Before you disassemble your engine be sure to clean your engine very well so no dirt can go inside your engine and be sure to follow the instructions below.
Proceed as follows:
| ||||
If you have problems to lift off the conrod from the pin(which is a good sign) we here use a small wrench No.7(see picture). | ||||
Normally the conrod will lift for about 3mm which is then sufficient to get behind the conrod and so you can use the small wrench to lift the conrod until it gets of the pin of the crankshaft, do this gently and also proceed 1 time left and 1 time right, etc... | ||||
| ||||
Heat up the crankcase on an electric cooking plate(position 6 should do). Wait until the oil which is inside the engine starts to smoke a little(after 3-4 minutes). | ||||
Take the crankcase of the cooking plate with a heat protective glove and hit firmly the back of the crankcase on a wooden plate until the main-bearing comes loose. Be careful not to burn your fingers and if the bearing does not come loose put back the crankcase on the electric plate and wait a little more so the crankcase heats up more. | ||||
The bearing has come out here. Please note that the bearing sometimes comes out of its place but is a little stuck after, this happens, just align the bearing so it falls out after. | ||||
Immediately after(while the crankcase is still at the right temperature) you must also take out the front-bearing. This can be done by introducing a round axle(here it is a tool for nuts) for which the diameter is smaller then the inside size of the main-bearing you just got out of the engine. Hit the front-bearing gently so it comes out, be careful not to damage the inside of the crankcase! | ||||
The front-bearing has come out here. | ||||
| ||||
Mount the new main-bearing on the crankshaft with the balls closest to the crank-flange. | ||||
Mount the front-bearing with the rubber(or metal) flange directed to the thicker part of the crankshaft, this because we need to insert the front-bearing in the crankcase. | ||||
Get the crankcase(carefull hot...) and slide in the front-bearing in the crankcase with the help of the crankshaft. Wait some seconds and pull-out the crankshaft, the bearing should stay in place. Put the front-bearing in place quickly otherwise the bearing will take the temperature and get stuck. If this happens, don't panic, you should be able to put the front-bearing in place after you have pulled out the crankshaft and pushing the bearing in place with the wood you have used the get the main-bearing out. | ||||
Pull-out the crankshaft a few seconds after you have put the front-bearing in place. | ||||
Then immediately after insert the crankshaft in the rear of the crankcase and let the crankshaft and bearing fall in place, turn the crankshaft to see if it turns free and let the whole thing cool down. Once again be careful not to burn yourself with this. | ||||
| ||||
| ||||
After you have exchanged the bearings, you can use the engine as is, normally no need to run them in but a little easy at the beginning does not harm the engine. |