The BSA A7-A10 Forum
Technical (Descriptive Topic Titles - Stay on Topic) => A7 & A10 Engine => Topic started by: chaterlea25 on 02.11. 2018 20:37
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Hi All,
Starting a new topic on this so hopefully these modification photos can be found in future
The spring and ball are as supplied by SRM, the spring is 1in. long (25.4mm) and ball is 1/4in. diameter
The oil gallery hole is enlarged to 5/16in, (7.9mm) diameter
The gallery depth to the face of the grub screw is 13/16in. (20.5mm)This dimension is for a roller bearing converted engine. The measurement for a bush engine is 1in. +- The new longer blanking screw should come as far as the rear edge of the drilling to the bush
There is no countersink or recess in the rear face of the SRM pump,
The ball seats against the pump face, even a very light "tap" on the ball will widen the sealing face noticeably
There is enough space around the ball for the oil to flow around it to the crankshaft bearings
Addendum,
I dismantled the cases today and measured the length of the plug that is fitted when modding to the A65 setup
The plug measures + - 17.5mm. 12.7mm for a bush engine
John
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Lovely work John 👍 Are you doing that bearing conversion yourself?
Dave
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Hi Daithi,
Are you doing that bearing conversion yourself?
No, that was SRM's work
I have rebuilt quite a few A engines with bush and needle roller conversions
Calculating the time involved and jigs that would need making it makes sense to me to hand the work to
people who do this every day
Having visited their workshop and seeing the tooling and machines they use, I feel I would be very hard pressed to equal their results
John
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Hi John, sorry, just read your posts in the "wet sump/mag cut out" thread. The ball and spring mod is one I would attempt myself.
BTW, I wonder if you can recommend a good machinist to do a timing bush and big ends? I have never used a reamer on a timing side bush but am thinking about it... a lot. *eek*
Thanks, Dave
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hi guys, dont know where i got this from but shows removal of existing ball and spring from pump side, also information from SRM when i purchased a new pump, may or may not be helpful info, cheers
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G'day kiwipom.
I would not try (in situ) to open up the hole to remove the ball and spring as one can not be 110% sure any swarf doesn't get into the oilway to the bearing/bush and prv. 3/8" is too large, 5/16" is the correct size.
Thanks John *yeah*
Cheers
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Kiwipom - I think musky misunderstood you post. As I read it you are suggesting a way to service the existing spring and valve, and the collar is to bring the hole back to normal size. Sounds worth investigating. but I'd really like to see a dimensioned section of that oil gallery before doing that. If someone were to section an old scrap casing, then we could produce drawings / dimemsions for these modifications.
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Thanks for that info, Chaterlea. Very helpful and informative. Just what we need to better understand the issues involved.
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On behalf of fellow sufferers, I raise a toast to the enlightenment furnished by Chaterlea John.
Swarfy.
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Hi All,
On behalf of fellow sufferers, I raise a toast to the enlightenment furnished by Chaterlea John.
Swarfy.
*red* *red* *red*
Embarrassed to say that the RGS engine is still in kit form having had the bottom end converted to needle roller, crank ground, dynamic balance, MAP rods, Wiseco pistons etc, etc back in 2011/12
Some of the strip down disasters here,
https://www.a7a10.net/forum/index.php?topic=4556.msg30787#msg30787
Hoping to get stuck into my own projects over the next 12 months
John
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Following on from Kiwipom's suggestion, does anyone know the dimensions of the bore for the original grubscrew / spring / ball?
The idea of accessing this by opening the oil hole from the pump side and then refitting the oriiginal spring & ball by using a sleeve for the ball to seat against is certainly appealing.
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Following on from Kiwipom's suggestion, does anyone know the dimensions of the bore for the original grubscrew / spring / ball?....
I would expect that to be only enough to allow the 1/4" ball to be 'free to move' *dunno*
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G'day RD.
