Kings of 50cc help with my Scootermotard

[rabidnz]

just got an sm50 gas gas , pretty nifty for a "scooter".
Anyone here know the difference between a minarelli am5 and an am6 engine?
As I can find parts for the am6 galore, but not much about the am5.
Also it says giraldoni on the cylinder, would this mean it is aftermarket?
May explain why its running like a bag of shit even after I cleaned out the thimble sized carby

[Yow Ling]

Nothing is going to be awesome with a 12mm carb, CDI is probably holding it back too.

[SS90]

just got an sm50 gas gas , pretty nifty for a "scooter".
Anyone here know the difference between a minarelli am5 and an am6 engine?
As I can find parts for the am6 galore, but not much about the am5.
Also it says giraldoni on the cylinder, would this mean it is aftermarket?
May explain why its running like a bag of shit even after I cleaned out the thimble sized carby

Gilardoni is the name of the company who makes cylinders for pretty much all the Italian manufactureres, 4 or 2 stroke, as well as cylinders for Rotax and so on.

They specialize in stuff for large production runs mainly, so stuff that is for the (now defunct) 125 GP for example where made elsewhere.

Actually they are about 300 meters from Moto Guzzi's head quarters.

As far as I am aware, the AM5 is a five speed and the AM6 is a six speed gear box, and the cylinders are different regarding exhaust port time area....would make sense if they saw fit to put another ratio in.

These engine have been pretty much the mainstay of Italian manufacturers for the last 15 years, and have been in pretty much every Aprilia RS 50, Pegasso 50, tuerno 50 so on, and the later model stuff all got the AM6.

Like a lot if stuff, Minarreli engines have been copied by all the Asian markets.

I am pretty sure that like has been said, the CDI will be the hold back, and the wee carb is going to be an issue, and of course the pipe as well.

Guys in Europe can get the 50's to over 19ps (mainly the Dutch guys), but the term "high revving" takes on a new meaning.

I seem to remember that a simple carb increase, performance pipe and CDI change will bring 12 or 13 PS, and the 75 kits get about 14.

The main power gains with these engines is with the pipe, carb, and CDI.

If I was doing it on a budget, getting the carb to something like 18mm would be my first move, but then I think the pipe and CDI would start to drag the chain.

It's a bit of a test of a tuners worth when it comes to 50's - I have met very accomplished tuners that have had engines in the pipelines for more than 5 years, and still have no plans to finish them!

There is a few spotty faced kits that have these type of engines in their bikes in the town I live in, and once they are derestricted (blind eye from the plod when it comes to tuned 50's) I would say they would make 110km/h, and not too shabby in how long it takes to get there either.

If yours is a road legal one that was E4 spec (most likely) it will only be set up to do about 50 km/h.......... I am pretty sure there will be a heap of tuning parts available from the Asian market, as this engine has been copied exactly (as has the bike design) and I see they are for sale all over Europe at a fraction of the cost of the European brands (which are all made in China anyway)

[F5 Dave]

Other diff was the AM5 barrel was ally & the AM6 for some queer reason was Iron, maybe to aid sales of aftermarket barrels which they also made? I am told the hot setup was AM5 barrel on an AM6, but of course you can buy after market stuff easily if you have no rules to abide by.

[rabidnz]

Thanks heaps for the input guys.
I have read posts with these engines tuned to 28hp, and an am-6 even holds the land speed record for a 50cc!! 160 mph or something crazy like that.

I realise she is really choking on the 12mil carb, and factory pipe, but it feels like it isnt just a minor issue of needing a bit more poke, it feels like it is revving out at about 6k. Anyway im going to go out and give her a proper good clean, then get the engine out and take the jug off, corsa motorcycles has piston kits for the rs50 for 70 bucks , cant go wrong there.

Should i need to pay for a cylinder hone or is that a box of beers job?

[SS90]

Thanks heaps for the input guys.
I have read posts with these engines tuned to 28hp, and an am-6 even holds the land speed record for a 50cc!! 160 mph or something crazy like that.

I realise she is really choking on the 12mil carb, and factory pipe, but it feels like it isnt just a minor issue of needing a bit more poke, it feels like it is revving out at about 6k. Anyway im going to go out and give her a proper good clean, then get the engine out and take the jug off, corsa motorcycles has piston kits for the rs50 for 70 bucks , cant go wrong there.

Should i need to pay for a cylinder hone or is that a box of beers job?

You may well find the pipe has a restrictor in it, somewhere near the header normally...... I wouldn't rush into pulling the cylinder off (jug?????? Are you American by chance?)

If the engine starts and idles well, then personally I would be skeptical about opening the top end, if it just won't rev out, then it is every chance it is E4 spec, and what they deem a "Mofa", and only allowed to produce a paltry 2ps and only go 49.9 km/h

I would suggest just pulling the pipe off and have a look down the header pipe, and that carb at 12 mm has to go!

I am interested as to what you find.

28ps? That I have not heard from a geared 50, the most I have heard about is low 20s, but that is not to say it isn't true.... The European scootermatic boys get around the high 20's regularly (gotta love that CVT )

[F5 Dave]

First off, what are you trying to achieve? A usable roadbike? A Bucket?

pipe could also just be hella clogged with oil residue, that stops them revving too.

