hypothetical cb 125s build
 

While i am finishing up my current cb 125s restoration i have been wondering somethings for when i do my next one (hopefully i find other one for cheap). I cant help to wonder if i did some things if they would work while keeping it looking stock. Here are a couple of my ideas that can be stand alone or combined (some procey also)1. Going up to the highest sprocket combation possible (stock is 15f 35r. 2. Stator delete with 12v conversion. Stator delete to reduce draw on the engine and 12v conversion so its easier to use leds and batteries (lifepo4). 3. Reduce/trim the body weight down. 4. led for all lights (see number 2). This is where things get pricey and more hypathical: 5. Titanium connecting rod, reducing the engine resistamce to rev up and weight (reducing the bob weight also will reduce the crankshaft and counter shaft weight). 6. Titanium or hollow/sodium filled vavles along with titanium or reduced weight keepers and retainers, which will reduce the unspring valve weight. So i can then decrease the valve spring pressure, rocker arm weight, valvetrain friction. And pssibley able to drill the cam out a little since spring pressure went down. And lastly 7. Ceramic coat the combustion chamber vavle heads, and piston. Along with other coating (oil shedding etc). To help reduce heat transfer to the head and pistons since it is a air cooled machine. Combined with compreasion increase maybe. Obviously some are really pricey and would require machine shops and calculations but would be a nice 125 after it all.

I don't think you would get the gains you were looking for with the major engine mods. You wouldn't find titanium engine parts that would fit your application. Because you mentioned "cheap", the cost would be prohibitive to do most of the engine mods because everything would need to be custom made.

Gearing up as high as possible doesn't guarantee efficiency. The small engine size would not be able to provide the torque needed to accelerate and you would be wide-open and bogging most of the time.

Depending on what you want to do with this, a few simple mods, moderate gear change, and a small windscreen may be a reasonable solution to achieve better efficiency.

Look over this page from Craig Vetter's website for some ideas on the mods that were done over the years to reach incredible MPG numbers - 470 MPG-Craig Vetter Fuel Economy contests, better mileage

Sorry i dont think i stressed the factor that i want to keep the bike look stock. I hate the look of cafe racers and or areo packaged bikes. Yes i do agree with you on the whole titanium prices and custom made parts and the gains but like i said hypathical. But also the bike only really makes around 8hp at almost max rpm so anything freeing up even a little torque would go a long way even.

Both of those factors will be working against you as speeds increase.

You can't have poor aero and low power and have efficient high speed cruising - or high speed at all.

What do you want to do with this? Ride it around town? Ride on the highway?

Around town it should do pretty well as is, but it's never going to work at higher speeds with no aero mods and that low of HP.

See MotoIQ.com for info on engine mods on the Honda Ruckus 50cc. Similar mods would apply to a 125cc. A cargo container such as a duffle or cooler behind the rider would give improved aero without looking too odd.

I considered efficiency modifications for cbr125r.
To determine if an efficiency mod is financially viable here consider the following.

Hypothetical

Efficiency Mod cost = $100.00
Petrol consumption per 100km = 2.5L
Cost of litre of petrol = $1.22
Cost of petrol per 100km = $3.05
Percentage Petrol consumption saved = 50%
Money saved per 100km = $1.53

Distance traveled = 100,000

Money saved in 100,000 km = $1,525.00

Money saved minus cost of efficiency mod = $1,425.00

If that last number is not positive then its not worth doing. If you were to make an expensive fairing that manages to save a few hundred dollars over 100,000 that would be worthwhile. However if the bike falls over and the fairing breaks you lost all your savings.

Saddly due to the bikes power if i was to full fairing it the weight would more then likely create a negative impact on mpg for sure. One its air cooled which limits the airmods and 2 the bike weighs a little shy of 200 pounds and with me a 180 poind rider that makes 380 pounds total weight. Ad like 20 pounds for aero parts and now your at 400 pounds which is a 5 percent. Yes highway cruising mpg will go up but it would never outweigh the fact the lower the like 40-50 mph mpg will drop badly due to added wieght. The bike top speed is 65 so i dont plan on extended highway useage so im my case a lighter motorcycle (reduce weight will be better)

Honestly, a battery delete may be more desirable than a stator delete in such a small carburettor-fed motorcycle.

Well the battery weighs about 4 pounds and is the size of basically 2 wallets put together (not kidding) also without the battery the stator if it has a spike (which they do alot) since 6v bulbs are more picky the small viltage spike blows out every single bulb (has happened to me before when i didnt notice there wasnt a battery)

It might not be any hard to get a 12-volt stator to replace the current 6-volt one. At least the majority of the old bikes that I still see once in a while have already been converted to 12-volt.