I have a Moki 1.80 and I have to remove the rear bearing. I've tried everything but using the proper tool.........a puller.......and the bearing is not moving. Does anyone know where I can get a puller?

Al

Heat the case up close to 300 F in the wife's oven. Then bang the crankcase against a board to shake the bearing out.

Al,


The rear bearing in the Moki may be pretty tight in its seat, so 300ºF should be used.
Most other engines can do with 200-250ºF.

It is best to bolt the back-plate back onto the crankcase. This is done to prevent any possibility of the crankcase becoming bent, or warped.
Hold the engine in an oven mitt and hit it sharply, on its back-plate, against a heavy wooden block.

You would then have to remove the back-plate again and the unseated bearing will be able to fall out.

One method for removing a very stubborn bearing is by using a Dynabolt expanded into the inner race. A length of dowel through the front can be used to help tap it out (crankcase heated of course) or with a little ingenuity can be used as a puller from the back of the crankcase.

SUCCESS!!!! I tried heating the front housing, cranksahft housing and backplate assembly in the oven at 350 then rapping the assembly against a 2 X 4. No luck. This boy was REALLY in there!

I then raised the oven temp to 450 and, while waiting for the oven to come up to temp, I kept ice cubes against the bearing. Once pre-heated, I placed the unit in the oven for five minutes then took it out and rapped it once more on the wood. That did it and one tap was all it took!

After cleaning out the front housing, I heated it in the 450 degree oven again for five minutes while the new bearings were kept on ice inside a plastic bag. The bearings literally fell into the housing without so much as a tap or a nudge. Once back to room temperature, they were as snug as could be. The engine is now reassembled and ready for many, many more hours of trouble-free operation.

Thanks Guys!!

Al

450 is way too hot. Five minutes is not nearly enough time. People using 250 are leaving their engines in the heat for 15 to 20 minutes. Set a timer, don't guess at it.

What tempurature do you have to start to worry about distorting the case. Why is 450 too hot?

JetPack,


The melting point of aluminium is significantly higher, at 660ºC, or 1,220ºF.

However, it rapidly becomes softer (its hardness is decreased) as its temperature rises.

At 450ºF it will be significantly more prone to bending and warping, as a result of the efforts to remove the bearing, than it would be at 250ºF.

Also, cast aluminium is often subjected to [link=http://www.csiro.au/news/ps196.html]heat treatment[/link].
This endows the casting with improved hardness and durability.

Heating the casting excessively can dramatically reduce the effect of that treatment; and thus weaken the metal.

Thanks Dar, I've often wondered what "softer" meant......

Well, hopefully the short duration at 450 degrees meant that the aluminum cases never completely reached that temperature and the durability of the aluminum wasn't compromised. I'll find out when the engine has run for a while, I guess. I do know that the bearing would not come out after heat soaking at 350 for between 10 and 15 minutes which is why I kicked up the temperature. I'll keep you posted.

Al

People have accused me of being hard headed...maybe I need to have it "Heat -Treated"...(think I'll go stick my head in the oven...)