My Yamaha SR250

[Tbird1983]

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.

[Hersbird]

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

[stiletto2]

Originally Posted by Hersbird

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)

[Daschicken]

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.



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


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.

[Tbird1983]

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.

[Grant-53]

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.

[Tbird1983]

Originally Posted by Grant-53

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.

[Ironside]

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.

[cRiPpLe_rOoStEr]

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.

[Tbird1983]

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.