Kymco zx50 super fever 50-60 mph free modification

[naughty lee]

Hi guys,
( thread renamed, follow instructions and your standard scooter will hit 50 mph minimum)

Original thread.
I'm in the uk and I've recently got hold of a zx50 super fever.

Gotta say, it's a reliable little thing for a 1999 model, I've had it to bits and reassembled it and I'm pleased with the build quality.

Recently though, the drive belt snapped. Prior to this the machine was hitting 40mph no problems.
Upon looking inside, I noticed the inner variator was badly worn, so I ordered a complete front variator and belt from wemoto.

The kit turned up with 8.5g rollers (originals were 7g)
During reassembly I noticed that the belt was too long. The bike runs but struggles to hit 25mph.

What I need are some definitive answers.
Aside from the standard bando belt, what is readily available in the uk as a direct replacement?

Secondly, the replacement boss is 38mm, what is the best proven length for max speed on the zx50?

I won't ask about roller weights as these differ so much dependant on machine and rider weight

[Raindrop]

my stock zx50 hit 45 mph .. with no mods just unrestricted cdi .. and washer out of exhaust .. u have to see if u have the af18 engine ..
im not sure you do .. thats why your getting wrong parts ... also you can find parts by looking up honda dio parts .. see what ur engine code is first ..

[naughty lee]

Where do I find this info ?

[Raindrop]

Where do I find this info ?

i looked at my engine code on engine and found i have the dio af18 engine ..

But i think you do cause they made af18 - 1999 - 2006 i think ..

[Raindrop]

Varitor for cheap .... http://www.ebay.com/itm/RACE-VARIATOR-for-KYMCO-ZX50-ZX-Fever-50-Fever-II-50-/400202207211?pt=Motorcycles_Parts_Accessories&hash=item5d2de90feb&vxp=mtr


Belt ... Measure it for sure cause google says u have a different belt than i do a 2004 ..

[naughty lee]

Ok, I've ground the boss down to 34 mm as per the info on here. The outer variator now fouls the starter bendix, now I need another boss or some shims, the 8.5g rollers were too heavy, back down to 7g now

[naughty lee]

Bit of an update, I acquired another variator yesterday, I weighed it with the sliders and compared it to the original kymco part. This new bit was within a gramme of the original. I fitted it with the new outer variator. It fouled the starter bendix with a 34 mm boss. I fitted the original kymco outer variator which has a lip on the inside. This lip gives just the right amount of clearance so that the teeth on the outer variator miss the teeth on the starter bendix once the engine is running.

Some ink from a permanent marker pen was put on the inner variator and the bike was tested for speed. An indicated 43 mph. More like it. When the machine is idling I can just hear the outer variator " chinking" occasionally against the bendix teeth.

A strip down of the drive system showed all the ink was removed from the inner variator.
So now what?

[naughty lee]

Today I've got hold of another boss. The plan is to grind it down to 33mm, it's likely that this will foul the bendix, so it will be tested tomorrow without the bendix fitted.
If there is an improvement with speed, the starter teeth on the outer variator will be filed down by 1 mm so that they do not foul the bendix. This will give maximum speed whilst keeping the electric start facility.

So what have I learnt so far?
If the outer variator on your zx50 is not the original part, then only skim your boss down to 36mm if you want to keep your starter motor in the equasion

[naughty lee]

Right, the spare boss was skimmed down to 33 mm and the machine was reassembled. At this length the kick start spigot will not reach the mating face on the outer variator, I haven't binned the boss though as I have another plan for later down the line. Messed about trying different weights, seems that 7.5 gramme rollers are giving the best accelleration whilst still allowing the bike to max out at 43 mph.. More to follow

[naughty lee]

A phone call from my local scooter dealer gave me the news I've been waiting for... The correct belt has arrived. ( genuine part ) I've not measured it but it was clearly shorter than the 720 mm one that was fitted, it's also thinner whilst remaing around 17mm in width.

Another speed test but unfortunately it was raining heavily. Nonetheless, the acceleration was down a little but the pull was constant and linear. The bike indicated a solid 50 mph and I was convinced there was a little bit more. Unfortunately a speed hump meant I had to scrub some speed off to avoid bring catapulted into Scotland !

More experimenting tomorrow on a longer road with a slight decline.
This little scooter has been fun to mess about with and hasn't cost the earth.
The mods are simple and cost either nothing, or pennies

[naughty lee]

Good results today, the particular stretch of road identified is a long valley with the south bound direction giving the longer run, unfortunately strong head winds limited the south run but the north run gave a surprise.... An indicated 61 mph!! Remember, this little ped has had NO engine or exhaust modifications. This speed has been achieved just thru mods to the boss, the ecu and the rollers !

[naughty lee]

Lighter rollers were fitted last night, weights to be confirmed but are around 7g, my son took the scoot out for a rip and told me that it now hits an indicated 57 mph on the flat.

I think it's safe to say we are now at the last few drops of speed on the budget modification list.

Race variators seem a bit steeply priced, I need some reassurance that another 5 mph is possible before buying one, the same for an aftermarket exhaust.

Total mods currently
Ecu green wire splice
Aftermarket drive belt replaced with original kymco bando belt £30 ouch
Front drive boss filed down to 34mm
Roller bearings 7 grammes each

Mods to do
Replace stock exhaust
Drill extra hole into the air box

Maybe mods to do
Fit a race variator

[LoveMyKymco]

I think but dont quote me you should have an AF05e derivative in yours and not the dio derived version. You should have a Kymco zx50 super fever if its a 99, and 03-05 is a zx50 super fever II/2. Ive only seen 2 of the older super fevers and didnt look at the engine because I wasnt into honda clones at the time.

[LoveMyKymco]

Can you post a picture of your scooter, I love when people live in europe and have cool scooters we dont have over in the US. Also does the exhaust come out of your engine at an angle or straight out? That will tell you what cylinder you have. Angled is AF05e and straight is AF16/18.

[naughty lee]