See reply #5 ^^^^^
Cheers
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Hi All
I need to address some of the measurements I gave for the conversion in my earlier posts
Those measurements were for a roller bearing converted engine
I have modified my original post now
On the converted engines the oil feed tube is nearer to the timing side than on the original bush setup
If the 17.5mm blanking screw was fitted to a bush engine it would block the feed to the crank *roll* *problem*
At the time I did not know or "twig" this vitally important point *red* *red* *red* *red*
It was only the other day when I went to change a Huntmaster engine to the modified setup that the penny dropped,
The "new" figure for the depth to the back of the oil feed hole to the bush is +- 1in. (25mm)
The new blanking grubscrew measures 0.5in (12.7mm)
Hopefully the Huntmaster casing is the same as A7/10 ? The important thing is to NOT interfere with the oil feed to the bush when fitting the longer blanking plug
OK, I realise the spring is now going to have less compression than on the roller bearing engine but figure 1/4in should work ??
John
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I know this has been discussed before, but maybe this is the place to clarify the spring issue. I believe the A10 and A65 springs are different, although some vendors apparently sell the same spring for both. So which one is recommended, and, to identify, what is its size - ie OD, LOA, no of coils and, importantly, wire thickness.
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I know its an old thread, tho can I clarify some points about this mod.
Is this exactly as the a65 anti wet-sumping ball valve design? I ask as the original a10 design has the ball pushed out of the oil passage and the oil flow only minimally impeded as it travels through the 7/32” oil gallery hole from the pump to the timing side bush. I guess the ball isn’t fully pushed out the way but mostly.
But this design has the 1/4” ball still inside the enlarged 5/16” oil gallery passage with the oil passing around the ball. The area around the ball for oil to flow past is about 25% less in the modded version than in the original.
So:
1. Are we concerned about reducing the oil flow with this? Or am I overthinking things again?
2. And did anyone figure out the dimensions of the ideal spring with the mod when still using a timing side bush? Like RD, I’m fairly sure the a10 spring 67-1400 is shorter and lighter than the a65 spring 68-0353 even tho some suppliers list the same for both
3. and RD – did you ever progress your idea of a sleeve in the enlarged oil gallery which the original ball seats against?
thanks
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Mikeb - in answer to your point no3, I was replying to Kiwipom's article - wasn't my idea.
I did change to the A65 system though. Drilling out the hole behind the pump (with an airline in the relief valve socket to keep swarf out of the oil galleries) allowed spring and ball to shoot out. Then plugged the end of the hole 'till just behind the gallery to main bearing. I machined a nipple in the centre to centralise the spring, so it wouldn't simply be lying in the bottom of the bigger hole. But it made little difference, mainly because - I believe - the A10 spring is too light. The bike now wears a valve below the oil tank, as I got tired of the hassle involved with draining the sump before every ride.
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Hi All,
Mike, I have run my SR with the modification for almost 20 years and a fair few miles, and it is still going great
(doing better than myself!!)
I have a SRM pump fitted and the wet sumping is not an issue worth mentioning
With the original pump it did wet sump as although reconditioned oil leaks out either along the drive spindle or through the mazac which can be porus, which is more than likely what is happening to RD's bike
John
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RD - was yours a roller conversion or a bush? i ask as the spring (25mm long) sits in a 20mm deep gallery with the roller conversion. But its a 25mm deep gallery with the bushed engine. So with this mod, would the standard spring be too short to stop wet sumping with the bush? maybe a longer spring would help?
has anyone had success with this on a bushed engine? Chaterlea - did that huntmaster wet-sump with the 25mm spring?
I don't have a set of a65 cases lying around to measure how far back the gallery sits - that would be interesting.
cheers
EDIT: pic below added re engine with bush - all measures a bit more or less, mix of old and new money.
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Mikeb - that sketch is just what I asked for ages ago. BTW, my A10 runs with a timing side bush. I'm of the 'it's perfectly adequate unless maybe you're racing' brigade.
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Hi Mike,
The Huntmaster engine is still on the bench, Waiting for a few small parts
It still has the original oil pump so I am not expecting 100% success on the wet sumping issue
I will start a fresh post on its PRV issue
John
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RD - with the bush, would it be possible that your wet sumping (post mod) was coz the a65 spring is 25mm length and the depth of the gallery is also 25-ish mm? ie no tension on the ball?
