MOPED ARMY

Man,this thread makes me appreciate Franco-Morini and Minarelli engines so much more!

This comment also confused me. Classic Don!

Queue up this track to set the scene:

So anyways, Here's my side of the story officer. Lets start from the beginning.

I picked up the ZA50 bottom end at last years Ride n Chatter in RVA; it was sitting on a blanket with some other random parts and stuff. I offered $60 for it and i thought that was reasonable but the older guy i got it from seemed like he only accepted that because I was the only person to make an offer for it. oh well. I have no idea why i bought it, but it seemed like a good idea at the time. I was probably drunk as it were. I pretty much brought it home then ordered a stator, seals, bearings and these motor mounts (which are very nice) then shelved the motor for a few months after that. It was a month or so later when i really looked at it and noticed that the case had been welded up on the flywheel side. it was a pretty good job, or at least better than i could do given that i cant weld aluminum at all.

I wasn't entirely sure what i wanted to do with it, but I ended up getting a hold of nice stock 50cc jug from a cobra that i had kitted for a friend and was like, hell yeah, i'll port this and use it. I had realized the case transfers were big but not THAT big. Just about any kit or stock jug i put on it left a big hole between the case and the base of the cylinder. So i began the search to find what the previous owner had run on it. I searched far and wide for a kit whose transfers pattern matched my case. The only thing i could find was the Hero kit.

Here's the bottom end next to an a55 for scale.

This is were Joey comes in. I was rambling incoherently as i usually do in a moped and alcohol induced trance and was showing joey the case and how i think only a Hero could save us and I'm not gonna stand here and wait (you can pause the video now if it's still playing). He was on board or so it seemed.

Fast forward to November 2018. The Avanti Supersport had been posted a month before on Craigslist for $150. The ad went down and i had assumed it sold. BUT ALAS, a month later it was reposted for $50 because now the guy reallly needed it gone. so im like 'ok' and went and got it cause i kinda like Garelli's and have not messed with a 2 speed.

Anyways, it must have been left with the spark plug out because it was filled with mud and shit as you can see in the picture Joey posted. I cleaned all that out and the cylinder is actually in pretty good shape. If anyone wants a VIP piston and cylinder let me know. But then i opened the transmission and pretty much wrote the motor off because the second speed clutch bell was exploded.

Oh well. Time to Chop it up!

The initial plan was to weld the new engine bracket onto the existing one somehow but the Avanti motor is muuch wider than the ZA50 so we just ended up cutting it all off.

The swing arm mounded to the old engine mount so that needed to be addressed. I grabbed a piece of tube and some bronze bushings from McMaster Carr. Ended up looking like this.

So I bolted the 2 plates together and drilled a big-ass hole through them both.

I was pretty neat because we could just slide the tube into the welded engine brackets, put the swing arm on, and slide the whole thing around to find the best fit.

Once the best fit was found, just slather some hot metal on the bitch.

yeah idk that's pretty much all i feel like writing now

haha sick

Other than reshaping the a and b transfer ports so they match better, we haven't done anything. I wish I grabbed a picture of how asymmetrical they were. Probably Need to get a smaller right angle tool to get in there and do any serious port work. I would like to widen the intake patch a bit and maybe do some other stuff, but I think we're going to run it as is for the time being.

At this point, I think the main goal is to keep the rpms down and not blow up the transmission. The long ass

exhaust header I think should do it. It pretty much falls flat on its face around 8000rpm. We can probably just regear to 18/32 or so and it will be good enough. Gotta get the timing and jetting sorted because it's running very hot, but it is likely lean.

First impressions are promising though. Very torquey

So, for the head on this pig, we are using one of the tomos o-ring heads that treats sells. There was one sitting in the shop and also it is huge like the kit so why not. This guy VVV

It was counter sunk for a 45mm bore, so made the whole thing flat using a 12x12x1/4" plate of glass and some sand paper. took forever, but it worked out. It's kinda therapeutic.

you can see the small ridge between the o ring groove and where the dome starts where the edge of the counter-sunk bit was. Looking at this photo now, i can definitely see that it was nowhere near being 43.5 mm (the size of the hero piston). oops. I had spun the head in a drill and did a fair amount of sanding to try and smooth it all out to 43.5mm.

SO, the first time we slapped it together, the piston didn't seem to be hitting the head after torquing everything down. We used 2 base gaskets at about 1mm thick to raise the exhaust port to a not terrible height, but the transfers are still not my favorite at bdc, but no biggie.

