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I'm a relative novice restoring a Series 3 Li125 which currently has a Dell'Orto MA18 BS5 (Series 1/2!) carb. No yet sure whether I'll be selling or keeping on completion so mindful of budget.

One upgrade option is one of the popular kits (e.g. Mugello 198) with a new GP crank. What other upgrades would be needed to complement this? E.g. carb, exhaust? Would the gearing also need to be changed?

Other cheaper options? 150 barrel, head and piston? However these would seem to provide only modest improvement in performance. Would the carb also need to be changed?

Any thoughts/advice would be welcome (once you've stopped laughing at my naivety!).

No laughing from me; you seem to have grasped the basics of improving the performance quite well.

You might need to think about sprocket sizes for a bigger engine and electronic ignition. Oh, a decent carb might help too; the standard carbs are rather simple and not particularly easy to refine for specific engines

There are a number of options around the 175 - 186cc mark that might be worth considering, but perhaps you want to think about what you want or need by way of performance. This might help us help you make a decision.

What is the scoot to be used for ?

Tootling round town and an occasional 10 mile stint,
"Boy Racer" spec' (quick round town but not really suitable for mile munching, motorway travelling),
Serious rally-going machine, capable of holding a decent top speed for long periods,
.......or other.

Once you've decided what you want the scooter for you can then decided how best to deal with the engine. The question then will be "what's your budget" ? A decent kit £500, carb (plus manifold, etc) £150, exhaust £100 -£350, electronic ignition + flywheel £200, crankshaft £150, etc, etc.

Plenty of help on here when it comes to the build but decided what you want and need before spending a (possible) fortune.

if doing the work yourself you've got to take into account things like opening the transfer ports and having the right tools for the job ie flywheel puller, clutch holder etc there is alot of hidden cost in up grading a scooter if you go for more than a 150 I would say you would need new bearings a gp crank and electronic ignition as well changing the sprockets and beefing up the clutch it all depends what you do with you scooter if you do mostly rideouts a well set 150 will easily keep up with the group

Thanks for your replies so far.

I think my boy racer days are behind me(!) and not really thinking of long haul. Guess that leaves required performance somewhere in the midrange.

Have already gathered some of the tools required so appreciate the associated costs. Have sort of assumed that GP crank, bearings, electronic ignition, clutch are desirable upgrades regardless. The cost of a 198 Mugello kit (or similar) at £400 - 500 together with further upgrades that the greater performance warrants is therefore likely to be pushing the budget. Options around 175 - 186cc sound interesting. Details of these and an idea of ballpark costs would be much appreciated.

My experience only.
I went down the same route as you with a 150.
Big kit or a slight improvement on the original.
I tried the less expensive option, GP barrel etc. I found it just too slow for modern traffic.
Tried a Ali 175 kit, but it was a pig to set up and never really worked right, Just not worth the hassle.
In the end I have opted for a MB RT kit.
If I had to do it again I would just pick a spec and go with it.
To keep costs down have a look at Scooter centre Koln, SIP and European suppliers due to the strength of the euro/pound.

I ride a with a GP150 top end/carb and have done some long distances on it. In town or in traffic it's no more than you need IMO. Out on the open road it always gets me there but a few more mph sometimes feels like it would be nice. Riding solo I always think it's fine, however - riding in a group of big boys I'm thrashing it a lot trying not to be too much of a burden on long hauls, and it's then you start toying with the idea/expense of tuning. Luckily the guys I ride with are very accommodating. As MickYork points out: start adding things up and you're looking at the thick end of £1000. Not to mention making it stop quicker too.
I'd decide for def if I was keeping it or not before going down the £tuning route.
Again, depending what you're going to do with it - a well set up standard engine is great.
I will now retire to behind the sofa

I run a sx 150 top end with 20 mm Dell,on my 125 li 62,goes well but lacks a bit top end,but I use mine for local knock about no rallies ect,i looked a the options same as you if you go for kit,you will need to upgrade a number of parts internally ,gearing seals bearings ect

I've got an sx150 and have thought about the different kits available it will do about 55 mph , I'm going to have a 175 rebore just so I can at least keep up with modern day traffic , it's no fun being overtook by lorries!!!

Nigel. S wrote:I ride a with a GP150 top end/carb and have done some long distances on it. In town or in traffic it's no more than you need IMO. Out on the open road it always gets me there but a few more mph sometimes feels like it would be nice. Riding solo I always think it's fine, however - riding in a group of big boys I'm thrashing it a lot trying not to be too much of a burden on long hauls, and it's then you start toying with the idea/expense of tuning. Luckily the guys I ride with are very accommodating. As MickYork points out: start adding things up and you're looking at the thick end of £1000. Not to mention making it stop quicker too.
I'd decide for def if I was keeping it or not before going down the £tuning route.
Again, depending what you're going to do with it - a well set up standard engine is great.
I will now retire to behind the sofa

I've been running a standard SX150 for the best part of 18 years now and while it struggles on the duel carriageway - its a great little goer a decent clubman and a upjet and will improve things quite a bit and still retain good fuel economy/reliability. Depends what you want it for really, I don't do rallies anymore and its fine for just blatting around however I'm a firm believer that with a bigger carb/ pipe combo and different gearing - the SX/GP (Italian though) 150 has potential to be a longer range cruiser
check out this post on scooterotica
http://scooterotica.org/forum/viewtopic.php?f=7&t=34829
Paul