Theres an interesting video of a guy fitting seats to a BMC A series head using a pillar drill
That could serve nicely as a how not to video. Unlike those in a mill, the bearings and the way they're installed in a pillar drill do not resist side thrust, which means the runout of any of them is greater than 0.001". Also, you don't want lubrication between the seat and head since it will decrease the thermal conductivity, and a proper how-to video would feature micrometers.
Originally Posted by gunner
It will be interesting to see how you machine the head and fit the seats
After being temporarily stopped by my valve spring remover yesterday, it only took a few minutes today to machine an adapter from a piece of thick-wall Al. However, even hammer blows wouldn't make the exhaust valve move more than ~1/4" so it was back to the hydraulic press to overcome its resistance.
Since I'm going to work on the rockers first there's no urgency to get the BSA head mounted in the mill so I dropped it in a 5-gal. bucket of derusting solution to marinate for a few days. I don't need the rust off to machine the pocket for the seat, but it will make handling the head less messy. Also, I'll never use the valve springs and valves again, and I should just throw them away, but they along with the rocker parts went in the derusing solution as well.
Hey MM! What's your de-rusting solution of choice?
I have a 5-gal. bucket filled with Rusteco that I bought ~25 years ago and have used many times since then. The company is still in business and I suspect it's just a molasses/treacle solution.
I went back through the early part of this thread because I remembered having used it before and I found the post that shows the results on a rusty mudguard after two days plus a light brushing with a Scotchbrite pad (nb. this journey back through time reminded me just how much work I did to rebuild this this bike), I wouldn't have needed the pad if I had taken the mudguard outside to hose it off instead, which I didn't do because it would have left a trail of dripping molasses across the garage floor.
Not because the solution didn't seem to be working well after 25 years and many de-rustings, because it did, but for no good reason at the time I added a bottle of blackstrap molasses. I also had no good reason to use blackstrap rather than normal molasses, other than it just looks more "heavy duty." I don't know if this made the Rusteco work better or worse, but it still works fine.
The 5-gal. plastic pail of Rusteco/molasses with screw-on cover sits next to the one of Gunk/diesel. De-rusting and de-greasing are the two dirtiest and time-consuming jobs in rebuilding a motorcycle, and being able to just drop parts into a bucket and retrieve them a few days later saves me much time and effort. The buckets are big enough for most parts on a motorcycle, and the mudguard post shows how I deal with bigger items.
Last edited by Magnetoman; 10/18/186:32 pm. Reason: added photo of head pulled part way out of Rusteco bucket
Molasses and water,about 50/50, removes rust quite nicely but takes a week or two
For anyone who lives in one of the few parts of the world where there's still permafrost, remember that chemical reactions slow down significantly as the temperature drops, so be patient if you do your de-rusting in an unheated garage over the next few months.
On another note, this thread just hit 250k views, and it's still picking up steam:
The normal rule of thumb is that a chemical reaction doubles in speed for a temperature increase of 10 centigrade degrees. Or putting it another way it goes only half as fast for a temperature reduction of 10 centigrade degrees--which is about 20 Fahrenheit degrees. So if you are used to doing your derusting in your garage in the summer when the garage temperature is 70F and you then do the same job in the winter with a garage temperature of 30F (topical as we had our first frost of the year last night in NJ) then it will take 4 times as long in the winter as in the summer. HTH BTW--MMan--congratulations on another impressive milestone with this thread. Interesting, absorbing and instructional----you should have been an educator!
When I was in a share hous with a fellow BSA enthusiast we did some Molasses cleaning in the workshop space under the house. Only did it once. After that it was a job for the patio took better than a year to get rid of the smell of a rancid brewery all through the house.
I don't know how much agitation of the mixture helps the de-rusting process, but every time I walk past it, I kick the bucket.
Originally Posted by Tridentman
you should have been an educator!
I discussed this with an employment counsellor but was advised I'm still young enough that I need to continue hunting. Although, now I need to focus my hunting on motorcycle parts. (sorry, but the link has both images as a single jpg.
