opinions on a 40:1 mix ratio

Aug 8, 2007
I have a 2005 yz250 currently running on a 32:1 mix ratio. It smokes a lot esspecially when warming up and makes a lot of black sploodge. I am not fouling my spark plug but it gets preety oilly after a day of riding.

I was thinking about switching to a 40:1 ratio to help with all this. Just wondering what people's opinions were on this and if anyone has other ideas to help me.



Hot Sauce
Oct 28, 2001
+1 on getting your bike jetted correct. decreasing the amount of oil not solve your problem :cool:


Sponsoring Member<BR>Club Moderator
N. Texas SP
Nov 25, 1999
IndyYZ85 said:
Get your jetting right, 40:1 will still smoke and spooge.
My 05 was jetted really rich. I switched to 40:1 and spent the time to jet properly using the guide at the top of this forum. Took several hours but I'm very pleased with the throttle response and NO fouled plugs since it was done.
The spooge is still there, not as bad as stock, but still there none the same.
Once you rejet, using a new plug and clean filter, pull your pipe and silencer. You can use a small amount of desiel fuel to wash out the pipe and repack your silencer. Be prepared for a messy power valve when you do your first top end.
If you have riden quite abit with the stock jetting your pipe will have an excessive amount of spooge still in it. Getting the jetting right first and then cleaning the pipe will at least give you a clean ride for a few times out.
Several of the Heartland Spodes have riden my YZ and have commented how crisp the jetting and throttle response is now. I ride at around 670' above sea level. I'll check to see what jets I'm using but I believe I dropped two sizes on the main and the pilot with the clip 2nd from the top. I've thought about trying a different needle but have been satisfied with the overall charateristics of the stock needle. My dealer gave me 4 thin shim washers for the needle to be able to adjust the needle between clip positions but I ended up not using them.
PS: Make only one change at a time when jetting and buy several new plugs before you start. Read the jetting guide several times and then start doing the procedure. If works very well and you will be an expert on jetting your bike when it is all done.
Feb 21, 2007
Also to clean out your pipe, clean all the carbon build up out of it to give it the correct volume. Clamp it down to a workbench and hit the mouth of it with a torch until it's red hot then, using a long standard screwdriver, scrape off all the carbon build up. It's a little work but if you're going to have it off clearing out the spooge so might as well, right?