DIY chainsaw powered bicycle Does anyone have any plans on how to build a chainsaw powered bicycle?   I've referenced instructables and YouTube but everything is so vague it doesn't really give me any sort of ideas as what I  need to do to attach the sprocket of the Chainsaw to the sprocket of the bicycle properly .  I appreciate all input, thoughts and ideas. Thank you for your time energy and effort.
We deal with bicycles here, and you're looking to replicate the early motorised bicycle (ie on the way to being a motorbike.)

Speaking generally, you need some way to put that power from the motor into drive, but to not compromise the function of the pedals and brakes.  


  As soon as you can't pedal it, then its a motorbike.


So the common way to wet-fuel power a bike is to chain drive the rear wheel through a freewheel threaded or bolted on the left side of the bike rear wheel hub.  Another way is to run the main chain through an extra sprocket.  Or you can use a rubbing wheel to push the back tyre around (this one can work on the front wheel too.)

You want a freewheel so that the back wheel doesn't drive the motor when starting from stopped, and you need a clutch in the motor to stop the motor stalling when you're standing still (at traffic lights etc.)

Most liquid fuel bikes cannot be started from stationary using the motor - you generally have to pedal or scoot up to 5-10 km/h and then release the clutch else the motor's RPMs are too low.

You absolutely want a throttle too.  Most chainsaws are ON or IDLING or OFF.  Really you want more levels of power between "Full blast" and "stopped"   And that throttle really must be on the handlebars for safety, not on the motor body.

Fuel tank becomes an issue too - you might have to relocate it from the chainsaw to somewhere further forward on the bike, to help with weighting issues.  Bike should be weighted ~40% on the front wheel and 60% on the rear wheel when ridden level.

A big consideration is BRAKING your bike will be able to stop itself and a rider in the dry from X km/h to 0 in y metres.   As your speed increases the stopping distance blows out.  Also the additional weight of the motor system will contribute to increased stopping distance.


  Uprate your brakes!


Continuing to pedal is another important safety suggestion.  Cars more-so will have a harder time seeing you as a moving object if you're just sitting over the bike.  If you're pedalling you look more like a moving thing.  Don't just potato-sack on the bike.

Legal - your location may regulate maximum power.  For me I can have up to 300W of electric or 49cc of petrol power+pedals wuithout having to register.  As soon as the bike hits 301W or 50cc or looses its pedals, then its a motorbike requiring registration and WOF etc.   Find the legal limits and don't exceed them.



I owned an electrified MTB for a couple years and it was a fun learning curve.  Some things I learned


Motorists, pedestrians, and other cyclists glance, see a fat man on a MTB and assume I'm trundling at 10-20 km/h.   In reality I could do 45+ km/h so there were innumerable times something would pull out or step out in front of me.  Ride defensively.
Wheel spin - in the wet or damp, and even just gravel was a lot more slippery.  It was massively easy to spin the wheel without getting traction.
Running out - you're on a bike.  If the wet fuel runs out then pedal.  Most countries will require a bicycle to have working pedals.
Locations - depending on your location, you may still be disallowed from bike paths and cycle lanes.  Check your local legal laws before implementing a build.