lean mixture i think

I just got a new top end put in by my local dealer last week. since it was put in the bike runs great and all but when I pulled the plug it was white. it wasn't burnt white like the picture in my manual but it was white. It always used to be a nice tanned brown over the electrode but now its just white colored like it was never put in the bike. It has a br9es in it now but I think I will switch back t o the stock br8es. will this help ? weather is 48 degress at sea level. any help would be appreciated. bike is yz250. jetting is stock I believe

The 8 series plug could actually make it run hotter. You need to re-jet (Go more rich) when riding at low altitudes and colder temps.

I dont undertsand why it is running lean. jetting was spot on before the rebuild and now its lean ( although it runs perfect ). unless the guys at the dealership chnaged my jetting. I have not had any experiance in tuning a carb. I guess I better learn

If it was perfect at 70 degrees it will be lean at 50. Did the temp change?

yes it was running perfect when the temps were around 60-90. Today it was about 48. that is enough to cause the lean mixture ? I just dont wanna blow or seize my new piston. there is still snow on the ground here so I prob wont ride again until its pretty much gone.

depending on the compression before and after the rebuild could the increase cause the jetting to be off since it would draw more air in with increased compression:excuseme:

The temp change would definitely have a greater affect though

yes it was running perfect when the temps were around 60-90. Today it was about 48. that is enough to cause the lean mixture ? I just dont wanna blow or seize my new piston. there is still snow on the ground here so I prob wont ride again until its pretty much gone.

The temp part of it is huge and would for sure cause the problem.

Please look in your PM's.....

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!


Register a new account

Sign in

Already have an account? Sign in here.


Sign In Now