My new kit came from GasBike; so I opened up the engine to see if it was as advertised. It claimed to have a needle bearing wrist pin; it does. It claimed to be 80 cc, and it is what is currently called 80cc, so that was okay, too. (Actually, the 80cc actually translates to 66cc, because the Chinese measure it differently than we do.)
The piston fit the cylinder nicely; and that's a good thing, because if it's not fit tight enough 2 strokes will tend to seize. Tight, means that there is better heat transfer from the piston to the cylinder; and there is less room for the engine to fire down between the cylinder and piston which will make them seize. Mine is fine.
There was one minor problem though. The base gasket was too wide and extended into each transfer port, thus blocking the ports by about 25%. Not good, but it is a simple fix when you remove the cylinder from the bike as I did. It's only soft gasket material, about like cardboard, and a razor blade or a sharp knife will trim the gasket back so it so it doesn't block the ports. It doesn't hurt anything to leave it like it is, but it reduces the engines power because it doesn't breath well. Of course you have to pull the cylinder to see if yours has the same problem. When you pull the cylinder it messes that base gasket up a little because it's glued in with some gasket cement. If you damage the gasket, you can repair it with a little, very little, silicon seal, RTV. But use as little as possible or you will squeeze some into the ports and it will restrict air flow, too. Unless you are comfortable removing the cylinder, I wouldn't advise doing it. The hazard is you could break a piston ring or something, and putting the cylinder back on the engine is not difficult, but a little tricky, because you have to make sure the piston rings are in the right spot, or you will break them. Not good.
I wasn't too impressed with the cooling fins on the cylinder and the head. They were sort of rough, but I smoothed them out with a file. A couple of the cylinder fins were bent a little. So, I took a wood ruler, like the kind we used in school, and used it to straighten the fins. It worked fine.
I'm pleased with the kit, because everything was good where it counted, and the $119.00 was a good price. I was particularly impressed with the gas tank. Other than the paint, which was serviceable but not the best I've seen, the metal and workmanship on that tank is superb, and so is the gas cap.
I could tell by the spark plug that the engine had been run tested a little at the factory, and that was a good thing.
When installing the cylinder head, you must torque it with a torque wrench, moving gradually in a cress cross manner. Don't torque those 6mm studs to 120 inch pounds, because that's too much. Probably 90 inch pounds is enough. Some engines use 8mm studs, and can be torqued a little higher. Go easy, because if you see that the head is leaking compression a little, you can always torque it some more. These are little engines; and ham-fisted maintenance will surely ruin them. That means work gently and gradually, and don't force anything. If you are not sure of what you are doing, don't try to pull the cylinder.
When you remove the spark plug, you should put some graphite powder on the threads. That serves two purposes. The plug will not seize up and strip the aluminum threads in the head. Also, graphite grounds the spark plug nicely making a better electrical connection.
While I've been writing this, FedEx delivered another GasBike kit. I liked the first one so well that I ordered another one for $119.00 plus shipping. Okay, so I'm going to eat cornflakes for the next six months. LOL
The piston fit the cylinder nicely; and that's a good thing, because if it's not fit tight enough 2 strokes will tend to seize. Tight, means that there is better heat transfer from the piston to the cylinder; and there is less room for the engine to fire down between the cylinder and piston which will make them seize. Mine is fine.
There was one minor problem though. The base gasket was too wide and extended into each transfer port, thus blocking the ports by about 25%. Not good, but it is a simple fix when you remove the cylinder from the bike as I did. It's only soft gasket material, about like cardboard, and a razor blade or a sharp knife will trim the gasket back so it so it doesn't block the ports. It doesn't hurt anything to leave it like it is, but it reduces the engines power because it doesn't breath well. Of course you have to pull the cylinder to see if yours has the same problem. When you pull the cylinder it messes that base gasket up a little because it's glued in with some gasket cement. If you damage the gasket, you can repair it with a little, very little, silicon seal, RTV. But use as little as possible or you will squeeze some into the ports and it will restrict air flow, too. Unless you are comfortable removing the cylinder, I wouldn't advise doing it. The hazard is you could break a piston ring or something, and putting the cylinder back on the engine is not difficult, but a little tricky, because you have to make sure the piston rings are in the right spot, or you will break them. Not good.
I wasn't too impressed with the cooling fins on the cylinder and the head. They were sort of rough, but I smoothed them out with a file. A couple of the cylinder fins were bent a little. So, I took a wood ruler, like the kind we used in school, and used it to straighten the fins. It worked fine.
I'm pleased with the kit, because everything was good where it counted, and the $119.00 was a good price. I was particularly impressed with the gas tank. Other than the paint, which was serviceable but not the best I've seen, the metal and workmanship on that tank is superb, and so is the gas cap.
I could tell by the spark plug that the engine had been run tested a little at the factory, and that was a good thing.
When installing the cylinder head, you must torque it with a torque wrench, moving gradually in a cress cross manner. Don't torque those 6mm studs to 120 inch pounds, because that's too much. Probably 90 inch pounds is enough. Some engines use 8mm studs, and can be torqued a little higher. Go easy, because if you see that the head is leaking compression a little, you can always torque it some more. These are little engines; and ham-fisted maintenance will surely ruin them. That means work gently and gradually, and don't force anything. If you are not sure of what you are doing, don't try to pull the cylinder.
When you remove the spark plug, you should put some graphite powder on the threads. That serves two purposes. The plug will not seize up and strip the aluminum threads in the head. Also, graphite grounds the spark plug nicely making a better electrical connection.
While I've been writing this, FedEx delivered another GasBike kit. I liked the first one so well that I ordered another one for $119.00 plus shipping. Okay, so I'm going to eat cornflakes for the next six months. LOL
