Has anyone done a bicycle engine project?

[grogee]

Have any of you dabbled in bicycle engines?

I'm mighty tempted to build something along these lines:

Post-2000ish cheap alloy frame (rigid). It will get drilled so nothing fancy
Disc hub rear wheel, tough eyletted rim, 36h (or 40h if I can find one)
Modified engine drive sprocket to mount directly onto disc mount (instead of clamping onto spokes - nasty)
Possibly modify single speed chain tensioner to work with engine drive side chain
Half decent front sus fork with heavy duty springs (or up air pressure)
Hydraulic front disc
Cable op rear V-brake (no room for disc) + booster
Possibly single speed (who needs gears with an engine?)
2" slick tyres

80cc engine
Move fuel tank to somewhere less close to test icicles (saddle mount bottle cage?)
Need to do something clever to co-ordinate throttle, front brake, rear brake and clutch levers/cables

Anyone any experience with this? Or have I inflamed the wrath of Retrobikers by mentioning internal combustion?

 

[boxxer]

Be as well to find a track or Fixie hub so you have disk on one side and drive on the other.....

 

[velomaniac]

Basically it comes down to where you intend to ride it. Your choice of slicks indicates some kind of tarmac which means if you put it on the Queens highway it'll be ilegal as hell !
Making an ilegal motorbike from a bicycle when much better perfectly legal purpose built motorbikes exist is I'm afraid just daft.
If you plan to ride off road with knobbly tyres then go for it but a cheap suspension frame would be your best bet.

 

[fun at fiftyish]

Hi ,I have done a couple,,The main problem is the engine mounting brackets,they dont work!I added a third bracket at the top of the motor and welded plates to frame..A massive improvement can be had by matching the manifolds to the barrel,both in performance and smooth running..the chain tensioner is rubbish and needs welding to frame...I also mounted the tank in a bag on rear carrier..found the 50 cc engine more fun and responsive...I still have one here,,a complete and working bike,not doing much,,lots of fun and scary fast,,,Any help you may need just get in touch and will happily help you out..
Mark

 

[02gf74]

^^^ what he said. you can't ride it on the road without MOT, tax and insurance, probably need MSVA test.

you can't ride to on footpaths nor bridelways, only on RUPs and BOATs of which there are precious few.

so not really worth the effort.

 

[Chrissy_J]

I briefly considered it but reckoned for street use it'd be a huge amount of aggro for little advantage - noise, fuel, weight, getting the power to the rear wheel - as well as the legal aspects. It'd be a laugh if you get it all right and had the private land to ride it on, though.

If I was to build a powered two-wheeler I'd go electric. Check out Atomic Zombie for ideas:
http://www.atomiczombie.com/LongRanger% ... ooter.aspx
http://www.atomiczombie.com/EStyle%20El ... 20BMX.aspx
http://www.atomiczombie.com/SilentSpeed ... ooter.aspx

 

[grogee]

Be as well to find a track or Fixie hub so you have disk on one side and drive on the other.....

:?: you sure about that?

How would the disc fit on?

How would it not unscrew when on the non-drive side?

Thought this might be a bit divisive... anyway my responses in no particular order:

- I'm well aware this is illegal on public roads!
- Using a full sus frame would cause all sorts of problems with chain tension. And, in almost all cases, packaging the engine and the rear shock would create a clash
- Good advice re: engine mounts, I thought they'd be the weak link. I was thinking I'd bodge something with proper 'through frame' mounts, ideally with rubber/elastomer sleeve.

 

[velomaniac]

As for flip flop fixie hub, disc can be fitted via one of these:
http://www.ebay.co.uk/itm/360710996273? ... 440wt_1170
Alternatively drill a fixie cog with 6 disc holes and bolt the disc to it
Fixie hubs have a counter clockwise threaded lockring that tightens on if the fixed sprocket tries to unscrew.

 

[grogee]

As for flip flop fixie hub, disc can be fitted via one of these:
http://www.ebay.co.uk/itm/360710996273? ... 440wt_1170
Alternatively drill a fixie cog with 6 disc holes and bolt the disc to it
Fixie hubs have a counter clockwise threaded lockring that tightens on if the fixed sprocket tries to unscrew.

Making more sense now, thanks. Agree fixie hub would be best, as the dishing ought to be symmetrical. Not sure I trust that thin thread with all that torque though.

 

[velomaniac]

I think your original plan with a sprocket bolted to the disc mounts makes more sense. If you used extra long bolts and one of those screw on rotor mounts as a spacer you could fit a disc and drive sprocket on the left of the hub. If you used a rear disc hub intended for a screw on freewheel as found on cheaper disc braked bikes you could move the centre line of the hub to the right and fit a freewheel on the right. I presume you still want pedal power as these engines tend to have only one gear which is generally not torquey enough for engine only pull aways. All should fit nicely within 135mm OLN dropouts and you thus get decent hydraulic disc brakes over rim brakes.