Tone down 250 two strokes???

[chump6784]

So i have been thinking lately, with 250 2T's running with the 250 4T's why couldnt the 2T's have their power mellowed out.

The main thing with motocross 2T's is that the power is very abrupt making traction an issue where as the 4T's produce very linear and tractable power.

So this got me thinking. lately in the enduro scene the 2T bikes have been coming out with adjustable power valve springs to mellow out the power and make more usable, more torquey power curves. Obviously this results in a loss of peak power but as 2T's already have a power and torque advantage by a substantial margin they could lose some of that if it ment a better power curve.

obviously this sort of defeats the purpose of a 2T as the snappy power delivery is one of the reasons why i and i suspect most of you bought a 2T but it would also make them a quicker bike on a track.

Now this is just what i have been thinking, it may have been tried before and failed so feel free to set me straight but i would be interested in hearing your thoughts on this as i really cant see it being a disadvantage

[TMKIWI]

Your not quiet right.
The adjustable power valve springs do not lower peak power at all.
All they do is control the speed at which the power valve opens.
If the power valve opens quickly the power will have a sudden surge (hit).
By slowing down the opening time it allows the motor to gain more revs and more power so when the power valve is fully open the "Hit" is less.
There are also Hydraulic adjustable powervalve adjusters available.
JRF & Porivoni ?. Not sure on the spelling.
Hope that answers your question.

[chump6784]

yeah it kind of does. my main question is why is no one doing it. it seems like the way to make 2 strokes faster is to make them easier to ride. make em faster and they will win. make em win and more people will buy and the two stroke is reborn

on another note. went into a yamaha dealership today and asked if they had any 2011 yz250's coming in as all they had on the floor were 4 strokes. the salesman then told me that they were getting more in as the ones they had just sold out. made me feel good that the 2 strokes went and the 4 strokes were sittin collecting dust

[MMS]

it seems like the way to make 2 strokes faster is to make them easier to ride. make em faster and they will win. make em win and more people will buy and the two stroke is reborn

With respect, I'd have to take issue with that as I don't believe that's the problem. Modern 250 2-strokes ARE easy to ride, many people would be just as fast if not faster on them than the expensive, money absorbing time bomb they're presently droaning around on, and if there was more of them out there they WOULD be winning.

The problem is perception, there are lots of young fellas out there now riding and singing the praises of the 4-stroke and they don't even have a genuine notion what a 250 2-stroke is like in comparison. The only perception they have is that which has been implanted in their brain by the manufacturers via the press and dealers.

All you need to do is to get these poor unenlightened souls to actually TRY a 2-stroke but sadly that's becoming increasingly difficult to achieve due to various factors.

[SwapperMX]

Hey MMS, very true what you say. Alot of guys I ride with have never even touched a 250 two stroke. They figure they are too fast and too hard to ride. I know I am faster on a 250 two stroke when compared against a 250F, but I have had to really pull my finger out and start training properly and hitting the gym hard so that I can be as fast at the end of the moto. That is the biggest difference for me, it is much much easier to go fast on a 250F when you have already started to tire, or are completely worn out. With the rules changing at the amateur level here in Australia to come into line with the pro rules, allowing 250 two strokes in the lites class, I know a lot of guys talking about making the switch to a two stroke. It will be very interesting to see how many actually line up on the startline of the Sunny State series for the first round next year. I know I will be there !!

Chump, you can definitely achieve what you are talking about. For example, the powervalve spring option on the Kato's is good, and if you keep going, and add extra flywheel weight, along with an adjustable ignition, play around setting up the timing, and possibly change to a chamber more suited to low end power, and boom, you have a torque monster. Obviously going to give up upper RPM power, but you understand what I mean, and that the power on a 250 two stroke can be easily modified to suit each individual rider/application !!

[evo550]

Hey MMS, very true what you say. Alot of guys I ride with have never even touched a 250 two stroke. They figure they are too fast and too hard to ride. I know I am faster on a 250 two stroke when compared against a 250F, but I have had to really pull my finger out and start training properly and hitting the gym hard so that I can be as fast at the end of the moto. That is the biggest difference for me, it is much much easier to go fast on a 250F when you have already started to tire, or are completely worn out. With the rules changing at the amateur level here in Australia to come into line with the pro rules, allowing 250 two strokes in the lites class, I know a lot of guys talking about making the switch to a two stroke. It will be very interesting to see how many actually line up on the startline of the Sunny State series for the first round next year. I know I will be there !!

Chump, you can definitely achieve what you are talking about. For example, the powervalve spring option on the Kato's is good, and if you keep going, and add extra flywheel weight, along with an adjustable ignition, play around setting up the timing, and possibly change to a chamber more suited to low end power, and boom, you have a torque monster. Obviously going to give up upper RPM power, but you understand what I mean, and that the power on a 250 two stroke can be easily modified to suit each individual rider/application !!

