The BSA A7-A10 Forum
Technical (Descriptive Topic Titles - Stay on Topic) => A7 & A10 Engine => Topic started by: Minto on 04.06. 2021 16:32
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Well, I'm expecting to get some time this weekend to finish putting the Ten back together, the lump and box are in the frame, and the clutch is back in. So just barrels, head, rocker box, oil tank and filter, re-timing the ignition and a few other loose ends to tie up. If, I get it running over the weekend, seeing as it's had new lMD pistons in honed out to size bores, new big end shells (not reground crank), new main roller bearing, what sort of running in do you reckon is required? Gently gently for a few hundred miles (which at my current rate of motion could literally take forever) or less careful but with oil changes every 100 miles for a while??? Advice and opinions welcomed.
Cheers
Jase
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Take off with a big handful of throttle, the very second it starts!
Then give it bursts of hard pulling for a few miles.
That’s it run in, apart from retightening things.
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Now you’re going to get the opposite advice!
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Jase. Pour oil down the pushrod tunnel via the rear rocker box. This will give the cam a nice oilbath start. This oil will soon reach the sump, and you can check the oil return is working and as the instruction manual says you can assume the pressure side of the system is OK. In other words the oilpump has drive.
Prolonged idling should be avoided, the bores, rings and pistons need to have some load, otherwise modern oils with their anti friction additives are said to contribute to glazing of the bore and poor bedding in of the rings. My preference is for the cheapest supermarket own brand oil as a first fill and to expect a fair amount of fine particulates to appear,
So like TT, I'd get under way fairly soon, but I would not be as brutal to severely wring its neck as TT's method, altho' this motor will already have a fair amount of internal clearance. Even so, no need to be a true pussyfoot but avoid heavy loading and constant high speed to start with. Light throttle, light load for the first few miles when there is the greatest potential for the new pistons to tighten up. If it behaves itself, sure, a little more spirited riding will not be amiss. Also ignition timing and mixture may require adjustment later on to get full benefit from the new parts, bearing in mind published data was for the fuels of an earlier time.
Swarfy.
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... Prolonged idling should be avoided...
... no need to be a true pussyfoot but avoid heavy loading and constant high speed to start with. Light throttle, light load for the first few mile..
This 👍
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Thanks guys,
What about adding some oil directly into the sump before I drop the barrels back on?
Should I oil the pistons and bores before assembly or will this hamper the bedding in?
What about oil changes? 50 miles first then every 100 for a couple of changes then at 500 sound about right?
Cheers
Oh, and for next time, is there an easier way to get that €~©π|∆¢ timing side engine bracket in place????
Jase
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Shut the throttle occasionally - lets oil get to the thrust faces of the pistons. Vary the load on the engine. Let it run on the downhills. The old 30mph for the first 1,000 miles was somewhat unscientific.
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Thanks guys,
What about adding some oil directly into the sump before I drop the barrels back on?
Should I oil the pistons and bores before assembly or will this hamper the bedding in?
What about oil changes? 50 miles first then every 100 for a couple of changes then at 500 sound about right?
Cheers
Oh, and for next time, is there an easier way to get that €~©π|∆¢ timing side engine bracket in place????
Jase
I always oil the moving parts while I'm building the engine.
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Shut the throttle occasionally - lets oil get to the thrust faces of the pistons.
Sounds highly unlikely. What’s stopping oil getting to the bores and thence to thrust faces of the pistons when the throttle is open?
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Shut the throttle occasionally - lets oil get to the thrust faces of the pistons.
Sounds highly unlikely. What’s stopping oil getting to the bores and thence to thrust faces of the pistons when the throttle is open?
I've always understood that closing the throttle creates a semi vacuum in the cylinders so sucks oil up to the piston skirts etc.
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Jase. The first few moments of running are the most critical for a newly built engine. Every moving part needs to have a lick of lube, makes sense and even if the motor just goes back into store the machined parts are protected from corrosion.
Bit late now but if the oil pump is off, prime the timing bush, crank and big ends by pressure fed oil into the oil gallery. Raise the ball valve on the pick up pipe and fill the scavenge side with oil as well by pumping oil into the ball valve housing. If the timing side is assembled, remove the PRV and pump oil to the timing bush etc from there. The oil pump can be primed before the oil tank goes back on or on assembly.
