My Yamaha SR250
 

Terence here from South Africa.

So here is my little bike, its an 80s designed engine, absolutely no aerodynamics at all on it, top speed is around 80-86mph, it will cruise happily at 70mph all day long. I have put a 1 tooth larger front sprocket only and a louder exhaust off an Yamaha Virago 1100. I use it 90% for daily commuting approx. 42.5 miles per day, mainly freeway and main roads, not too much stop and go. My other vehicle is a Nissan 1400cc pickup (same shape as the Datsun 1200 ute) which is not at all fuel efficient, does approx. 30-36mpg driving as economical as I can LOL

I started tracking my fuel recently (a few weeks) after quite a while. Its winter here currently (we in our coldest part of winter actually) and im getting 79.94 mpg. Last year when I tracked over the period of 4-6 months (summer weather) I was getting 90+ mpg and I wasn't trying to be economical LOL, so I think this bike has good potential if I can get some decent fairings for it and start employing some hypermiling techniques. I also need new fork seals as they are leaking and my battery is going bad, have to push start in the cold mornings, after work, starts up fine with the electric start.

So any suggestions for better fuel economy? In my country at the moment, fuel increases on a monthly basis due our really bad economy so im trying to cut costs wherever I can.

https://ecomodder.com/forum/attachme...2&d=1532072469

https://ecomodder.com/forum/attachme...3&d=1532072497

I don't know about your questions, I would be happy with 80-90 mpg, and it looks good to me! Welcome to ecomodder.

The OP seems to want to be more economical... no reason needed to explain why one would want to do something better. (especially if they could do it on the cheap)

I think if he is using mostly freeway and main roads that his speeds would have him up where streamlining would have significant results. (depending on how well the streamlining is implemented of course.) So I'd say it's up to him to decide the balance between the cost in time and money of what he would be willing to invest and the complexity/completeness of the streamlining efforts.

Riding technique is basically free so I guess asking bike hyper-milers here would be a good first step; even before doing any streamlined fairing work. And when it comes to streamlining, I think it would be best to start working from behind the rider where the air trails behind.

This is just my opinion since I am not as well versed in the finer points of ecomodding as others here. (but I'm thinking I'd not be too far off the mark)

If you want to focus on aerodynamics, you could start with an aero front fender, just cut up a panel and attach it to the forks and curve it up to the front fender. The more you cover, the more winds will affect you however.

Here is what my CBR 250R's stock fender looks like compared to an aero fender for the older CBR 250 Four.
Attachment 24566


On the bike. It took a lot more work than I thought it would!
Attachment 24567

I haven't run the fender on my CBR enough to confirm the difference is noticeable, and won't be able to confirm until it comes back from painting. I had it on for one whole tank, and that was my best tank yet, but it just squeaked above my previous record and I was tucking on highways with very little romping for that whole tank.

I would take a guess that the tires on your bike right now are bias ply with tubes. You can seal up spoked rims to run tubeless, but you shouldn't do that without tubeless tires. I believe there was a rim profile change around the 80s, so not all rims are tubeless compatible, even non spoked rims. Finding a radial tire in an old bike size is usually pretty difficult, but worth a shot.

Running a dying battery can lead to other much more expensive electrical problems later on, continue at your own risk.

Thanks for the reply and yes I know the economy is already good but I feel I can get it even better.

Im from south Africa so we work with kilometer and litres, I have been playing around with riding style, slower pull off, riding a bit slower and coasting with the engine off on long downhill sections for the past week or so and have already increased the fuel economy to 32km per litres (90mpg) based on distance driven between refuels. Will keep tracking and monitoring. Still need to sort the battery issue and im sure it could improve a bit more.

As a rule ecomodders find that the combination of hypermiling techniques and a full aero package results in doubling the stock fuel mileage. What materials are readily available locally?
Your riding position determines your shoulder height and the top of the main shell. The optimum body shell would likely be a 3:1 airfoil shape with a Kamm tail (0.85 x length) and curved sides. See the classic sailplane designs and the HPV body shell design software at recumbents.com. Attach the shell to the frame and not the forks. This greatly reduces the effects of side winds.

Great, thanks for the advice, I have no clue what is locally available, would need to research and see what I can get my hands on for cheap.

Hi Terence, because you bike has cruiser styling and consequently an upright riding position, it would be impractical to go with dropped bars and an aero tuck, so work with what you've got.
My suggestion would be to try a Harley style top half fairing similar to this one https://www.ebay.co.uk/itm/392002175883.

Cheap copies are available from China, but I don't know what sort of import duties you pay on Chinese products. A pair of panniers might also help, and turn your bike into a mini tourer.

