What's the proper mix ratio for a 2001 YZ250?

I would keep it at 32:1. Rather foul plugs than seize a piston. Mind you 36:1 isn't bad either. I run my 125 at 32:1

squale said:

BTW.. when using the VP Red Racing fuel, why would you want a more lean mixture such as a 36:1 ?

and what is the Octane rating of the VP Red Racing fuel? why is it better than using regular 93 octane unleaded gasonline?

Click to expand...

VP red is rated at 105 octane (motor method), which I believe would be comparable to ~110 octane using the "R+M" rating that is standard at US gas stations.

The ratio 36:1 is actually more gas per unit than 32:1 so as far as the air/fuel mixture it will yeild a richer mixture. I don't understand why the previous owner would recommend a richer mixture when using a higher octane fuel because you would normally use a higher octane gas so you could run leaner.

Certainly one question you should ask the previous owner is if the engine is stock or if it has been modified to increase the compression ratio. If the engine has been modified then it might require the higher octane gasoline. If it still has the stock compression ratio then perhaps the use of racing fuel was just a cheap insurance and won't be necessary if you don't push the engine to its limit.

I would definately stay at the same oil/gas mix and use the same oil that was used before unless you want (or feel that you need) to change the jetting.

Rod

i have a full mod yz250 and run a mix of 50/1. i use klotz r50 and sunoco 110 fuel. i don't foul plugs and as of now 1 full season of racing and comp is still very good! 160lbs. same piston and rings. i am not trying to start a big fight about oil or mixtures just giving you info to help you make a well informed decision. good luck

I think Klotz recomends 40:1 on the r50 dont they, at 50:1 for a full season thats a good commercial for the oil. I use it a 36:1 just to be on the safe side and never foul plugs, but do get some spooge util warmed up.

It all depends I have an 01 yz250. On average we run it 32-1 it runs fine. Sometimes well lean it out more depending on the location an weather. All depends where u kinda ride to...But ide go 32:1 been basically running thta past year or so, no problems here....

I use Opti-2 oil for my 125. I don't know if it's available in the states or not. Anyways. On the back of the bottle/jug it says suggested mixture should be 100:1 . I laughed when I saw this and didn't believe anyone would ever try this. That is until I was looking to purchase a new bike and saw a 94 Cr250. While was inspecting it I asked him what his mixture was that he used and he told me 100:1. I asked him why and he responded that's what the bottle tells me. I immediately finished looking at the bike and walked out of there and the bike looked really beat up in the first place. I always run a mixture of 32:1 regardless of what type of oil I am using. No matter what the bottle tells me. I would suggest 32:1 for your 250 as well. just thought I'd share that story with you all