[rabidnz]

My aim is to get the missus onto 2 wheels for summer, with the thoughts in the back of my mind of spending a grand on her and havin a rather interesting convertible (road legalable) f5 or f4 bike, maybe not competitive speed wise but thats ok because its just for fun, and the brakes and suspension on this thing are better than my last 4 bikes put together :P (albeit their combined age is rather close to 100(although their combined caliper piston count numbers ~30)

Yeah it does feel like this mofa you speak of :P
I have looked into the throat and arse of the spannie and cant see any washers in either end, have stuck a footlong bendy magnet stick in along the inner wall and it doesnt seem to hit anything , but i could be wrong. Also i found the snorkel to be off the airbox, and it was covered in kids skate stickers so i guess someone already had a crack at derestricting it. It has a 75 mainjet in there now, not sure if its standard but the exhaust can is pretty damn gunky wondering if its overjetted or the carb just cant put enough air through her ?
The pipe doesnt feel blocked but perhaps the endcan is saturated give it an open cat bypass this afternoon instead of rushing to pull her head off.

[SS90]

My aim is to get the missus onto 2 wheels for summer, with the thoughts in the back of my mind of spending a grand on her and havin a rather interesting convertible (road legalable) f5 or f4 bike, maybe not competitive speed wise but thats ok because its just for fun, and the brakes and suspension on this thing are better than my last 4 bikes put together :P (albeit their combined age is rather close to 100(although their combined caliper piston count numbers ~30)

Yeah it does feel like this mofa you speak of :P
I have looked into the throat and arse of the spannie and cant see any washers in either end, have stuck a footlong bendy magnet stick in along the inner wall and it doesnt seem to hit anything , but i could be wrong. Also i found the snorkel to be off the airbox, and it was covered in kids skate stickers so i guess someone already had a crack at derestricting it. It has a 75 mainjet in there now, not sure if its standard but the exhaust can is pretty damn gunky wondering if its overjetted or the carb just cant put enough air through her ?
The pipe doesnt feel blocked but perhaps the endcan is saturated give it an open cat bypass this afternoon instead of rushing to pull her head off.

I'm gonna take a bit of a stab in the dark here, because I don't have any experience with this model, but, when I worked on aprilia almost ten years ago, any small 2 stroke that was restricted had a 2 piece header, and where the header had a join, it was by 3 nuts, which where tack welded in place.

I just wonder if your header is the same.

It was just a case of grinding the welds off the nuts to separate the two halfs, and that exposed a conical restrictor in the exhaust, which was tack welded in, and you had to again grind the welds off to remove it.

Of course if your header is not like this, disreguard all that!

[rabidnz]

nah its a proper expansion chamber, all smooth and welded, no bolted joins, though i have read about the kind you speak of ! cheers mate. I had wondered if there is a restrictor further into the pipe that I havent located, Gas Gas NZ is no help whatsoever unfortunately.

Regarding the compression, I can easily turn the engine over by spinning the flywheel with my thumb and forfinger, doesnt feel very tight, but then again its a lawnmower engine :P

[Spearfish]

This link could help a we bit

http://www.sgnc.dk/documents/00020.pdf

Check your pipe first they often fit a washer by the head.
Check out scootling for small engine parts

http://shop.scootling.co.nz/index.ph...ewCat&catId=29
http://shop.scootling.co.nz/index.ph...ewCat&catId=30
http://shop.scootling.co.nz/index.ph...iewCat&catId=9
http://shop.scootling.co.nz/index.ph...ewCat&catId=86
http://shop.scootling.co.nz/index.ph...ewCat&catId=32

Tuning has a domino effect though so make sure you really know what you want it to do.

[F5 Dave]

Huh, I just had a quick look at one of those links. Shite! that's cheap for a PWK.

Surely it's a Koso or whoever replica. . . Sure enough ". . . This PWK type carburetor feature. . . " Hmm, not saying it but it isn't kosher I bet.

If it's a roadbike get it to std unrestricted form & stop there. That's why I asked. Carb swaps mean you will have to tune the carb, does that then affect how the oil pump is operated?, what about an airbox.

and it gets more detailed from there on.


A race bike is a race bike, a road bike is a road bike. Never more so than on a 50, esp if you find a hill.

[rabidnz]

if there is a washer in the header section, is it going to be obvious? or "around the bend" a bit? As i said i have stuck a magnet stick up each end and it doesnt seem to hit anything.

Just took the can off and it is pretty little black sambo'd, so is it fair to assume the spannie and the piston may be looking somewhat similar?

[rabidnz]

its my little project bike, so i dont mind tinkering and hunting and trialing things, thats why i bought it, and have a decent amount of carb tuning experience for 2 strokes, hell only having one carby is a dream come true, and id much rather have some control over what is flowing down the throat, as the little piddly carb on there now has just a main jet and an emulsion tube, and im at sea level pretty much and would like at least an idle mix and needle position adjustment.

[TZ350]

Those PWK type carbs from Scootling look very much like the Taiwanese OKO copies of the Keihin PWK and Chambers is using a modified OKO on his RD125 engine.

If it is the OKO carb, it’s bad point is that its bored straight through with a parallel bore instead of the tapered bore found in the real Keihin and the std OKO flowed slightly less on our test rig than a real Keihin did. But after a few mods it was much the same and way better than the std GP125 carb.

The good thing we found about the OKO was that it was made of a better, stronger alloy that machined well and all the std Keihin jets and needles fit.

We also found the real Keihin’s die cast body to be relatively soft and easily crushed in the jaws of the lathe, a common problem with most makes of carbs and we had to make special holding fixtures when maching them but don’t need to with the OKO as its strong enough to be gripped securely by the lathe chuck.