Originally Posted by BSA_WM20
we did some Molasses cleaning in the workshop space under the house....took better than a year to get rid of the smell of a rancid brewery all through the house.
Like I said, I've been doing de-re-rusting this way for more than 25 years. But, I don't have it (or a solvent tank, or an open can of brake fluid, or...) in the house.
While waiting for the molasses to do its job I've been planning my attack on the lifters. Although I didn't have any issues with cracking of the Stellite when I made the pushrods, it seems the safer way to apply it is over a layer of ERNiCrMo-3, also known as 625. This alloy is even stronger than steel, but it isn't cheap. Despite that, a pound of 1/16" TIG filler rod is on its way to me.
I only managed indirect Ariel progress today, starting with housekeeping (garagekeeping), followed by the arrival of a new tool that I didn't need in the strict sense of the word, but did "need" in the same way I "need" three Gold Stars.
I came across a (relatively) inexpensive, but very expensive-when-new, Storm-Vulcan connecting rod tester that, after giving it much careful consideration, I decided I didn't really need because of the very limited use I would have for it. Along with a surface plate, other instruments I have do the same job, albeit take longer to set up. So, because I didn't need it, it took me a few days before I decided I "needed" to have it. It arrived today.
There is very little information about this tester on the web so it was a gamble that I would be able to fix it. I spent a while figuring out how it worked, then disassembled it to find a rod had fallen out of its slot. With that rod back in place, and after some gentle cleaning, it's now ready for me to accurately calibrate.
At the top of the bar (and also another at the back, for measuring twist) that passes through the big end of the rod is a long metal piece that pivots in the middle like a see-saw. As it pivots it pushes on a rod, that pushes on a lever, that pushes on the rod that had fallen out of its slot, that pushes on another lever at the top of a spring-loaded rod that's connected to the pointer under the scale in the base. If the big end is precisely parallel to the gudgeon pin then both ends of the see-saw will be at the same height and the scale will read '0'.
Long time readers will remember I had to straighten the Ariel's rod, calling the job done when I got the height of one end of the 2.4" gudgeon pin within ~0.001" of the other. All I had time to do today was make a very crude measurement of the sensitivity of this new unit and, very roughly, it appears each number on the scale corresponds to a bend of ~0.001" over the length of a gudgeon pin. So, its sensitivity certainly is in the right ballpark.
Well, that is a good device to have, I'd never seen on before. I always did it on a surface place with height gage etc. I want to thank you for taking the time to put up all of this information on your progress- it's been instructive and interesting to lots of people in the Britbike world.
Have you come to a conclusion of what was causing the exhaust guide to wear so quickly?
The most plausible explanation consistent with the observations is that once the thin case hardened layer wore through the greater friction of the soft base steel resulted in a larger side force on the valve stem that increased the rate of wear. Hopefully, once I face the lifter with Stellite and polish it and the lash cap to a mirror finish the side thrust, and the wear, will be greatly reduced.
Originally Posted by old mule
I want to thank you for taking the time to put up all of this information on your progress- it's been instructive and interesting to lots of people in the Britbike world.
Thank you for your thank you. Quite a few restoration topics and techniques are covered in this thread because I had to deal with a pretty wide range of repairs.
Originally Posted by old mule
Well, that is a good device to have, I'd never seen on before. I always did it on a surface place with height gage etc.
The photograph gives a better view of the layout of the Storm-Vulcan rod aligner and the cutaway shows how it works.
A connecting rod is supported by its gudgeon pin in the Magenta V-brackets and the horizontal bar in which the Cyan see-saw is located is pushed against the top of the big end of the rod. If the big end isn't perfectly perpendicular to the gudgeon pin one side of the Cyan see-saw will be pushed down slightly further than the other side, which pushes against the Yellow rod. That rod pushes against the Red lever that in turn presses against the Green rod (which was the one out of place on my unit). The Green rod pushes against the spring-loaded Blue indicator vane which rotates under the scale at the front of the unit. There's a second see-saw at the back of the horizontal bar which is used to measure twist in the rod the same way, by pushing it against the back of the big end of the rod.
