More bottom end power?

[FoxRocket]

Ok, since I am only planning on keeping the bike another year or so, I have decided, with the help of all you fine people, that the big bore kit is not the way to go to get more bottom end power out of my 01 CR125. I have bolted on everything under the sun to the bike, and now realize that I am going to have to do some kind of engine work. So what is a good alternative to the big bore kit for more bottom end power? My CFO said I could spend around $250.00 on it w/o being in trouble! lol

[Satch0922]

first tell us what you have already done to the bike.

[ossagp]

LOL let me get this straight: You say that the bigbore kit is not the way to go to get more bottom end???? I didnt read anyone that owns one say that. But here goes anyway: There is no repacement for displacement. NONE. ok, that said here is what I would do if like you I was against the bore kit and wanted more low end. Now since you already went catalog broke bolting things onto the outside without the result you wanted the last remaining thing would be to retard the port timing. That will require you to have the cylinder milled at the base gasket surface. You may need some headwork done (on the bike too) to clear your piston. If you are going to do that I would sell that PhatHead and have the stock one modified, heck you might find it works better anyway. If low end was all you wanted for less than the price of the three piece head that is where I would have started anyway. (Anyone know of a pro running one of them?)

[FoxRocket]

Originally Posted by Satch0922

first tell us what you have already done to the bike.

FMF Fatty Pipe / FMF Shorty Silencer
V-Force2 Reed Valve
Geared up one tooth in the rear to pull harder down low.
Bike is jetted very clean, 1/2 premium pump to 1/2 race gas.

These are the only mods I can think of that I have done to ensure bottom end power.

[FoxRocket]

Originally Posted by ossagp

LOL let me get this straight: You say that the bigbore kit is not the way to go to get more bottom end????

No, I KNOW that the big bore IS the way to go for bottom end power. However, I am only keeping the bike another year, and spending ANOTHER $500.00 to get the 144 kit doesn't seem all that practical. As well, I don't think that anyone is going to appreciate me racing the 125 class with a 144.

[Thumprding]

Put a flwheel weight on. It will not really increase lower rpm torque (that is what you want) but it will increase the rotating inertia and store more energy.

To really increase low end power on a two stroke you need to alter the combustion chamber shape, the porting, the ignition mapping and the pipe design. Those changes do not come cheap plus they will take away from the upper RPM power. Ya don't get something for nothing on a engine.

Remember too you are on a 125. You are only dealing with 15 cubic inches of displacement. I would say buy a stealthy flywheel weight and put the remainder of the money on buying a new bike. Say like a 250 two stroke.

[Aus_Rider_22]

Looking at the mods you have done I think you have pretty much exhausted all the things you can do to get more bottom end without going bigger displacement.

Probably not what you are after but you could put a larger sprocket on rear or put 12t on the front if you haven't already. Hope this helps.

[kuritaro9]

or maybe try a diff.pipe combo. i dont think you will ever get a cr125 to have great low end without going to a overbore kit.if your worried about racing it in the 125 class, ahhh,just dont tell anyone

[Aus_Rider_22]

Come to think of it, If I was in your shoes I would be tempted to send to Eric Gorr.

Just tell him you are wanting as much bottom-end as possible and he would port and work the bike to gain maximise horsepower at lower revs.

Btw, what bike are you getting after the CR?

[LoKi]

Might drop a tooth on the front sprocket, and mess with the gearing a bit. A flywheel weight would also be my suggestion.