CBR 125r 150cc upgrade kit

[bailz]

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]

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]

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%20HEADS_CRANKSHAFTS.htm

[F5 Dave]

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]

Any advice on this project would be greatly received, cheers

Buy a 2 stroke!!!!!!!

[richban]

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:sweatdrop

[bailz]

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]

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]

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]

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]

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.

[richban]

Fixed that. No need to thank me.

Funny cos its true. A 30 hp 4 stroke might come along one day. you never know.:corn:

[speedpro]

It won't be 150cc. How big could you get an FXR out to, hypothetically speaking of course?

[goose8]

Not sure how big you can go but he runs a sv650 piston in his one , doesn't he ?
It won't be 150cc. How big could you get an FXR out to, hypothetically speaking of course?

[richban]

It won't be 150cc. How big could you get an FXR out to, hypothetically speaking of course?

With a 73mm cheapo Akunar piston you could get 204cc. Nice.

[richban]

Not sure how big you can go but he runs a sv650 piston in his one , doesn't he ?

No off the shelf stuff for me buddy. Custom 650 piston.:bleh:

[Yow Ling]

With a 73mm cheapo Akunar piston you could get 204cc. Nice.

Wouldnt have to rev it so hard to make the power, sounds legit to me

24.2 Engines must be derived from competition motorcycles. Motocross, Road Racing, Enduro and Go Kart motors and transmission parts mandatory. There shall be no restriction on the make, type or design of carburettor, ignition, exhaust, piston, cam, valve springs or cooling system except for class eligibility.F4 watercooled s strokeengines will not exceed 124.9cc. All engines must be normally aspirated except F4 4 stroke engines of less than 100cc capacity, which may be turbo or supercharged.F4 4 stroke engines over 158cc will have 10,500 Rpm limit. F4 2 stroke engines over 104cc are restricted to carburation equivalent to a single 24mm carburettor on the main engine, unlimited auxiliary engines, F5 4 stroke engines over 53cc are restricted to carburetion equivalent to a single 20mm carburettor. F4 4 stroke buckets will be required to start off the front row if painted yellow.

[TZ350]

F4 2 stroke engines over 104cc are restricted to carburation equivalent to a single 24mm carburettor on the main engine, unlimited auxiliary engines, F4 4 stroke buckets will be required to start off the front row if painted yellow.


Sounds fair .......:lol:

[Pumba]

F4 4 stroke buckets will be required to start off the front row if painted yellow.

It has got my support:2thumbsup

[Henk]

Right, I'm off to buy some paint. Yellow for me and whatever is cheap for anyone else with the same idea.

[speedpro]

I'm going to paint them all yellow while everybody else is at riders briefing.

[Yow Ling]

I'm going to paint them all yellow while everybody else is at riders briefing.

The way we normally work out the grid is we use the warmup lap , whoever gets there first gets the grid. Unless its MCI then we have transponders and get allocated grids, which is probably good as we are mixed with 250's, RG150's and buckets (development class)

[all4A50s]

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


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

Hear hear Dave. A road well traveled and trodden for me. PM me if want help.

The basic problems I'm now looking into as good as the handling is the bikes straight speed sucks;

1st weight; currently my bike weighs in at 120kg loaded with duel = looking into transplanting engine into a RS125 rolling chassis. By transplanting the engine and running in-line fuel pump should lose 20kg.

2nd narrow rims; Came painfully (while fun) crash last Sunday racing in the wet and the bike sliding out from underneath me = either by previous mentioned transplant or by fitting 2013 CBR150 running gear.

3rd engine flow; from what I can gather the 125 throttle body is 2mm smaller than the 150 throttle body = pull things apart and measure, measure, measure then source the parts.

If anyone has any (non smart arsed) suggestions please post.

[richban]

If anyone has any (non smart arsed) suggestions please post.

Do what I did. Read 4 stroke tuning by Graham Bell. Then read it again and again. As I mentioned at the track, to me your engine looks strangled at both ends. Intake and exhaust. Free that up with a bigger throttle body and a better exhaust and you will make more power. From a quick look on the web it may be 30mm. OK for a carb but not a TB.

[F5 Dave]

maybe find a really terminated 600 & saw off one good body