스크랩 (강좌) 엔진 베어링 교환하기

[TMgaia지민기77]

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.

1. Work on a clean spot !
2. Use adapted tools!

Proceed as follows:

• Clean the entire engine on the outside, the less dirt you have around the better it is for the engine.
• Take off the carburetor.
• Unscrew the glowplug.
• Unscrew the 4 head-screws(do this crosswise!).
• Take off the cooling-head and the combustion chamber, be careful with the head-shimms(the one's between the combustion chamber and cylinder), don't loose them.
• Unscrew the 4 backplate screws(do this crosswise!).
• Take off the backplate, be careful that when you want to take off the back-plate to have the piston in the upper position, otherwise you can damage your piston.
• Take out the cylinder.
• Take out the piston/conrod(when you do this the position of the crankshaft must be that the piston is at its highest position).

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...

• Take out the crankshaft.

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.

• Now you can let everything cool down or immediately mount the new bearings, for this we suggest that you put the crankcase on the electric plate again and do the following after.

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.

We also have available a special dedicated tool which aligns the bearings perfectly and you can use this tooling to mount the bearings also when the crankcase is cold. This tooling is available for the following internal bearing diameters: 14mm #01150-14T 13mm #01150-13T 11.5mm #01700-475-11.5 11mm #01700-075-11

• When everything has cooled down, check if the crankshaft turns free.
• Mount the piston/conrod in the engine by placing the conrod over the pin of the crankshaft(when you do this the position of the crankshaft must be that the piston is at its highest position).
• Mount the cylinder, first slide the cylinder about 5mm into the housing and then let put the piston in the cylinder, then put the cylinder in place(add a little oil #1400 to make this all go smooth.
• Mount the backplate, be careful that when you mount the back-plate to have the piston in the upper position, otherwise you will damage your piston.
• Mount the back-plate screws and tighten them crosswise.
• Mount the combustion-chamber and do not forget the shims!
• Mount the cooling-head and fix the cooling-head with the screws, do this crosswise.
• Tighten again the glowplug.
• Mount the carburetor.

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.