I’m curious what other 125 owners have done to their motors and what the results were.
What I have done, ordered from most effective to least.
Replaced the TMX with a Keihin 36mm PWK. This is the most bang for the buck. Bottom end and midrange are greatly improved. The power is very smooth and linear. The bike is much more forgiving if the jetting is off a bit. I think I lost a little top end but I don’t really notice it on the trail. I would really like to try a 38mm PWK.
Unless you run wide open all the time jetting is very important on this bike. If too lean or rich it is just too hard to keep the bike on the pipe without a lot of clutch abuse. If jetted sharp the bike will pull well on the bottom and mid and get up on the top end when needed without any problem. Since needle swaps can be done in about 3 minutes on the trail it is very easy to dial this bike in.
Turbine Core II silencer. I originally bought this just because the stock unit is such a PITA to repack. I like my bike quiet but the stock one was loud anyway once on the pipe. I was really surprised when the silencer change gave a substantial midrange boost. I had to lean the jetting a bit for best results.
Head cut by RB Designs. The stock squish is really not bad. It was 1.2mm. Since RB is right near where I live I figured it was worth $45 to get it perfect (1mm). Replacing the stock .5mm base gasket with .3mm would do the same thing but I didn’t want to mess with the port timing and I wanted the bowl reshaped to keep compression from getting too high. This mod made the midrange come on harder. It also makes the fuel burn more complete which makes jetting easier.
V Force II reads flipped to “low end” position. Very minor difference.
Timing advanced just a hair. Very minor difference, I run straight Av gas though so I knew I could get away with it.
What I haven’t done but am curious about
I was thinking of having RB Designs bore my carb to 37mm and put a divider in it. Or just get a 38mm PWK. Not sure it is worth the bother though.
Porting. When I did the top end I noticed the case and cylinder ports have virtually no mismatch so nothing needs fixed there. I don’t know if porting could do much for this motor or not. I wouldn’t want to make it a top end only motor. I have not heard any report from anyone running a FBF ported 125.
Big Bore. I considered this before I did a top end rebuild. Really the bike has enough power as is so I don’t want to mess up reliability. From what I have read a 133 still feels like a 125 and is reliable. Some say it is not enough of an improvement to justify the cost though. Eric Gorr can do a 144 which is what I will probably go with if I just decide I want more power. Uptite does a 166.
Pipes. On the older models different pipes, especially the Dynoport, are supposed to help a lot. The newer bikes have better stock pipes so I don’t know if there would be much improvement or not. I will wait until the stock unit is smashed and then probably just get a FMF.
Reeds. I would like to try a Boyeson Rad Valve some day (I assume the Honda CR125 would work) but don’t feel like going through the rejetting that is mandatory for it. I noticed that most of the YZ owners prefer the Boyeson over the V-Force so it might be good.
08 cylinder. I have no idea if it will bolt onto my 06 or not. I have heard a couple reports that it produces a lot more power but then others like Ajaxauto make it sound like the 06 and 08 run the same. I guess I need to spend some time looking at part numbers. I’ll probably get more excited about this option if Husky brings out a factory 144 cylinder. I am guessing this would be a real expensive modification.
Ignition – I am curious what the CR ignition does but I doubt I will every try it unless I get a ride on a CR and really like it. The FBF ignition looks cool assuming it has some good woods maps. This all sounds way too expensive for the benefit though.
Actually I am real happy with my bikes motor and consider it “done” but it’s fun to tinker. I’m curious what else gives the 125 a good boost.
Realistically, I’ll probably look for a set of TC/TXC 50’s or FBF 50’s before I spend any money on the motor.
What I have done, ordered from most effective to least.
Replaced the TMX with a Keihin 36mm PWK. This is the most bang for the buck. Bottom end and midrange are greatly improved. The power is very smooth and linear. The bike is much more forgiving if the jetting is off a bit. I think I lost a little top end but I don’t really notice it on the trail. I would really like to try a 38mm PWK.
Unless you run wide open all the time jetting is very important on this bike. If too lean or rich it is just too hard to keep the bike on the pipe without a lot of clutch abuse. If jetted sharp the bike will pull well on the bottom and mid and get up on the top end when needed without any problem. Since needle swaps can be done in about 3 minutes on the trail it is very easy to dial this bike in.
Turbine Core II silencer. I originally bought this just because the stock unit is such a PITA to repack. I like my bike quiet but the stock one was loud anyway once on the pipe. I was really surprised when the silencer change gave a substantial midrange boost. I had to lean the jetting a bit for best results.
Head cut by RB Designs. The stock squish is really not bad. It was 1.2mm. Since RB is right near where I live I figured it was worth $45 to get it perfect (1mm). Replacing the stock .5mm base gasket with .3mm would do the same thing but I didn’t want to mess with the port timing and I wanted the bowl reshaped to keep compression from getting too high. This mod made the midrange come on harder. It also makes the fuel burn more complete which makes jetting easier.
V Force II reads flipped to “low end” position. Very minor difference.
Timing advanced just a hair. Very minor difference, I run straight Av gas though so I knew I could get away with it.
What I haven’t done but am curious about
I was thinking of having RB Designs bore my carb to 37mm and put a divider in it. Or just get a 38mm PWK. Not sure it is worth the bother though.
Porting. When I did the top end I noticed the case and cylinder ports have virtually no mismatch so nothing needs fixed there. I don’t know if porting could do much for this motor or not. I wouldn’t want to make it a top end only motor. I have not heard any report from anyone running a FBF ported 125.
Big Bore. I considered this before I did a top end rebuild. Really the bike has enough power as is so I don’t want to mess up reliability. From what I have read a 133 still feels like a 125 and is reliable. Some say it is not enough of an improvement to justify the cost though. Eric Gorr can do a 144 which is what I will probably go with if I just decide I want more power. Uptite does a 166.
Pipes. On the older models different pipes, especially the Dynoport, are supposed to help a lot. The newer bikes have better stock pipes so I don’t know if there would be much improvement or not. I will wait until the stock unit is smashed and then probably just get a FMF.
Reeds. I would like to try a Boyeson Rad Valve some day (I assume the Honda CR125 would work) but don’t feel like going through the rejetting that is mandatory for it. I noticed that most of the YZ owners prefer the Boyeson over the V-Force so it might be good.
08 cylinder. I have no idea if it will bolt onto my 06 or not. I have heard a couple reports that it produces a lot more power but then others like Ajaxauto make it sound like the 06 and 08 run the same. I guess I need to spend some time looking at part numbers. I’ll probably get more excited about this option if Husky brings out a factory 144 cylinder. I am guessing this would be a real expensive modification.
Ignition – I am curious what the CR ignition does but I doubt I will every try it unless I get a ride on a CR and really like it. The FBF ignition looks cool assuming it has some good woods maps. This all sounds way too expensive for the benefit though.
Actually I am real happy with my bikes motor and consider it “done” but it’s fun to tinker. I’m curious what else gives the 125 a good boost.
Realistically, I’ll probably look for a set of TC/TXC 50’s or FBF 50’s before I spend any money on the motor.
)
