My Big Race Help Needed

[jerbear]

I have a Roketa Bahama MC-07-50 (spec below)
and this guy want to race it with a 86 Honda elite 80cc I know with the stock setup I can't win but I plan on getting the 100cc bore kit, maybe a better cdi and put a uni intake on it. What jet sizes should I get and with these part should I win?

Specifications

• Displacement : 50cc
  
  
• Max horsepower : 3.3ph/7500rpm
  
  
• Max torque : 3.1n.m/6000rpm
  
  
• Bore*stroke : 1.54*1.63inches
  
  
• Max speed : 31 mile/h
  
  
• Battery : 12V/7Ah
  
  
• Carburetor brand : PD18J
  
  
• Engine oil : SAE15W/40SF
  
  
• Tires,front/rear : 3.5-10/3.5-10
  
  
• Fuel capacity/type : 1.1 gal
  
  
• Weight,G.W./N.W : */ 198.4lbs
  
  
• Max load : 220.5lbs
  
  
• Wheelbase : 51.2inches
  
  
• OA L*W*H : 71.3*28.5*41.3inches
  
  
• Min ground clearance : 3.9inches
  
  
• Carton size : 74*22.2*46.5inches
  
  

[Rebel]

Here are some suggestions for you, sorry I cut and pasted from a post I did on another forum. As far as the jet goes, it will be a trial and error 88 - 92maybe.

Performance Mods
Transmission
On a 50cc four stroke scooter the easiest way to change the performance for your scooter is to change the weights in the variator.
Going to a 4.5 or 5 gram weight will make it much peppier. The motor will rev higher and you will be in the power band of the motor.

Additionally installing a performance type of variator like a Dr Pulley or a Prodigy will help because they are larger, being a larger pulley on the front end you get a higher final gear ratio and if the belt will go all the way to the edge of the pulley you can take advantage of the taller gears, it might require a longer drive belt. Any variator change will need a proper tuning and you need to experiment with the weights to get it right for you.

Ignition
There are people that swear by using an iridium spark plug, these very well may at minimum make it start easier.

Performance Coil/CDI, mixed reviews on this, I've heard both sides make comments. You will certainly get rid of a rev limited problem, you should get a hotter spark and that can give a better combustion and use of the energy in the fuel, they are cheap enough to buy and not loose sleep over if you don't think it helped.

Carburetor
A lot of scooters come tuned for smog regulations and are running lean, you should try to adjust the air/fuel scew, most of the time it will be covered with a metal plug and may be a pain to get to. Getting a new one may be the way to go and then you can make your adjustment and replace the jet should it need to be and it is highly likely that it will need to be.

Remember that with any changes in the intake or exhaust you need to adjust the carb, otherwise it could be running very lean and burning a valve.

Head
On the head there is the cam, a performance cam can be a big help in the power. You will often see cams sold as an A-9 an A-10 ... These are numbers that imply the higher you go the more power you will have, as far as I know there is no industry standard on this.

The head itself can be improved porting and polishing the intake and exhaust ports on the head can be a big bang for your buck, this is something you can try to do on your own if you are adventurous, but myself I think it is smarter to just keep the stock head as a spare on the shelf and order one from the pros that know how to do it. You can find performance heads at the dealers we have in our banner ads here.

Big Bore Kit
As the old hot rodders say, there is no replacement for displacement.

A good quality big bore kit can add some power, you really should get one with a matched head so that things just go together right. Some kits will include a head, cylinder, piston rings gaskets, jets for the carb, an air cleaner.

If you really want displacement you can get a stroker kit, that is a new crank and connecting rod that will give the piston more travel, this will really crank up the cc's you have.