Forum

[DaveP350]

Hello

I'm new to the forum and hope you can give me some advice. I'm attempting the renovation of what I appears to be a Model G engine. I've been trying to remove the worn looking main bearing outer races from the crankcases by heating them to 120degC and striking them with a wooden mallet,but they refuse to budge. Is there anything else I can try or is it a case of repeating the process over and over until they concede defeat?


many thanks

Dave

[Leon Novello]

Hi Dave: You are heating the wrong parts, making them expand and getting tighter. You should heat the cases and try to keep the bearings cool by pouring cold water on them or packing dry ice into them. If that doesn`t work, you might have to use a deremel tool to grind a slot along the length of the bearing so that it can compress. When fitting new bearings, keep them in the fridge and heat the cases. I presume there are no circlips behind the bearings.

[Thack]

If all else fails, you can drill two small holes from the other side of the crankcase and then punch the bearings out. Then you can weld or epoxy the holes up, or tap them and put some screws in ready for next time. Obviously you need to measure just where to drill very carefully.

[Davie Hall]

Hi Dave, if you have a welder you can run a bead of weld around the inside of the bearing track and when it cools it will have shrunk slightly making them easier to remove. When I did the mains on my electra X I just heated the crankcase away from the bearings and they dropped out when I banged then on a block of wood

[Beezabryan]

When I did the preventative bearing swap on the Infamous Enfield I heated the case to spit spitting temp then whacked the case edge on onto a timber sitting on the concrete garage floor & the race clattered to the deck
If that will not do it then the weld round the inside if the race, you do not need to have your own welder to do this, there are places & people about (body shops, engineers etc) who will generally do it for free or a donation to their tea & biscuit fund
Fit new bearing as Leon procedure

[Mark M]

Dave, main bearing races are particularly tight and 120 degrees isn't enough in my experience. The oven I use down in the workshop (handy for cheese on toast too,) goes up to 250 deg C. I get the cases up to that temperature by stages over about 20 minutes and let it cook at max for about 10 mins then try removal. If that doesn't work try the other techniques! REgards, Mark

[DaveP350]

That's great thanks for the replies.

I'll try turning the oven up first(while my Wife is out of course). I should have said it is the whole crankcase getting heated up not just the bearing outer race.
If that fails I'll try getting the trusty MIG out. It should be easy to weld a bead on the timing side, but the drive side race is quite long (both the roller cages and spacer fit into it) so may be tricky to get a weld bead very far down into its length.
But all great suggestions thank you, I'll keep you posted if I succeed.

I'm wondering if a pair of conventional roller and ball bearings could be used instead of the seperate races and roller cages, like on the later Bullets. However I'm not sure there wiould be off the shelf parts of the same dimensions as those used in the Model G.

many thanks

Dave

[DaveP350]

Thanks for all the replies. I'm glad to say that heating up to 250degC did the job, a few sharp taps and the bearings were out. Many thanks Dave