Main bearing removal

AussieCombat · Mar 5, 2011

Hello again from sunny South Australia where the days are hot and the beer is cold... Guys please tell me if I can heat the crankcases to remove the bearings without hurting them as they have only done about 300 miles since they were fitted...I did attempt to dislodge them cold, by banging on the bench but chickened out pretty quick...AC.

ILLF8ED · Mar 5, 2011

Heat up the cases to about 400F and the bearings fall out on their own. Do it in the oven, but not when the wife is at home.

Davo · Mar 6, 2011

I did mine in the Pie oven at work. Only needed 200 degrees C and they fell out easy.
Strangely all the pies at work now have that old english flavour!
You could also use a hot air gun

Cheers

Dave

Sweenz · Mar 6, 2011

Hi Aussie,

Just did mine a week ago with a cheap ozito heat gun from Bunnings.
I was shimming the end float on the crank with new mains & didn't want to use a flame near them.
The heat gun was quick & easy. The bearing fell out on its own with no need to bang the case on the bench.
I like it when it comes out like this as it should be nill wear in the bearing bores.

Sweenz

john robert bould · Mar 6, 2011

Fellers, Does this mean when the engine gets hot the bearings come loose?

Tintin · Mar 6, 2011

john robert bould said:
Fellers, Does this mean when the engine gets hot the bearings come loose?

If you reach 200°C at the crankcase while they are installed and not in an oven you don't care anymore. Your bike is gone up in flames by then anyway. :twisted:

Seriously: Off course they get loose as the case is aluminium and the ring is steel. That's why they need a proper interference fit when installed so that there still is enough residual tension under running conditions to ensure the outer ring is and stays stationary - and quite often they don't. That is why there are several kinds of anti-rotation devices which can be found e.g. in the Dunstall tuning leaflet.

Tim

marinatlas · Mar 6, 2011

Hi there, I am fighting right now with the crank end play, I had something around 25 thou at the start so I slip a ten thou on one side then a five thou the other side and now when the cases are fully bolted , I can't feel neither measure any play , thougfh the crank was free spinning, it's after several trials (with only two bolts for the case but not cement, so I had assumed I had a safety margin, but no way ...........) should I dismantle it again or sit and pray after my lucky star the cases will expand with heat ..........Pierre ( totaly lazy on this Sunday)...........

grandpaul · Mar 6, 2011

I use a pre-heated oven at 250F for exactly 15 minutes.

The bearings and/or outer rings fall out when I drop the cases on the front porch from about 6" - 8"; no beating or banging.

If you have the new bearings (in the case of a swap-out) in a baggie in the ice drawer of your freezer, they'll drop right in with zero fuss.

pete.v · Mar 6, 2011

AussieCombat said:
they have only done about 300 miles since they were fitted....

300 miles? Are you reusing them. My concern is that every time bearings are pulled and pressed from the soft cases it wears the machined surfaces to the point the races will not seat.
Otherwise turn the case over, heat around the race with a heat gun till the bearing falls out. It doesn't take that much. This is like what is shown on the Old Britts website where they set the case on a heater.

AussieCombat · Mar 6, 2011

Hey pvisseriii,... Well I am certainly considering reusing the bearings, that's why I want to get them out with out harm, I really don't think there is any reason to buy new (at 300 miles of age) except now the seed of doubt has been planted. I wasn't going to ask for opinions on this, but....... AC.
Thanks for the heat gun thing. I better not stink the oven up, or the Bar B Q for that matter... Hair dryer?...AC.

DogT · Mar 6, 2011

I used a small propane grill to great effect on the crank cases and the gearbox too. It doesn't stink up the kitchen and doesn't seem to leave any residual effect in the grill. The wifey didn't mind at all. If you are worried, just heat the grill to max for an hour or so after and everything is gone. It wasn't like I was spilling oil and grease all over the grill surface either, I cleaned it up good before heating. Plus I used a small aluminum pan to put it on and catch the bearings.

Dave
69S

pete.v · Mar 6, 2011

AussieCombat said:
Hey pvisseriii,... Well I am certainly considering reusing the bearings, that's why I want to get them out with out harm, I really don't think there is any reason to buy new (at 300 miles of age) except now the seed of doubt has been planted. I wasn't going to ask for opinions on this, but....... AC.
Thanks for the heat gun thing. I better not stink the oven up, or the Bar B Q for that matter... Hair dryer?...AC.

Hairdryer on steroids. Heat gun for like stripping paint. A propane torch will also do the trick. Mappgas too but keep it moving for even heating.

Davo · Mar 7, 2011

Here's a picture of my cases baking in the pie oven.
This is baking the paint on but I did the bearings in there too.
You cant beat it, nice slow temperature and glass doors to see what's going on. (nothing really until you hear the bang)
Every shed should have one. Hot food whilst you're fettling the machine.

AussieCombat · Mar 7, 2011

Job's done,... In the oven they went. It's all good..AC.

grandpaul · Mar 7, 2011

AHA! That's one of those downunder ovens where the bearings fall UP when they fall out!

Main bearing removal

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