Hello Scooter people! I posted this build on one of the Facebook Scooter Mods forums, and someone suggested that you all might get a kick out of it here, so I figured it was time to finally stop lurking and post a build thread for my ride! So hang on, this story gets wild
I bought my first Buddy, an orange 125, in 2008. It was my intro to 2 wheeled life and I fell in love with it instantly, I commuted on it daily and racked up a ton of miles on it. As I do with nearly all my vehicles I started to modify it. Back when I started there wasn't much in the way of performance information for the Buddy, so I started to forge a path to crazier and crazier motors. My 125 became a 161cc then 180cc (long before Genuine released a 170!), clocking in insane speeds and crazier parts. Finally one day around 2012 my poor little Buddy told me it had had enough and cracked a crankshaft on the motor. That was the end of that poor motor.
Not one to be dissuaded by a little engine failure I picked up a used Vespa GTS250 engine and began the crazy task of grafting it into the Buddy's little frame. The project was going well until I got to electronics. I discovered that the GTS had an immobilizer system that I did NOT have the keys for, and Vespa would not sell me new ones. They wanted $700 to give me coded keys and proof that I owned the GTS which I didn't have since I had just bought a used motor, not a whole bike. This brought my project to a screeching halt and the poor Voodoo Buddy was stuck in the back of the garage destined to never see the light of day again....
I had long since moved on to bigger motorcycles(The current is a Yamaha RD350!) and rarely thought about the little buddy until recently. I had just completed doing a Megasquirt ECU install on the Porsche motor in my 1980 VW bus and it popped into my head like a spectre of the past that Megasquirt can run almost anything, including my GTS engine. Out from under the pile of cardboard and dust I pulled out the long sleeping Buddy and evaluated where it was at.
It was a bit sad looking and I had misplaced some parts in the 10 years its been sitting, but it was mostly there. After some tests I discovered the GTS motor had VERY low compression (60psi) and likely needed a top end... Since I'm never one to just replace stock with stock, I headed to eBay which provided a big bore top end and crank from a GTS 300 that took the engine from it's original 244cc to 282cc(The 300 is actually 278cc stock...) . Some modifications to the fuel tank to accommodate a fuel injection pump and return line, and a random fuel pressure regulator I had lying around in my parts pile and it fired up! It sounded healthy even with a mess of quickly bodged wiring and absolutely 0 tuning!
Now that I knew I could make it run, I had to make it ridable which would still be a lot of work. The stock engine was air cooled but the GTS was water cooled, so I had to get a cooling system stuffed into the frame somewhere... After some research I opted for a rear mounted radiator over the wheel. It works for sportbikes I figured it could work for me...
Because of the much longer wheelbase I had to cut down the rear fender so the rear wheel cleared the body for when it was ready to ride.
It was kinda starting to sorta look like a bike again.... Maybe.... And I was starting to see where the wheelbase and ride height would be when I finished it.
I got the exhaust mounted on it, and swapped the GTS's stock narrowband O2 sensor with a wideband sensor so I could tune, and did some initial tuning to get a baseline for the engine. At this point I still didn't have a proper cooling fan installed so I couldn't tune for long without starting to heat the motor but luckily I got it baselined fairly quick!
After finally getting a fan for it, it was time to start getting the body of the bike back together.
The Voodoo Buddy got a good wash(It sorely needed it after 10 years...) which revealed that a lot of the panels have a fair bit of paint fade. But it looks a whole lot better now!
The wiring harnesses were mostly complete and all the sensors installed, it was really starting to look like a bike again!
At this point I had the initial fuel and timing maps setup, and verified with a timing light, the engine was running great and though my initial maps were conservative it seemed very healthy. I took a moment to rewire the 'high beam' light as a 'check engine' light to report issues that the Megasquirt ECU detected so I could pull off while riding before something went horribly wrong.
When I first started this project, a friend of mine who also had been tuning a Buddy Blackjack when I first started out sent me a present. He was a graphic designer and had designed me some new emblems for my project, they had been hiding in the back of a drawer for 10 years. I felt it was finally time that the Buddy got to wear its new flair, so off with the old logos, and on with the new!
