Need KTM powerband from a YZ

I rode YZ 250's for years in the deserts of California and they worked fantastic there.  Now I'm based in the jungles of Thailand, slick clay, tight 1-3 gear singletrack, roots, ruts etc.  Thinking of 250 two stroke again but it needs to be loads more mellow than my ported YZ of yore.  Rode a friends YZ250 with a FWW and ignition timing retarded.  it still hits too hard to hook up over here and he sold it.  A friends Husaberg and anothers KTM 300 on the Yellow spring powervalve are loads more controllable. 

 

Sooooo what else can be done to tone the power delivery down?  I'm thinking something like a Vortex ignition to completely adjust the ignition maps to what i need but I find very little info on them in the YZ forum.  Has anyone had luck with the Vortex?  What else can be done to tone down the delivery?  My YZF 250 makes the perfect power delivery, how can I turn a YZ 250 into 250F like powerband?

 

I love the flick-ability of the two strokes.

You could try a flywheel weight that's heavier than the one you previously used. An FMF Gnarly pipe should bring the power delivery down lower and make it easier to control in the tight stuff you're riding now. 

 

Another approach would be to raise your final drive gearing by going to a smaller (one tooth or so) rear sprocket. Obviously, you don't want to gear your bike for the desert, but by raising your final drive gearing you will mellow out the hit. 

 

Getting the head milled for more volume / less compression will also decrease the hit. 

 

 

I doubt the ignition will do much. I have a ktm and the different ignition maps seems to make very little difference in the woods. You only notice it on the track and open areas.

How feasible is shipping where you are? It would probably be cheaper to ship the cylinder and head to a reputable tuner for porting than to buy all the bolt ons like pipes and FWWs.

A throttle cam system may be helpful, but it ultimately does not change the power characteristics. It just gives you more control.

A very low cost mod worth trying is just stacking base gaskets (or cutting your own out of thicker gasket paper). That did wonders for a cr250 I used to run in the woods.

See it for what it is...

You want it like a YZ250f, buy a YZ250f...

You want it like a KTM 300, buy a KTM 300...

There is only so much you can do with a YZ.

Edited by Monk

Put a rekluse clutch in it.

buy a KTM. Simpler than moding YZ.

See it for what it is...

You want it like a YZ250f, buy a YZ250f...

You want it like a KTM 300, buy a KTM 300...

There is only so much you can do with a YZ.

You gave this same reply to me in the same situation.  You told him to buy a YZ 250f, but he already has one, as indicated in his post.  I had asked about the turning on my YZ 125 in reference to my KTM and Suzuki that I already own, and you told me "if you want a KTM, buy a KTM, and if you want a Suzuki, buy a Suzuki".  

 

We already have the bikes you are telling us to buy.  The nature of the question is how to move the new bike (or proposed new bike) in the direction of existing bikes.  I would think that most riders with multiple bikes prefer to have a similar setup on their different mounts.  That is all.  I wanted to move the turning/steering of my YZ toward my other bikes.  He wants to move the power delivery of a proposed YZ toward his existing bike.

You could try a flywheel weight that's heavier than the one you previously used. An FMF Gnarly pipe should bring the power delivery down lower and make it easier to control in the tight stuff you're riding now. 

 

Another approach would be to raise your final drive gearing by going to a smaller (one tooth or so) rear sprocket. Obviously, you don't want to gear your bike for the desert, but by raising your final drive gearing you will mellow out the hit. 

 

Getting the head milled for more volume / less compression will also decrease the hit. 

 

Yes I could try a heavier flywheel weight and see if it allows it to hook up a bit better in the slick stuff.  I also notice my 250F (has a 300 piston) also hooks up better on steep rocky uphills without the coming on the pipe too hard that the two strokes battle with often.  The f;ywheel weight will be a definite tool I'll be utilizing.

 

The final drive gearing is a bit more awkward since i can't gear it overly tall for the tight stuff i ride in because of the taller 1 & 2 gears in the MX gearbox.

 

Addressing the head will be an option I can also utilize, I would need to find out how much take out of the combustion chamber though.

 

Thanks for the tips.

I doubt the ignition will do much. I have a ktm and the different ignition maps seems to make very little difference in the woods. You only notice it on the track and open areas.

How feasible is shipping where you are? It would probably be cheaper to ship the cylinder and head to a reputable tuner for porting than to buy all the bolt ons like pipes and FWWs.

A throttle cam system may be helpful, but it ultimately does not change the power characteristics. It just gives you more control.

A very low cost mod worth trying is just stacking base gaskets (or cutting your own out of thicker gasket paper). That did wonders for a cr250 I used to run in the woods.

 

 

 

Interesting you do not notice much changes with the different KTM maps.  What KTM are you riding with the different map options?  I ask because the timing thread in the YZ section has people talking great effects on traction.

 

Shipping is a pain.  Everything is taxed at supposedly 40% on imported items.  My new stator from Trail Tech that cost $189 was actually closer to $300 by the time I got it in my hands, 555.  However if I can produce smooth seamless power with porting and head mods I'll do it.

See it for what it is...

You want it like a YZ250f, buy a YZ250f...

You want it like a KTM 300, buy a KTM 300...

There is only so much you can do with a YZ.

 

Not overly helpful there mate.  The reason for the question is to see if I can adapt the YZ to be more mellower power delivery not what bike I should purchase.

 

A new KTM will cost me close to $15k here, there are no used kTM's to speak of over here.  A used YZ250 $6k, hence my interest in turning the YZ250 into a tight woods weapon.

