Horizontal AC Minarelli Swapped Prebug - Chadbullet

[chadbullet]

I was lacking motivation on this build, but the ball has been rolling on it lately.

Horizontal Minarelli from YW50

Stage6 Racing MK2 70cc cylinder
Doppler Endurance crank
SCR Corse Handmade 70 pipe
2TR intake (subject to change)
Polini CP24 Evo or PWK 24

Malossi LFR Overrange 
Stage6 torque control clutch
Stage6 R/T clutch bell
Doppler 14/42 primary gears



The crank went in this past weekend.





The threads on this Doppler crank were horrendous. It doesn't inspire too much confidence in it's overall quality. I ran out to Harbor Freight for a $20 tap and die kit. It's already earned it's value to me. I used it to clear crud out of the engine stud holes as well. I cut the handles down on the tool so it'd fit inside the case. The shorter arms are more than enough leverage anyways.





I wanted to remove the abysmal passenger hump from this seat. While at it, I thought it'd look cool to trim the seat down anyways. I'm really liking the lower profile. We'll see how it feels on longer rides.








And here's where we're at today. I'm waiting on the correct piston. Somehow I ended up with 10mm wrist pin piston, but the correct 12mm pin and circlips came in the 12mm labeled box. hmmm... While waiting I mounted everything up so I can start working on the wiring harness.

[chadbullet]

This is how it looked when I first purchased it. This was my 2nd scooter ever, so I hadn't quite bitten the bullet and jumped into modifying scooters. After months of ownership and really enjoying the bike, it was stolen from my apartment. Over a month passed and while getting gas for my car, I saw my scooter going down the road. I got in my car and followed until it was eventually abandoned.





It was rough. The tweekers messed a lot of stuff up. Fortunately they didn't get into the wiring. While this scooter was missing, I had replaced it with a twin. Now having 2 prebugs in my fleet, I decided I could tinker with the theft recovery. It got a Polini Corsa and a Yasuni C16. This is how it was until earlier this year when I decided to build a horizontal. The corsa was swapped into the other prebug.

[chadbullet]

I had a donor bike. It was going to require a bit of elbow grease to clean up before sending it to MvS.

[chadbullet]

Some pictures from ManVsScooter porting and trenching

[chadbullet]

New rear tire arrived. I decided to give the Kenda K764 a try. It's hard to find 130/90-10 in higher than J rated, and this is M rated. Rubber feels soft to the touch. I'm looking forward to seeing how it does. I also decided to run a front wheel from a Kymco Agility. It's a 12" wheel which will be better for tire options. There is a negligible difference in diameter between 120/70-12 and the stock 120/90-10. And it is ready for 12mm axle which will match the NCY legs I'm using on the bike without having to use shims. It also didn't hurt that it was $80 shipped in great condition.

edit: oh! and that they fit the more common rotor size. Otherwise would likely have kept original front wheel.

[Lucass2T]

Thats one super clean porting and trenching job! Nice!

[chadbullet]

Dec 31, 2021 4:07:47 GMT -5 Lucass2T said:

Thats one super clean porting and trenching job! Nice!

That's why I paid a professional! haha Anything that requires a steady hand isn't really a task for me.

[hellish100]

Nice engine build! Can you share more about the engine mount?

[chadbullet]

Dec 31, 2021 10:12:51 GMT -5 hellish100 said:

Nice engine build! Can you share more about the engine mount?

it's made my a company called easyboost. pretty simple. just bolts right in a zuma/booster that originally had a vertical minarelli.

Here's their site:

www.easyboost.fr/en/scooter/9-easyboost-racing-mounting-brackets-for-mbk-booster-yamaha-bw-s-3770007214010.html

[aeroxbud]

Going to be a nice bike when finished.
I have seen a couple of swapped vertical Minarelli to horizontal before. Is always an interesting build.👌

[chadbullet]

I've been putting off the electrical side of things for a bit, but today was a step in the right direction. The original coil location could have worked, but it would have required a really long spark plug wire since the top of the cylinder has moved a bit further away. This spot seems nice though!

I decided to put the CDI nearby as well. I ran a long bolt through the battery box so I'd have somewhere to attach it to. Then I used a couple of rubber grommets and a small piece of foam weather-stripping to dampen it.

Now that everything electrical is in place. I don't have any excuse for why I can't start running wires.

[chadbullet]

Got the correct piston in! Squish is set.

[chadbullet]

I do wonder what Stage6 thinks people should do to measure CHT on their air cooled cylinders.

Not my best work, but it'll do.

[chadbullet]

Leakdown test. I saw that some people just oil their base gaskets so I tried that in lieu of Hondabond. Well, the only spot leaking is front the base gasket, so I'll pull it apart this evening and retry with sealant instead of oil. No noticeable leaks from any of the seals, head gasket, or intake, so that's good!

[Lucass2T]

I use silicone sealant on everything (except o-rings, oil seals and exhaust) downstream of the carburettor. Intake, reeds, cases, base gasket. Some say it's unnessecary but a very thin film never hurt nobody.