CBR 125r 150cc upgrade kit

[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.

[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 .......

[Pumba]

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

It has got my support

[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