The BSA A7-A10 Forum
Technical (Descriptive Topic Titles - Stay on Topic) => A7 & A10 Engine => Topic started by: limeyrob on 16.12. 2024 17:07
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OK I've got an alloy sump plate I want to fit because its got a nice big drain plug.
Its about 5/16 thicker than the steel one so I'll need longer studs.
Part is 31-0222 which is listed as 1/4 BSW x 1/4 BSC x 7/8"
Does anyone know of a longer stud - around 1 1/4"?
I'm thinking perhaps one of the oil pump studs?
Its all a bit of a faff as I'll have to helicoil the crankcase threads in-situe as I know at least one is on its last legs. Once helicoiled I could go for 1/4 Whit cap heads but I'd prefer studs.
Plan is to drill and tap the drain plug on the new sump and put a brake bleed nipple in so its easy to drain the wet sump oil into a tube and jar. Looks do-able as the plug is at 45 deg on the rear so there's some space.
Plan is to lay the bike over, stuff the engine with clean rag then drill, tap and helicoil then flush with brake cleaner.
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a car brake bleed nipple? , golly gosh have you a day spare to let it drain *whistle*
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Is this an SRM-like one Rob? Theirs are supplied with capheads, or were, but studs 'n nuts (two of, or nylock or those steel ones with grippy tops) have to be better. The drain plug on theirs is quite accessible if the plate is fitted with drainage in mind, no need for a bleed valve I wouldn't think. I quite liked my SRM one after I'd ditched their screws. Studs are an easy 'make' if you've got a die or two and a bit of 1/4" round stock. There may be off-the-shelfs that would do, dunno.
Good luck helicoiling the c/case threads . . . Bike laid over on side? Or up in the rafters? Need 'em in straight, or the thicker plate will argue with you on its way on and off.
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My gut says studs are better, even with helicoils I'm wary of unscrewing in ally but reality is it should never come off so I've ordered some cap heads as a stop gap. Plan is a bleed nipple in the drain with tube into a jar - I can leave it open and close it before riding off after I've poured the oil back in the tank. Well that's the plan.
I'm looking for simple reversible mods that have less risk of me forgetting and can't seize the engine if I do. At the moment I drain the sump before a ride but its a tapped 3/8 BSC plug in the steel plate and there's not a lot of thread. The brass drain in the ally plate is much nicer than I expected so i may just file a flat on that 2 turns in so i just undo it 3 turns to drain.
My absolute biggest fear is messing up the helicoils and screwing up a case. Plenty of tea and thought before the first metal comes off!!
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When I fit these, I enlarge the four holes on the sump plate and use tappet cover nuts so their sleeves reach into the sump plate. The tappet cover nuts will then thread onto the original studs. I skim the nuts down a bit so they are a bit slimmer.
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Motalia, does a nice set of long studs and you are in UK so postage wouldn’t be a killer.
Have used them a few times and are of good quality!
https://www.motalia.co.uk/W1-18..html
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Dont be lazy Rob cure the wet sumping issue ;)
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*razz*
I know that's where this will end up, there's an awful inevitability to it. *smile*
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A numpty question, is the non return valve (the ball and spring) only serviceable with the engine out? I'm thinking of my '57 A7 here.
When I changed the sump plate on my Barracuda I had the same issue with studs. I swapped them out for bolts in the end, it was the easiest path for me.
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If you are talking the anti wet sump valve, strictly speaking it's more of a hold back the tide valve. Sadly on a standard engine this can only be accessed with the crankcases split. Later A65 etc put the valve under the oil pump, so can be serviced in situ. A7/A10 can be adapted, in a similar way, plenty on the Forum.
Non return valve in the sump is on the return or scavenge side of the pump .Just a simple ball valve, held closed by faith, hope and gravity. In theory this can be removed on S/A crankcases without dismantling, but why this would be needed beats me. Plunger bikes have a different arrangement, pipe has a welded bend, which splits, pump can't scavenge. Engine out, down to bare crankcase to fix.
Swarfy.
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What frustrates me about this is that my current A10 is all rebuilt with a new spring, re-seated ball etc and it wet sumps 1/4 pint a week. I've had clapped out engines sit for months and smoke for a few minutes on start up. *problem*
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Depends how often you run it I guess Rob, but I wouldn't bother draining for 1/4 pint, or 1/2 for that matter. Just don't top up until it's run for a bit!
