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Trail Built yz250

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I'm starting this thread in hopes of some direction advice.   I got a great deal on an 08 yz with a strong, stock motor.  The goal is to tune it for a very easy to ride smooth technical trail slayer.  The basics are there:  guards

steahly flywheel (don't know the weight)

retarded the timing already         /         250x cdi installed.

gearing is 13/52 (its tight here but I considered going towards 50 or 51T)

The carb is where I am stumbling the most.  Stock is too strong and mx like.   JD blue is what I was hoping to get right but no combo seems to be working.

For example:  they recommend:  Blue #2 / 45 / 172  -    this combo has a soft, lean , weak bottom end and a qwik snappy transition thereafter.   tried 48,50(best) clip 2,3 &4 (3best)178-ok but not great.    The power is too fast and abrupt.   Is there a jetting combo I could use that is very user friendly and not finicky?????   my 250x was easy to jet, but this bike is more difficult.    (sea level -1400ft)  80's, 85% humidity.       I have some zuk needles, jd red, some straight tapers  (ccl, ddl, dcl - this needle rips! , cek, etc....)

Other thought was to put the stock 250x head on as I have one.   Couple base gaskets maybe?  A shorty silencer to cut into the top end?  throttle cam?   reklu$e? ( I have one on my x- was thinking maybe just put in on the mx'r for better trail manners.

 PC or eric gorr or harris porting?

How about removing the powervalves?  or disabling them.    I don't need them for the riding we do here.

 

Lots of options, but I'm not sure what to do.   I know for sure something has to be done because if its hard to ride this bike when its dry, it will be impossible when its wet.

and a picture of how it looks now for your troubles.

yz side shot.jpg

yz yes.jpg

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I robbed the suspension off the x in the background to see how similar the chassis were between 08 yz & 16x.    Conclusion is that the two bikes are identical.   I couldn't tell much difference except that the yz is so much quicker thru the power that I would slow down the rebound compared to the setup on the x.  I notice a nice black puddle under the bike after riding.  looks like the pv breather hose is spewing.   need to clean pv now?  

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The Suzuki needles are smoother than stock but still pretty snappy, they're the best you can do jetting wise to tame the bike.

I'd put the X head on it, this lowers compression a lot taking away the wheel spinning snap, adding base gaskets will help too but likely wont be wanted or needed with the X head.

You can also put the X power valve spring and washers in it, this helps smooth out the power too.

Shorty silencer's make the bike snappier off the bottom, you want a long spark arrester silencer to tame the power off the bottom like the fmf Q2.

There's a long thread on how to turn your yz into a X full of ways to tame the power down.

My bike had 13-52 gearing on it when I got it, it made it pretty much unridable in first and I stayed in second in technical stuff. Taller gearing is smoother unless you want to avoid shifting from first to second then the lower gearing is ok just don't try to use first, I'm at 13-48 now which is pretty close to stock which works best for me as I need some top speed too.

If I wasn't 240 pounds my bike would be lighting the tire up everywhere every gear when I get on the gas, all I have to tame my 06 down is a 11oz flywheel weight so its still pretty snappy it just doesn't spin up quite as quick as stock. I read a ton of threads on taming down yz's but ended up liking the snap so all I have is the flywheel weight.

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I put an XCW head on my SX KTM with great results.  The XCW head is lower compression with a dome shape (no distinct squish band).  Based on this, I would just have Gorr or another tuner take a little material out of the head.  I would think you could pick up a spare YZ head real cheap.  They should be the same all the way back to 98.

An even cheaper option might be increasing the base gasket thickness.  Years ago I made a temporary repair on a CR250 with damaged cases by cutting a thick base gasket of automotive base gasket material.  This repair had the happy by-product of producing a perfect woods powerband, so much so that I continued to used my self-made base gaskets even after repairing the cases.  

Good luck with your modifications.  I have a fair amount of seat time on YZ 250s.  It's a classic "braaap" motor that is fun on the track, but no so much in the tight woods. 

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I would say get the suspension right and either get a hotter plug if your running rich or jet a little leaner

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First, go back to stock or 14/48 gearing.  That in with combination with some work with the left hand will lessen the abruptness and allow the bike to hook up better vs spinning up and loosing traction.  Counter intuitive to some, but riding this bike is much easier lower in the rpm using the torque vs rpm in the slow knarly stuff.  It can chug better than many  4t's if set up right.  

I run my pilot just a tiny bit richer than if I were riding the track or open terrain in addition to retarding the ignition, using a G2 throttle tamer, and 9 ounce weight.  This really smooths out the first 1/8 to 1/2 throttle opening positions.  Still rips when the terrain opens up and you are using more than 1/2 throttle.  .I've also gone back to the stock pipe from a Knarly in combo with a FMF Turbinecore II.  Smoother combo for me.  As already mentioned in another post, really soften up the suspension compared to track settings.  Again, allowing the bike to hook up.  

I will be trying a new head cut to X specs when I return from vacation.  But as a slow Senior C rider, I've been really happy with this set up in slow knarly terrain on my 02 YZ250 woods bike.  Ridden back to back to orange bikes, havent felt the need to switch colors.   Try the cheap or free stuff first.  Gearing, G2 etc.

Just my experience, others may vary.  

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