Yamaha Neos 50cc, increase top end?

Hey there everyone.

I'm wondering how can I increase the top end of my Yamaha Neos 50, it's a 2 stroke I have done the following to it; I've put in a "performance" clutch (though I doubt it actually made much of a different) with a race torque spring, I also have 5.7g rollers which gives it very consistent and strong acceleration up to about 45-48mph on a flat. It also has a sports exhaust but it has a stinking dent in it, I thought it might be effecting the performance but in all honesty I've got no clue how it works; anyone know how I could possibly remove this dent or where I could get it done at a cheap cost?

I'm yet to put a performance air filter on, would doing so increase the top end -- what about a bigger carb (17.5mm as oppose to 12mm)

Thanks all

 

Thats about it for your neos.

your 50cc engine only makes so much power and the rear drive ratio is where you get a higher speed, BUT problem is its possible the engine will not make enough power/torque to pull a longer gearing ratio. you could find it becomes slower if you add a primary gear kit/secondary gear kit. and that because the motor itself just does not have enough power/torque to pull that longer gearing you add. the motor would just be worked harder and nodoubt not be able to reach optimal rpms.

adding a 70cc bore would increase power and torque so you would have a bullet like take of speed but still maybe struggle for a higher top end speed , thats all due to the rear drive ratio. adding a gear up kit would see you gain a longer top end But to what i can muster from interweb it also reduces your accel a bit. then its down to variator weight tuning to some what balance that loss and harness that extra power and torque produced by the larger bore and that longer gear up kit thats added.

Filter will NOT add more speed but it will allow the engine to breathe more freely , ie its not restricted so much in the air it can draw in.
a bigger carb will maybe add a slightly better throttle response but it also means re-jetting it and adjusting it for optimal use.

exhaust dent, if it seems not to have any ill effects i would leave it how it is personally , usually its either pulled out or the exhaust needs to be chopped open, the dent hammered back out then welded back together again.

my little sym run stock clutch - variator -carb, has a little leo vince tt exhaust and tops out at 75.6kmh (47mph) thats using 3x6g and 3x8g rollers , low end its a boring slow ride, but as it hits around 35mph my power kicks in and the scoot starts to wind up at 47mph i am flat out at max rpm, hills are a pain unless i keep above 30+mph and the rpm up high.
your little neos sounds about right for a derestricted 50cc and is about as far as one can go without increasing the capacity with a bore kit and added gear up kit that adds a bigger wallet eating bill.

 

Another way to fix dents in pipes:



I would keep the stock air box because you will get no benefit from an open filter, just frustration. Open filters are for mid-race and higher.

 

Apologies for the slow reply mate, your response was super informative and helped me to understand my scooter a lot more. I'm seriously considering getting a decent 70cc kit, a bigger carb and a set of jets just for the better acceleration. I live in a really hilly town so it becomes quite a problem going up a hill at like 10-15mph & a lot of the roundabouts in my area are on hills and there are drivers who hit me almost regularly cus they overestimate my speed. I have a lot of my power up to about 30, then it loses a bit of power and once I get to 40 it just stomps on up to about 49-ish, though I do need to get a GPS on my phone and see how fast it actually is, realistically.

This may seem like a silly question but would a better quality tyre on the rear affect acceleration? My rear tyre is a bit turn up (has plenty 'left' on it) but it's just a bit shitty quality. I want to get the most I can out of this little scooter because it's a joy to ride when the weather is fine but I want it to be fun to ride even with a bit of wind

 

tyres affect drag, rolling drag. a flat tyre will make the bike slower as it produces more of a footprint on the tarmac. a correctly inflated tyre has slighly less drag and a lower footprint on the surface. and its a very good thing to get into the habit of checking both front and rear tyre pressure's when the bike is cold ( air expands with heat, your 22psi tyre will expand as it warms up from road contact just like a cars tyre does). your bikes rider manual/service manual will give you the correct air pressures for the rear and front tyre. a good make of tyre does not add speed it offers better road handling and control / grip factors, a correct tyre pressure can give you a better rolling resistance and hence slightly faster speed.

