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Making my 2t into a 4t

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Im trying to mellow out the hit on my RM 250 to make the power more manageable for an old guy.....me. Want to make it mellow like my 450. I know a flywheel weight is a good start. I have a PC pipe and silencer on it now. Any other thoughts?

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Buy a CR500, add Flywheel weight, FMF Fatty, and you're golden.

 

Fer your 250 I'd say Flywheel weight (as you mentioned), FMF Gnarly, Porting/head work (if you want to go crazy with it), and gear it a bit taller (helps lessen the hit).

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Flywheel weight10-13oz,preload the powervalve adjuster,reed spacer-10mm,fmf q with fmf gnarly,18in rear wheel.Lower port timing with thinner base gasket-make it or buy cometic or athena. Send carb to rb designs for divider or get a ktm 250xc pwk 36mm. Spacer for pipe-spacing out where exhaust flange mates to cylinder gives more bottom. Play with the ignition. Move stator 1 line front or back-see which you like. For even more bottom and smoother mid,get the cylinder base shaved to lower port timing and then get the head cut. So many ways to alter the power. I just run a thinner base gasket,gnarly pipe and a 10oz fww. Has tons of bottom end and transition is smooth from mid to top. Slight loss of over-rev makes it perfect in the woods. Lug off the bottom or keep it high in the revs. Makes power very friendly. Longer silencer like the q will really mellow the power. I also run a yz250 reed spacer and 06;rm250 boot. My poervalve has 1/4 turn more preload than stock. Cant remember where my ignition timing is. Think its slightly retarded.

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Flywheel weight10-13oz,preload the powervalve adjuster,reed spacer-10mm,fmf q with fmf gnarly,18in rear wheel.Lower port timing with thinner base gasket-make it or buy cometic or athena. Send carb to rb designs for divider or get a ktm 250xc pwk 36mm. Spacer for pipe-spacing out where exhaust flange mates to cylinder gives more bottom. Play with the ignition. Move stator 1 line front or back-see which you like. For even more bottom and smoother mid,get the cylinder base shaved to lower port timing and then get the head cut. So many ways to alter the power. I just run a thinner base gasket,gnarly pipe and a 10oz fww. Has tons of bottom end and transition is smooth from mid to top. Slight loss of over-rev makes it perfect in the woods. Lug off the bottom or keep it high in the revs. Makes power very friendly. Longer silencer like the q will really mellow the power. I also run a yz250 reed spacer and 06;rm250 boot. My poervalve has 1/4 turn more preload than stock. Cant remember where my ignition timing is. Think its slightly retarded.

Sounds like this aint your first rodeo. That's all the info I was looking for. Thanks a lot

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What year RM do you have?

 

It's an 06.  Thanks

Edited by scoot450R

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My poervalve has 1/4 turn more preload than stock.

Can you elaborate on how to do this.  I have never owned a 2t with a power valve so I don't really understand the concept of how it actually works or how to adjust it.  Thanks

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Can you elaborate on how to do this.  I have never owned a 2t with a power valve so I don't really understand the concept of how it actually works or how to adjust it.  Thanks

This may help: 

 

https://www.youtube.com/watch?v=GD8QnsY925Y

 

At lower rpm's the exhaust valve is closed (or lower/smaller) on the side of the cylinder.  you get more time for the burning gas to push the piston before escaping into the exhaust pipe.  At higher rpm's the valve opens making the exhaust port larger/higher on the cylinder wall.  allowing the gas to leave the cylinder faster to begin the next compression cycle. 

 

This gives your bike low end and top end in one package.    Without a power valve it would be either a grunt or rev decision.... or a compromise of something in-between.  It gives modern 2 strokes more power everywhere.

 

Changing the spring tension/preload adjusts when the valve opens....changing at what point in the rpm range extending or shortening your low end grunt.  More tension on the spring the more it resists opening early.

Edited by RhinofromWA

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Thanks Rhino,

I should have looked for that myself before posting. I did look for how to adjust it but got no results. Can someone tell me which way to turn it to get more bottom end and lessen the powerband hit? Thanks

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Left side above ignition cover-you will see a little dial with 2 bolts on the cylinder. That is the powervalve adjuster. Lossen bolts but hold the dial with a pliers. Now add 1/4 turn clockwise. This will preload the pv more allowing smoother power. If the bike has some hoirs on it-the powervalve assembly shoukd be taken apart and made sure it functions properly. Also,alot of people do a top end and assembke the pv incorrectly. This will make the bike run like a slug or hit like crazy. My bike had both issues. Mine was worn,assembled incorrectly and no tension on powervalve. Once everything is dialed,power is pretty linear with a strong mid punch on these bikes. If the hit is violent and the boke has no bottom end-something is wrong.

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Left side above ignition cover-you will see a little dial with 2 bolts on the cylinder. That is the powervalve adjuster. Lossen bolts but hold the dial with a pliers. Now add 1/4 turn clockwise. This will preload the pv more allowing smoother power. If the bike has some hoirs on it-the powervalve assembly shoukd be taken apart and made sure it functions properly. Also,alot of people do a top end and assembke the pv incorrectly. This will make the bike run like a slug or hit like crazy. My bike had both issues. Mine was worn,assembled incorrectly and no tension on powervalve. Once everything is dialed,power is pretty linear with a strong mid punch on these bikes. If the hit is violent and the boke has no bottom end-something is wrong.

Great info. Thanks a lot.

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Great info! I have been struggling trying to find the right setting on my 98 rm 250

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Another suggestion is to get a rekluse auto clutch. It allows you to ride a gear higher which basically smooths out the power.

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