New DIY Motor Idea

Well I don't need to go 120 MPH nor does anyone else but it might be very nice to go 40-50MPH a stock motor has about
1.50 - 1.75HP what would 7 be like?

If thats all you want why don't you just mod a chinagirl? 45mph is easy.

Doesn't start getting difficult until ~50-55mph, which is OK since at that point you start needing high dollar supporting mods to be safe anyway...at 45 you can get away with GOOD v-brakes or manual discs and decent quality aftermarket wheels or mags but at 50+ you really want hydraulic disc brakes, HD wheels (real HD wheels, not the ebay/amazon crap thats just a $30 hub laced with some 12ga spokes), strong frame like the faker or a gusseted steel one, expensive tires, etc.
 
I think Im gonna start looking at Goodwill thrift stores and pawn shops for one, pawn shops however still try to scalp ya.
It might be bitching to ride a FWD friction for high end and regular stock motor for low end hill climbing.
 
If thats all you want why don't you just mod a chinagirl? 45mph is easy.

Doesn't start getting difficult until ~50-55mph, which is OK since at that point you start needing high dollar supporting mods to be safe anyway...at 45 you can get away with GOOD v-brakes or manual discs and decent quality aftermarket wheels or mags but at 50+ you really want hydraulic disc brakes, HD wheels (real HD wheels, not the ebay/amazon crap thats just a $30 hub laced with some 12ga spokes), strong frame like the faker or a gusseted steel one, expensive tires, etc.
Just where do you find them chinagirls looked for them heard a lot about them do you have link?
 
most conc saws are about 100-125cc.

now... an rs125 can get over 160km/h. stock.
thats got gears and clutch and a tuned pipe and reeds n stuff. its meant to do that sort of speed. it also has really damn good BRAKES.

the conc saw can easily be worked to rip out power... a decent pipe should do it.

the engine has a pulley attached... easy to drive from.

the air filters and housing though... all this excess crap you cant remove cus you need the pull starter left on.

theyre heavy. i would be looking at a stihl chainsaw instead, they usually run an engine that is separate to the cases. very important. cheap saws use the tank etc as the crankcase, half of them are plastic, and they suck...

the husky saws run this weird porting system and are probably incompatible with tuned pipes, but i havent tried one yet.

yes, conc saws dont accelerate that fast.
because they are attempting to spin a steel disc 16 inches across at a 1:1 ratio to the engine. maybe 1.1:1... basically direct drive. im yet to see any grinder over six inches start and reach full speed nearly instantly. even a baby 4 inch grinder takes a second or two. ever tried a 9 inch grinder BEFORE they used soft starters? they break your damn wrists. a big 36inch wheel can take over two minutes to reach full speed when driven with a 30hp motor...



you need about 12:1 for a regular twostroke for decent speed yet still take off. a big 125cc should cope with 9:1 or better.

but who wants a bike frame to collapse at 160kmh?
if i wanted that i would buy a royal enfield...

i havent seen any conc saw, even the cheap clones at pawn shops go for less than $600 or so.
but you can buy a clone stihl engine by itself for about $180 new...
 
or better yet, a morini or denardis are proper race engines that are about $500 new. KTM50? they boogie, go hard, and are almost ready to bolt in. just make some mounts. already have the starter and clutch and sprocket and all that jazz.

better than any saw will be...
 
Got any pics?
How bout a little link to the $180.00 clone and what cc is it.
I was thinking of taking the gas tank off and just run a line into the carb it would hold more volume.

The guy in the vid had a 65 cc and used a friction start not a pull start.
 
look on ebay or aliexpress...

friction drive with any engine is stupid enough already. get a 125 on there and see how long the tyre lasts... the crankbearings... etc. if youre going to do it, do it properly.

the 65cc saw is the smallest of them all(demo and concreye saws at least). and if thats friction drive(in the vid), the roller is way too big, the engine doesnt get to rev out at all, and its got way too much pressure in the attempt to stop it slipping. again, too much load for for the job. could swear the one i saw he pull started it? still geared too high. way too high. that engine should be screaming...

friction drive is a waste of time unless you use a 6 inch rubber wheel for the roller, which still requires some reduction. rubber on rubber with a large arc of contact doesnt chew tyres and will not slip even if doused with diesel. steel rollers on the crank stuff your crank bearings, your tyre, and slip if they get even slightly damp. i dont care what anyone says. i gave up on FD fifteen years ago. run a chain.
they dont make friction drive motorbikes or lawnmowers or cars for a reason...
 
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