Before I split my cases and replaced said bits while sorting out the drive side shimming on my A, it would sometimes have at least that in there, but it pumped it back pretty quickly if run at a fast tickover for a few. My B never let a drop through, nor used a drop between oil changes, even better.
Replacement of the ball and spring on the A did the job in my case ;D and it never leaked afterwards. A far cry from several other less continent machines round here, but as I suffer from the delusion that the Perfect is the Enemy of the Good, I'm not averse to taps (big bore ones mind) and mag cut-outs on them.
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I have 3 bikes that all wet sump to various degrees - I just fire them all up every 2 -4 weeks and let the pump scavenge away the excess oil - seems the obvious thing to do.
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I have a Matchless and the A10, both get run every week of two. The Matchless does wet sump but it only shows on the return (no bubbles) its not smoky. The A10 however will produce a solid could of smoke that goes 2 or 3 gardens down and lasts for ages. Considering how good a condition the engine is its beyond annoying. It has an oil filter on the return and I'm now wondering if that empties into the engine too. If its that I should see a rapid rise int eh first day or two then a much slower one. Its a bit cold just now but I'll check when the weather is nicer.
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The problem could be "both get run every week or two" as if they're fired up and run for a couple minutes, the oil never gets hot and thin, and so the ball valve never gets to seat properly again due to the viscous cold oil.
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The A10 however will produce a solid could of smoke that goes 2 or 3 gardens down and lasts for ages. Considering how good a condition the engine is its beyond annoying. It has an oil filter on the return and I'm now wondering if that empties into the engine too.
Blimey! That isn't good, don't blame you for wanting a cure then. Could be as Rex says above, but if, per your original post on this subject, we're talking 1/4 pint in a few days, or 5 fl oz, I'd be amazed if that would be enough to smoke out all the neighbours and take so long to clear. Maybe there is a return-side filter drainage problem . . . but what comes out the bottom will tell you what's dripped in, from wherever.
And there will always, I presume, be some oil in the bottom when it's been standing after a run, as the oil from the top end drains back down, plus some from the crank probably, and some from the timing chest maybe. 1/4 pint wouldn't be far off I don't think . . . If there wasn't some oil down there, there'd be no quick oil return on start up: there'd be the sort of delay we see after an oil change and full drain-off. (Some other bikes I have hereabouts are supposed to have about 8 fl oz in the sump . . .)
Good luck with further tests.
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G'day Rob.
As Groily said, there will always be residual oil in the crank case. On both mine after a run and stand for an hour there is at least a cup of oil in there.
My A7 plunger used to wet sump a full tank into the sump in a few weeks, hence the full rebuild a while back. If I neglected to drain the sump (only 1/2 tank in there) she smoke a little but I wouldn't have to leave the shed. Now she doesn't sump a drop.
For yours to smoke that much I'd say there's other problems like rings, valve guides, blocked return holes from ex side of head.
Cheers
ps: may have to split this topic.
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Well back on topic I've helicoiled two of the 4 sump threads. The 2 on the D/S were OK which was handy because there was less metal around those whereas the 2 one the T/S were pretty much stripped. Tricky job because the drill supplied with the helicoil set was VERY sharp and wanted to grab the ally, took a lot of very controlled slow drilling but its done now and the new ally sump plate is on with the nice big brass drain plug. I've gone for 1/4 Whit cap heads rather than studs. Helicoil kit came with about 20 helicoils so I'm well supplied *smile*
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Hi Rob
Best plan when drilling like you did into soft alloy is to use a tap wrench to wind the drill into the alloy
or dull the drill edge.
Rather than punch away the tang on the helecoil which can sometimes jump the last coil into the next groove I made a small hook from 1.6mm stainless welding rod and pull the tang back through the helecoil
I often further weaken the tang with a diamond needle file to help removal but you need to be very careful doing this
John
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Put the new screws in with a smear of thread sealant/anti-seize in the threads to stop them seizing in the helicoils and hopefully prevent any oily drips.