Even though it was technically now 282cc, the badges show this is no longer your usual old Buddy 125!
We had some rainy days for a bit, so it took a few weeks to finish the next stage of the build but it was coming together slowly!
Finally for the first time in 10 years it rolled out of it's hibernation and onto the driveway as a ready (more or less) to go for a ride!
It was now long and low and had GOBS of power! The engine wasn't broken in yet so I didn't want to hammer on it yet but I took it for a spin around the block and it was a total BEAST. It wanted to spin the tires easily and took off like a rocket. At this point in the build it now went under it's own power, but stopping was still and issue. The stock front brakes worked fine, however the bike originally had a cable-pull drum rear but the GTS engine was setup for a hydraulic disc. So time to get cracking!
I ordered a new vented rear rotor, caliper, pads, and a new hydraulic brake handle for up front. I used a heat gun to re-form the headset plastics so they would fit over the new brake reservoir which worked surprisingly well. Then I had to get some custom brake lines fabbed for me, courtesy of a local hydraulic shop. Installed them, bled the lines, and boom! Rear discs were good to go!
The next few weeks were lots of short runs with a laptop balanced on the floorboards to get the tune dialed it. The bike was a beast. It'd burn rubber easily, and wheelied just as easily. It was super fun to run around on, and I was getting a handle on how it rode.
Just as I was completing the tune however, the water pump went south and chose to dump the contents of the cooling system right into the engine cases... The way the GTS engine is designed the water pump is separated from the oiling system by a single little seal. Apparently 10 years of sitting that seal had gotten brittle and had decided to fail resulting in a 1.5 mile sad push of my scoot back to home base. Again eBay to the rescue, another used pump on the way, installed and back on the road!
At this point I had borrowed a drag timer from a friend of mine to try and get a HP baseline for the bike... Remember, bone stock a Buddy 125 was 9.7HP. A stock Vespa GTS 300 has 23HP, but I was no longer stock with my big bore and some tuning I knew it was now more, but how much?
First I needed to know what it weighed with all its new toys installed. it came in at 263lbs which is a weight gain of 23lbs over a stock Buddy 125. I then headed over to a big empty parking lot at a local college and going for a 1/8th mile 'drag race'. I ran an 1/8th mile in 10.1, with a little bit of maths I calculated that my engine was putting down about 25HP. a 15.3HP increase over stock! Not too bad!!!
But my life philosophy seems to be anything worth doing is worth REALLY overdoing, I thought that just MAYYYYBBBEEEE I could do better.... Que the suspenseful music.
This little snail is a copy of the IHI RHB31 turbo charger, perported to be designed for a 125-600cc engine. Right in my ballpark.
After a lot of research and a LOT of naysayers telling me it was 'impossible' to turbo a scoot(Spoiler, its not...) I set to work.
Pulling out the trusty welder and a bunch of bits I fabbed an initial turbo header to see what we could find out.
I was lucky that the GTS engine had a high pressure oiling system, which is atypical for a scooter. That meant I could feed it
off the engine's oil pump no problem.
After plumbing up the oil lines to feed and cranking it a few times to be sure it was well primed and oil was falling out the other end I fed the return line back into the oil fill port on the motor and fired it up.
Ok, that worked. It started, it spun, it made some wooshy noises? Good right? Not so fast....
Its been a long time since I've played with turbos, and never on a bike. Apparently this little turbo was VERY sensitive to oil feel pressures and angles. I quickly converted a bunch of oil into a huge cloud of smoke, and fouled out my plugs...
Thats not ideal... No problem, we can deal with this! For testing I used my favorite high tech pressure restrictor device. A pair of vice grips on the feed line. With some line restriction it fired back up and ran!
I revved it up on a test stand, to see if it worked, everyone said 'bah, you might get a pound or two of boost TOPS!' so I wanted to know what I was gonna do.
