Step by step installation guide for a 70cc kit

Estimated time: 1-3 hours

A 70cc kit will give you more horsepower which also means increased torque, faster acceleration, and a higher top speed. You will need to follow the regular break-in procedures after installing a 70cc kit, because you are after all, breaking in a new piston and cylinder. I would also recommend not just doing a 70cc kit by itself, upgrade the carburetor and pipe while you're at it. With just an Airsal 70cc top end, Arreche 19mm carburetor, and a Technigas RS pipe, I have hit speeds in excess of 70mph. I have heard of those that can get 75+ mph out of such a kit on a Triton R4.

The first thing to do is remove the cooling fan cover from the right side of the scooter. There are several 8mm bolts as well as a screw that hold the plastic casing together.


If the oil line (coming from the bottom of the oil reservoir) is going to get in your way, clamp it off like a garden hose, and pull the hose off from either end. You could get some zip ties and when you go to put the line back on replace the dinky metal clamp on the oil pump with a zip tie. It will secure the line much better than the stock clamp and it actually fits, unlike a screw down clamp.

Pull out the spark plug, here is a reference if you don't know how.

Take the other side of the plastic cooling fan housing off, if you have a stock airbox on (Triton / X-Peed), you will need to remove it to get the housing off. There are two pegs on the side of the scooter with the airbox (plastic pegs slide in rubber housing to secure this side of the housing), pull the whole thing towards the front of the scooter and it should slide right off.

Take the two bolts out of the exhaust at the bottom of the cylinder, and then remove the other bolts that hold the exhaust on. After you have removed the exhaust, you can get a 10mm socket out and take the four cylinder head nuts off.

Once the cylinder head nuts are removed, you will be able to slide the head and the cylinder straight off. There is a paper gasket at the bottom of the cylinder, it should just come right off with the cylinder though. Try not to tear it in case you need to use the stock top end in the future.


After you have everything off, you will see the rod with a piston attached at the end. There are small clips on either side of the wrist pin that holds the piston onto the rod, you should be able to get one of them off (needle nose pliers) and then use a blunt or soft object (so you don't scratch the wrist pin) to push the wrist pin out towards the side with the clip removed. It should let you get it off without removing both clips. Be careful when removing the clip, they are very small, and very easy to lose since they seem to fly off upon removal.


You could have either a 10mm or 12mm wrist pin if you have a 2004 Vento, 10mm if it's a 2003 I believe, 12mm if it's a 2005 or later. Take a look at this picture, the stock piston is in the middle (12mm wrist pin), the 70cc 10mm piston kit is to the right, the 12mm piston kit is to the left. See the difference between the sizes?


Now I put my 70cc kit on at 7100 miles. I broke in with Penzoil, and used Amsoil TDR for a month or two before I switched to Blue Marble. This is after about six months of usage. You are supposed to decarbonize the cylinder and the exhaust at 6000 miles, so I was 1000 miles overdue. There was literally no carbon on the head, and minimal carbon deposits (more like a thin residue) on the top of the piston and at the exhaust ports. The only discoloration on the piston was from heat. So Blue Marble is good for more than just getting an extra 5mph.
At this point you can clean up and re-grease the rod bearings, it should just slide right out.

You will need a piston ring tool (found at any auto parts store) to put the ring on the new piston. You can attempt to do it with plenty of other methods, but why take a chance, the ring tool only costs about $10. Use the ring tool to push the ring apart so you can slide it over the piston and get it into place.

Apply a thin coat of synthetic 2-cycle oil on the new wrist pin, or a thin coating of grease, and put one of the clips in the new piston and slide it over the rod. Now slide the wrist pin into place, and put the clip in the other side.


Now you are ready to put the 70cc cylinder into place. First apply a good coat of synthetic 2-cycle oil on the new piston and the inside of the cylinder. Next you will need to find the notch in the piston and align the gap in the ring over this notch. Now hold the ring down from both sides with one hand, then slide the cylinder on with the other hand. Once you get it past the ring it should be very easy to slide it the rest of the way down. Just make sure that you're not trying to slide it crooked because it will bind up on the bolts. Once you have the cylinder on, slide the head gasket and then the head on, and tighten the head nuts back down. Be careful not to over tighten the nuts, if you strip the bolts, it would be very bad. And it's very easy to do (and because it's so easy, it's a very common mistake). If you are using a hand ratchet, the bolts should slightly squeak when they are tight enough (but they may not, use common sense -- how much pressure did you need to apply to get the nuts off in the first place?). If you strip your head bolts, you have two choices, purchase new ones from Vento ($cheap$ and slow) or get a helicoil kit (time consuming but easier to get).


The only thing that isn't obvious from here is the little copper ring that came with your 70cc kit (possibly, well hopefully). This ring will give a good seal between the cylinder and the exhaust. It's very tricky to get it all lined up. I would attach the exhaust at the rear of the scooter first, but only one bolt so you can move the end by the cylinder around a bit. Get the two exhaust screws started, then slide the exhaust on the bolts (or line the exhaust up, and get the bolts started). What you're trying to do here is give yourself enough room to slide the copper ring into place so you can tighten the exhaust bolts down and it will stay in place. The shiny side goes towards the cylinder, the grey or split part goes towards the exhaust. Tighten it down, but be very careful, I broke the head off of a bolt when I initially installed my exhaust. You just need it tight enough where it is sealed, not where the copper ring is completely flat.

After you get the exhaust attached at the cylinder, you can reattach the oil line if you removed it, and finally re-assemble the cooling fan housing.

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