piston into block

I took the head and the block of my moped to decarb the head and the piston I cant get the piston to go back in the block. I dont think the rings are causing it. I think my angle is wrong any tips. Do I need to take the piston out an insert into head? Im lost please help.

Re: piston into block

Make sure that the openings of the rings match up with the notches on the piston. They are sometimes hard to see, but you'll see a little dimple on the piston where the rings belong. At that point, push in the rings with your thumb and middle finger while fitting the remainder of the piston into the shaft. Takes patience--better to get it right than have cyninder problems.

Cheers,

Brennen

Re: piston into block

Aaron Alt /
biga OP

Thanks for the reply where are the notches located and is there only one notch or 2?

Re: piston into block

There is a pin built into each of the piston ring grooves.

You have to make sure that the ring gaps are where the pins are. Line them up and work one ring into the cylinder at a time and you should be good to go.

Re: piston into block

Lube the rings and cylinder with 2-stroke oil, that seems to help some.

Grey

Live to ride, Ride to work

Re: piston into block

Aaron Alt /
biga OP

I dont know about a pin I dont remember seeing any thing like that could you explane a little bit more about the pins.

Re: piston into block

A piston ported two stroke has a problem that if the piston rings are free to rotate the ends of the rings could get aught in the cylinder ports and cause major damage. To prevent this pins are manufactured into the piston ring grooves to keep the rings from spinning. Look completely aroung the groove in the piston. There should be a pin in each groove. The ends of the rings are sometimes ground to match the pins. There is usually two rings. The pins will be separated to keep the gasses from finding a direct path down the side of the piston. For instance, the pins might be at 2 o'clock and 10 o'clock.

Re: piston into block

Aaron Alt /
biga OP

Thank you very much that is a better description. It makes sence to put those pins in there. This is more than likley the problem. I really appreciate this info. Thank you Aaron

Re: piston into block

Here is a hint:

If the cylinder has been removed from the crankcase it is easier to install the piston in the cylinder while on the bench. These little pistons are hard to get your fingers around.

Once the piston is in the cylinder, push the piston out of the cylinder only far enough to clear the piston pin hole. (make sure the piston is in correctly. There is usually an arrow on the top of the piston that should point to the exhaust) Put one piston pin keeper in the piston and start the pin into the other side. Stuff a rag into the crankcase mouth. You do not want to drop anything into the crankcase,

Slide the cylinder onto the studs just until the hole in the con rod lines up with the piston pin. Then push the pin home and install the other keeper. Then push the cylinder the rest of the way down.

This method will only work if the pin is a sliding fit in the piston and con rod.

Good luck. Let us know how things go.

Re: piston into block

make sure u put some two stroke oil directly into the cylender, if not, on your first kick you could seize the motor( not likely buty could happen) also it might help the piston to go in easier.

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