There is always a first time!
Things I did with my mopeds and 150cc bikes , 13-14 years old, are not so interesting for today's young kids with all game consoles, electric guitars, skateboards, clubs, bares, etc.
So for my youngest son it took a bit longer to get things done in the garage. But one day he started to complain about a low speed of 60-70 and a lot slower up hills with a girlfriend on the back, so I've told him it was time to start fixing the shit himself.

We decided to do an easy stage 1 upgrade to start with. To get (a lot more) more power up hills, and over all. Not so much for speed.

This step is to change the cc from the original 49 to a larger 70. We will keep the original crankshaft, exhaust and carburetor.

(a change of exhaust and carb is easy to do but it will for sure break the crankshaft after a while and that can be dangerous if you are in full speed.)

So next step is a bit harder to do as you have to go deeper in to the engine..



After taking the seat of, a lot of plastics etc, you will find the engine. (all this depends on what type of moto you have, this is an peugeot trekker)

The cylinder, with head, is attached with 4 long pin bolts, and there are 2 bolts holding the exhaust so it´s a quick an easy job.

1) When the cylinder is taken of we put a rug in the hole to prevent any stuff to fall into the engine, especially the small springs that hold the piston bolt in place. Then we took the old piston off and mounted the new bigger one.



- You have to put a lot of oil on the new parts before assembling them. We use a simple plastic cup, top of a spray can, filled with motor oil and just dip the parts in oil.
- Make sure the piston rings are correct mounted with the little "pin" facing the middle of the opening.
- And the small arrow on top of the piston pointing towards the exhaust outlet.

As you can se here the intake from the carburetor goes strait down in to the engine (not in to the cylinder direct as on old bikes) and this is the second thing we have to change.
2) The house is attached with 4 bolts and has to be taken out and cleaned. Take the 3 screws out and replace the membrane to the new one delivered in the kit.

3) More power means that we need a bit more gasoline so we have to make a few minor changes in the carburetor as well. First we disconnect the gas wire and throttle to take the needle out.

On this model the needle is set in the top.



so we just move the clips one step down..

..which will make the needle shorter and let more gas in to the carb.

3B) The second step ( sorry, have no picture) is to take the bottom cup of the carburetor (se other picture of carburetor) and attach a small extension piece of metal tube, delivered in the kit, on the thinner and shorter of the two pins under the cup, so it will end up 3 mm shorter the the bigger one. (the bigger one holds the jet).

4) After assembling the carburetor its time to put the new cylinder on. Ours was easy to slip on ( oil, oil, oil) but sometimes you need to hold a piece of wood under the piston so Its not moving down.
- Make sure both gaskets are correct mounted before you mount the bolts, little by little cross over.



We choose to put the plastic cover/cooling back on. Some choose not to so we might change that later. We also added a new harder sparkplug for 70cc and a new air filter.

We cleaned and mounted a new metal gasket on the exhaust..

Started on the first kick. Now Its 50 km on maximum 3/4 of the throttle before we can test it full out, but its a huge different from what it was before even on half the throttle...



Mission accomplish in a couple of hours..

So what kit are we using?
Its a Polini 70cc Sport kit

(img from Motoscoot.es)

We bought it online from www.motoscoot.es
all needed parts included except for the spark plug and the air filter.

By Haze and Haze II