Modern Vespa

It's actually usually the case that the lining is nikasil on aluminum kits. Iron kits wear well and can be honed and rebored. Nikasil aluminum kits are kind of "single use". The porting on that looks aggressive - I think that's a good example of a kit that will need a 17.5 and more aggressive pipe to ride right and at potential

Thanks for the input. So that setup more for high revving performance and less for puttering along at 60km/h to get to the shops then. I guess I'll stump up the extra $100 for the Malossi kit then.

Good old nikasil. Porsche use it on a lot of their engines so I'm aware of that one. That stuff is very tough.

They claim its for "regular use" but I suspect it's not a grunty kit (I don't know from experience with it, just eyeing the ports and the fact that it's an aluminum kit)

Here's a thread where max from motorsport raises concerns with this budget aluminum kit (but it sounds like it might not be too aggressive): Cylinder Kits: Airsal vs Malossi

(Fwiw I thought the malossi was really nicely made and worth the dough)

Can't find where they're located in Aus, but www.scooterstreet.com.au has some good videos on YouTube and say they sell go fast parts. See if they're competitive price wise.

I'm whipping up a spreadsheet with the parts list and prices from different shops. Scooterstreet was the first one, but half the stuff I need is in their OS warehouse anyway...

I've been buying car parts from overseas for years so I'm well aware that it's generally cheaper to buy from overseas and pay the shipping unfortunately.

The cast iron Malossi 70cc kit is a goodun. Good power/torque. Stock derestricted exhaust, with a rejet, will top out at a genuine 75km/h on the flat (as long as your belt, pulleys etc are in good order).

So getting up to 60 will be easy, and you won't be revving the nuts off your bike when you head to the shops. Enough poke to carry you and your beer.

There's a Pollini cast iron kit too. Horses for courses.

Neither are rev monsters. I think the factory CDI cuts out at a fraction over 10,000 rpm which is absolutely fine for those kits.

No need for pre-mix with those. The standard oil pump (autolube) will be fine on a cast iron 70cc kit. Just use a good quality synthetic 2T oil, and you can make a tiny adjustment to up the autolube for peace of mind.

As soon as you get into the aluminium cylinders, you're getting into high revving kits, which need other bits and pieces done to the to get the maximum performance, premix, etc. $$.

Pricing up things on Racing Planet, they have Malossi and Pollini 70cc kits at just over $190 each, then there's a Naraku 70cc kit at $115.

They also have a Naraku full circle crank for not a lot more than a stock replacement.

I haven't found anything bad about the brand just a lot of posts about them being good value for money, so I think I'll take a plunge on that.

I just need to confirm what carb I have so I can order some jets and I'll pull the trigger.

It's $100 to ship here from Germany, and the price for my parts list is about $400 cheaper than buying locally, so it's a no brainer there.

Here's my parts list. It there anything I'm missing? I'd prefer not to be stuck waiting another few weeks due to leaving something out.

Belts (oil pump and drive) need replacing?
Little end crank bearing?
Variator half with the worn teeth?
Gonna play with the clutch and springs?
Air filter?
Exhaust?
Hoses?
Battery?

A full circle crank might increase compression slightly, and probably, you won't need to jet as high. No needed for a mild/street setup though.

They recommend chamfering new cylinders… depends on the quality of what your get. My Malossi seemed fine to me, so I didn't.

Suppose have a look here at everything that I personally changed/cleaned/inspected: ET2 - Mechanical Resurrection.

21 year old bike (10 years off the road in a garage). Only 7500km, but a lot can deteriorate over such a long time period so I took the cautious approach to essential components.

The drive belt looks pretty new but I'll check it a little closer. It's a very low km scooter and the casing been apart before. I'm blaming oiling on this failure so the oil system is being removed. I'll premix instead. It's not a big deal.
The crank wasn't worn in the end. That's how they come, so the plates are fine.
I'll leave rollers etc stock.
The rest of the stuff like hoses etc I can grab locally.

I'll definitely check on the little end bearing though. Good catch.

Thanks. I'll have a look through that.

Good point - my cylinder kit came with a new one in the box, so didn't need to order one separately. Same with Reed valves. 👍

Suppose you can check what the Nakaru kit comes with just in case. Does the Nakuru kit come with a matched head? If not, you might opt for a 'complete' kit instead (which might bump the cost up).

The Naraku kit reuses the stock head, which looks pretty new actually.

A mate suggested I check the reeds too, so, note to self:
Carb jets
Check drive belt
Check reeds
Little end bearing

OK, I'm getting confused with jets. The bike has a stock 12mm weber, but reading through the thread below weber jets are different from Dellorto jets. They are both 6mm, but different threads apparently. What's the go? Why don't jet kits for the 12mm weber exist? Maybe I'm just too tired...


https://modernvespa.com/forum/topic68617

I think it's an oddball little carb, so motorsport decided to make their own for it. Unless they stopped selling them, why not just order a few sizes from them? I haven't called them in years, but they used to be super knowledgeable and would talk you through what you might need for your desired setup right over the phone

Do you have a link to them? Searching motorsport brings up a few hits, mostly not related

For whatever reason they have two names

https://www.scooterwest.com/

Indeed - we got that 12mm Weber carb here in the UK too. Mine had it. Not sure if/when it changed.

Standard jet on ET2 12mm Weber is a 76, so you'll want to go up from there. You can get a jet reamer, however that means you can only go up not down! 🙈

So, guestimating will be a challenge.