4.4PSI boost. Not too bad! I could live with that if thats all it did. Using a turbo boost calculator, that told me that if I was making the previously calculated 25HP 4.4PSI of boost would push me to 32.5HP. Thats nothing to complain about!
I pulled the bike off the test stand and took it for a ride... Honestly it rode like crap. It was still smoking a fair bit and surging as it tried to burn the oil instead of gas. The AFR was all over the place, and it was very obviously not a happy bike. Ok, I'm not oiling properly lets call it quits and order some parts.
I hit the internet to get a proper restrictor and a better oil line designed for this turbo. After looking at other projects using this turbo I discovered it has no internal oil seals, so it'll leak back if installed at an angle over 20 degrees, which I certainly had with my current install. Time to pie-cut the header and get the install angle a bit better.
Fast forward a few weeks and my new oil lines were in and the turbo was a bit more level(Still not totally level as the water pump interfered with that) well within the 20 degrees the manufacturer recommended. I also weleded up a quick straight exhaust pipe to get the noise down a bit when it was running though it was still REALLY loud.
I took it for a run with the correct oil restrictor, and this time clocked a max pressure of 7.2PSI at redline. The math on that said I was now pushing around 37.25HP at full throttle. It felt mean, but was still smoking pretty badly. Obviously I was still having over-oiling issues... I had the right restrictor what was going on??? Turns out that there was just not enough height to gravity feed the turbo where I had it installed and the oil was backing up in the return line and causing the turbo to overflow. So how to solve this?
The internet suggested that people building small turbo Go-Karts were using small electric fuel pumps as scavenge pumps after the turbo to return the oil more efficiently. Luckily my parts bin had an Edelbrock 4PSI electric fuel pump I wasn't using... Now while I was sorting all this out I discovered a growing puddle of oil under the bike leaking from what APPEARED to be the oil pan seam. Yay! Something else to solve!!!
Turns out that the GTSs have an issue where the CVT belt can tear the oil pan gasket at very high RPMs. This isn't normally an issue with an actual GTS because they're rev limited at 9050RPM. But with my Megasquirt setup and no rev limiter I'd tested the motor up to 11K RPM. And trashed my oil pan gasket... The fix was to just use silicone sealer instead of a paper gasket so I set about pulling the oil pan to fix that. While I was in there I drilled a return bung into the pan so I didn't have to lose my dipstick to the return line to make checking and filling oil much easier(I had to pull the return hose off the bike and make a big mess to check or fill the oil at that point).
After that, I installed the scavenge pump and fired it up. It took a while for the pump to prime up, as oil is a lot thicker than gas obviously. It smoked massively while doing this, and just barely ran but when it finally cleared the oil out of it's intake it settled to a nice happy purr of an idle like things were finally on the right track. Checking over things, my AFR was steady, meaning I was just burning gas and not sucking oil too so it was time for another run.
I noticed instantly it was a LOT peppier. I was building boost almost right off the line and was at a new record of 8PSI at only 30MPH which was well below my redline peak of 7.2 previously.
I figured what the hell, lets see what it would do now! I stopped to start my ECU logger for data for later, then pegged the throttle!
3PSI, 5PSI, 8PSI 8.1PSI.... Ohh, is that some clutch slip??? 9PSI.... Yep, the clutch is definitely slipping gonna have to do something about that.... 10.... 11PSI.... BANG!!! ohh, crap. Yup. Clutch grenaded.
Pulled the clutch to find one of the arms in pieces and springs and bits all over the CVT. So thats not ideal. But I exceeded the max PSI I'd pulled by quite a lot so at least I had some good data!
11PSI meant I was putting down just a hair shy of 44HP! a 34.3HP increase over stock. a 454% increase. Not too shabby! And I was nowhere near redline on that run so there's likely even more to be had. I just need to solve the clutch problem...
Which brings me up to current. I've got to solve the clutch before the project moves forward. I feel like one of those Reveno multi plate clutches might be a good solution, but I've got research to do.
If you read all this way, thanks for following along. I'd love to hear your comments!