i know the feeling well, i myself run a 50cc from 0-35 its a slow beast with a lotta noise, but once it gets to a certain point it flys off the handle, its the nature of a twostroke they need high revs where the powers produced. mine slows down to a crawl on hills to 20mph was my lowest and i felt like getting off and pushing it but the huge lorry behind me stopped me doing that lol.
Problem is this fitting a 70cc kit is all good if your 17+ years old (legal law says upto 125cc ) problem here is most 70cc kits are not for road use, and because your adding more capacity its NOT a 50cc no more so its not classed as a moped more so a motorbike.

now lets say your in an accident your scoot has a 70 kit fitted but it says 50cc on the V5, the bike is check over and found to have had that capacity upgrade your in some deep do do. your licence may be fine but your riding a bike thats been modded and not reported to dvla for one, your insurance is not valid as in there eyes your bikes a 50cc not a 70cc so thats thrown out the window to. you will end up in court with points and a fine.
OR your caught by mr plod cruising down the A road at 55 mph, he has been sat behind you and anpr checked your bike it comes back as a 50cc YET your topping out at 55mph he is going to stop you whatever happens, they are not daft and know a 50cc only goes quick if its been tampered with or upgraded and not registered with the authoritys, again your licence may cover your for upto a 125cc BUT the V5 is incorrect and your insurance is not going to be valid, so again its a court summons points and fine.

i have also notice myself when looking for a new bike that 70cc kitted scoots tend not to sell as easy as a standard derestricted 50cc , and the owners state its still registered as a 50cc on the documents its the problem becasue most folks after a 50cc are young lads 16yr old, and nearly all 17yr olds will step upto a 125cc as soon as the hit that magic 17yr old number, the other problem is you cannot take your A1 light motorcycle test on anything lower than 115cc-125cc capacity, so 70cc kitted scoots go out the window and even the 100cc scooters and those 110cc scooters to.
some of us riders can be on the road for like 10yrs before we are pulled over for the first time others not even two weeks after passing cbt and they are tugged its the risk you take when running a 70cc kit illegal or a legal stock 50cc so the ball is in your park.

 

Yeh I was reading up something about that a while ago, some bloke got in an accident on his 50cc and they ran his bike on a dyno and it got something like 10hp which is a bit unrealistic for a 50cc and they ended up taking his bike off him and giving him a huge fine for riding a bike which was not registered with the DVLA as a light motorcycle. You're also buggered if you hit into the back of a nice car and they find out you're running a 70cc

I was just having a chat with one of my mates and he has a 21mm carb but I'm not sure whether or not it would fit my scooter (he doesn't know the model, either). I'll post a picture below;



What sort of affect would a bigger carb have on performance?

 

for your standard de-restricted 50cc NOTHING, its just going to cause more headaches as you will have to fit smaller jets in. 21mm carbs are something you would see on a 70cc race kit.

our little bikes tend to come with either a 12mm or a 15mm carb when we derestrict them we tend to adjust the carb to allow a more fuel air mix or we upjet the stock carb a size of two bigger , we can also on some carbs adjust the needle hight but only on some carbs. a needle can have three to four slots in the top, and a little C clip usually sits in slot 1 or 2 , the needle is for your mid range high end running and makes it either leaner or richer on mix, bit like adding a bigger jet to get a more rich setting, or a smaller jet to get a very lean setting.

tuning a carb is a three step system, the air/fuel screws - the needle setting - the jets ( there are two jets inside a carb usually, a pilot jet for idle and a main jet for when throttle is active ) having these three items adjusted correctly gives your motor the best delivery of fuel and air mixture and also the right amount.

a 17.5mm carb may give you a better throttle feel but its not going to do much unless you are going to add more capacity to the motor via a big bore kit or having the barrel skimmed and a oversized piston fitted.

if your still young hang on until your 17yrs old then look at something like a 100cc or a 125cc, if your 17yr old maybe look at upgrading by saving a few pennys up then selling bike and grabbing another.

You can have a 50cc doing 60+ mph but the amount of money required is mind blowing, its going to be expensive porting work, timing work, polishing, re-flow work and the likes and a lot more beef added to the crank and likes, ie full stuffed cranks, top end race exhaust systems and a lotta dyno work and even then your going to be rebuilding that motor ever couple 300 miles or so due to the excessive wear and tear of the racing styled tuning its had. and a lotta mechs/enginners will just say " its not worth the money or time " unless your racing it and have a truck full of money to throw at it.