Changing engine bearing

[X]

Any sit that show how to change the engine bearing?

Regards,
x

[R-4-L]

i heard that you you need to disassemble the whole engine, and then heat the ballbearing from the inside using a torch or similar, the bearing should pop out with a few knocks! i didn't try it but that's what ppl told me.

Ali

[SteveL]

I use the oven (if your married dont get caught. I set the oven @ 350 and let the engine (already completely disassembled) sit in there ~10 minutes. I just tap the block on the back flat on a peice of would and the bearing falls out. I use a peice of wood or toothbrush to knock out the front bearing. I freeze the new bearings and re-warm the block and they just slide right in.
Be careful the block will be hot when you remove it from the oven.
The hardest part of the whole procedure is aligning the ring with the pin on the piston for reassembly. Take your time doing this or you will break the ring

[RC-Bearings]

www.rc-bearings.com Click on the obvious button.

[DavidH]

i heard that you you need to disassemble the whole engine, and then heat the ballbearing from the inside using a torch or similar, the bearing should pop out with a few knocks! i didn't try it but that's what ppl told me.

Ali,
I would quit listening to the people that told you the above.

SteveL has the right directions. Also here is the page from Paul's website.
Bearing replacement



The procedures that follow are generic in nature and will be valid for most sport engines. If your engine is different, please contact the manufacturer for specific instructions.



Engine disassembly:



Remove the head, backplate, carburetor and prop drive washer (you may need a small gear puller for tapered collar types)

Remove the cylinder sleeve from the crankcase. If it is stuck, try heating the crankcase in an oven at 200 deg. F for 10-15 minutes or soaking it in kerosene (paraffin) overnight.

Remove the connecting rod from the crankpin. The crankshaft may need to be rotated to a particular position for this. (Mark the front of the piston for later assembly)

Slide out the crankshaft.



You are now left with the crankcase and bearings. To remove the bearings, heat the crankcase in an oven at 200-250 deg F for 10-20 minutes. The bearings should fall out, but if they don’t, you can try a firm rap of the crankcase against a piece of soft wood such as pine or fir to dislodge the bearings. Small dowels or wire hooks can also be used to pull out stubborn bearings. Thoroughly clean the crankcase and crankshaft where the new bearings will be installed.


Installing bearings



To install the new bearings, place the new rear bearing on the crankshaft. Heat the crankcase in an oven as before. Fit the front bearing* into the crankcase and then slide the crankshaft into the crankcase and gently push the shaft in until the bearing is all the way in place. Do not force the bearing in and do not use the crankshaft nut to pull the bearing into a cold crankcase. This will damage the balls and races of the bearing and shorten its life considerably as well as cause increased drag and noise. Install the prop drive washer parts and install a prop onto the crankshaft but only tighten the nut finger tight. The crankshaft should rotate completely freely with almost no drag. If there is any binding, remove the prop and place the crankcase back into the oven for an additional 10-20 minutes to allow the bearings to reset.



* If the front bearing has a metal shield on it, install the bearing with the shield towards the prop.


Reassembling the engine



Replace the piston into the crankcase and slide the connecting rod lower end on the crankpin. Check that the piston is facing the correct direction (remember your mark?)

Slide the cylinder sleeve back into the crankcase. Make sure that the exhaust port in the sleeve lines up exactly with the crankcase opening.

Lubricate all internal parts with an oil compatible with the fuel you use. Pure castor oil is good for this as is commercial glow oils such as Klotz Super Techniplate. Other lightweight motor oils can be used as long as they are compatible with the other parts of the engine.

Reinstall the backplate (make sure that any gasket or O-ring is in good condition).

Reinstall the head (make sure that head gasket(s) are properly installed and in good condition) and incrementally tighten the screws in a crossing pattern.

Reinstall the carburetor.



Your engine is now ready to run again. Remember that it will require a short break-in period for all the parts to reseat to their normal running positions. One small tank run at a rich setting should be all that is needed.


David

[X]

Thank you very much to all of you.
Regards,
x

[R-4-L]

glad i haven't tried the method i heard. oven seems to be the safest and more reasonable way.. thanks steve

[BarracudaHockey]

Some of us do it with a torch but you have to be careful or you will distort the crank case, the safest way is the oven because it gets heated evenly.

[RC-Bearings]

You can find small toaster ovens at garage sales for under $10. These work very well for engine bearing changes. Just make sure to use an oven thermometer to make sure the temps don't go above 350 degrees. Much above that and you can have dimensional changes in the parts.

[Alfred]

Nobody seems to use the easiest and most obvious device?

A Heat gun for paint stripping.
Mine also comes with a smaller nozzle that can be fitted over the end.
It's basically a Hairdryer,,just a lot hotter.
No open flames
The small nozzle let's you gently heat up around the mainbearing area of the crankshaft....a few gentle taps on a soft piece of timber...done.
Do the same for the Front bearing, but now I use the crankshaft and re-insert it..gentle push and the front bearing is out.

No ovens and cranky wifes...no open flames..no running out of gas.
I assume you all have electricity and Power Points in you house.

[RC-Bearings]

Heat guns generate upwards of 600 degrees. This is far too hot for most engine parts. the same problems exist with heat guns as with torches: No control over the temperature of the parts.

Cheap yard sale toaster ovens are much safer.

[Alfred]

Sorry
I have been using a heat gun for 20 years on Rossi, OS, Webra, HP, YS, TT, ST........
Yes, I did assume that people use common sense, sort of a pre-requisit in this hobby.
If you hold the dam heatgun on it for 10 minutes and possibly on the same spot then yes...that wouldn't do the bearings or the case a lot of good.