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Premix ratio and jetting

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I have a 1999 ktm 250exc and have been running amsoil interceptor at 50:1 with a 42 pilot jet, n85D needle in the 2nd position from top and a 170 main with the air screw at about 2 turns out, running at about sea level. The bike seems to run great, but I want to make sure I get the best protection I can for my motor, I want my bike to be reliable and last a long time. Is anyone else running this oil at 50:1? I have heard that this is great oil, and it's made to be ran at 50:1. And how does my jetting sound? I mostly trail ride, but do ride hard when I get a chance. Thanks.

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Here is the jetting chart for your bike. It is based on 50:1 with pump gas. KTM says to run between 40:1 and 60:1.

You have to jet for temperature as well as elevation.

 

99KTM250-300mxc-excJettingChart_zpsd6215

Edited by Larry63r

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I have a 1999 ktm 250exc and have been running amsoil interceptor at 50:1 with a 42 pilot jet, n85D needle in the 2nd position from top and a 170 main with the air screw at about 2 turns out, running at about sea level. The bike seems to run great, but I want to make sure I get the best protection I can for my motor, I want my bike to be reliable and last a long time. Is anyone else running this oil at 50:1? I have heard that this is great oil, and it's made to be ran at 50:1. And how does my jetting sound? I mostly trail ride, but do ride hard when I get a chance. Thanks.

that oil must be synthetic, correct?

 I believe that most synthetic pre-mix oils are similar regarding fuel/oil ratio.

50:1 might be a bit on the lean side; you would have more protection if you ran ~ 40:1. . . but if 50:1 is working, keep mixing it there.

 

Interesting fact about mixing ratios: You're getting more fuel thru your motor at 50-1 than 40-1 (Less oil = higher flow thru jetting due to lower viscosity mixture.)

FWIW - I run ~38:1 in my smokers (using synthetic oil) KTM200 and '82 YZ490. They like that mix.

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I have used 52:1 with Golden Spectro since 1970. I have used it in KX65, TM75, KTM85, 05,07, TM400, IT175, IT465, Penton 250, KTM495, KTM250s of several years 83,85,87,01,03,06,11, KTM150, and several others that I can't remember. I have used it in all my chain saws and weed wackers. I have used it in all my jet skis and out board motors. Through it all, over all the years I have NEVER seized a motor or had a lower end go out!

52:1 is plenty of protection. More oil than that is just a waste of oil and money, unless you are using an inferior oil.

Edited by Larry63r

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Yes it is fully synthetic, and I think I will keep running 50:1 as that's what it's made to be run at. Does anyone else run the same jetting as me?

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that oil must be synthetic, correct?

 I believe that most synthetic pre-mix oils are similar regarding fuel/oil ratio.

50:1 might be a bit on the lean side; you would have more protection if you ran ~ 40:1. . . but if 50:1 is working, keep mixing it there.

 

Interesting fact about mixing ratios: You're getting more fuel thru your motor at 50-1 than 40-1 (Less oil = higher flow thru jetting due to lower viscosity mixture.)

FWIW - I run ~38:1 in my smokers (using synthetic oil) KTM200 and '82 YZ490. They like that mix.

 

I run 50:1 using Amsoil Dominator, all Amsoil products are full synthetic.  That's what the oil is engineered for, that's what I run and have had no problems.  Ever.

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I run Motul 800 at 60-1. Have for many yrs. On the 2nd piston in my 02 300 EXC.

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