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Mag Dynamo Rebuild, crank bearing seals

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bs_doug:
Hello,

This is my first post and look forward to sharing my Bridgestone experience and memories with you people.


My 350 GTR restoration is under way. After pulling down the engine (because I found all kinds of gasket cement on the cases, and wanted to see why the engine was opened) I found a few problems.

The oil seals on the crank must have been replaced and one side seems to have rubbed on the case. There is no damage but the seal that has been secured into the flywheel recess by center punching the flywheel around the perimeter, appears to have come out of place at one area.

Question: What is the correct procedure to install these seals and can I corect this problem?

The Mag Dynamo bearings are shot and I can't get the clutch side bearing off. I suspect pounding on the shaft will result in a broken case.

Question: I plan to remove some material from the snout of the bearing holder so I can get a puller around the bearing and pull it off rather than pounding the shaft through the bearing. Sound reasonable?

What a great engine to work on. I am thoroughly enjoying working on this bike. I ahve a running 90 Sport and a none running hurrican to work on after the GTR is running. Please advise on any experience you have with this 350 engine and tips to rectify the problems I found above.

Thanks for the help,

Doug

czmike:
Hi Doug,


I haven't overhauled my GTR's engine yet so my "two cents" worth below should be checked out with others who have more experience & knowledge however, I have looked inside one and at a dismantled crankshaft so I can't resist a comment or two:

Why do those previous owners use so many different kinds of sealant?

Surely the crankshaft cheek oil seal (the thin, large diameter one) that has come out has done so precisely because it was staked in place. I don't think this technique would have been applied by Bridgestone during original manufacture as it will damage the sealing region in the crank and distort the seal's thin flange. This would destroy any possibility of a good pressure seal while encouraging the seal to release its tenuous grip on the shallow recess in the flywheel. I think the integrity of these seals under pressure is important as they appear to help maintain the oil pressure as well as direct oil flow from the injection pump to the rotary valve's sealing surfaces and the connecting rod bearings (the "big ends").
I think I will be fitting mine with a, yet to be made, seal installation tool. This will be a ring of appropriate diameter that is a good fit in the seal's shallow channel and will permit the application of sufficient insertion force to be applied evenly and squarely around the fragile seal rim without any distortion occurring (there might be a PVC plumbing pipe of the right size?). An appropriate sealant applied to the seal rim would also be a good idea I think. I would use a small amount of old style "Aviation Gasket Cement". Permatex #3, non-hardening is my favourite for seal installation.
This sealing arrangement is unusual and its purpose appears misunderstood by the writers of some articles I have read about the GTR engine. They are not crankcase gas seals at all (there is only one of these necessary, at the drive gear end) but oil control seals.

That "Mag Dynamo" is actually an Alternator (or AC Generator/Dynamo if you like).
Its neat isn't it and does look like a Mag-Dyn or some such. Pity it doesn't have a little more output though. Have no help for you with the bearing removal yet but hitting small things with big hammers is never a good idea I reckon. This sort of engine responds better to a bit of thought, like your suggestion, rather than brute strength. They are products of Japanese culture after all.
I have a few of these alternators so I'll look at one tonight (I'm at work at present) and see if I can offer an opinion. I've embarked on a project to fit an electronic replacement for the ignition points in one of these so no time like the present to get acquainted properly.


Let's know how you get on please Doug.



Best Regards,

Mike Munday,
Seaford,
Australia

bs_doug:
Mike,
Thanks for the advice on the seals. I will pull the bearings to see what's going on there. This GTR was some ones source of parts for a race bike. It came with all sorts of modified parts. Rotary valve covers with enlarged intake, one with a Amal TT carb flange) shaved heads, Ported and raised barrels, an empty generator with only the shaft and points (no coil), clutch cover with numerous, meticulously, drilled holes  for cooling. A lot of crank pins and rod bearings. Alas the expansion chambers were sold seperatly as were the TT carbs. Someone was serious about racing for sure.

Doug
Canada

Bridgestone Man:
Doug

Tapping out the Mag Dynamo bearings is no big deal, just strip unit, heat up bearing
with a small torch and tap out with a brass bar, works pretty good

Jeff Bar:
Doug and Mike, are you aware that you do not use the thin large seals that were installed from the factory?
I am taking about the two that are about the thickness of a quarter but around 4 inches across?  They
were deleted from the factory service papers

Jeff Bar

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