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I could have done with that hook idea; getting the tangs broken and out was a bit of a pig. I did think that dulling the drill would have helped, after I'd done the job of course *sad2*.
i was surprised at the variation between the TS and DS case halves in the "meat" around the holes, plenty on the TS but a bit marginal for going out to the helicoil size on the DS.
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I have not read all the replies. The studs for the rocker box covers are ok for the thicker sump plate; that's what I used. Studs are far better than bolts as the case threads will not be constantly getting worn. Also the courser Whitworth thread is not suitable for nipping up the sump plate; a finer thread is better. I cannot give you an engineering explanation but think of the cycle thread as having a higher gear ratio.
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I have not read all the replies. The studs for the rocker box covers are ok for the thicker sump plate; that's what I used. Studs are far better than bolts as the case threads will not be constantly getting worn. Also the courser Whitworth thread is not suitable for nipping up the sump plate; a finer thread is better. I cannot give you an engineering explanation but think of the cycle thread as having a higher gear ratio.
It is necessary to use coarse threads in aluminium due to the softer, granular nature of the material. It is difficult to cut a fine, shallow thread in aluminium, as the resultant thread is very weak i.e. the granular nature of the aluminium causes it to crumble. However, coarse threads are prone to vibrating loose, as the slightest turn on the nut causes it to release its tension on the stud immediately. Hence why studs have a coarse and a fine thread, coarse thread into aluminium and fine thread for attaching a nut and reducing its likelihood of vibrating loose. The coarse thread end is steel into aluminium, the fine thread end is steel nut onto steel stud. Studs into aluminium are designed to use the full length of their thread so that the tapered shoulder (where the thread meets the plain part of the stud) taper locks onto the open end of the threaded hole. This reduces the likelihood of the stud vibrating loose, but overtightening can cause the aluminium component to split, which is why the use of threadlock is not a bad idea in permanent joints.
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G'day GB
As CB says. Cycle thread 26 tpi and metric 1mm pitch are a poor mans self locking thread. Proper "self locking" threads are harder to mass produce and costly.
Cheers
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Having re-acquainted myself with my heli-coiling skills, (unused for 40 years!) I'm pleased with how they worked in the sump studs. I had planned to put studs / BCS nuts but impatience and the ready availability of some 1/4 Whit cap heads go the better of me. Actually its worked well. Got a good clamping force on the home made gasket and the heads are below the level of the plate fins.
I did not loctite for fear of pulling the heli-coils so I will watch the cap heads closely and check tighten in a few weeks. I did use spring washers but if there is a problem I will drill and wire-lock, once I've stocked up on 1/16 drills *smile*
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Some good points, well made here. I'll just add that a fine thread (CEI,BSF,UNF, Metric Fine, camera threads etc etc) also give a higher axial clamping force for a given torque /thread diameter so as well as resisting vibration they also don't need to be done up so tightly. You can also more easily over tighten them too so beware. Reason being the helix angle is shallower (lower pitch) and so the axial movement per revolution is less which equals lower gearing, higher mechanical advantage.
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Yes. We do see a disproportionate number of issues with the sump stud threads into the case. Stripped, cracked or poorly welded repairs, far more so than the same 1/4 Whit threads in the chain case or timing case. My bet is the BSC nuts feel soft and get an extra nip up and all this does is pull the stud out the case. That was part of my thinking is abandoning the studs and going all Whit, if its fine in the chain and timing cases it should be fine in the sump and the "feel" I'm getting is accurate when I do them up.
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Sump stud issues always seemed to me to be down to the owner scrabbling around on the ground trying to locate an oily dirty nut or bolt, and then not being very careful when getting the thread started squarely, back when our bikes were no more than cheap transport for work.
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Reason being the helix angle is shallower (lower pitch) and so the axial movement per revolution is less which equals lower gearing, higher mechanical advantage.
Yes, that👍
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A note on BONs comment. When I fitted a new SRM oil pump, I wanted to retain the Cycle thread studs. I did some study on torques for fine threads vs coarse threads and concluded that fine threads need only 10% less torque to achieve same tensile. The extra leverage of the finer thread is largely offset by the additional friction of the much longer thread area.
Col
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That makes a lot of sense and explains why the industry liked them so much as that friction also stops them coming undone.