Some of the guys in the C90 club have reported an improved fuel consumption after fitting a screen which doesn't look in the least bit aerodynamic.
It also has the effect of making your ride much more comfortable, especially when riding in the rain or through bug infested countryside.
Just my tuppenceworth, or should I say '2 cents worth'

Whatever you decide to do, please keep us informed, that's how we build a database of knowledge that we can all benefit from.

Pete.

Trying to improve the aerodynamics in a motorcycle with a "classic" style like that without turning it ugly is quite challenging. Well, I'm gonna second on the suggestion of the "batwing" semi-fairing and a wind deflector.

Thanks guys, initially considered an old retro race fairing or something similar to the above. As Ironside said, the least it will make it a comfier ride in unpleasant weather. Already have saddlebags but they material and definitely not aero at all LOL.

Thanks guys, will start a builds thread for the bike and pickup truck. Planning on doing loads of mods to the pickup, its ridiculous on fuel. Bike gets more than twice the mileage than the pickup truck.

IIRC the bakkie still uses that A-series engine originally designed by Austin, which clearly has some limitations of an older project. Would you ever consider an engine swap?

BTW what about the Diesel scene there in SA? I see lots of people there adapt Ford Essex V6 and a variety of V8 engines into nearly everything back there, but I don't find too many references of Diesel swaps (except for a Landcruiser 79 with a Cummins ISF2.8 replacing the 1HZ).

I did consider an engine swop, possibly the Nissan SR20 engine as its easily available and has been done many times before.

The Ford Essex engine swops are from back in the 80s-90s. These days the majority is 1jz, 2jz and Lexus V8 swops into anything and everything LOL but more for performance than economy.

Older diesels are not popular here for some reason. Id love to find a diesel power plant that would fit but ive been advised against it on the Nissan 1400 as there are not many options available. Newer model cars with tdi engines are pretty popular but to get one of them to fit would require more work than its work unfortunately.

Relatively cheap gasoline made out of coal by Sasol :D


There are many engines between 1.7L to 2.5L that wouldn't be too hard to fit into the 1400. Even the 1.3L Fiat Multijet could get the job done if you would consider something with electronic injection, and IIRC it has already been used in at least one RWD application in India before the phaseout of new Chevrolet car sales there.

One option to improve the efficiency of the gas engine would be to increase the compression ratio to say 10.5:1 by planing the head, and porting intake and exhaust passages. Depending on the fuel available alcohol injection or some other means to reduce pre-ignition might be needed. A local machine shop could do this without pulling the engine.

If the OP settles on more extensive engine mods instead of the aerodynamic and riding style adjusts it would be quite tempting to try a Prius-ish emulation of the Atkinson cycle in order to avoid the need for either premium fuel or any supplemental injection. Even though I am favorable to warer/alcohol injection for special/high-performance applications, it may not be the most practical approach.

BTW it may be easy to do the tuning without removing the engine block in the motorcycle, but in the bakkie if the OP eventually decides to get a fuel efficiency-oriented cam regrind it wouldn't be so easy to do so without taking the engine out since it features an OHV engine.

Yamaha Sold, New hypermilers dream bike
 

So after a long time of thinking about it, I finally decided to let my old faithful go to a new home.

Managed to find an almost brand new (its a 2009 model with 1100km on the clock, the guy bought it new for his daughter when she graduated high school, not long after she met a guy and lost interest in the bike so it just stood for the past 10 years ), its an Indian built Bajaj Pulsar 180cc with a claimed fuel consumption of 45km per litre of fuel. Comes from the same factory as the new small engine KTM bikes.

Link to specs:
https://www.bikesmedia.in/bajaj/pulsar-180-dtsi.html

Done some online research and apparently in India people get 40-60km/l consumption depending on speeds travelled as their roads are bad over there so 120km/h+ riding is not always possible. These bikes are built for durability of their harsh climate and roads and are very reliable from the reviews ive read online, some older models have 90 000+km on them and still drive perfectly.

Took delivery of the bike last night, it has a half tank of fuel which il ride out before filling up and testing the fuel economy for myself, I will be taking it easy until about 2500-3000km to make sure the engine is run in properly, it was serviced recently and the mechanic gave it a once over to make sure everything is still in decent shape after standing for 10 years but il give it an oil change at 3000km in any case.

But yea will definitely keep a log on here of how things go.

PS, the bike will be eco-modded to try up the fuel econ even more.

As a general rule, stay away from Batwing fairings. Unless you want to go with full streamlining, a vintage style race fairing with an extended windshield, and a tapered tail trunk is the best thing for a small bike

Thanks for the tip, the Yamaha was sold, new bike already has a fairing, will be looking to add a top box for better drag.

The biggest gain will likely be from a tail box that fits close to the rider's back. See sendler's box or the Yamaha Rifle fairing at craigvetter.com.

IIRC some Bajaj motorcycles are available in some export markets rebadged as Kawasaki too.