The BSA A7-A10 Forum
Technical (Descriptive Topic Titles - Stay on Topic) => A7 & A10 Engine => Topic started by: eugenius on 06.01. 2024 19:46
-
Hi all, I have tried to decarbonize the cylinder head after changing the piston rings of my BSA A10 (I have mounted the +20 size as adviced) and I have noticed these streaks above the flat side of the valves. Is that normal? I have also noticed that both left sided valves are marked with an A whereas the opposite ones do not *????*. I send you an image in attach. Thanks
-
eugenius try a magnet on the valves normally inlets are magnetic exhausts are not
-
I don’t have a clue what the “A”s stand for. Maybe Julian has documentation on it. The scratches in the valves appear to be something like the use of a die grinder (Dremel) to remove carbon. I don’t think that would fly in a high-performance engine, but for weekender puttering, it probably won’t matter. The thing that gets me is the out-of-round cutaways at intake valves that seems like a mistake that was made, possibly while cutting for new valve seats. Maybe others have seen this before and will say it’s normal.
Richard L.
-
thanks Keith I'll try the magnet; and thanks Richard for reassuring about the streaks. I will try to dismount the valves to check behind as soon as I will find a spring compressor that may work better of the chinese one I have bought recently and which bended when trying to use it (no way to reinforce it, i have tried twice with no success); a really chip and anuseful tool . A nice we
-
Great Keith! I have applied the magnet and actually both inlets are magnetic both exhausts are not. They seem placed properly. Thanks again
-
The scratches in the valves appear to be something like the use of a die grinder (Dremel) to remove carbon. I don’t think that would fly in a high-performance engine, but for weekender puttering, it probably won’t matter.
Let’s see if others think the scratches are more serious than I’ve implied. Maybe they need to be blended-in (without going any deeper) to avoid hot spots, or possible points for cracking.
Richard L.
Richard L.
-
Not ideal but I would run it. What compression are you running?
-
also curious about the centre punch marks look like 3 on 1 side and 2 on the other .....I would pour a bit of gas on intake and exh ports see if it leaks past the valve seat , looks like someone used a dremel or die grinder on the valve face
-
Thanks for replying. I don't know exactly the compression of my engine but should be that of a normal BSA A10 road rocket engine 7,2:1? The engine has been probably replaced in the years 60' the serial number is DA10 R 9027. I put in attach an image. Regarding the number of possible marking signs on each valve that's strange but possible. It seems a little too much just to mark a valve. Nonetheless thanks a lot for the advices, I would try to check if there is a leak.
-
Is it me or do those valves look a little low in the inserts? Almost "pocketed" as we used to say. Reckon it needs further investigation. Valves can be refaced, but taking away too much material reduces the diameter, so they may be the correct valves, but not true perfection. Same goes for recutting the seats. Bare minimum of material removed to restore back to an unbroken seal.
Odd marks, dots etc are probably of no consequence. Quality valves from times gone always had some makers' mark. BSA stamped the heads with the part number, JAMES and ALPHA marked the stems.
Try ALPHA BEARINGS http://www.alpha-bearings.com/Valve%20cat/valvehp.htm for a replacement valve catalogue,
Drags also have a valve chart with stem, head, length, OE part number. Takes some finding but it's in there somewhere.
Swarfy.
PS When using a valve compressor to dismantle a head, tighten it up until there is some pressure on the valve cap, then give the valve spring compressor fork on the cap a smack. This will break the bond between the valve collets and the valve cap......then all the compressor has to do is compress the spring and if it can't do that it really is crap. Save your energy, let the hammer do the hard work.
-
thanks Swarfy, indeed I have few experience and I will try as you advice with a hammer smack to dismountle the valves. We'll see
Eugenio
-
The inserts do look pocketed, but I'm confused as the ridge is not where you would expect it from wear or grinding. The reason I asked about compression ratio was i was curious about the state of tune. If its soft there's no point in doing a lot of work to do a triple angle on the valve seats.
-
G'day Eugenio.
