main bearing fitting

Information relating to the Matchless G5 or AJS Model 8 350cc Lightweight
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corbal
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Joined: Thu Dec 06, 2012 8:17 pm
Location: GLOUCESTERSHIRE UK

main bearing fitting

Post by corbal »

Hi All - Just preparing for the ground-up re-build of my 1960 Model 8 engine. I am replacing both bearings on drive side using the later mod to fit a roller bearing 012543 instead of ball bearing for the inner support. The roller cage is different on each side, does anyone know whether the open side of cage faces the flywheel or the more closed side, or perhaps it does not matter! Would you heat the casing as well as putting the bearings in the freezer when fitting?
SPRIDDLER
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Re: main bearing fitting

Post by SPRIDDLER »

Don't know about L/W main bearings but you certainly ought to heat the casing which IMHO will be far more effective than freezing the bearing. Do both.
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cbranni
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Re: main bearing fitting

Post by cbranni »

Hi there, as Nev says warm the casing, I set oven on 150ish, you can freeze the bearings if you wish, regarding the cage, its usually same both sides so doesn't matter which way around it goes, the inner race should slide out of the outer race both ways, if it doesn't then I don't think it's the right bearing, it maybe right in size but if the inner doesn't slide out both ways then you may have an issue with endfloat, thats only my humble opinion.

Warm case make sure its clean and drop, sorry fit the ball bearing making sure its fully home, dont hit it home or you may knock out the end of the casing, it's very thin at the bottom, fit breather stator and its bolt and then fit roller bearing outer race, the race should be flush with the casting.

Fit roller inner race to main shaft, fit the thin breather key, fit breather rotor, dry fit the crankshaft to the cases and tighten a couple of case bolts there should be .020" min of endfloat. Strip it down clean all mating surfaces coat with sealing goo, give bearings and bush a good dollope of oil and assemble.

Colin

PS
I may have missed something out but someone will notice I hope
only dead fish go with the flow
corbal
Posts: 50
Joined: Thu Dec 06, 2012 8:17 pm
Location: GLOUCESTERSHIRE UK

Re: main bearing fitting

Post by corbal »

Thanks all so far, used a blowtorch to heat casing to remove old bearing (it worked well) but the oven I guess gives a more even expansion. The inner race will slide in and out of both sides of outer. Good tip about thin casing, I am hoping the ball bearing will drop in without any knocking. Manual suggests peaning the outer race of the roller bearing in three places. Have you done this with yours? Great idea to dry fit and check float before finalising. I am planning to use Hylomar sealant between the case joint rather than Wellseal which the book suggests. 45 years ago as a turbine fitter (power station type) we used Hylomar to seal casing joints, any thoughts would be appreciated. Thanks again for input.

Alan
cbranni
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Re: main bearing fitting

Post by cbranni »

Hi Alan, no harm in putting a couple of centre pops to hold the race in place, either sealer will do the job, I use wellseal because I have a large tin of the stuff.

Colin
only dead fish go with the flow
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Ozmadman
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Re: main bearing fitting

Post by Ozmadman »

Wellseal is the business in my opinion, Hylomar is more rubbery and bits that squeeze out can break off. I use Wellseal for everthing with and without a gasket and it has never let me down, its thin, sticky and non setting it's just the best.. Recommended by VW for the VERTICAL non gasketed crankcase joint on the air cooled bug engines I rebuilt a few of those and have been using it ever since, the only one I know will work every time.

Paul
Paul
1960 Model 8
1974 Yamaha RD250B US Model 6 speed
corbal
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Joined: Thu Dec 06, 2012 8:17 pm
Location: GLOUCESTERSHIRE UK

Re: main bearing fitting

Post by corbal »

Thanks Colin & Paul - will centre pop and I think I will invest in some Wellseal. If its good enough for you (with both your vast experience with lightweights) then I will not chance a leaking crankcase.

Alan
corbal
Posts: 50
Joined: Thu Dec 06, 2012 8:17 pm
Location: GLOUCESTERSHIRE UK

Re: main bearing fitting

Post by corbal »

Thanks again all - crankcase put in oven and heated up to 150c leaving for 10 minutes, bearings wrapped in cling film and put in freezer for 2 days. Job done, ball bearing dropped in easily and seated on bottom face, followed by stator ring (which entered easily prior when cold), breather tube screwed in and followed by roller bearing outer race, which also dropped in easily seating nicely flush with casing. Now letting crankcase cool slowly and naturally and will centre pop outer race in 3 places as manual recommends.

Alan
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