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Written by NSR-Dan    Wednesday, 06 May 2009 23:12   
Custom "Chinese" 50 ITS ALIVE
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Custom "Chinese" 50 ITS ALIVE
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milf hunter update 1
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Ok all this is a new project from a contributor here in lil' ol' New Zealand a ground up very fast 4T scooter build. We will try and keep you all up to date with the project... Code Named "Milf Hunter" (the builders name, not ours so don't give us a bunch of crap about the name.)

I bought a crap chinese scooter from trademe (NZ's version of ebay. ED) for $54 dollars it wasnt working, but it had what i needed which was an un bent frame and a GY6 50cc engine case that wasnt wrecked.

I started by ripping the engine right down for a blue print and full rebuild with new (non chinese) parts. I dremmeled out all the machining marks in the engine case and ground all the oil tracks to the honda GY6 spec cleaned it all up so it was all nice and tidy.

Ordered all the internals which was a new crank from scooter attack in germany, the cylinder is a 90cc made by BGM with a super corsa piston, head is a performace variant with big valves and larger porting and a race cam shaft also from BGM in Germany.

Put the engine all back together checked timing and valve gaps. Now coming to the carb it was difficult as i could not find a matching intake manifold for the carb to the head that was a 21mm, so a i bought one that matched the head and modified to suit but filling with JB weld and port matching to the carb with a custom made insulator.

Gearbox being a CVT needed an overhaul so a new sport variator from Naraku in Japan that is designed for modified engines above 72cc, the clutch needed to be good to cope with the power to the wheels, so an RMS racing clutch with adjustable springs which i have set to release at 3000rpm, also fitted a heavy duty contra spring and racing clutch drive plate for better acceleration. I replaced all the bearings in the final-gear box that i sourced from SKF and filled with motul performance GB oil.

I still need to make up the loom for the scooter but i have already got a racing CDi and racing coil for a Yamaha scooter, a new Trailtech vapour will be hard wired into the loom with an RPM guage and engine temp, also got a digital rectifier from KOSO to help with getting the right voltage through the system as the chinese ones tend to suck, tail light to be fitted is from an 07 ZX-6R, have yet to decide what to do for the front (suggestions welcome. ED).

Frame has been cut up and re-welded as its going to have a naked rear end. fuel tank has been lowered to allow for a lower seating arrangement, handle bars are to be replace with a downhill mountainbike set up, so it should have a good setup for knees down scooter riding haha. Brakes have been tidied up and have been fitted with braided lines that my friend made up with earls fittings and airoquip lines, Suspension on the front was overhauled with new valves and oil along with a YSS racing shock for the rear. New wheels join the package as the others were... lets say a little worse for wear, the new hoops are fitted with some nice Michelin S1 tyres.

Still a bit to do with the welding and electrical, I have to put the gearbox together and get the engine started but I'll keep everyone posted as i update everything. and if anyone asks why a chinese scooter, well the answer is that parts for the engine are cheap and easily available, and the only chinese stuff left is parts of the frame and the engine casing, otherwise its German, Japanese and a bit of Kiwi inginuity.

I'm not 100% sure about the seat location as yet but I will be welding some pegs on for a slightly different seating position.

Some more parts have arrived from Scootling.

Stage 6 Racing clutch bell
Naraku High Speed variator
Malossi kevlar belt
str8 Belmouth filter
and some fuel hose

Latest additions. Put together the gear box, and if anyone is interested the set up is naraku high speed variator with 6.3gr weights, 1000rpm contra spring, RMS racing clutch with weener springs set to 2500rpm, stage 6 winged racing clutch bell and all connected with a malossi kevlar belt.

Keep your eyes open for further updates and when it is all together the Scooter Review will have a full feature on this bad boy.



Update to the build. I have been working on the wiring which is complete for all the engine components only lights to be done. I have fitted the carb on the best angle with the adapter plate so the fuel can feed into the carb freely, and have started it. It seems to run fine but with no gasket between the adapter and head I suspect an air leak is making the revs fluctuate, which is not a worrying as i need to dremmel out the adapter to port match the intake.

The engine is going to come off the frame as the shock needs to be repositioned due to a clearance issue with the shock and tyre (only 1mm clearance with a 3.00/10" tyre) will be moving a good 15mm over which will gve plenty of clearance to fit a 3.50/10" slick.

While the engine is out I'll finish the frame with its front end and handle bars which are downhill mountain bike bars kindly donated by a friend.

Here is a full list of mods for the scooter I'll add to the list as i go.

139QMB GY6 Honda copy, 50cc, 4 stroke.