Looks to me as if the previous owner put standard A10 valves instead of the larger Super Rocket valves. Can you give us a pic of the valve springs & collets (they are different). The left spark plug hole has been fixed with a "Timesert" almost touching the inlet valve seat *eek*
Cheers
-
Hello friends, Thanks for the insights! Yes indeed the impression is that smaller valves have been pocketed in a wider housing. I continue to learn a lot from all of you and that's great. Here's an image of the valve spring and collets. Now the problem will be should I change the valves or not and if yes the normal or the large?
Eugenio
-
big valve intakes are 1 1/2 inches dia ...
-
The head number is just visible in the pic, looks like 67-1120 or is it 67-1126?
-
There is something not quite right here, but using the sources I posted you should be able to identify the valves and whether they are the correct parts or the previous owner's best guess. A smaller valve head will obviously sit lower in the valve seat, but as long as the seal is good the engine will run but not achieve the performance you could get with all the right bits.
Alloy head uses different valves, caps and collets from the standard iron head engine. Alloy head collets fit a narrow groove in the valve stem, standard valves have a much wider groove, so easy to tell if at least they are the correct type.
Alloy head valve stem shown below, this is actually an aftermarket ALPHA valve V128, Super Rocket Exhaust.
But Rob's added a further conundrum. The head casting number 67 1120 is the basis for a Shooting Star 500cc, with 66 mm bore. So
measure the combustion chamber and compare with the bore....all may not be as it seems. For an A10 you want 70mm or thereabouts. 67 1126 is more like correct, 56/57 Road Rocket.*
Swarfy.
*Casting numbers differ by a few digits compared to part numbers listed as complete assemblies, cylinder heads being a case in point.
-
The head number is 67-1126 actually, regarding the valves size and codes I will check and reply, thanks a lot
Eugenio
-
I'm following with great interest as I'm about to rebuild my 67-1126 head. Your problems and replies could save me a lot of time *smile*
-
G'day Eugenio.
OK valve gear looks right. Measure the valves, should be 1.41" inlet and 1.38" exhaust.
You really need to check the valve guides before you get too deep. No good having a rebuilt motor that smokes like a 16 year old!
http://atlanticgreen.com/a10alloyhead.htm
Cheers
-
Hi muskrat, I eventually dismounted and measured the valves. According to my caliper, inlet 1.458 and exhaust 1.380 I cannot read well the codes onto the valves it seems something like 322 VK England but I must check better tomorrow with a lens.
Eugenio
-
I believe the 67-1126 head is 1.455 inlet so your measurements look correct. I'll be getting my valves out this week as the head is on the bench, its also a 67-1126.
-
the "big valve" is 37mm and earlier is 36mm.
I think that Eugenius has 37mm valves.
-
eugenius try a magnet on the valves normally inlets are magnetic exhausts are not
So exhaust are stainless of some level ?
-
G'day Mac.
Yes sort of austenitic stainless steel.
"The exhaust valve is usually non-magnetic.
Commonly, in modern automobile engines, intake Valves are made of a martensitic steel alloy and are magnetic. Exhaust valves are commonly an austenitic stainless steel, called “Sil1,” which is non -magnetic. Sometimes, especially in higher performance engines, especially boosted engines, exhaust valves are made of inconel, which is a nickel based super alloy. While pure nickel is magnetic, inconel alloys, due to high chromium content are typically non-magnetic."
I have used inlet valves (just for size) in a road motor but hasn't or expected to do thousands of miles.
Cheers
-
G'day all, a lot of interesting information from a great forum! I am approaching to try dismount the valves' guides as soon as I will receive a brass bar to make a custom made instrument for the purpose. Someone say that after removal it is always necessary to rebore the valve guide seats, someone not. Any advice on this regard? Thanks everybody *smiley4*
-
In my experience if the head bores are in good condition and the guides are good quality - ie concentric and true, then a light valve grind is enough. Its easy enough to put the guides in then drop the valves in and take a look how they seat. Don't be tempted to grind out any big discrepancy as you are grinding the valve away at the same time as the seat. Its all well and good advising the seats be re-cut, but if the new guide is that far out compared to the old I would suspect the quality of the new guide or how its seated rather than go taking metal off the valve seats.
