How to change crankshaft bearing on OSSA '14 ?

[temps0n]

Oil form gearbox comes to engine, because rubber on the bearing is bad. I changed out ring rubber, but it still dont work, and oil going to engine. 

Is anybody know, how to change bearing?? I dont understant how to unlock this bearing.

I cant find information on manuals...

I think, i need pull gear and make hot, and after pull bearing...

[peterb]

Dobroe utro, the viton seal on the inner side of the bearing does not usually fail, but if you must change the bearing, you need to heat up the gear with a hot air gun and use a bearing separator tool, with an extractor to withdraw the gear, it is a very tight interference fit on the shaft and takes a lot of force to remove. With the gear off, there is very little room behind the bearing to fit the bearing separator tool, some of these tools are a little more narrow than others and may be able to fit behind the bearing. If not, you can grind up two very thin wedges to use behind the bearing to drive it off the shaft, it is not a very tight fit but the bearing has an O ring seal on the internal diameter of the shaft so may be a little tight at first. At this point in time it would be a good idea to replace the bearing, which comes complete with oli seal and both inner and outer O ring seals. You can use a Gas Gas bearing from a PRO trial model, but would need to grind a slot accurately on the outer sleeve for the locating pin. (I don't know if you can still get an Ossa main bearing)  To assemble the crankshaft into the casing is not so easy. With a new bearing and seals fitted and with a gear in place, position the con-rod at bottom dead centre, turn the bearing outer until the slot is at bottom, mark the locating pin hole along the inside of the crank case, up to the outer edge of the left side, using a marker pen. Then mark the slot position of the bearing to the left outer side of the flywheel, so you can align the slot with the locating pin hole when you fit the crankshaft to the crank case. Then, put the crankshaft in a freezer overnight without moving the bearing. The next day, heat the crank case in the over to 100C, when ready carefully fit the frozen crankshaft into position, it will easily fall into place, being careful to line up the marks. Tried to write this in Russian but gave up after "hello"  Bye, Peter B.

[temps0n]

1 hour ago, peterb said:

Dobroe utro, the viton seal on the inner side of the bearing does not usually fail, but if you must change the bearing, you need to heat up the gear with a hot air gun and use a bearing separator tool, with an extractor to withdraw the gear, it is a very tight interference fit on the shaft and takes a lot of force to remove. With the gear off, there is very little room behind the bearing to fit the bearing separator tool, some of these tools are a little more narrow than others and may be able to fit behind the bearing. If not, you can grind up two very thin wedges to use behind the bearing to drive it off the shaft, it is not a very tight fit but the bearing has an O ring seal on the internal diameter of the shaft so may be a little tight at first. At this point in time it would be a good idea to replace the bearing, which comes complete with oli seal and both inner and outer O ring seals. You can use a Gas Gas bearing from a PRO trial model, but would need to grind a slot accurately on the outer sleeve for the locating pin. (I don't know if you can still get an Ossa main bearing)  To assemble the crankshaft into the casing is not so easy. With a new bearing and seals fitted and with a gear in place, position the con-rod at bottom dead centre, turn the bearing outer until the slot is at bottom, mark the locating pin hole along the inside of the crank case, up to the outer edge of the left side, using a marker pen. Then mark the slot position of the bearing to the left outer side of the flywheel, so you can align the slot with the locating pin hole when you fit the crankshaft to the crank case. Then, put the crankshaft in a freezer overnight without moving the bearing. The next day, heat the crank case in the over to 100C, when ready carefully fit the frozen crankshaft into position, it will easily fall into place, being careful to line up the marks. Tried to write this in Russian but gave up after "hello"  Bye, Peter B.

Thanks so much. Can you look please, is it correct action on the photo? 

[peterb]

I would use a stronger puller, here is a photo of a bearing separator 

This type is better to get in behind the gear. Best not to use a flame to heat the gear, use a hot air gun. The gear will be hardened and tempered and you may damage the tempering with a flame.

[temps0n]

12 hours ago, peterb said:

I would use a stronger puller, here is a photo of a bearing separator 

This type is better to get in behind the gear. Best not to use a flame to heat the gear, use a hot air gun. The gear will be hardened and tempered and you may damage the tempering with a flame.

I have to remove gear and after bearing like this?

 

[peterb]

Yes, with hot air first on the gear. The bearing is easier, but you might not be able to get the bearing puller halves behind the bearing and so would need to use two wedges. Use the puller like in this image: 

[temps0n]

On 9/2/2019 at 3:24 PM, peterb said:

Yes, with hot air first on the gear. The bearing is easier, but you might not be able to get the bearing puller halves behind the bearing and so would need to use two wedges. Use the puller like in this image: 

Hello, Peter B. I got it, thanks so much for information!

 

Somebody open engine before me, i think bearing is not original, because bearing has i line, and its not stock.

 

Spring on the rubber is broken.

 

Bearing has model NAS 34.001 size 52*25*23 mm. Can you help me, i need to buy the same bearing, or maybe buy other model? Maybe from Gas-Gas, like this https://www.zonetrial.com/ArticleDetail.aspx?langue=E&Modele=Crankshaft+bearing+GasGas+TxT+pro&Id_Article=12118

 

[temps0n]

Can i use this hole for lock pin?

 

[peterb]

Dobroe utro, I would say that you cannot use the oil hole in the bearing outer as the hole for the locking screw. Even if the hole was the correct distance from the edge of the bearing outer, it would be almost impossible to get the hole lined up to the retaining screw. The bearing outer needs to have a slot cut in the correct place. If you cannot get an Ossa bearing, look for a GG one, then calculate where the slot should go and grind one in. The slot was quite a narrow cut. The intention of the location screw was to help prevent the crankshaft from moving out to the left, your model year would have tighter crankcase bearing housing dimensions than the first models and this really alleviated the chance of crankshaft float. You should have the internal and external viton bearing O ring fitted. When you get the new bearings, sometimes the seals are supplied loose, make sure the oil seal is fitted the right way round with the spring facing the pressure area like this photo. The bearing should go all the way home on the crank shaft, then the gear. The gear should be a really tight interference fit, which you can press on or use a puller to draw on the gear. Dosvidania, Peter B. 

[Paulfromholland]

Hello ossa people,

I have recently had my 125cc TRI 2013 engine all rebuild because the crankcase was all split open at the air-inlet side below the cilinder.

Now I got it back with a new crankshaft in a new case.

When testriding I noticed I didn't have power and I can not get the frontwheel of the ground like normaly. 

I was told by the store that it takes at least 10hours to losen up the new crankshaft so that my horspowers will return to normal. 

When opening the throttle I notice how the RPM's are slower comming up.

Indeed it feels that the engine is so tight that the piston is not running lightly.

Mecanicaly the gears and clutch seem to work fine and also the injection seems ok.

Anybody familiar with this aspect on the Ossa TRI ??