I was looking up jet drills last night. Always an option, but as you said it's difficult to drill a hole smaller 😂

For future reference the Weber carb on the ET2 50cc has a main jet that is M6x1.0mm thread.

Dellorto carbs seem to use both M6 and M5 size. No idea on thread size but apparently different to the Weber.

Gosh - that's a bit of a grimy carb (compared to what I'm used to).

If you want, I can take photos of the Weber and Dellorto jets side by side for comparison. Just ask.

Yes, it is filthy. I'll clean it up before I refit it.

I was looking up jet drills last night and I found a set with an 0.81mm drill, so that should be the right size to embiggen the existing jet. Only $20 too. Scooter west seem to be the only place that sell the correct jets and they have none in stock.

It'd be great if you could take a pic of the weber and dellorto jets side be side just for future reference. It may help out the next guy who's looking for info.

Naraku is a Racing Planet brand. Most of the parts are made in China, and the quality control seems pretty good. The packaging is edgy, and they make a lot of parts for engines that the Italians don't bother with. The top end kit without a head is usually for someone who destroyed the piston and cylinder, but the head of their old big bore kit is still good. You can use the 50cc head with the cylinder kits, but you won't get as much out of it as if you get a kit with a head that was developed to work with the cylinder and piston.

Thanks for the input. I'm just after something reliable to putter around on, so not getting the last few % of performance will be fine for me.

Another Racing Planet brand is 101 Octane. Their stuff is usually about half of what Naraku is, but the parts are still pretty good.

IMO I would pump the brakes on kitting much then. Stock crank, stock carb, 70cc cast iron, simple pipe like a Leo Vince, maybe rollers and spring tinkering just to keep the transmission in agreement with the new power profile.

Based on what? Astrology, Karnak or something on the internet? You can clean up that carb, play with the jets, maybe even melt a new top end and then get a new carb, or you can buy a new carb and ride. 17.5 is a better choice with a big bore kit.

Based on science and common sense. Carbs aren't a new thing, and neither is resizing jets.
Weber was nice enough to use metric, so an 0.81mm drill bit creates an 81 jet size which should be fine for 70cc and stock intake and exhaust.

I was doing some random jobs in the shed tonight and looked at the used but very new looking Malossi head sitting on the bench and it occurred to me I'd never measured the piston in the seized engine. This scooter hasn't even done 5000km according to the odo, and the head and barrel look very new. I pulled out the caliper, and what do you know, it's a 47mm dia piston. It's still stuffed due to being seized, but I'm guessing big bore kit on stock carb and exhaust, joined with a potentially sub par oiling system was never going to last long.

Do you have better pics of the piston and bore? You might only need new rings, gaskets and bearings if they're OK.

Running a 70cc kit on a stock carb and exhaust is fine, provided that the jetting is right, needle position is right, and that everything else related to the engine works, seals and is cleaned/maintained as it should be (oiling, gaskets/seals, air filter, flywheel fan, fan shroud, etc etc)… and a good quality fully synthetic oil is recommended.

If you're questioning the oiling, you'd have to check that system thoroughly (i.e. was the: belt intact, cable adjusted so that the cam notch lines up with the guide notch, system bled, hoses connected/intact etc etc).

The pic of the carb that you posted, assuming it's the original 76 Weber main jet (that wasn't reamed to a bigger size) - that's your smoking gun TBH. That jet was meant for a stock, restricted 50cc bike.

The carb is quite dirty too - what on earth got into it over that 5000km, and now did it get in? Mine didn't look like that at all, despite covering over 7000 km and sitting for 10 years.

The piston looks pretty stuffed to me. The bore isn't much better. The big end bearing is seized and the crank bearings are pretty loose. This engine lived a short, hard life.

A bit of light scuffing there. 🤣

I'd be keen to know whether that Weber 76 MJ has been reamed or just left stock. If the latter is true, what on earth were they thinking?

I can't recall if it was discussed already or not, but the autolube system works well - and is adjustable. Because of this, it should be perfectly fine for your kitted bike. However, it looks like the story unfolding is the previous owner didn't know what they were doing with regard to the kitting so this, like the carb, were probably not set up right for the beefier ride

The oil system had a belt and was full of oil but I know nothing about it, so I'll just premix for now just to be sure. I may check it and refit in the future but slopping in some oil with each refuel isn't a big deal for me. Plus I can run a fat ratio to keep it happy, hopefully.

OK, so a sufficient amount of time has passed since I pullet this apart, meaning I've forgotten how to put it all back together. So, obviously now's the best time to start the rebuild!

First up I grabbed a small file and cleaned up all the sharp edges in the ports and on the piston.

Then I spent 10 mins making a spacer to press the new bearings onto the crank. Then I heated the bearings up to 80 with the heat gun and they just slid straight onto the crank anyway.

Then I cleaned up the casing halves and ran over them with a flat file, then a knife stone, to make sure they were nice and flat.

I cleaned out the bearing area with some brake cleaner, then heating the casing up to 80 and the crank slid straight in! I'm just grabbing a quick bite to eat while the case cools and I need to grab the three bond from the fridge. Now I'll go heat up the other half and plonk it on and seal it up!

Ok, new crank in and spinning freely, unlike the old crank. Next, seals.

Years back I bought a pair of flag tip pliers. Turns out these are perfect for spreading the rings! Easy.

Fitting the circlips that hold the piston pin in place is a pain in the butt! I ended up putting them in without the barrel in the way. Got there eventually.
Now I have to try find the head nuts. They will be around somewhere.

Small setback today. I believe these are supposed to be round...