Best way to get little more bottom end out of yz 250

I have a 2009 yz 250 that I would like to have a little more bottom end power out of . It is was a little muddy the last time I rode out doors and I noticed that that would benefit the most if I little more power in the bottom to midrange to help pull me out of some of the slower corners. I currently have a 51 tooth rear sprocket and a 14 front sprocket . I was thinking about adding a flywheel weight or changing changing the gear ratio or porting it please advise what is the best option

What all have you done to it? Where do you ride, woods or track? The reason I ask is that different venues change everything. I run the same gearing, a light FWW, spark arrestor and have tried to get & keep my jetting as close to spot on as I can get it. Plus I'm generally in the 160 lb range in season :rolleyes: not now of course. I ride mostly woods and MX in the 70 class, but do not have any problems with pickup out of a corner other than I will fan the clutch if I get down too low or get caught in the wrong gear. I have not done it to my 09 as yet, but when I change reeds I will go to the Boyesen super stock reed which seems to help in that department. If you are a big guy and want to spend the money, send it to E Gorr for more displacement - lots of discussion in here as of late.

If you want a smoother delivery, the flywheel weight will help. If you want more bottom end, you'll want to try some other things.

Best mod you can do to improve that bottom end is a head mod. This will trade some over-rev for bottom end and mid range, but it will increase the "hit" as well.

The way to get back that over-rev and tame down the hit from the head mod is to retard the ignition timing a small amount.

The combination of those two items is a great place to start for bottom end with smooth delivery. You can dial in the timing where YOU like it. Advance = bottom end and hit, retard = over-rev and smooth.

Make sure you re-jet after those mods. The head mod and timing both actually make the bike easier to dial in perfectly.

You still won't have a 450F, but it's a really good start.

I might be alone in this opinion, but I'm a fan of the PC pipe vs the stocker. It fills in a little hole and removes some of the hit as well.

Bar-none, the best mod for bottom end that I've tested is the EG295. Even with the mid-top porting and the race-gas head, my 295 pulls like a diesel out of the bottom end and has a really smooth delivery for a two stroke.

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