CBR 125r 150cc upgrade kit

**bailz** · 31st May 2013, 08:50

Am looking at building my first bucket racer, and am needing some advice. As it's very difficult to get hold of a descent CBR 150, I've been told the next best option is purchase a CBR 125r and put a 150cc big bore kit on. Has anybody else tried this? Any problems I should be aware of? Where are some options for purchasing a good 150cc big bore kit?

Any advice on this project would be greatly received, cheers

**kel** · 31st May 2013, 09:59

The CBR is the expensive 4 stroke option for bucket racing, but it is the best 4 stroke.
Converting a 125 to 150 will surely cost you more than buying a 150 in the first place. Try Akunar.com for big bore kits, note they don't list prices which means its going to cost lots!
Why not buy an FXR? Theres still plenty around at reasonable prices plus performance upgrades are cheap and theres lots of advise and knowledge kicking around.

**Moooools** · 31st May 2013, 10:59

Akunar did do them for about $1000 a while ago. Not bad given the number of parts involved. (All genuine honda).

http://www.akunar.com/BORE_KITS_RACE...RANKSHAFTS.htm

**F5 Dave** · 31st May 2013, 12:09

125 is Fi vs 150 is carb, George here did it that way & found it was a pain involving different rod small ends & drama.

Better to find an importer or buy an engine on Evilbay to reframe it.

Or build a real engine like Kel's

**jasonu** · 31st May 2013, 13:10

Originally Posted by bailz

Any advice on this project would be greatly received, cheers

Buy a 2 stroke!!!!!!!

**richban** · 31st May 2013, 16:52

Originally Posted by jasonu

Buy a 2 stroke!!!!!!!

From akunar

A full 4valve conversion kit including everything from the cases up using genuine honda cbr150 fi parts which is $600 USD

Just happend to have that on hand

**bailz** · 1st June 2013, 09:25

Fantastic replies......very very helpful. I've e-mailed Akunar and they have given me a price of $600 US + shipping for the full 150cc kit. They now need to know the size of piston I will require? The options were: 63.5,64,65,66,67 and 68mm. Does anybody know what the NZ new factory size the CBR 125r piston was?

Also Akunar needed to know if the kit would be needed for Fi or carburetted model. What year did the NZ new CBR 125r become fuel injected??

Thanks heaps for your advice so far, if I find out all the answers I'll be ordering the 150cc kit ASAP

**speedpro** · 1st June 2013, 10:13

If you have a 125 and it's FI, the FI will be for the 125. Chances are you will need to upgrade the throttle body and then tune it as well with some aftermarket device if one is available for them. Other option would be to install an aftermarket FI solution like Ecotrons. Either way the FI route is going to cost plenty. Mind you a pretty carb isn't cheap either, ask Richban. You probably should have a good idea of the finished package before ordering anything and also the cost of "all" the bits. It can add up real fast.

**Yow Ling** · 1st June 2013, 10:21

Originally Posted by bailz

Thanks heaps for your advice so far, if I find out all the answers I'll be ordering the 150cc kit ASAP

Can I suggest you get a bike first then worry about the kit later, 125 's are still legal in buckets , you could learn alot on that before dropping another grand on a bigbore kit.

I personally think you might be a bit fixated on the CBR, stock they make 15hp , FXR 13.5hp FXRS are easily available and relatively cheap for the grand you are going to throw at the 125 you will get 15hp, if you spend a grand on an FXR you will get around 20hp, I have a CBR150 but i lent it to somebody, I still ride my FXR so Im a bit biased but have a foot in both camps.

**richban** · 1st June 2013, 13:13

Originally Posted by Yow Ling

Can I suggest you get a bike first then worry about the kit later, 125 's are still legal in buckets , you could learn alot on that before dropping another grand on a bigbore kit.

I personally think you might be a bit fixated on the CBR, stock they make 15hp , FXR 13.5hp FXRS are easily available and relatively cheap for the grand you are going to throw at the 125 you will get 15hp, if you spend a grand on an FXR you will get around 20hp, I have a CBR150 but i lent it to somebody, I still ride my FXR so Im a bit biased but have a foot in both camps.

What he said. It is a money pit. If you want a fast motor then yeah spend money, but. You will be looking more like 3k after you get a new trottle body, a Power commanda. Dyno time to tune it. Then what have you got. A stock FI CBR 150. Spend another 2k and it will be really fast.

**speedpro** · 1st June 2013, 18:06

Originally Posted by richban

What he said. It is a money pit. If you want a fast motor then yeah spend money, but. You will be looking more like 3k after you get a new trottle body, a Power commanda. Dyno time to tune it. Then what have you got. A stock FI CBR 150. Spend another 2k and it will be really fast for a 4-stroke.

Fixed that. No need to thank me.