top speed

[Lolipop]

Hi; I am new to this site. I just bought Sh150i on Nov. 12, 2010. I also have a Buddy 125 but
wanted to move up to something bigger but not to big. I am disappointed with the high end speed.
I only weight around 127 lbs and going up hills isn't to fast. Also with a head wind scoot only hits
55-60 mph full throttle. My Buddy did better than this. I do like the bigger tires and bike is more
comfortable to ride just do not like the top speed when needed. Its like nothing else left. I have
610 miles on bike. My son does my mechanics and has owned numerous type of bikes. Are there
any suggestion to get more speed from scoot yet not voiding the warranty?

[bigbird]

55-60mph full throttle into a headwind is normal for the SH150i. Flat out, no wind, level road you're looking at 65-70 mph tops. If that's not enough, look at a Burgman 400, Majesty 400, or like I have, a Silverwing 600. The Silverwing has a top speed over 100 mph.
They're very different scooters than the SH150, but for highway riding, they can't be beat if that's your thing.

[robber57]

I also was a bit surprised and confused at the topspeed of the SH.

Some things to think about:
The speedometer on the SH is ridiculously accurate, on a long stretch of road i checked it against a gps device and found not more then +2km/h deviation, doing 100 km /h the speedo shows 102 or near 100, the difference was about the thickness of the speedo needle which is negligible.
So doing 90 means actually doing 90 which is different from most speedos which have a deviation of aprox 5 tot 10 km/h on the plus side so doing 100 on one of these means your doing probably 92(or worse)

Maybe Honda doesnt want the SH to reach a higher topspeed because the frame cant handle more without being dangerous?
Keep in mind , this bike has a flat step-trough framework which limits the rigidity of the frame, the engine-rear fork is completely in rubber bushings making it flexible and the frontfork is scooter design (fixed only at the bottom of the steering stem), all these things ad up and certainly limit the possibility to go fast in a safely manor.
Not every one has the skills to go +130 km/h on this thing and do an emergency stop.
Where normal motor cycles are usually without any compromise to handle topspeed this thing clearly has compromises to make it more useful/comfotable in situations where it is supposed to be: the city and small roads.

I must admit; it is supposed to give 16 hp but that seems a bit off if you consider the topspeed, i have had scooters with less power going faster.
There may be a few possibility's why its not faster.
* it doesnt deliver 16 HP
* it may deliver 16 HP but the transmission setup is in such a way that it can not deliver its full potential\
* it may deliver 16 HP but only if certain requirements are met.

On the first; the only way to find out is put it on a dyno and luckily a friend of me has one, unfortunately it is winter (race season off) so almost every day his bike's(its a whole team) sit at the dyno trying to improve them,he said "come back in april" also i have to make some kind of fixture to block the variator otherwise the dyno will give a flat reading due to the variable transmission.
In the mean time you can investigate the dyno chart made by Two Bro's: http://www.twobros.com/Cust_Service/Dyn ... L_dyno.pdf
Keep in mind; its wheel hp you see, not engine hp so there is the inevitable loss from the transmission and in this case (a variable belt drive) the losses are significant as with all belt drives.
The two bros dyno chart suggests the engine loses 4 HP due to transmission, thats 25% and that seems a bit high, usualy a belt drive eats between 5 and 10% and a simple transmission about 5% making the total expected loss about 15%.
So maybe its not delivering 16HP.
I already noticed this bike goes faster the hotter it gets, i mean really hot like outside temperatures reaching 35 to 40 celcius(86 to 104 F) this thing finally starts talking.
This is probably due to emission regulations, the engine is very lean on petrol to make it as fuel economic and exhaust gas clean as possible so the hotter it gets the better it runs.

If the chart is any good you may notice the little dip in the "original-stock" blue curve around 7400 rpm and the flattening of the curve up to 8300 rpm which suggest the engine is choked in some way probably a combination of exhaust,ignition and/or injection.
Even the two bro's exhaust shows the choked area although less pronounced.