 

I've owned a YZF 250 with WR gears installed and it was a peach.  However kickstarting a 4 stroke when cartwheeled down a hill and flooded is a bit of a pain.  The two stroke kicks over when dumped worlds easier, is more flickable, and has easy service options compared to replacing valves and recutting valve seats over here, hence my interest in a two stroke.

 

Hopefully you can provide better more insightful contributions on your next post.

 

All the best.

Put a rekluse clutch in it.

 

I could do that, it will also add some flywheel weight if I get the Z start Pro.

buy a KTM. Simpler than moding YZ.

 

See my post two above this.  Cost reasons have me looking at the YZ's. 

 

Thanks for the suggestion though and point taken.

 

If KTM's were available used I'd get one over here however good modern one's less than five years old are rare as hens teeth.  Thats the reality I'm dealing with so trying to see if a YZ would fit my needs.

Is my thinking incorrect?  If I retard the timing I can reduce the hit of the powerband.  I'm wondering if anyone has done it more than 2-3 degree's and what their thoughts were.  Retarding the timing will also give me a few more RPM's on top which is always nice as the two strokes run out of revs waaay quicker than my 4 strokes.

 

This is the reason for my interest in the Vortex.  That I can retard the timing a bunch and tune with different map variables to try for a power delivery more in tune with what I'm searching for, smooth linear power.  Just not sure if I can accomplish it with the Vortex or not.

 

Thanks all.

Edited by team FTB

Interesting you do not notice much changes with the different KTM maps.  What KTM are you riding with the different map options?  I ask because the timing thread in the YZ section has people talking great effects on traction.

 

Shipping is a pain.  Everything is taxed at supposedly 40% on imported items.  My new stator from Trail Tech that cost $189 was actually closer to $300 by the time I got it in my hands, 555.  However if I can produce smooth seamless power with porting and head mods I'll do it.

I have a woodsified 09 250 sx. I just don't notice any difference of the different maps in the woods (riding or racing). It is somewhat noticeable on fire roads and other open areas.

The single most useful mod for me in taming my sx for the woods was a throttle cam system.

Is my thinking incorrect? If I retard the timing I can reduce the hit of the powerband. I'm wondering if anyone has done it more than 2-3 degree's and what their thoughts were. Retarding the timing will also give me a few more RPM's on top which is always nice as the two strokes run out of revs waaay quicker than my 4 strokes.

This is the reason for my interest in the Vortex. That I can retard the timing a bunch and tune with different map variables to try for a power delivery more in tune with what I'm searching for, smooth linear power. Just not sure if I can accomplish it with the Vortex or not.

Thanks all.

advancing the ignition timing will make the bike more responsive in the low to midrange of the powerband. Retarding it will make it more responsive up top. I wouldnt go more than 2 or 3 degress. The engine could run hot, detonate, overheat etc.

advancing the ignition timing will make the bike more responsive in the low to midrange of the powerband. Retarding it will make it more responsive up top. I wouldnt go more than 2 or 3 degress. The engine could run hot, detonate, overheat etc.

I think you have that backwards....

Not overly helpful there mate. The reason for the question is to see if I can adapt the YZ to be more mellower power delivery not what bike I should purchase.

A new KTM will cost me close to $15k here, there are no used kTM's to speak of over here. A used YZ250 $6k, hence my interest in turning the YZ250 into a tight woods weapon.

I've owned a YZF 250 with WR gears installed and it was a peach. However kickstarting a 4 stroke when cartwheeled down a hill and flooded is a bit of a pain. The two stroke kicks over when dumped worlds easier, is more flickable, and has easy service options compared to replacing valves and recutting valve seats over here, hence my interest in a two stroke.

Hopefully you can provide better more insightful contributions on your next post.

All the best.

I could do that, it will also add some flywheel weight if I get the Z start Pro.

I understand what your saying, I have a YZ. But there has to be a compromise somewhere. The cheapest and simplest way is a port job and FFW. $250 for the porting and $100 for the FFW. If money allows, throw a Rekluse in and you're set. Possibly look at a Cisco PV spring as it opens the powervalve up slightly sooner. All that in and your looking at a $1500 motor now but it will be quite a bit more manageable then before. The Rekluse is nice as it lets you ride a gear high everywhere...

I think you have that backwards....

this applies to 2 strokes. Google it . It's the opposite of what you would think.

this applies to 2 strokes. Google it . It's the opposite of what you would think.

heres a good eric gorr article about 2 stroke timing. Www.dragonfly75.com/motorbike/timingcurves.html It explains it all.

My thinking may be flawed, but I would think an SST pipe would be better than a gnarly pipe in your situation because it favors top end rather than bottom. It should be mellower at lower revs. Also, I know there are lighter power valve springs that move the powerband lower. You could try to find a heavier spring that does the opposite. And a heavier rear wheel should help, too. Get an 18" rim, a 120 tire and a UHD tube. As mentioned, gear changes, G2 400 throttle cam, 13 oz FWW, retard timing.

See my post two above this.  Cost reasons have me looking at the YZ's. 

 

Thanks for the suggestion though and point taken.

 

If KTM's were available used I'd get one over here however good modern one's less than five years old are rare as hens teeth.  Thats the reality I'm dealing with so trying to see if a YZ would fit my needs.

 

 

I bought mine from a dealer who brought the bike from the US brandnew price tag US$ 9500, 2 year later I brought a use RM250 from Miami from a dealer in Miami for US$ 3500 plus shipping with US$ 1000 and a few piston kits.

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