The problem with upgrading or tuning engines is that, if you want to do it right and make your bike run substantially faster/better, you have to upgrade every component in the system, in order to avoid the 'weakest link' syndrome.
For a significant increase in the CBR150R's HP, one would have to replace the various parts that make up the 'breathing & feeding system': the carb & air filter, e.g. combine a Keihin 32mm (if I remember correctly) with K&N filter, and the exhaust system (header and muffler).
From what I gathered, the OEM carb on the CBR150's in particular is very restrictive, so this would be the first thing to replace before modifying anything else. Of course, when one modifies the 'inhaling' part of the breathing/feeding system, one should also adapt the 'exhaling' part, and thus free up the exhaust.
Next step-up would see replacing the CDI unit (increase the revs) and cam shafts (increase valve opening) to make full use of the aforementioned modifications to the breathing/feeding system.
The final step-up to really put the cherry on top would be a bigger bore and piston to increase cylinder capacity to nearly 170cc and do the porting of the head to improve the 'flow'.
Combined, these modifications should result in a substantial increase in power/speed, but from what I read somewhere it would also double the CBR150's gas consumption. But you would definitely have a bike to surprise guys on much bigger bikes once you hit the twisties.
Of course, with all this increase in power, you'll be entering corners at much higher speeds, so steel-braided brake lines would be a welcome addition, as well as upgraded suspension (USD forks and after-market shock absorber).
It all depends on where you want to take this project and how much money you want to sink into this bottomless pit that bike-tuning can become (you're talking to a hopeless addict here, and hopefully my wife never finds out how much money went into turning a stock KTM 525 EXC into a worldclass full race-specs supermotard). Just replacing the muffler with a cheap 'Endurance' can is only going to increase the noise level substantially, without any significant gain in power. You might have the impression of having gained some power, but that'll be mainly due to the psychological impact of the higher noise level. You would at least have to mount a bigger carb and K&N filter in order to reap the benefits of a free-er exhaust. But a carb and filter is still a modest investment.
When I returned from EU last week I was excited to find a nicely looking CBR150R sitting in my garage (my wife is a darling, isn't she?!). She had even bought the orange/black model so it would match well with my KTM's (She's a designer after all).
I never thought a small road bike like the CBR150R would ever be able to get me enthusiastic, but now that I've taken it for a spin around the outer ring road, pushing it to 155km/h (down the tunnels and bridges) and the Samoeng loop, I am really surprised what a great little bike it is. I'm still getting familiar with the bike in its stock version, but the first impression is impressive!!! The bike handles very well, although the forks are undersprung (at least for my 88 kgs/190cm).
I have to admit I'm very much tempted to turn this bike into a project, but I wonder how much such an exercise would diminish its "daily practicality" factor as a transportation/commuter bike. The purpose for getting me this bike was to allow me to commute the 41 kms one-way between my home in Hang Dong and my resort in Mae Rim. Of course, now that she has bought me this new toy, the wife has started visiting the car dealerships as she wants a new car. I tell you, shopping for cars/bikes/upgrades is a bottomless pit...
If Ian Bungy and a few others would join the CBR150 club, we might turn it into a GT-Rider sub-chapter that exchanges info and go out together for fast & furious rides along Samoeng loop and other twisting roads...
Klaus, please do post Faddy Bike's price list for the special parts, no use all of us emailing and annoying them with the same questions. Any other info on tuning CBR150R's is always welcome, as it will help me sustain my addiction...
Cheers to all.
]