Oil in the bores will aid initial sealing and will soon be burnt off. The critical part of the running in process is to ensure all parts continue to be lubricated adequately to prevent seizure. How you Vary the speed, load, duration etc is subjective and there are varied opinions as you can see.
Don't forget to clean out the oil tank and oil lines, and a check of what's in the sump after a few miles is a wise precaution. I would consider 50 miles to be OK for a check, but if all in order, a bit early to change the oil.
As for that cursed engine plate, it's all a matter of technique. Having the lump down to basics, cases, crank, pistons, gearbox all helps and it's a matter of holding the loose mounting plate in place on the engine and almost diving the unit down and then to swing upwards at the front into position with a final sideways twist at the rear to locate the gearbox mounts as you rattle the mounting plate to fit.
Those folks with S/A bikes can laugh now, those engine plate gymnastics only apply to Plunger Frame Semi Unit Models.
Swarfy.
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Oil in the bores will aid initial sealing and will soon be burnt off.
Swarfy.
Depends on "how much" oil though. I find a thin smear on the rings will "bed in" the rings far quicker than 1/2 pint of 20/50 sloshing around the bores. Some modern oils are too effective and never allow the rings to seal properly.
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Blindly following trendy Americans on the Internet, I stopped applying oil to new rings many years ago and get very good results.
I also make the second ring gap 25-30% bigger than the top ring gap.
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TT - why have a larger gap for the 2nd ring? Makes no sense to me as it doesn't get as hot as the top ring.
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TT - why have a larger gap for the 2nd ring? Makes no sense to me as it doesn't get as hot as the top ring.
I’m no expert, so I can’t declare it to be right or wrong, but it’s fairly common knowledge these days.
The larger 2nd ring gap relieves pressure buildup between the 1st and 2nd ring, so the effect of compression pushing the top ring out against the bore is not compromised by pressure equalising above and below the top ring.
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Thanks all, didn't get as much done as I wanted today, other jobs getting in the way. Barrels are now on and a few other little bits done. Ignition timing and head tomorrow and hopefully quite a bit closer to starting up.
Jase
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Don't wish to labour the point, but the idea regarding the 2nd ring completely escapes me. The top ring takes the full force of the 'explosion' on its top face, pushing the ring against the supporting land and pushing the ring out to the cylinder wall by getting behind the ring. If the 2nd ring is getting equal or near equal pressure, summat's wrong. Maybe the top ring is too tight in its groove, denying gasses getting behind the ring (which is what forms the seal to cylinder wall, not the ring's springiness as is often assuimed). Whatever, if the 2nd ring is doing anything more that backing up the top ring, the engine needs taking apart to discover why.
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Pressure escapes through the top ring gap, to the space between the top and second rings.
The pressure that forces the top ring out against the bore is the difference in pressure above and below the top ring.
A bigger second ring gap relieves the pressure between the rings, so the pressure differential above and below the top ring is better maintained.
Nowadays, they can measure pressure above, below and between the rings on a running engine.
Under normal circumstances, all the second ring does is some oil scraping.
To have this conversation usefully, you’d have to buttonhole an automotive engineer. I’m just a nit having a go at old bikes.
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Thanks everyone,
Regarding the rings, the manufacturer advises not to do anything as they are pre gapped for optimum performance, so that's the way I'm going (lazy? Maybe!)
Cheers folks
Expect imminent incoming update of disaster.
Jase
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Thanks everyone,
Regarding the rings, the manufacturer advises not to do anything as they are pre gapped for optimum performance, so that's the way I'm going (lazy? Maybe!)
Cheers folks
Expect imminent incoming update of disaster.
Jase
Just check the gaps please.
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Yes, assuming gaps are not too small is a big risk to take.
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Hi Jase,
I fitted IMD pistons recently. I had the crank balanced, and the pistons came back with rings removed, so I took the opportunity to check gaps ( at the bottom of the bores). Otherwise I would not have checked. All were 12 thou except one of the top Compression rings was 9 thou, so I opened it up to match the others. Traditional recommendation was 4 thou per inch of diameter, although the tech world has moved on since then. I have also read that 2nd Comp ring is often set at 25% bigger gap than 1st Comp ring as TT suggests.
I suspect that unless you are going to flog the motor that may not be so important.
The IMD top ring is Moly coated, so recommended hone is 280 - 320# with a 400# plateaued finish. That is very different to traditional hones for cast iron rings - 150# seems normal. IMD didn't provide the recommendations for honing or running in, but the machinist who honed the bores did.
