Sump plate studs

[groily]

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.

[muskrat]

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.

[limeyrob]

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

[chaterlea25]

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

[BagONails]

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.

[limeyrob]

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 .
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.

[Greybeard]

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.

[CheeserBeezer]

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.

[muskrat]

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

[limeyrob]

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

[BagONails]

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.

[limeyrob]

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.

[Rex]

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.

[Greybeard]

.....
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👍

[Colsbeeza]

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