Author Topic: '48 LS Engine rebuild  (Read 133 times)

Offline fffcycles

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'48 LS Engine rebuild
« on: 17.02. 2021 19:59 »
Hello Folks,

Now that I found a new cam for this from Feked, gasket set from Draganfly and the correct bushes from Baxter's I have started on the engine assembly this morning. I have some questions on a few things and would appreciate some guidance on a couple of points.
Got the rivets I needed and replaced the gearbox oil seal, no problem; but is there no drive side oil seal on the crankshaft ? All my Nortons have them and many others I have done, though not the Ariels, so need to confirm this one.
For this age of machine I understand the castellated nuts with split pins but since the PO put this together I will open these up and check shells and clearance again. Any tips on the crank shells and experience with the split pins?
Frank
Frank P
1948 A7 Long Stroke, a collection of BSA D1/B44/B50/A65 from the 50's thru 70's, Ariels/Nortons/Triumphs and a smattering of Japanese

Offline trevinoz

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Re: '48 LS Engine rebuild
« Reply #1 on: 17.02. 2021 20:36 »
No seal on the crankshaft, Frank. Just a slinger between the bearing outer race and the case.

Online Swarfcut

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Re: '48 LS Engine rebuild
« Reply #2 on: 17.02. 2021 20:57 »
Frank, All engines before 1953 Model Year do not have a crank oilseal.

  These engines have an oil slinger outboard of the main bearing, clamped against the inner race by the cush drive sleeve. it's a simple flat washer with a pressed edge Part 67 349 listed as a bearing shim. Offer into the bare case before fitting the bearing (early ball race type) or the outer race used in the later demountable roller bearing type design. These bearings are different sizes and do not interchange.

   The drive sleeve on these pre-oilseal early engines is a close fit to the crankcase, and most have a scroll cut onto the outer edge, others are reported to be plain. Trev nailed it that bit quicker.

    All is detailed in Service Sheet 208, here the A7 references are mainly for your early engine, which confuses owners of the later redesigned versions of the A7 & A10. Service Sheet 207 details crankshaft journal dimensions which are the same for all small journal split conrod type cranks.

  WARNING!!!!  No if's or buts, the crank needs the blanking plugs removed and the narrow oilway between the big end journals cleared out, this so called sludge trap really needs a clinical standard excavation. This is a known weakness in drive side big end lubrication, obstruction of oil flow here is the cause of many catastrophic  engine failures.  Big end bolts for this Longstroke engine are unique and  not readily obtainable, so preserve them if you can.

 Most aspects of assembly are the same as for the later engine, all have been featured on the Forum and it is a matter of having a good dig into previous posts.

 Swarfy.

Offline fffcycles

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Re: '48 LS Engine rebuild
« Reply #3 on: 21.02. 2021 02:59 »
Hello Swarfcut,
Got out my bulletins looked up some of the details and testing crankshaft end float today.
I always clean out sludge traps on all engines I rebuild and this one was plugged on the gear side really badly. Explains why the PO had to weld up the case from a thrown rod but all is good now.
Frank
Frank P
1948 A7 Long Stroke, a collection of BSA D1/B44/B50/A65 from the 50's thru 70's, Ariels/Nortons/Triumphs and a smattering of Japanese