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[Chris Tindal]

Does anyone have any tips as to easy main bearing insertion into late Redditch bullet cases? I froze the bearings and heated the cases in the oven. In the drive side I dropped in the small outer washer, then the seal, then the large washer, so far so good. The outer ball bearing was then taken out of the freezer and I expected it to drop in with minimal pressure. It was in fact very tight and I had to hammer it home with a drift on the outer race. It was slow going with the bearing sinking in only millimetres with lots of taps. It finally got down to beneath the circling groove but I felt very uneasy and felt like I might crack the housing. I've left the inner roller for now as my circlip pliers aren't big enough for the circlip. Am I not getting the cases hot enough? Should the bearings press in easily? Suggestions welcome...Chris.

[Tim NZ]

When the cases are at temp, the bearings simple drop into place with minimal effort. Having to hammer them in means you were barely halfway to temp...

[Mark M]

As Tim says, obviously not nearly hot enough. I cook mine at 250* for half an hour (building up in 50* increments over that time) before attempting this job on a Bullet and I put the cases back in the oven between outer and inner bearing fitting to get back up to temp. A few minutes won't hurt the fitted bearing but will get your clearances back. And also, I keep the new bearings packed in ice while keeping to hand between fittings.

REgards, Mark

[binary]

Yes you need to heat the cases up more or leave in the oven longer. My bearings just slipped in with out having to put them in the freezer. You must have got the heat ok to have dropped the old bearings out. I have an old electric stove in my shed that I use its oven for this work. My old $20 stove is very handy for doing a lot of different things on and in.

[John M]

Glad you asked Chris, I'm approaching the re-install of my new main bearings, as soon as they drop through the letter-box. My old bearings were a bit of a pain to remove, I will have to leave the case in the oven longer when I re-fit. As far as the cir-clip is concerned, I found that normal thin nosed pliers worked rather than cir-clip pliers.

[Chris Tindal]

I'll try the plier tip John. Thanks for all the replies, lesson learnt, more heat!! Will it do any harm to the bearings already in when I heat for a second time?

[Tim NZ]

IF the bearing metal (raceways) change colour by even the slightest tinge during the heating process you will have well-and-truly, 100% totally and irreversibly, fornicated it


To remove bearings so as to re-seat them, a broad flame blow torch licked slowly and steadily around the bearing seats in the crank case would be MUCH better than placing the cases into a Hot oven.


Saturated temps over 120c and polyamide bearing races start to degrade. Hit the plastic cage with direct flame and you have killed it. Temperatures over 150c and the temper of the steel in the bearings starts to be effected. Cool the case down after seating a bearing to preclude any potential excess heat transfer into the bearing


Smacking bearings in or out cold is a surefire way to dramatically reduce its life expectancy AND fornicate crankcases by smearing alloy and destroying the interference fit


May you be forever haunted by 'Spun Bearings' if you insist on cold fit/remove of bearings!


(Praise be for Loctite bearing fit)

[Bullet Whisperer]

Hi Chris, Don't cool an alloy casing suddenly after heating it enough for a bearing to drop in or out, unless you want to risk destroying that as well. I use a propane / oxy torch to heat the cases EVENLY and up to a temperature where any old oil in the vicinity of old bearings starts to bubble. Sometimes, the old bearings still need to be driven out, even at this sort of temperature, but the new, cool [room temperature usually works for me] bearings should drop straight in. It helps if you have the open bearing housing facing dead vertical upwards and offer the bearing[s] in dead square to the housing. I drop the drive side ball bearing in, fit the clip and spacer, then heat around the area for the roller bearing outer race again for a minute or two, then drop that in. When removing old bearings, if the outer race of the roller bearing refuses to drop out, running weld around the inside diameter will shrink it and get it moving, the same applies to old valve seats. Regards, Paul.

[Chris Tindal]

Thanks Paul, Tim, I'll try the blow torch instead.

[Chris Tindal]

Well all the bearings are in. Had to heat the cases till oil was bubbling out of orifices and spit sizzled. Next time I think I'll get someone else to do it, this bikes already had a history of ham fisted Neandethal owners