We ran a compression test and got about 185psi; pretty high, but yolo. We checked the squish and it was stupid close (maybe .25mm?) but again, yolo. We rode the bike around a little bit over several heat cyclings probably about 6 miles all together. The last ride was the longest at a little over 3 miles. It got very hot. Not exactly sure how hot since we didnt have a temp sensor on it yet. Spit test and beer splash test indicated it was pretty damn hot. A sensor has since been added.

The head was pulled to see how everything was doing.

The piston wash is interesting. It is very clearly getting more intake velocity or just a leaner mix from the one side, but that makes some sense since the transfer port on that side is a little smaller (top quality casting form india). But alas, no contact with the head. that's good right? It was pretty noisy when it was running, but not that crazy.

I like the O-ring gasket heads. The o-rings are only really stable to like 400°F and then it looks like they melt. Which i think is what happened here. Makes sense, cause we got it p hot.

anyways, we put a new o-ring in, and clamp it all back together. Now the piston is very clearly hitting the head. Maybe the base gaskets have compressed some more? idk.

I think joey ran it for a little bit before it made contact. idk. maybe an oopsie but everything inside still looks healthy. You can see the mark from where the piston was making contact.

As i write this i am thinking maybe that's why it was a leaner burn on that side since the squish is not perfect? I'm not sure.

ANYWAYS, we ended up putting a piston stop in the head. chucking the piston stop into the drill press, combustion end up, and running a dremel on it to form a better squish. Hillbilly lathe worked pretty good and no one lost any fingers from the spinning chunk of pointy aluminium.

Squish is still pretty close at .55mm but it's a step in the right direction. It is way less noisy now so that's neat.

it's a pretty big drill press for a bench top press, but it was just about all the way open. I was surprised it fit. Keep in mind, we put the smaller stop end in the chuck not the 19mm hex end. There wasn't a lot of room to workand the head ends up preyy much touching the chuck but we were working on the edges anyways so it worked out.

The lowest speed it'll do it 650rpms. that's a bit fast for my comfort but it worked rather well. Idk why i didnt get a picture of the before and after. I'm bad at this.

FINS ARE TOO BIG BRO. GOTTA GO FAST

So to continue on the head saga, the demeled tomos head was getting super hot still. It was much less than before, but still the squish was too tight. I will revisit it one of these days and try to make it work better.

Ended up putting on an old school Graham Motzing Puch polini head.

With the head gasket and all, the squish was muuuch bigger. Around 1.3mm at its narrowest probably more. The profiles not perfect for the hero piston but the temps dropped by about 100 degrees and I didn't need to care about blowing it up for our Sunday ride.

This kit is fun as shit though. So much torque. It just goes.

I had flipped the second gear clutch and I may want to flip it back. First gear revs out pretty much past the power band of the pipe and it's a little goofy to get it to shift. It's not bad if you diddle the throttle the way it likes.

The current gearing is 18/32 which was a close fit and it gets to 40 if you let it. We could probably put a 20 in there idk.

That should put it between 7500 and 8500 rpms based on the transmission. The internal gearing is 6.5:1 from flywheel to output shaft. IDK if that makes it a 1 or 1.5(2)HP transmission. I haven't counted the teeth inside. Anyone know?

It's after. You can see the few bolts that's are injured. It adds character

flipped clutch you just gotta didle the throttle! It's the best, like a manual shift on demand with zero effort. I love the flipped ZA "shift" it's one of the most satisfying mods in mopeds. feels great IMO

On my chopper it feels so right to ride first for too long blip shift at 35mph

20x35 (edited)

So I didn't really try running it with the .45 squish cause that's too small.

Instead I just added another base gasket putting us at 361 base gaskets.

The fancy trickMETRIC gaskets crushed a lot. Like a lot. I'd say it's damn near 25%. Look at this cookie.

Whatever no problem. I have a few sheets of this dank ass lit number 1 best fire 100 gasket paper so I just laser cut another one with my hands. Totally legit reproduction.

Totally legit. I ripped the thin parts a bit punching the holes so I put gasket goop Honda bingo on there like a real professional mechanic. Copper spray to help bond the new gasket to it's homiez. We'll see how it goes.

Uncompressed, it's 2.5mm of gaskets. Squish is .9mm now. Good enough for the girls I go out with.

Here's a bonus pic of the bore and pretty asymmetrical ports