I also have the bush and am getting cold feet about this.
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Hi Mike,
The spring is compressed by the ball bearing, so the best part of 1/4inch..
John
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John - my point is with the bush, the gallery is 25mm deep so there's no compression. with the roller bearing and the shallower gallery there there would be compression... yes? at least this would be so if my measurements are correct (bush setup - the 'modified' section of the sketch above).
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Hi Mike
*????* *????* The depth is more or less the same length as the spring, but the ball is pushed into the hole
by almost its full diameter by the pump
John
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https://cybermotorcycle.com/archives/bsa-a10/mybsaa10rollerconversion.htm (https://cybermotorcycle.com/archives/bsa-a10/mybsaa10rollerconversion.htm)
Mike,
in one of the roller conversions that's published, the spring pressure is set by a spacer behind the a65 spring.
Was just attempting to reassemble my race engine and have managed to misplace that spacer and spring *conf2*
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That conversion page is interesting Tim. I've got a spare new SRM a65 spring if you need it. No spacer, but I do have a spare longer grub screw if you still use one (3/8, 16 tpi from memory)
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That conversion page is interesting Tim. I've got a spare new SRM a65 spring if you need it. No spacer, but I do have a spare longer grub screw if you still use one (3/8, 16 tpi from memory)
Thanks Mike, would like to take you up on that. neither of the two main local parts suppliers have them in stock and would like to get pump back on. Ordering from offshore for a spring or two seems overkill. The a7 race motor will get this mod ( the a65 ball valve) when we do the crank this year .
I did find my engine case grub screws ok and there should have been other bits with them *doubt*. I might need to come visit ...
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A friend of mine suffered a couple of partial seizures (the bike, not him, fortunately). I asked him to check the oil flow back into the tank and he said it was OK. I went round to his place and thought that the oil flow back to the tank looked weak when compared to the return on my bikes. The engine had the SRM mod which included the A65 ball valve conversion. We swapped the oil pump, still no improvement. So I removed the A65 type ball and spring - problem solved, a dramatic improvement in return flow to the tank. I can only assume that the spring behind the ball was becoming coil-bound and blocking the hole to the timing side bearing, or some other similar failure. The drilling, size of ball, and length / gauge of spring are critical. He now runs the bike without the anti wet sump valve and, remarkably, doesn't seem to have a wet sumping problem. Presumably the oil pump must be in very good nick! The moral of the story is, if you're going to do the A65 type conversion, proceed with caution!
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To add to the comments about the A10/A65 spring - this is the one I removed from an OIF A65 during summer 2021. The bike was a derelict and had been laid up since the mid 1980s ( no doubt due to 2 x frame fractures)
Length of spring is 20mm not including the ball.
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OK, apologies for thread resurrection, but this is very topical for me.
I'm looking at pictures of the A10 spring, 67-1400 and it has much lower spring rate so it will move more (my guess is about double) for the same force, this is not the same as the un-seating force which will depend on pre-load. Do we have any numbers for what it takes to move the A10 ball off its seat? I mean force on a rod poked in the oil hole. The 2 cases I have are really different just from feel, the "rebuilt" one takes about half the force of the apparently original one.
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Who knows what lurks beneath. Have a look at previous posts about that spring. New, Old, Fatigued, Spurious, Broken. The only way to be sure is to obtain the genuine article from a trusted supplier, and replace along with a new ball onto a well sealing seat.
Dunno, but there may be some data on the Forum already, as this topic regularly makes an appearance.
Swarfy.
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I did a lot of searches but no one seems to know the spec. Since I posted that I've bought a NOS spring and ball so I'll fit that and compare with what comes out.
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Hi All,
Just too finalise my previous posts, the Ariel Huntmaster got a Hepolite oil pump and has the A65 ball position against the pump..
No sighs of wetsumping even when left sitting for almost a year *eek*
John