project bike

[zooter]

Greetings, I've got a bit of a project on and would appreciate any knowlegeable advice. The nearest bike wrecker is over 200 k's away and doesn't have anything suitable.

I need the lightest possible engine that will give me enough power to keep up on the highway, 14 HP should do it methinks but always open to advice.

I need lights to light the way in pitch black at that speed.

I need a kickstart as I'll be running without a battery to save weight.

A racing dirtbike puts out heaps of horsepower and needs rebuilding far too often. There are lighting coils available for some models but I don't know if 50W is enough with a led tail light. There is an attraction in the layout of the exhaust chamber round, up and over rather than slung underneath, so I wonder if they can be tuned to run more like a roadbilke?

I saw a '99 RG'something' 150 with a kickstart but it looks kind of bulky compared to the dirtbike motors. Weight is everything. If I use a roadbike I'll need a custom chamber as the rear wheel is going to be a 10" rim jammed up close to the motor, possibly with motor suspended on the swingarm ( I know it's nasty but handling is secondary to compactness and simplicity)

Anyone with the good oil? Lightest possible please!

[avgas]

if i were you i would try an be air cooled (so that means RGV instead of RG). 50w for a led tail light? what do you mean exactly as most led use about 0.05w (or less) each so using a bizzillian leds still isnt going to use that much. What about a XR motor as these are bullet proof, torquey and easy to get. try and use SuperBright Leds or some low power/high candella light source for the light, something with an efficacy of about 50 or better would be good.

[FzerozeroT]

if you were going to do a low, very aerodymamic bike, you could use a TS50 engine r similar, but with the compactness thing you'll probably want 4 stroke, the engine is slightly larger but you don't have a bulky (expensive to fabricate for custom bike) exhaust chamber, maybe an older four stroke? or if money was no object a wrecked scoter (new epicurio)?

[FlyingDutchMan]

There are lighting coils available for some models but I don't know if 50W is enough with a led tail light.

I have a single 5W LED for use as a head mounted torch and can easily see 30+ meters when its dark (can see it light up road reflectors about 2km away). Use that for a tail light and you will blind who ever is following. For tail/brake lights, you'd probably need 20 super bright LEDs, which use about 50mW each - that totals 1W. You only need to be worried about your headlight for using 50watts or more.

[FROSTY:Me]

DUDE YOU HAVE AN ISSUE --COOLING-- if you follow the plan I think youre following no aircooled motor is gonna last more than a few operating hours before ya cook it.
I hear where you're coming from but id be tempted to suggest a rg50 motor or possibly one of its big brothers.

[BUBBLE]

Another company has done some thing similar along the lines of a dirt/mountain bike. 45kg, it was on show at big boys toys. Im sure you could build it lighter for the road because you would not need it as strong as to handle huge jumps.

Check this link out http://www.fxadventure.com/

[zooter]

DUDE YOU HAVE AN ISSUE --COOLING-- if you follow the plan I think youre following no aircooled motor is gonna last more than a few operating hours before ya cook it.
I hear where you're coming from but id be tempted to suggest a rg50 motor or possibly one of its big brothers.

How so cooking an aircooled engine if it's out in the open?

Somone up there raised a good point about the bulk of an expansion chamber, the space is achievable but if anyone's got numbers on the weights of 2t and 4t motors ( plus exhaust ) that will put out the power I need please don't be shy. An XR250 is probably ideal in terms of reliability but what does it weigh??

The FX adventure bike is encouraging from the point of what is acheivable with the flash alloys, for my bike a vertical cylinder is the go for saving on length (and a Kitaco motor is a tad expensive)

Regards the lighting I wasn't aware you could use LED's as a roadgoing headlight I was figuring on a couple of those wee halogen ones chewing most of the juice and an LED tailight.

[BUBBLE]

Where are you actually heading with this??
A XR250 is a heavy motor, XR200's on the other hand can put out almost as much horsepower and are much lighter, cheaply obtained, cheap to rebuild, easy to rebuild (I pulled my first XR to bits when I was 13 (yes it still went)).
XR200's can even be bored oversize for more horsepower, no extra weight & still extremely reliable.
All XR's & XL's 125, 185 & 200 are so similar its not funny, main difference is the bore diameter. Most bits are interchangable.
Keep an eye on www.trademe.co.nz , often much cheaper than a motorcycle wrecker and many many parts available.

[BUBBLE]

The FX adventure bike I saw in Auckland had a honda stepthru motor, available in both 90 & 110cc. Im sure its not a problem to mount a Honda with cylinder vertical, no worse than pulling a wheelie 500m up the road or climbing 1000m up a steep farm hill. The only problem with altering the angle of Honda is that you may need to trim a little bit out of the chain guard.
Easy tip for mounting the motor, run a straight edge from the centre of the rear wheel axle thru the centre of the swingarm bolt. The final drive sprocket coming out of the gearbox should be in line with this during normal riding, i.e.rider sitting on bike. The sprocket should also be as close to the swing arm bolt as practical.

[FzerozeroT]

maybe you should post a rough scribble of what you want, engines are designed to operate in a certain position for carbuerattors / oil feeds, a 150cc two stroke puts out somewhere between 30-40hp crank, good for 150-160 in a roadbike, four stroke is about 20-30, good for 140 (i think)

[FROSTY:Me]

I. as the rear wheel is going to be a 10" rim jammed up close to the motor, possibly with motor suspended on the swingarm ( I know it's nasty but handling is secondary to compactness and simplicity)
!

by this comment i guessed it would be REAR engined -I couldnt imagine the rider sitting behind the swingarm so the engine will be behind the rest of the bike. so bad cooling

[avgas]

how is a motor sitting on a swingarm simple?

[zooter]

Motor on swingarm takes away any concern about the small distance between sprockets leading to excess change in the chain length with suspension movement.

I'm not sure that being between rider's boots is a bad place for an aircooled motor but if anyone cares to add anything I'm listening.

Those horsepower figures are surprisingly high. I rode an old GN 250 recently which cruised at 100 ok but ran out of puff on the inclines. It was a loaner so I wasn't inclined to rev the tits off it to maintain speed.

Anyone got access to a wrecker's shed full of motors????

[Blakamin]

Anyone got access to a wrecker's shed full of motors????

*pedant alert*
I think what you would be after is an Engine... a motor wont do you much good without some mean batteries




geez... thanks Hitcher, JR, FS and crew... didnt know this happened when you became a whore!!!
should maybe shoot myself.... before I rise/sink to the highs/depths of being forum "pleece"

neh, fuggit.....

[zooter]

I guess that's why we call them "enginebikes" ,
I've tried calling some wreckers in my Otago yellow pages (chch and wellington would you beleive) they are permanently engaged. :spudwhat: at the risk of being a pain in the ass can I recap:

WTD smallest lightest "motor" capable of reliably powering a highway going minibike, cylinder orientation preferably vertical.