Making a Two Stroke like a Four Stroke

Hey guys,

I was just kind of tossing the idea around in my head for a little while, and I was wondering if you could make a 250 two stroke and, say, make it pull like a four stroke. I was shooting for the tractor like pull off the bottom to smooth mid and a strong top. Now, I have come up with a few mods that might do the trick.

1: Port and polish. I wonder if Eric Gorr does that kind of thing....

2: Flywheel weight. It would make the bike rev a little bit slower and be more tractable.

3: Pipe. Not sure which one would give the most linear power, but I have heard the FMF SST smooths power out.

4: Reeds for the power gains

5: Higher comp piston to make it pull a little bit harder right off idle.

and thats where I get stuck. If anyone can suggest a few mods that would accomplish the above listed characteristics, it would be great :thumbsup:

P.S.

The reason I want to make a 250R more like a 450 is mostly because of maintainance costs. This would make a dominant 250C racer

your best bet is to get a 4 stroke.

^ What he said.

2 strokes ride like 2 strokes. 4 strokes ride like 4 strokes.

If your spending that money JUST to achieve a certain power delivery, you should save that money, buy a four stroke, and use it for the higher rebuild cost.

Agreed, it's not gonna happen.

The only 2-stroke that can come close is a toned down 500.

When I had my Rekluse Pro on my YZ250 it gave it amazing low end power. Added a FMF gnarly which gave it too much low end snap IMO. The rekluse was the one bolt on that made it unreal torque wise. :thumbsup:

Eric Gorr can give you a big bore and port for low end too.

Regarding the comment of high cost four stroke rebuilds.... :confused:

Well... You could always put a bigger rear sprocket on... You'd lose a whole bunch of topend, but it'd be sweet on the low end.

Never heard of someone wanting to dumb down their bike. Whatever floats yer boat I guess!

GasGas ec300 or the KTM300

Agreed, it's not gonna happen.

The only 2-stroke that can come close is a toned down 500.

That is so true! when my CR500E had the restrictive road legal muffler fitted it really tamed it down, it behaved like a 4t, didn't want to rev out as much and a lot of smooth torque.

A bigbore (300) European 2T is exactly as you describe

Copy a KTM300. So have an engine builder make it a 300 and adjust the ports and PV for low end. Throw on an FMF Gnarly, Q Stealth, and DbSnorkel. Add a flywheel weight and steel clutch plates.

I considered finding a cheap YZ250 and going this route but decided it would be so much easier and worth it in the long run to drop the $$$ on a new KTM300 instead.

People who say this have no idea, unless they're only talking about engine braking. My 300 would freak them out.

2 strokes ride like 2 strokes. 4 strokes ride like 4 strokes.

With a larger displacement, you could tune it anyway you want. A 450 2 stroke would have far more bottom end pull than a 450 4 stroke. For a good example of this, check out modern, normally aspirated 2 and 4 stroke outboard engines. Displacement is limited by how much weight you can hang off the back of the hull. When displacements are equal (or relatively so), it is the two stroke engines that has FAR more bottom end punch. My neighbor and I both had boats with the same 20 foot hull. He opted for a Yamaha 4 stroke 150, whereas mine was fitted with the "ancient technology" 150 smoker with carbs. Both boats had the same top-end, but the 4 stroke had a much weaker hole shot, and was really bad at pulling up heavy skiers and other tasks that need a strong bottom end. My boat would literally "jump" on plane as soon as the throttle was punched. The main virtue of the 4 stroke was that it could troll all day at idle speed without loading up.

flywheel weight, bigger rear sprocket,porting, power valve adjustment. Not trying to be mean here, but you could just learn to use the clutch better. I have a 250 and ride a 300 as well. The 250 will pull like a tractor when I feather the clutch, it will pull up anything. The 300 pulls like a 4t on the bottom. I prefer the 250 when my wife's not on it b/c I miss the snappy power, but that's just me

My GasGas 300 is basically what you described, its a moster on the bottom end and pulls like my yz250 up top. Must smoother then the yz250. Ive ridden KTM 300's too. basically feel the same...minus alittle top end compared to the GasGas. Never rode the husky 300. If I were you I would just switch to a Euro 300 2t.

Hey guys,

I was just kind of tossing the idea around in my head for a little while, and I was wondering if you could make a 250 two stroke and, say, make it pull like a four stroke. I was shooting for the tractor like pull off the bottom to smooth mid and a strong top. Now, I have come up with a few mods that might do the trick.

1: Port and polish. I wonder if Eric Gorr does that kind of thing....

2: Flywheel weight. It would make the bike rev a little bit slower and be more tractable.

3: Pipe. Not sure which one would give the most linear power, but I have heard the FMF SST smooths power out.

4: Reeds for the power gains

5: Higher comp piston to make it pull a little bit harder right off idle.

and thats where I get stuck. If anyone can suggest a few mods that would accomplish the above listed characteristics, it would be great :thumbsup:

P.S.

The reason I want to make a 250R more like a 450 is mostly because of maintainance costs. This would make a dominant 250C racer

Quit being lazy and learn how to shift, Sandbagger!

One more to add to your list is retarding the timing. There is a thread you can find in the FAQ of the Yamaha 2-stroke forum. Basically, retarding the timing will take a little of the snap out of the engine and help with traction if I understand correctly.

I love my 2 stroke but I love riding the 4t's too! Wish I could afford to own both!

I love my 2 stroke but I love riding the 4t's too! Wish I could afford to own both!

plus 1 to that:thumbsup:next year when taxes come back im gonna get a used cr250,i love my X and am keeping it but i miss 2ts and want to be able to switch back and forth,though admittedly i have considered just trading out my X for a ktm300exc next year,mabey wait one more year and see if honda gets off its ass and developes a 2t trail bike?????:thumbsup::worthy::confused:

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