thedktor Posted February 25, 2009 Report Share Posted February 25, 2009 On my 349 I need to replace the gearbox bearings, two of which are in blind holes.... I have been told to support the case, behind the bearing, heat the case, and jam in the heads of a couple of large nails under the bearing to lever it out. Anyone got any further tips? Thanks Steve Quote Link to comment Share on other sites More sharing options...
feetupfun Posted February 25, 2009 Report Share Posted February 25, 2009 If you heat the case with gravity helping they will probably just fall out. Use an oven to heat it evenly to about 160 degrees C. Quote Link to comment Share on other sites More sharing options...
lee harris Posted February 25, 2009 Report Share Posted February 25, 2009 (edited) You need a blind hole bearing puller. It is a steel expanding head with 8 "expanding fingers". The ends have a very small lip which is max 1mm thick which will sit behind the bearing. Screw in the dowel which expands the ends and you hook up on the bearing. Finally screw un the centre screw and out it comes. I dont think it will fall out, even at 160 degrees and nails will be a waste of time. A similar tool is used for clutch plate alignment. I have made one for 300 fantic crankcases which use the same principal. A trip to the local engineering shop I think..... Let us know how you get on Lee Edited February 25, 2009 by Lee Harris Quote Link to comment Share on other sites More sharing options...
portman Posted February 25, 2009 Report Share Posted February 25, 2009 If I remember correctly these are bronze bushes rather than needle rollers. If they are, then try putting some grease or thick oil into the hole/bearing (into which the shaft fits). Support the other side of the case in the area of the bush then fit the shaft and hit the other end with a soft but heavy mallet. By hydraulic effect you should find the bush is driven out, but be careful of oil/grease being squirted out into your face. Be careful you keep enough grease/oil in the bush so that the shoulder of the shaft does not contact the shoulder of the bush you're trying to remove. Quote Link to comment Share on other sites More sharing options...
b40rt Posted February 25, 2009 Report Share Posted February 25, 2009 If I remember correctly these are bronze bushes rather than needle rollers.If they are, then try putting some grease or thick oil into the hole/bearing (into which the shaft fits). Support the other side of the case in the area of the bush then fit the shaft and hit the other end with a soft but heavy mallet. By hydraulic effect you should find the bush is driven out, but be careful of oil/grease being squirted out into your face. Be careful you keep enough grease/oil in the bush so that the shoulder of the shaft does not contact the shoulder of the bush you're trying to remove. This works if bearings not to tight. Boiling water pored over casings is the Haynes recommended way to get blind bearings out. Quote Link to comment Share on other sites More sharing options...
thedktor Posted February 25, 2009 Author Report Share Posted February 25, 2009 Thanks for the suggestions. They are standard ball bearings so they have the advatage that the inner race should move enough to allow "something" to hook behind, and I guess the hydraulic method won't work. In fact it wont, will it! Steve Quote Link to comment Share on other sites More sharing options...
wayne_weedon Posted February 25, 2009 Report Share Posted February 25, 2009 No it wont! But you have already discovered the hot air gun is your friend! You know I have had two of those in the last 20 odd years and I think I may have only tried to strip paint with one once! Invaluable tool for fitting and extracting bearings. You may find that with enough heat around the housing, possibly from the back you will be able to make it just drop out. At worst with the assistance of tapping the back of the housing with something thats not going to damage it. Or in the oven with the whole thing and just let gravity work for you, It does work usually. Wayne.... Quote Link to comment Share on other sites More sharing options...
348mate Posted February 26, 2009 Report Share Posted February 26, 2009 I bought a blind bearing puller from Machine mart a few yrs ago. What luxury have done 3 montesa g/boxes now. Worth every penny... S_M. Quote Link to comment Share on other sites More sharing options...
thedktor Posted February 26, 2009 Author Report Share Posted February 26, 2009 I bought a blind bearing puller from Machine mart a few yrs ago. What luxury have done 3 montesa g/boxes now. Worth every penny...S_M. Ah. Yes, look good, expensive though! I will see if simpler methods work first as I doubt I would use such a device again http://www.machinemart.co.uk/shop/product/...tive-hand-tools Steve Quote Link to comment Share on other sites More sharing options...
woody Posted February 26, 2009 Report Share Posted February 26, 2009 Yes, I got a blind bearing puller from MM too - useful on any gearbox with blind bearings but also quite handy for wheel bearings too, especially on those that you can't get any purchase on to drift out. Someone told me about the 'fire them out hydraulically' method many many years ago when I was doing my first Ossa gearbox. They have a blind bronze bush and they will not come out at all with heat, they are in far too tight. So, tried the hydraulic way and punched a very neat hole straight through the case behind the bush and got an eyeful of WD as well. So, damage already done I removed what was left of the case around the bush, drifted it straight through and then got the casing welded back up. So it worked - but not in the way I thought it should.... Never tried that one again. Also had a Bultaco years ago that only needed boiling water poured on the cases to release the bearings. Wish they were all that easy. I'd try the heat method first, if that doesn't work get a puller - they're always going to be useful. I've used mine a good few times now. Quote Link to comment Share on other sites More sharing options...
b40rt Posted February 26, 2009 Report Share Posted February 26, 2009 Try hiring a puller. Quote Link to comment Share on other sites More sharing options...
thedktor Posted March 1, 2009 Author Report Share Posted March 1, 2009 Sorted! Well, it was not simple, as everything is proving with this bike! One bearing came out easy- heated the case with the hot-air gun, placed the (cleaned) gearbox shaft back in the bearing and gently tapped the shaft with a rubber mallet, and it worked its way out in no time. The shaft fits quite snuggly into the bearing so with no oil on the surfaces it gripped when held at a slight angle. Now, the other was a pain, a conical bearing on the clutch shaft. Heated the case again, a bit of gentle levering with some nail heads and the inner race popped out leaving the conical surface with absolutely no chance of gripping anything onto that! So instead I spent 30 minutes with a dremmel and a small grinding head Quote Link to comment Share on other sites More sharing options...
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