Changing bearings
 

Been out of the hobby for a few years and have an older Thunder tiger 61 Pro that needs the bearings replaced (which I've never done). The engine is pretty gummed up from sitting for a few years. It doesn't look like I can access the rear bearing very easy and I am assuming they are pressed in. I can't find a forum here that covers this so any pointers on getting them out?

Thanks.
Mike

RE: Changing bearings
 

Put the crankcase in an oven set to 300 degrees. While hot smack the back of the engine onto a wood block. The shock will drop the bearing out the back. When it's time to put the new bearings in Freeze them first. When the crank is in with the new bearings put a prop on it and smack the case with a screwdriver handle. this will actually align the bearings. You will notice the difference after doing this. After this step re install the piston and liner.

RE: Changing bearings
 

Excellent, I will give it a whirl.

Much thanks!

RE: Changing bearings
 

Oven to 300, biscuits on a pan, engine on the upper rack. Presto, dinner and a bearing removed.

Thanks Speedracer! Worked like a champ!

RE: Changing bearings
 

I use a drill press to push the bearings in rather than whacking them.
Also, I've never needed to freeze them either, just a nice snug press. If you do freeze them make sure you are lubed up good to prevent the condensation from starting the R word.

RE: Changing bearings
 

Hi!
If you heat the crankcase enough the rear bearing will just slide in (provided you have it mounted on the crankshaft).Bearings on our aluminium engines should not be pressed in!

RE: Changing bearings
 

I have always heated the crank case and with the bearing on the crank shaft slip the crank shaft and bearing into the crank case. The case cools and snugs up to the bearing. I also use a propane torch to heat the case in both removing and installing the bearings.

Frank

RE: Changing bearings
 

I have used the heat gun the heat up with good results as well. It was my first time and was uneventful...

RE: Changing bearings
 

I use the torch for heat too.

RE: Changing bearings
 

Hi!
Same here, a propane torch

RE: Changing bearings
 

Interesting crank mod:D

RE: Changing bearings
 

Thanks for the info! I will try torching the case and pushing the bearing in on the crank. Sounds simple.

RE: Changing bearings
 

A torch can warp the case by over heating an area more then another. I have done it but I just drop the case in a pot of boiling water to get the bearings in and out these days. Never have had to freeze the bearings to get them in. Oven, water, torch, what ever works for you, it isn't a hard thing to do.

RE: Changing bearings
 

Here is a good 2 part video for changing the bearings

http://www.youtube.com/watch?v=hVFrbil903I

RE: Changing bearings
 

Back in the oven for 10 minutes at 300 worked like a champ for installation. That's will be my routine in the future. I agree with the suggestions above that a torch would work but unless you have no other way, why risk uneven heating or too much heat?

RE: Changing bearings
 

Why you ask?
Mainly since the oven heats the whole engine, including the cyl bore. I really don't want much distortion going on there other than what is induced while running. Using the torch keeps the heat very localized to where the bearings are and not moving the rest of the engine.

It may or may not make a difference but in my work I use heat for straightening shafts often and have a good idea of what heat can do and it just makes sense in my small brain.;)