Kimjon

Holly fuck, double the power! Scary!!!

Thanks for the heads up. That's a disconcerting scenario you've got there. Normally the weight transfers to the front and the rear brakes in effect achieve nothing at all...often the rear wheel stops turning all together under emergency braking as it lifts off the ground. Here's a micro view of this in this clip of me riding the kids dirt bike...I stop hard 100% front braking only, feel the rear lifting off, reduce to about 50% front and lock the rear on. Im not too sure why yours is doing that, best guess would be the geometry (or flex) possibly changing under hard braking

Cool, good score. Those motors go okay. That's what's on one of my drift trikes. You can get the pull starts off trademe for about $20. But on eBay they only $8 with free delivery if you don't mind waiting a few weeks. Try searching "G scooter" if looking for parts. You can also start it with a drill too, for a short term fix. I've put a bigger carb on mine and an expansion chamber and its doubled the power. If you want crazy power then another motor would be the best option.

As all of us know, NZ is a small country. In other countries say the USA even if only 0.00001% of the population was into a niche activity (like gopeds) that'd still equate to over 3,230. In NZ 0.00001% of the population would only be 45 people. You can see why no one would make a living here doing anything that's not mainstream. So that's my long way of saying I was unbelievably lucky, to find/buy this on trademe last night! Seriously...I couldn't believe my luck, a box of go-fast bits for my motor. Fuck yeah! Stoked!!!

Welded both sides for extra over the top strength. I'm not too keen on coming off like @Muncie at top speed and braking my neck. And done! It's all getting a paint job later, so that will tidy up the ugly.

Now jumping on to brakes. I've added a disc brake to this goped. It was missing its brakes, so I hacked off whatever brackets were there and started again: A few holes and a couple minutes with a grinder made this sexy bracket. Gotta love a good bracket! Tacked in place.

Finished the manifold. I'm pretty sure its going to work. Here it is loosely in place

Original manifold milled down flat, this will bolt to the motor. Port matching to the other manifold shape. A pulse port drilled in the side to run the fuel pump/diaphragm. Test fit...Fucking ugly as sin, but should be functional. I'll grind off any excess material later to try make it look a wee bit better than it currently does.

I ordered a diaphragm style carburetor kit from eBay, it arrived in record time...But it would have been awesome if they'd sent me the right one. The manifold in the kit was for a completely different motor! It only has two mounting holes, but my motor has four. Countless emails, achieved nothing in the end...I just wanted the shitty Chinese manifold for fuck sakes...But in the end they offered a part refund instead, which leaves me no further ahead. So, solution:

As they say...you can't keep a good drift trike down. I bent it back into shape, and got it ruining again all be it with different mounting holes on the motor as the old holes broke off. Crack in case, but it's just the fan cover side, so this was my solution. Got in tuned, but the power band is way up in the rev range so I'm not seeing its potential in my driveway (not enough room)...But it increased power all the way through the range as well, so still way better... I'm happy its only 49cc.

So today I dragged this out, added a much bigger walbro carb, made a custom manifold to adapt this carb to fit. Then made an expansion chamber...and ended up with about double the power!!! Then thrashed it for about 20 minutes off and on tuning it...got it dialed it sweet...Then smash!!! I stacked it hitting the tow bar of our family car. No damage to the car, but drift trike - ummmm yeah/nah. Motor still goes surprisingly. So I may be able to weld up a new bracket to pick up the bolts on another part of the motor? Oh well, guess it's true..."the faster you go,

Exhaust then got VHT ceramic paint And that's about it for now.

I further milled a step on top to add clearance, and used the dremel to smooth it out And then installed it, perfect! Follows the crank, allows a nice wide opening, flow is now going the right direction...think it's getting there now.

Now they fit: But I don't like the angle, its to restrictive and the reeds hardly open. So hell bent on thinking I can do better than the factory i further milled the base to change the angle.

On to the reed valves. In my opinion, they face the wrong way in these motors? The air/fuel is dragged in, up and around the massive reed support. I've flipped them around so that the air/fuel mix is pulled cleanly through them unobstructed. Fingers crossed this is the right idea??? However, problem is they don't fit! So I'll make them fit!!! Okay...truth be told it was never going to hold how I clamped it above and it moved on me, so take 2 below: Mmmmm pretty...

Okay...more porting, followed by more porting... I'll do a bit more on the flow side and then polish it up again.

Piston received a little love. It was black as black can be with carbon build up. Here it is after 10 minutes sanding: Still looked shit...so I broke out the random orbital, couple minutes on that, then on the buffer wheel...finally got the dome polished where it needs to be. That was way more work than anticipated.

My wife sent me a couple photos off the internet with some ideas for holding jewellery. She casually says "you could whip this up eh?". Well I'm not sure about the whipping part, i think you'd need an underground room for that sort of behaviour...But I did manage to make these:

Here's a before and after photo to see the difference And after And hopefully that equally more flow, and will be one of many things that add up to more power. Next up for the motor is to calculate its port areas, timing, squish band and compression...then tweak those with yet more porting.

Cases polished Transfer ports case matched

Roughing it out Still a bit of work to do, but already a huge improvement. When I'm happy with the "flow" it will get polished up. The intake should be rough, the rest should be smooth

Here's a view of the piston placed exactly where it ends up at BDC. note the skirt is to long and the sides of the barrel don't match. And here it is after matching Now it's a matter of matching to (barrel) to the cases.

Here it is with the crank and piston installed. The open style of cylinder with a removable head allows me to port time the motor. I'll stick a degree wheel on the crank, turn it over and measure the degrees at which the ports open and close. Once I have this data, I'll know where improvements can be made.

I'm going to flow the bottom end by porting/blueprinting it. Things like this lip the cylinder makes as it protrudes into the lower case will be reshaped to "seamlessly flow". The arrows I've drawn on indicate crank rotation. That sharp shelf in the photo above will receive a lot of work in this area. Any area like this will create poor flow due to an eddy forming in the low pressure area. The basic idea is that a motor is simply an air pump, and the more efficient that pump is...the more power you'll make.

Jumping back to the motor. This motor was a $20 buy off trademe. It came on a totally fucked pocket bike, that was stored outside with no spark plug in the motor for God knows how long? In that time the motor filled up with rain water. I turned it over by hand and it pumped the water out. Luckily the oil in the 2-stroke mix saved the internals. But the bearings are toast! I used an old clutch to make a gear puller to remove the clutch on this motor. It was well stuck...but this tool popped it right off! With that out of the way, I stripped the motor right down.