokes do not use an oxygen sensor, so you can use leaded gas if you want (Lead will destroy an O2 sensor). Just for fun, I've tried about all types of gas in my 4-strokes.... but I'm not looking for more power out of a 450. The only benefit to me is that VP U4.4 smells good.
For a new bike, I run mine for a hour or two on the first oil change. But typically on my KTM 450, I get 6-8 hours on the oil before I noticed the bike doesn't shift as well. I've had a friend do oil analysis for me, and even at 8 hours, the Motorex Cross Power is still within specification. Also, I like to get a baseline on my valve clearance, so I check that at the first oil change and note it in my manual (along with any adjustments).
Don't waste the money on race gas unless you have the supporting mods. 93 will work fine.
They offer up anywhere from 10W-30 to 10W-50 as acceptable so your selection may vary depending on your riding conditions and ambient temperatures. If you're going to push it super hard, you may want to go up to the 50 for longevity's sake.
You can run leaded race fuel no problem. You can cut it with a good pump gas to get some mileage out of it. No need to run it straight. I've never run oxygenated fuel so I have no comment on that.
I've been running Maxima Synblend (10w40) in my 4 strokes for 15 years plus. Price point is great, it's made in the USA and Maxima is very active in moto. I will support companies like that.
For context, I'm 56 and have ridden dirt bikes since I was 5. I started racing in 1982 and know my around 2 strokes. I've rebuilt bottom and top ends on them 100's of times through the years.
I've never had a 4 stroke, never had fuel injection and mapping options. Never had electric start. So, hence, my questions on the oil for the trans possibly being different than what I currently run and of course the fuel, not wanting to hurt the motor if I ran a leaded race fuel like I do in my 2 strokes.
With this bike, I currently own 5 mx bikes, so it was only to get perspective from 4 stroke riders since they've been around now for a long time. I appreciate the input
My 250f KTM seems to run the same on pump or a mix of 110 leaded / e free 90.
The bike will run just fine on non ethanol 93 pump gas. A leaded fuel won’t do anything for you and I believe oxygenated fuel would need a remap to utilize it.
Plus this is just me but after break in ride, I drain coolant and refill with Engine Ice.
Pit Row
I have the same bike. I love it. Keep an eye on the chain, mine wore pretty quickly and is almost ready for replacement.
I use the white coupler, I feel way better with that vs the green one.
Vital also has some recommended suspension settings. I used those as a baseline before making a few minor adjustments, and I’m super happy.
A good explanation from the internets.
'The lead oxide acts as a cushioning agent, and protects the valve and the valve seats. The lead oxide is also a lubricating agent. This reduces wear in the valve guides, as the valves slide inside them.'
I also forgot to add. Try finding a race fuel with an lubricant additive for the fuel pump. This will be important if you are keeping the motorcycle for the long haul.
I guess it makes sense all modern fuels should have a fuel pump additive (if they advertise it or not)
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