Needed changes for 50:1 to 40:1 mixture

[G22inSC]

I have a 97 KX 250 that the previous owner jetted for a 50:1 Mobil 1 MX2 premix. Am I wrong in wanting to change to a 40:1 mixture. I just feel 50:1 is cutting it too close. What changes need to be made to change to 40:1. Would I need minor adjustments or needle changes. I have no idea what needles are in the carb now, so any suggestions on good jetting specs would be greatly appreciated (for South Carolina in the summer). Thanks in advance.

 

[MikeT]

I'd switch it to 32:1 like it says in tha manual, then rejet from there. Run it a little with the new mix and see how it does then you'll know which way you need to go with the jetting.

 

[Enduro_Nut]

I run anywhere between 40:1 to 50:1, depends on my oil - full mineral oil, 40:1, semi sythetic 45:1, fullsynthetic 50:1. This advice was given to me by an ex-team green rider - he mentioned the manuals were written with 20 year info. regarding qaulity of oil -oils have changed ALOT in 20 years!! So, unless you want to spend extra $$$ - save it and go have fun!

 

[a454elk]

I agree with the Nut, hehe, I run golden spectro between 42 and 50:1 and it's fine. Tried at 32:1 like manual said and it spooged excessively. I stay around 40:1 now and jetted one leaner on the main and it's great.

 

[Enduro_Nut]

You calling me a "NUT"?? :laugh:

 

[KX02]

I couldn't imagine having to rejet to switch from 40 to 50 to 1. Think about it... 50:1 is 2.6 oz. into a gallon, 40:1 is 3.2oz. .6 oz into 128 oz of gas. You won't notice a difference in jettiing. Changes in temp affect jetting much more. I experimented from 32 to 50 to 1 with my KX and didn't notice any jetting related changes. Using less oil, did help clean up allot of spooge. I ended up sticking to 40:1 with Castrol TTS.