Hey Swapper, rule changes, what rule changes?

[2T Institute]

Increasing crankshaft inertia IS the way forward

[SwapperMX]

Hey MMS, very true what you say. Alot of guys I ride with have never even touched a 250 two stroke. They figure they are too fast and too hard to ride. I know I am faster on a 250 two stroke when compared against a 250F, but I have had to really pull my finger out and start training properly and hitting the gym hard so that I can be as fast at the end of the moto. That is the biggest difference for me, it is much much easier to go fast on a 250F when you have already started to tire, or are completely worn out. With the rules changing at the amateur level here in Australia to come into line with the pro rules, allowing 250 two strokes in the lites class, I know a lot of guys talking about making the switch to a two stroke. It will be very interesting to see how many actually line up on the startline of the Sunny State series for the first round next year. I know I will be there !!

Chump, you can definitely achieve what you are talking about. For example, the powervalve spring option on the Kato's is good, and if you keep going, and add extra flywheel weight, along with an adjustable ignition, play around setting up the timing, and possibly change to a chamber more suited to low end power, and boom, you have a torque monster. Obviously going to give up upper RPM power, but you understand what I mean, and that the power on a 250 two stroke can be easily modified to suit each individual rider/application !!

Hey Swapper, rule changes, what rule changes?

Yeah man, from all the information I have been able to gather, and I have been working at it for a long time, that will be the case.  250 two strokes legal in the lites class at all levels for next year !!!

[JohnN]

I believe that Swapper is talking about the Amateur program in Australia with the 250 vs. 250. Please confirm if I am correct.

Chump6784 - you bring up an excellent point. Although this has been tried in the past with the 500cc two-strokes. In the 1980's the manufacturers were attempting to get more and more power out of the bikes, but the pro racers were finding it more difficult to race the machines, so they began lowering the peak horsepower, making the bikes more tractable. This helped them to ride faster.

Another important factor is throttle control and gear selection. On the four-stroke you can be lazy on both and still do well in the amateur ranks. When you get lazy on the two-stroke, you end up breaking the rear wheel loose at times that can put you in trouble.

That "explosive" power that so many of you look forward to, is not necessarily the fastest way around the track. Ridden properly by a great racer, even a stock 250 two-stroke can be easy to ride.

Check out this video to see what I'm talking about.
MXPTV Rider Profile - Randall Everett (No Music)

To answer your question, can it be done? Yes.

But then the question becomes will the advantages out weigh the dis-advantages?

[burn1986]

Heck, just get a flywheel weight.

[factoryX]

lol

[miedosoracing]

Rob Peter to Pay Paul.  But I ask this to anyone who has ridden either.  Do you really want 4 stroke feel?  I had an XR600 lately and hated it so much that I traded it off in a short time.  I just couldn't stand the no bark feel of a 4 stroke. It was boring, even though it had all kinds of power.

[Turquine]

If toning it down is your goal, why not try something like this. Instead of buying say the KTM SX motocrosser, buy the enduro 250, and set it up for MX riding. I personally, always want more power, but it would be interesting to see if one could turn quicker lap times on the enduro version of the KTM 250 in the SX frame and same gearing. I stated elsewhere that I believed KTM could make a 450, just like their 300 enduro, only bigger, and have a bike with about as much power as an old KX 500, but which is easy to ride like their own 300. I don't think that would be hard to do at all, but maybe 2T Institute can straighten me out here if I am mistaken. I wouldn't want that for a desert playbike though. For that, I want all the power I can get. Might help in MX though, who knows.

[chump6784]

Hey MMS, very true what you say. Alot of guys I ride with have never even touched a 250 two stroke. They figure they are too fast and too hard to ride. I know I am faster on a 250 two stroke when compared against a 250F, but I have had to really pull my finger out and start training properly and hitting the gym hard so that I can be as fast at the end of the moto. That is the biggest difference for me, it is much much easier to go fast on a 250F when you have already started to tire, or are completely worn out. With the rules changing at the amateur level here in Australia to come into line with the pro rules, allowing 250 two strokes in the lites class, I know a lot of guys talking about making the switch to a two stroke. It will be very interesting to see how many actually line up on the startline of the Sunny State series for the first round next year. I know I will be there !!

that was my point, the smooth power is easier to ride more consistantly. i am not looking to tone my bike down as i dont race but was just thinking that for racing application it could give the rider an advantage

[SwapperMX]

I believe that Swapper is talking about the Amateur program in Australia with the 250 vs. 250. Please confirm if I am correct.

Hey John, yes that is exactly correct. All of this year, the pro's have been allowed to compete on 250 two strokes against the 250F's, and for next year, any racer, at club level, state level, or again in the pro ranks, can compete on a 250 stroke in the lites class.