With all the excitement about the Scomadi 200, it’s inevitable that those who joined the party early with a TL125 feel a little left out; particularly in terms of performance.
Let’s be straight, the engine fitted to the TL125 is very basic fare: a 2-valve air-cooled 4-stroke of the GY6 ‘family’. This is a family with an extraordinary diversity in terms of variations of casing length, engine mount position and details surrounding construction.
Around the world there are many GY6 variant engines and many people making tuning parts for them, but which ones are they making for?
It turns out that the Scomadi engine – rumoured to be a SYM development – is not a common type and as such, those who are looking to fit tuning parts find it a tough and confusing operation because few off-the-shelf parts seem to fit.
VIDEO | Scomadi 170 road test
Jerome from Readspeed has very strong links in Taiwan, and through those he’s managed to source a selection of parts, some of which he modifies, so he is able to offer bolt-on conversions for the Scomadi 125.
The core component is an iron-lined 170cc cylinder conversion kit, however that on its own boosts torque more than anything, resulting in improved acceleration but little improvement in top speed because the engine is already revving high. Trying to draw even greater capacity of gas through the single inlet valve does not really help matters.
The only way to captialise on the increased torque is to modify the transmission. The key component required was an upgear kit that Readspeed commissioned specifically. This raises the overall transmission ratio by 22%.
Breathe with me
Jerome set himself the ambitious target of getting a Scomadi 170 to 70mph. Doing this required more than the bolt-on parts, which include:
- Readspeed 170 cylinder kit
- Readspeed Scomadi gear-up kit
- Readspeed adjustable CDi ignition box
- Scorpion Scomadi TL125 exhaust
- Softer rear pulley spring
- Readspeed oil cooler kit
- Free-flowing induction kit and re-jetting
Jerome found this package gave a good performance boost on its own, but the limiting factor became the standard 2-valve head; which is designed more with economy than performance in mind. Unlike many scooter shops, Readspeed do also have a background in 4-stroke tuning, and possess their own flow-bench, so Jerome modified the standard head and valves to allow the engine to breathe more effectively.
Jerome rates the head modifications at around £200, however he doesn’t want to be swamped with engine work. Instead he is in the process of sourcing a higher-performance 2-valve head which he expects to sell for around the same price. This will come complete with valves, lifters and a new cam with sportier timings.
With all these parts, power jumped up from 9.8hp to 13.1hp, but more importantly, the engine held on to its peak power to a much higher top speed. Despite this, the 70mph target remained elusive due to the poor aerodynamics of the Lambretta-aping bodywork, so a windscreen was added.
On the road
Given that the 2-valve air-cooled Scomadi is a bit timid when stock, we chose to test it against a Vespa GTS125. In standard format the Vespa is a good town scooter making almost the legal power limit for a learner engine (though that output is being reduced with the new i-get Euro-4 version) and the Scomadi 125 can’t touch it.
With the 170 conversion, the story is reversed. Now the Scomadi has decent punch around town, allowing you to overtake vehicles in the city at the twist of a throttle. By contrast the Vespa GTS is completely left behind on acceleration and can’t recover any losses on top speed either.
Overall, the 170 engine turned a fairly weak 125cc four stroke into a much more pleasant experience than I remember from my last go on a TL125. For riding 2-up or climbing hills, the difference will be night and day.
The noise from the Scorpion, which was fitted without its removable baffle, is throaty but certainly audible. I think I’d keep the baffle fitted if I owned one.
To my mind, this conversion makes the TL125 a perfectly viable scooter for town and occasional open road use where previously the standard one left me distinctly underwhelmed.
Jerome explained that one of the chief limitations of this design is the amount of heat the engine produces when tuned; hence his fitting of an oil-cooler.
“Without the cooler you can fry an egg on those casings”, he warns.
This kit consists of a clever adaptor that screws in to the casing to replace the original oil filter, and instead an in-line oil filter is employed on the hose to the small underslung radiator.
Even with the cooler, Jerome says that the oil capacity of the engine is small, so regular oil changes are recommended. This, he reminds me, is essentially only an air-cooled motor intended for city use, not for flat-out on the motorway.
Another problem Jerome found was with the quality of the standard carb which had an erratic auto-choke mechanism. He has converted their standard 24mm carb to flip-choke to eliminate that variable.
While essentially most of these components are ‘bolt-on’, the conversion requires more than spanners because all the usual engine-building, tuning and set-up are required. For instance it is still vital to check the squish and adjust using different thickness gaskets supplied. Also, each engine will need to be jetted to set the correct fuelling.
Readspeed are not the only place to buy these parts. Several Scomadi dealers now stock them and offer these kits as an upgrade.
As ever, 4-stroke tuning is not cheap compared to bolting on a 2-stroke kit. Jerome has done his best to keep it affordable by minimising the amount of parts needed to upgrade the transmission.
While he has found different rear pulleys and variators, for the moment the engine runs only the gear kit and contrast spring. Even the variator rollers are standard.
- Readspeed 170 cylinder kit – £240 (*10% off for SLUK readers)
- Readspeed Scomadi gear-up kit – £79.99
- Readspeed Scomadi adjustable CDi ignition box – £49.99
- Cylinder head flowing work – £200 (optional, replacement head to be offered soon instead)
- Softer rear pulley spring – £15
- Readspeed oil cooler kit – £199 (*10% off for SLUK readers)
- Scorpion Serket Scomadi TL125 exhaust – £299
In order to qualify for the above discounts, please mention SLUK either on the phone to 01299 828 037 or via email to email@example.com
As you can see, this isn’t a cheap conversion, but it does deliver 30-50% improvement in power – depending on speed – which is a massive gain for a 4-stroke.
For the near future Jerome should have the bolt-on replacement 2-valve head available. He’s also in the process of developing an even bigger capacity conversion kit with a 4-valve head in his bid to make the Scomadi 125 out-perform a standard Scomadi 200.
Is that even possible?
Jerome reckons it is.
Words and images: Sticky