SQ Engineering - Projects - Suicide scooter

Suicide Scooter

For a long time I wanted a petrol scooter and after many years I finally had the means to do it, so I ended up going ahead with it. I started with a used frame without wheels and went from there. I didn't really have that much of a plan at the time but just went ahead and did what I could, considering this it turned out okay for the first version. I used the rear forks, wheels, dummy engine and brakes off a pocket bike that was sacrificed for the cause. The engine that was to be fitted was a highly modified 50.2cc pocket bike engine. I used the 40cc engine off the donor bike as the template and swapped later.

Whats new: The engine has been taken apart, porting the intake has now
been finished and its ready for a clean and reassemble.

Current Status: In pieces with engine work being done, pic soon.

Stage One:

Starting with my old frame I stripped it bare (bar the handlebars and fork) and did the following steps:

-welded on the rear fork of a pocket bike in place
-braced the frame
-remade the front fork to suit the pocket bike wheel
-shortened the front part of the frame to suit the smaller wheel

Stage Two:

-Started doing test fits for the engine
-Made engine mounts
-Extended frame for engine support
-Welded mounts to frame
-Made and welded in a front loop for extra support
-Test fitted an expansion pipe

Stage Three:

Perhaps in hindsight of my impending doom I worked hard to fit the disk brakes off the original pocket bike wheels to give me a slightly better fighting chance of survival. I went a bit over the top making a fuel tank bracket but it was fun and works great. I also fitted the fuel filter and fuel line. The fuel tank bracket was also made to be tottaly removable in the advent of maintenance/further modification.

Stage Four:

-Kickstand lever shortened to work with frame
-Setting up levers
-Making a custom stem bolt
-Extending the head-stem
-Deck plate made and fitted
-Brake cables fitted
-Throttle cable fitted
-Rear brakes connected
-Ready to haul!

Stage Five:

At this stage the scooter was rideable, it rode well and was heaps of fun. Of course that wasn't enough so I fitted the fat-boy pipe and was planning on making some serious parts. I started with the basics of modding a "Fat boy" expansion pipe and then later modding the pipe itself to take a nasty step out of it. After which I refitted the pipe and re braced it.

Stage Six:

At this point I found an engine that interested me more so I bought it to use it instead of my Cag engine. It was a 40CC Blata Rep F1 engine. With it's sleeved 5 port design with a twin reed V-block it was meant to be rated at 7hp unmodified and reported to make 9hp with the 19mm carby I bought with it. Thanks to Darren from Ozminimoto for the supply and assistance for this engine. I knew that even the most highly modified Cag style pocket bike engines are barely on 5HP so I was home free before I even opened it. I also knew that these engines responded very well to modification. The first four pictures show the engine on the side and then partially taken apart. Looking down the barrel it shows that the exhaust ports are so massive they overlap the transfers. The head was taken off because the engine mount originally faced the back, good for motorbike but not me. I happily found out that the head was fully reversible so I could face the mount downwards. I figured it was a bit of a waste that I spent so much time on my engine mounting and it looked decent but the lure of huge power was too much.

The old engine was removed and the frame under it chopped out. I made up a new engine cradle out of Cro-mo (4130 aircraft steel) and did my best to have it as close to possible to the wheel. I initially dummy fitted the engine to get an idea of how it was to sit before making some mounts up to hold the carb level. I cut and welded recesses in the frame for more clearance which ended up looking pretty neat. With the chain fitted along with the power pipe and the temporary fuel tank mount it was ready to go.

When I first rode this thing I didn't know what to think, to be honest I was thinking if the claimed power was true or just B.S. Taking it for its first spin with its new heart I got it going for about 10 meters before it snapped a chain link. I wheeled it back home and modified a BMX chain-splitter to split a link instead.

Back on the road I went up a hill near me where I lightly touched the throttle for it to just lift the front wheel straight up and throw me off. Worried that I might damage the threads holding the exhaust I wheel it home again and welded a brace on the power pipe. Welding was difficult at the time because my hands where shaking pretty bad.

Back on the road once again I was really careful and I found it would lift the wheel up in a crazy mono whether it be going up a hill or down, truly scary. While I was riding up a gravel path up a hill I accidently give it just a tiny bit too much power and it lifted up the front wheel and because it was an off-camber track it of course just steered off the track and down an embankment. After using my increadibile butt saving technique I stopped myself getting too many induries and then decided to go home.

At home once more my hands where shaking badly and I am left thinking "I have made a monster..."

I changed the gear ratio to have less pickup and more top end which helped considerably but instead of being scared of it throwing me off it instead scared me by the speed and rapid acceleration.

Below is a video of my brother during early testing. Note not much more than half the throttle was used because it was simply too hard to control.

Stage Seven:

At this stage I started to look to make improvements in how to control this thing. My first port of call was to make it have a longer wheelbase. I figured that the longer the wheelbase the easier it would be to keep in a straight line. So I chopped the center out and extended with more Cro-mo tube. I added a third piece down the middle to add more stiffness. This ended up making the frame much more rigid and thus reducing flex. In the process I chopped off part of the rear frame because I was never happy with it. I replaced the hap-hazard original design with something triangulated and neat. I also made up a neater and simpler front engine mount. I was really happy with my new frame but it meant I would have to discard my old deck plate. I temporarily used the old plate but with plans on making something new later on.

During this time I also took the engine apart and did some porting to smooth the flow, nothing serious just some grinding to make the flow better. I also started to make some new expansion pipes to try down the track

After remounting the engine I found the frame was pretty useless in adjusting the chain tension, so to get around this I made up and installed a sprung loaded chain tensioner. This worked very well.

Stage Eight:

Due to a change of residence, an engine build and other things the scooter was left to rust for some period of time. So seeing the frame had to be stripped anyway it was an opportunity to modify it further for added stability. So the plan was to change the front wheel to a larger diameter road tyre, increase the stem angle further, raise the handlebars and increase foot room. A road wheel of the right size was not readily available, so a 10" wheel off a mini dirt bike was purchased. This wheel was then taken apart for just the rim. A 10" scooter road slick was also sourced that was compatible. To fit it to the scooter frame it was decided to use BMX/MTB parts, however a 28 hole disk brake hub was not available. So to get around this a custom hub was machined up. Pictured in the send from the left is the mini-motorbike wheel next to a red wheel that is identical in size to the original for the size comparasin.

This video shows the machining of the custom hub. Some intermediate machining was done on a milling machine and was not shown in the video.