90:1 on a KTM 250 SX 2018

Question

Is it ok to run 90:1 on a KTM 250 sx 2018. Running 60:1 but fouling plugs. Friend recommended me to run 90:1.

Mark Smith:

Its the jetting . Use good gas ..preferably ethanol free . Amount of oil has a small effect on jetting . Ktm recommends 60:1 . More rpm’s you generally operate at the more oil you need . So small bores need more oil , big bores less . Most all modern 2 st. oil is good , Pick an oil & a ratio , stick with it , jet your machine

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Robert 3 years 43 Answers 1314 views 0

Answers ( 43 )

  1. Id say no and get your jetting right.

  2. What oil? If you’re fouling at 60:1 your jetting is way off.

  3. I always use motorex or yamalube

  4. Thanks for the help I will rejet my bike

  5. Before you rejet your carb, have you thought of using a better quality oil?

  6. That oil has run faultlessy through my bike for 110 hrs so far at 60:1

  7. 90 to 1 is not enough oil

  8. Unless it’s amsoil Sabre no…

  9. If your fouling plugs its due to your jetting not premix..

  10. Just remember guys that running high ratio’s (90:1) puts more gas/oil thru carberator guicker for it is thinner.

  11. In reality 90:1 makes it run richer. Less oil means more gas. Try running a good quality oil at 40:1 or 50:1. Of course get your jetting in line and start from there.

  12. Its the jetting . Use good gas \n..preferably ethanol free . Amount of oil has a small effect on jetting . Ktm recommends 60:1 . More rpm’s you generally operate at the more oil you need . So small bores need more oil , big bores less . Most all modern 2 st. oil is good , Pick an oil & a ratio , stick with it , jet your machine

  13. I wouldn’t, it’s pretty widely known that in general more oil usually makes more power, either something is wrong with your bike or its not jetted correctly, fix the real problem, it’s not the oil ratio that’s causing your issue. are you by chance running castor oil?

  14. If you’re fouling plugs it’s probably sucking oil through a crank seal

  15. As long as the oil is designed too run at such ratio

  16. I’m lost explain to me how 90:1 is richer ? U aren’t putting any oil in .60:1 recommended on Ktm’s I use it on mine and my sons 150 no issues. 90:1 seems like it would burn piston up because lack of oil. Most jap bikes 32/1

  17. I’d probably throat punch my buddy if he told me that

  18. Richness describes how much fuel ( gasoline ) is getting to your motor . Less oil = more fuel .

  19. He bike would be so lean at 90:1

  20. Check float height before re-jetting. 50:1 with good oil is typically a good mix. If you are running high rpm on the pipe i would go closer to 45 or 40:1.

  21. Get your jetting right

  22. Let’s see a picture of the plug

  23. 60:1 and run through the jetting. Problem solved.

  24. 90:1 is risking it

  25. Less oil means more gas in mixture making it richer. Wonder when it was started that more oil meant it was rich?

  26. 90-1? That’s crazy you are making it more rich. 50-1 and ride

  27. Sounds like you need to re-jet if you are even considering a 90:1. I would think if you are out of it running good in the 50:1 or 60:1 range, then you need to look at jetting problems.

  28. You will melt your piston at 90 to 1. Jetting or crank seal.

  29. No no no^^^^^

  30. The oil in picture is for injector or premix. Web site says max ratio is 50.1

  31. Why go by what the engineers in the owners manual say,what possible thing could they know about the bike they designed?

  32. Pre mix ratio discussions are always controversial lol I’m surprised it hasn’t got ugly yet

  33. Adjust your carb not your mixture.

  34. It’s very hard to tell what your rod bearing and crank bearings look like after a hundred hours unless you split the cases

  35. Gob with what oil manufacturer recommends. A soil is different than Motorex is different than Motul. And so on. Don’t just assume 60:1 like manual says, it’s based on oil you are mixing.

  36. Fouling plugs is not from mixing too much oil with ur gas it’s not enough air mixed with your fuel so it ain’t burning all the way thats why the plug fouls so ya got figure out what is restricting the air clogged filter worn engine seals or rings for jets in carb allowing more fuel than air and remember elevation and climate (winter to summer) the air gets thicker and thinner if it’s thicker cus it’s colder haha and u need to allow more room in the Jets to allow it to flow in easier east way to look at it

  37. If I were you I would do some research on Jeff slavens YouTube site he has some very good information about two-stroke oils and he is very knowledgeable when it comes to KTM Motors I run 50 to 1 Amsoil because that’s what it recommends on the back of the Amsoil bottle some Amsoil oil you can run their recommendation 90 to 1. I fouled plugs with this mixture but my Jets were too big and I only would foul a plug on very long downhill runs now I run an iridium NGK plug and lean my Jets out no more splooge a lot crisper less smoke bike runs amazing never have fouled any more plugs also I clean or clear out my motor by bumping the throttle a lot on Long downhill runs or just shut the motor off and Coast

  38. Robert, don’t change your mixture. Check your KTM manual you’re gonna want to be somewhere around 60:1. Change your jetting instead. Check the manual for the jetting for your altitude and adjust accordingly

  39. Same as Jason Albers check the float level. That fixed mine.

  40. Fowler plugs are not due to premix ratios, jet your bike properly. If you want to run 90:1 that’s fine, but use an oil made for that like Amsoil Saber. I’ve been running 80:1 for 2 years.

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