If you have had cams or followers or other rubbing parts renewed, then a high zinc oil with no friction modifiers is advised for break-in. If you go supermarket cheap oil, it still may have friction modifiers. Quite a few companies supply running-in oil.
Col
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Cheers lads
Unfortunately the barrels, head and rocker box are all back on. I did however, check the compression ring gaps when I got the pistons, 12 thou, I didn't check the oil rings though.
The bores have been honed a further couple of thou since as well so should be ok for clearance.
Do wish I'd rechecked after I got the barrels back from the engineer's.
Cheers
Jase
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Ok, I'm sufficiently unsure and concerned that I've made the decision to strip it back down and do some more measuring, ring gaps and piston to bore clearance (the bores were done at a MC machine shop, but I hadn't checked them after I picked them up, and am starting to wonder if they have been honed out as much as was required). It would be daft not to when it's only rocker box, head and barrels, hopefully I can leave the magneto in situ, ignition timing was a right faff, way more fiddly than siting the push rods in the rocker cups.
So, current status, going backwards!
Cheers all
Jase
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Well rocker box, head and barrels off by 7.00am rings removed and gaps measured in the bores, 12.5 thou top ring 14 thou second same for left and right, also rechecked the piston/more clearance, a gnats sneeze over 4 thou, so I'm happy to proceed, barrels and head back on by 9.00am. leaving the rocker box as I want to helicoil one of the screw threads for the tappet cover studs which is barely hanging on. Helicoil kit hopefully be here in a couple of days.
It was definitely worth getting up early for, I feel much happier about things now.
Thanks for the prompts guys
Jase
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Good work! *smile*
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12.5 thou top ring 14 thou second
So they made rings with the second ring gap 12.5% bigger than the top ring gap.
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Probably didn't make them that way - they're just a used batch thrown in.
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12.5 thou top ring 14 thou second
So they made rings with the second ring gap 12.5% bigger than the top ring gap.
It would seem they did, and as they were the same on both pistons I assume it was by design not chance.
I don't really get the science behind this but would welcome enlightenment if anyone could translate it into English.
Cheers
Jase
Never mind, just re read your post on the last page, not sure the extra 1.5 thou gap in my case is going to do that much.
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Hi Minto, I put IMD piston and rings in during 2017. I couldn’t actually get the rings out to gap them because the are “modern” - deeper and thinner. I took Adrian Wright’s (IMD proprietor) advice and made no further attempt. I trusted my good reconditioner to follow IMD’s detailed “boring (and honing) instruction”. I was concerned about glazing so I put the rings in dry with just a little light oil on the skirts. I followed the “Klaus” method of “static” running in - see earlier posts. This was still with good high-zinc oil in 3 10-minute stints on stand with fan, changing oil (1 litre only needed each time) and tightenig tspprrts. This was st 3k rpm. No
Long idling. Lugging or too high rrve for 1st 500
Mile. Still running fantastic burns no oil...
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Hi Scott, or Jay??
Before I ordered my pistons I spoke with Adrian over the phone who invited me over to their HQ, where he measured my bores and advised me on options on how to proceed, he was extremely helpful and very personable. While I was there he removed the rings from a set of pistons in order to measure them in my bores. So I knew they were ok to remove, though as you say are thinner than old ones and little trickier to remove and replace.
Not sure my neighbours would let me get away with the static method, so planning on a few circuits of the block to check everything is ok, then a couple of short local runs of about 40 miles each before taking it any further.
Jase
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Just avoid high revs and lugging for the first couple hundred miles has always been my motto....
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Just avoid high revs and lugging for the first couple hundred miles has always been my motto....
Simples!
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Just avoid high revs and lugging for the first couple hundred miles has always been my motto....
Simples!
I've learned since buying and attempting to sort this bike out, there ain't nowt "simples" about it.
Lol.
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At risk of saying what has been said before but unable to resist the urge to comment, I have had a couple of machines fail to bed their rings in and have since then assembled the bores dry. The motor is otherwise fully lubed and I spend a considerable amount of time kicking the bike over without plug/s in order to prime the pump. I have, since I adopted this method, had no problems with rings bedding in and my A10 now slowly turns its oil to a rich mahogany colour without a hint of black. I also think that the first 1000 miles should be travelled without labouring the motor and with the occasional burst of revs in order to fully sweep the bores.