-
G'day all, a lot of interesting information from a great forum! I am approaching to try dismount the valves' guides as soon as I will receive a brass bar to make a custom made instrument for the purpose. Someone say that after removal it is always necessary to rebore the valve guide seats, someone not. Any advice on this regard? Thanks everybody *smiley4*
re cutting the seat after a guide install is done because the new guide might be at a slightly different angle in relation to the valve seat you can check with layout blue on the valve sealing side and a valve lapping tool .
I used colisbro valve guides and G and S valves from SRM tight tolerances but havent had a problem with them.
-
G'day Eugenio.
Your iron head will use cast iron guides. If the old ones are pushed out hot (200C) new oversize guides may not be needed. If pushed out cold I'd use 0.001" oversize. Best to have a very accurate "cubit stick" to measure.
9 times out of 10 the seats will need at least a lap or cut if bad.
Cheers
-
Thanks all, I have a 67-1126 super rocket alloy head with bronze valve guides; then if I will succeed in removing I will measure them and buy the new a little oversized if I understood well? Indeed I have found a little play when moving laterally the valves particularly the inlet valves, less with the exhaust ones...
-
if you are going to hammer them out remove as much carbon build up as possible, it makes life easier
-
G'day Eugenio.
Sorry I didn't realize you have an alloy head. In which case yes bronze guides. Heat head to 200C and they will push out by hand. Then measure them with a micrometer. They may have been replaced before and you need to know if any or all are oversize already.
Cheers
-
Good morning friends, thanks for the advices. I'll do as you suggest.
-
Alloy heads are valuable...and fragile. I'd be thinking along the lines of making sure the existing valves are the correct ones, because earlier pictures looked as if the valve heads were too small for the seats. Also slop in the guides is also down to valve stem wear. In other words a new set of the correct valves may be a better way to go, rather than changing the guides for very little gain.
It all depends on what you actually have and how much you want to spend. Recutting the seats is indeed the standard practice, to ensure the bore of the new guide is concentric with the seat and the seat angle matches the valve. All fine and dandy, but some practitioners are heavy handed, and as suggested a check with blue and a light "tickle" may be enough....if only to preserve the seats.
Swarfy.
-
Hi Swarfy, thank you for a balanced suggestion that clearly originate from great experience. Indeed I am tempted to check with blue following an already accomplished light 'tickle' as you say and then decide how to proceed. It is a pleasure to receive so many advices from you all *smiley4*
-
Hi eugenius,
If you have access to machining facilities the best way to remove the guides is the machine away the top half , then heat the head as suggested and drive the remainders of the guides down into the ports, the reason being that any car on stuck to the guides will not damage the guide bores,
Otherwise bead blasting the ports around the guides to remove the carbon , be sure there are no beads or carbon left in between head and guide..
Measuring the valve stems for wear may help with diagnosis.. The guides wear at each end Oreos than the centre
Colisbro guides should be honed to size, not everyone has the equipment to do this
John
-
thanks John for further details!
Eugenio
-
Hi all. I have bought a new set of valves (still waiting the exhaust ones) and removed the inlet valves guides because there was too much play. I now should buy the new guides but which measure should I choose provided my guides measure 0.566 inches?
-
Hi all. I have bought a new set of valves (still waiting the exhaust ones) and removed the inlet valves guides because there was too much play. I now should buy the new guides but which measure should I choose provided my guides measure 0.566 inches?
I replaced my guides with colisbro ones from SRM they were plus .020 and turned down the OD to fit the interference spec for each hole as they were all slightly different .
-
Thanks Sean for the insights *ex*
-
The reason that valves need to be lapped -in after fitting new guides is because a previous owner might have lapped in the old valves whilst the old guides were still fitted. Consequently, the valve seat may have been ground off-centre or crooked because the valve would not be straight in the guide.
