Best mods to yz250 2smoker

carver

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Joined

9/3/2017

Location

Torrance, CA, USA

carver 11/22/2021 12:09pm

11/22/2021 12:09pm

Back in '07-'08 some of us were having detonation problems on 91 pump and I did a thread on it at TT.

After some digging, it looked like many of the bikes were timed incorrectly from the factory.

The thread took off and it's a long 34 pages of info. but here's the long short of it.

Many bikes are at .009-.010 timing setting instead of the factory .007.

To run this advanced timing you basically have to run a % race gas and/or jet rich and/or machine the head.

An easy fix if you want to run pump gas and jet cleanly without cutting the head is to adjust the timing.

Basically, stock .007 will work with 93-94 pump and .004-.005 works well with 91 pump with similar powerband.

If you want to smooth the hit a little, .001-.002 will do this along with adding a little overrev.

The smoothed hit setting also works well for off road/slippery conditions etc.

For those that want a long read, grab a beer, here's the 34 pages of the topic.

https://thumpertalk.com/forums/topic/584339-yz250-timing-thread/

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CornflakeJackson

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Joined

4/10/2020

Location

San Clemente, CA, USA

Fantasy

1102nd

CornflakeJackson 11/22/2021 2:54pm

11/22/2021 2:54pm

yz133rider wrote:

22.5 mm clamps are a massive improvement. Check out luxon’s clamps. One other thing on yz’s from that era - keep the axle as forward as...

22.5 mm clamps are a massive improvement.

Check out luxon’s clamps.

One other thing on yz’s from that era - keep the axle as forward as possible. I’d always lose the front with the axle adjusted back, but move it forward and bam it would turn again.

Changing the clamps gave it unreal front end steering but the axle is a free “mod” to get it better.

That's interesting about axle placement. Moving the rear wheel forward would mean less weight on the front wheel, all other things remaining constant, which seems like it would make it easier to lose the front end. Must be the shorter wheelbase that helps. I'll have to try this next time I get a new chain/sprockets.

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torq5252

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Joined

5/11/2011

Location

Chattanooga, TN, USA

torq5252 3/11/2022 11:36am

3/11/2022 11:36am

yz133rider wrote:

22.5 mm clamps are a massive improvement. Check out luxon’s clamps. One other thing on yz’s from that era - keep the axle as forward as...

22.5 mm clamps are a massive improvement.

Check out luxon’s clamps.

One other thing on yz’s from that era - keep the axle as forward as possible. I’d always lose the front with the axle adjusted back, but move it forward and bam it would turn again.

Changing the clamps gave it unreal front end steering but the axle is a free “mod” to get it better.

CornflakeJackson wrote:

That's interesting about axle placement. Moving the rear wheel forward would mean less weight on the front wheel, all other things remaining constant, which seems like...

That's interesting about axle placement. Moving the rear wheel forward would mean less weight on the front wheel, all other things remaining constant, which seems like it would make it easier to lose the front end. Must be the shorter wheelbase that helps. I'll have to try this next time I get a new chain/sprockets.

I think it has more to do with how a shorter wheelbase will turn tighter and transition quicker mid-turn when accelerating. I always feel like my 01 is pushing the front through the exit if my axle is back and/or the forks are flush in the clamps.