The effect of that little dip is what i already noticed; if you got head wind the bike stops at aprox 90-95 km/h but if you have the opportunity to slipstream behind a car you may get it up to 105 then come out of the slipstream and it will continue to go at 105 km/h, thats clearly the effect of a dip in the power curve.

The cheap way to overcome this could be messing around with the variator weights and i am at the point of starting to try this but it is winter here(Holland) and so it is freezing,snowing and very very slippery so this has to wait until the weather clears.
If you want to try this keep in mind you only have to change the weight of an individual rol 0.2-0.3 grams to have effect.
The other and probably better solution would be to change the final reduction gear a little bit, Polini have a small kit which will probably do just about enough.
If you want to get this bike go faster(more top speed) it is the first thing you would have to do because calculated the bike does exactly 115 Km/h at 8500 rpm and making it rev more is not what you want, you want more torque and convert the higher torque by a higher end-transmission to higher speed.

A longer end transmission would also give the meaningful possibility to use a ecu converter, its a little black box which converts the ecu (electronic control unit)signals so you can adjust fuel to air ratio and or ignition.
Making the fuel mix richer and the ignition less retarded would probably even out the dip in the powercurve and maybe a wider powerrange(keeping the curve climbing up to a higher rev count).


But: without voiding warranty? , not a chance...

[robber57]

I will get this bike faster and i also really dont care about the danger, i think i have enough experience to recognize when the situation goes bad.

But that was not the state of mind of the designer at Honda when they build this thing, it will never go over 70 because the engine revs out at 8500 and you can bet your life there is a reason why Honda made the bike like this.
Its important you understand this logic before you start tweaking and realize that bad things CAN (maybe will) happen if you raise the topspeed of a bike.
Death-wobble or speedwobble being one of the more severe hence the name....
If a certain bike design has a good chance of getting in to this problem then it surely is a design like the SH, wobbly frame, wobbly front fork and a rear end fitted in rubbers....
And it's not necessary to raise the speed by dozens to get it these kind of problems, the bike can be completely stable at 121 km/h and suddenly at 123 hell can brake loose.

A long,long,long time ago i owned a Kreidler Van Veen GP50, it was my first race bike and i bought it as a cheap 50 cc bike when the regulations where changed to a 80CC class.
I modified the bike to 80cc thanks to a record breaking friend, he had a record breaker bike, the light-streamlined type and tuned the 50cc kreidler engine to a 80cc whopping 32 HP(compared to the 20 HP of the 50cc engine) and broke the land speed record in its class with the thing, if i remember something like 249 km/h.
Two years later the record was broken and i could buy the complete engine for a bargain.

I modified the frame somewhat, welded some ridges ,bigger brakes and so on.
The first test drive i got it up to about +200km/h which is probably 20 Km/h more then the thing ever was designed for, all went well up to the point i thought it was enough and raised my body from behind the fairing to start breaking....
It was my first encounter with speedwobble and it scared the shit out of me and mostly due to luck i didnt crash horribly.
Later on i made a steering stem with adjustable castor angle and got the problem solved but i never forget the total feeling of helplessness when it starting shaking and wobbling, that's scary shit and i dont want to even think about this happening on a highway....

The bike, think about getting in to speedwobble on this thing at +200km/h, its scale is not clear but if stood next to it the seat was a bit above my knee.
This is still in 50cc trim weighing 55 kgs :

KVV.jpg

[bigbird]

And I can park in on a sidewalk without the cops hassling me with tickets cuz it's "cute".....Not very manly mind ya, but works for ME!

I had the opposite experience when I had my SH150i. Three times the cops hassled me about parking on a sidewalk. I asked why the 50cc scooters could park on the sidewalk and they answered "they're not allowed to either". But I guess the 150 is big enough to get their attention here. Thankfully I never argued and I never got a ticket. I would never attempt sidewalk parking with my Silverwing!