-
Yes in fact it is hard to understand what was exactly made by previous owners. So far, I will buy new colsibro guides and afterwards get those placed by a specialist to face the new valves and if necessary adjust the valves seats accordingly. Thanks cheeser-beezer
-
Yes in fact it is hard to understand what was exactly made by previous owners. So far, I will buy new colsibro guides and afterwards get those placed by a specialist to face the new valves and if necessary adjust the valves seats accordingly. Thanks cheeser-beezer
you dont need colisbro you can go with the regular cast iron valve guides and depending on where you live you may have a problem finding the tools to hone the colisbro valve guide id, you need a special material on the hones and you will need a tool [ ball micrometer ] to measure the id of the guide and a 0 to 1 in outside Micrometer ....if I remember right the intake clearance was .001 on intake and exh .0015 ....I ordered my hones from a company in the USA but I believe they are also in UK " Brush Research "
-
Thanks Sean! I have an alloy head with bronze guides so maybe colsibro guides should fit better? As far as the mounting issues, there are some specialized centres in Rome that may adequately face these problems hopefully but I will ask better. My main problem will be to decide, which size of guides should I buy, standard or oversized? A nice day
-
0.566 looks quite big already. I just took mine out and they are 0.5625 which is 9/16" 0.566 would be +4 which is the largest (normal) oversize. My bores in the head are worn and the +4 guides are out of stock here in the UK (I did a lot of searching) so I have +14 on order from SRM and I'll get them machined to fit. The SRM +14 are about the same prices as the Dragan +4 but there's the added cost of machining. I can't be sure my head is not worn so I feel I have little choice now other than to get the new guides honed and the seat cut (just s skim) to line up. You may end up at the same conclusion.
-
Thanks Limeyrob, I have removed the 4 valves guides and remeasured all more precisely the size of the guides is actually smaller 0.535inch (maybe I smoked something too strong..), so which bronze guides size should I take? Regards
-
Have you thought about having the exhaust seats changed to adapt to the latest ethanol fuel? It may not be a problem in your country but the fuel over here in the UK is now rubbish.
Just a thought but if you do heavy milage its worth doing
-
Alloy head will already have seat inserts. Any problems running unmodified alloy heads on E5 or E10 here in the UK?
Swarfy.
-
Hi bikeboy, thanks for the suggestion but I do not use my A10 that much. I am just waiting the newly ordered valve guides (SRM colsibro) to reassemble the engine and see if I can eventually enjoy a bit this bike on springer..
-
Have you thought about having the exhaust seats changed to adapt to the latest ethanol fuel? It may not be a problem in your country but the fuel over here in the UK is now rubbish.
Just a thought but if you do heavy milage its worth doing
We have E10 here in Canada and talking about E 15 havent had any problems yet but I agree ethanol fuel is bad for carb engines.
-
Any problems running unmodified alloy heads on E5 or E10 here in the UK?
--------------------------------------------------------------------
The fuel in the uk is awful it takes a lot of messing around with the timing etc at times just to stop the pinking
-
Any problems running unmodified alloy heads on E5 or E10 here in the UK?
--------------------------------------------------------------------
The fuel in the uk is awful it takes a lot of messing around with the timing etc at times just to stop the pinking
...I put 7 to 1s in my super rocket when I rebuilt the motor no problems with low compression and crap gas and easier to start for me at 76
-
The valveseats are not the problem, the y could run without lead and with ethanolfuel.
Running on hight compression is the problem. Compression ratios 9to1 and more in conjunktionn with Megacycle cams is a pain with this bad fuels. Pinking under load, engine running hot and lost of power. Runing fairly only with premium fuels.
cheers Klaus
-
Eugenius, apologies for not replying. I've bought the oversize guide from SRM and I'm having them turned to fit the head. They come undersize on the bore so they have to be honed out too. Its been at the shop for 3 weeks now so I can't tell you how its worked out yet.
-
Thanks limeyrob and thanks all for replying. I also made the same with my guides SRM colsibro oversized adapted to be mounted. Resolved small issues with carburator leaks, once reassembled the engine with new valves, springs and guides it seems to run quite fine, it starts on the first attempt and keep nicely the minimum. When riding for a small round near my homeplace (I still have no insurance) however carburation seems not perfect and I suspect I will not be really able to adjust it. Yet I am learning a lot thanks to you all. We will see... Ciao