Engine blueprinted and fully rebuilt.
BGM Crankshaft (with nachi bearings)
BGM Big bore cylinder 94cc
Super Corsa piston 53mm
BGM Performance head (bigger valves and ports)
BGM Sports Camshaft
Sports cooling fan
Tecno Racing Exhaust

Transmission (CVT)

New bearings from SKF
Naraku high-speed variator
Naraku Drive Plate (ordered)
BGM Clutch Torque plate
RMS Racing Clutch
Malossi Kevlar Belt
Stage 6 racing clutch bell


21mm PWK Carburettor
Str8 Drag bell
Custom modified intake manifold
Direct fed fuel with manual shutoff tap
High flow filter


Racing CDI
BGM Racing Coil
Denso Iridium Spark plug
Trailtech vapor dash with speedo, RPM and temp
Custom made loom
ZX6R tail light

Frame, wheels & brakes

Custom modified frame
Downhill mountain biking drop bars (to come)
Disk brake front, drum rear
Braided brake line
EBC brake pads
Alloy wheels with Michelin S1 tread
Rebuilt front shock
YSS rear Racing shocks

Took the bad boy for its maiden run yesterday, didnt have a spare bike battery so i strapped a car battery to the floor of the frame.

was very happy with the result, suspension felt good, engine felt good, and it powerwheelies of the mark with little effort and this is with the engine untuned and running rich as F%^K.

I welcome you to the completed (well it may get extra parts later) Milfhunter.

Now when i went to register it down at the local vinz they said i couldnt call it the milfhunter as it would be offensive to some people. so instead i had to settle for name #2, which is Frankinscooter, as thats probably what it looks like.

Comments (8)add
written by weedboy , October 11, 2009
nice one

im working on a project peugot v-click 4t tuning with GY-6 motor
my setup 80ccm + malossi multivar + 24 racing Carburettor - bgm pro and it's alive too ;) prety much alive

but there is a problem

my supercharged cdi bgm pro is giving me a headache it's not working... only the fuse will burnout it should add over 8000 rpm but nothing... can anyone help me?
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written by joa , August 19, 2009
I am impressed. I am working on a scooter designed form the ground up. I've TIG welded an aluminum frame and plan to add only the best parts to this. We are working with the design now, and we've made moulds so we can use carbon fiber insted of plastic. We are making two scooters. They are almost identical. The other one has a stainless steel frame.
We are going to fit them with a 300ccm engine from Honda.
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written by sid maley , July 24, 2009
that is the coolest 50cc mod i have ever seen. i would love to talk to you about other custom mods. please get a hold of me.
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written by Daniel , June 09, 2009
It all really depends on 2stroke vs 4 stroke, as a 90cc 4 stroke would probably have the same output as a 70cc 2 stroke. however on the racing side there has yet to be a 4stroke compete, so we will see how mine goes. with the 125cc's i would say they are in the same class as the 180cc's.

If you are looking at a larger scooter get the 125cc (make sure its shortcase as its smaller, better handling and lighter) if its a gy6 engine it will fit a 180cc big bore kit.
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written by GW , May 20, 2009
Daniel: thanks for a good reply.

I read about some moped racing where the rules allowed 50cc liquid cooled engine or 70cc air cooled engine. Where the more serious teams have mopeds that basically look like light road racing bikes.
But I guess the ruleset simply depends on who arranges the race.
It however almost seem pointless to have one class for up to 100cc and one for up to 125cc. Or does those last 25cc make enough difference to have two separate classes?

I'm thinking of getting a 125 scooter. If it would be to slow, are there any tuning that makes sense / is worth it ?
Would perhaps a small compressor / turbo make sense, or would it be to complicated or expensive to be worth it?

When will it come an update to your project ?
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written by Daniel (the builder) , May 14, 2009
I had looked at getting a 125 and modifying but there was a few things that put me off. firstly the 125cc and up are very heavy usually over 100kgs, and there wheel base is longer which i find them to a bit whale'ish to ride compares to the 50's. also the main reason is that there is a huge range of spares and modification options for the 50cc's, and for some strange reason alot of tuner's have managed to get larger increases in power out there 50's compared to the 125's.

In racing the thing in NZ there isn't really any classes specific for 50cc's and even overseas most classes are usually classed as under 100cc as most 50cc racing scooters are modified 2strokes running 65-70cc big bore kits. Plus this scooter of mine even though highly modified it wont be compeditive against for example a race tuned suzuki streetmagic.
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written by GW , May 11, 2009
This may be a dumb question, but what are the advantage of your scooter compared to other light bike scooters? (Scooters of 51 - 125cc, typically 100 - 124cc) ?

If you would do some organized competing with it you most likely would go up against 125 bikes/scooters since you exceeded the 50cc limit.
It most likely will not be street legal any more either, at least not as a moped.

Probably still a fun project though.
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written by ants , May 07, 2009
Awesome, looks like a good project.
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Last Updated ( Thursday, 24 September 2009 22:40 )


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