It's a clever design, and the mechanical advantage of the various levers is such that a height difference of less than 0.001" is magnified to a pointer movement of ~0.5". That is, very roughly, ~500:1, although a precise value awaits careful calibration. Also, the instrument relies on various components being precisely perpendicular or parallel to other components so I'll have to check that as well and correct if necessary.
Update: I checked the sensitivity today. If the bottom of a rod were 1" wide each numbered unit on the scale would correspond to the two ends of the rod being out of parallel by 0.0020". As a concrete example, assuming a BSA connecting rod were being tested (0.86" across the big end), that would be 0.0017" for each numbered division, or 0.0003" for each tick mark between numbers. The scale pronounces as "good" a deviation of 3 tick marks or less = 0.0010".
Looked at differently, the big end of a rod is always in the crankshaft and hence is the "fixed point" and the small end is the variable. What this means is if the rod aligner showed the Ariel's rod to be at the limit of the "good" range the total difference in height between the two ends of the Ariel's 2.4" gudgeon pin would be 0.0028" (one end 0.0014" too high, and the other end that much too low). For reasons described months ago when straightening the Ariel's rod, this means the crown on one side and the skirt on the other would be almost touching the cylinder wall. Hence, the scale really does indicate the boundary between "good" and "passable if worn," so it would be, ahem, good to work on straightening a rod until it wasn't near that boundary. Having an instrument that lets the remaining amount of bend be quickly determined will make the process go faster. That is, the rare times in the future that I need to do this again...
I am confused. I thought the rocker did not wear through the hardfacing until you removed the wear cap. If the wear on the rocker caused increased side loads on valve stem wearing the second guide out what was the cause of the first guide wearing out?
what was the cause of the first guide wearing out?
Ah, I misunderstood your question. Unfortunately, because of several variables I only have speculation, not a definitive answer.
What I know: Inlet guide lasted 3000 miles with minimum wear. It was made of G2 cast iron and lubricated at the top with the same grease as the exhaust guide but the fuel had 1 oz. of 2-stroke oil per tank.
The first exhaust guide was totally worn in 2000 miles. It was made of G2 cast iron and lubricated at the top with the same grease as the inlet guide, but my use of an oil control ring for the first 2000 miles meant minimal oil got past the piston.
The second exhaust guide was from your stock of Norton guides and was significantly worn in 1000 miles. However, the lifter was worn as well so there was additional side thrust on the stem. The guide was lubricated at the top with the same grease as the inlet guide, and I had removed the oil control ring at the time it was installed so some unknown amount of additional oil got past the piston the entire time the second exhaust guide was in place.
What I don't know: I don't know the composition and wear resistance (compared with G2) of the Norton guide, how much additional side thrust the worn lifter caused, and how much oil got past the piston before and after the oil control ring was removed at 2000 miles. I also don't know if the 1 oz./tank of oil was responsible for the lack of wear of the inlet guide. That is, maybe no oil at all, or significantly less oil, would have had the same result since the situation with the inlet guide is different than that of the exhaust in that the "vacuum" in the inlet track tends to suck grease down the guide to provide lubrication.
Speculation: Assume the 1 oz./tank was the key factor in keeping the G2 inlet guide from wearing, and also assume a G2 exhaust guide with no additional side thrust and with "sufficient" oil leaking past a 2-ring piston wouldn't have worn either. Under these assumptions, how much oil would have to leak past the piston?
The oil flow rate I arrived at that seemed to keep the engine happy while resulting in only small puddles of excess oil under the bike when I stopped was ~1 drop/sec. That equates to approximately 1/2 qt. (16 oz.) / 125 miles, which is roughly the range of one tank of fuel. So, to have the same oil content in the exhaust as in the inlet this means ~1/16th (6%) of the oil that passed through the sight glass would have to leak past the piston to be "burned," with the rest of it leaving via the two breathers.
The head is already off so I can't measure the leakdown rate of the engine with only the two rings, but 6% isn't that bad for a 3-ring piston in an engine that's in pretty good shape. That is, it doesn't appear to be unreasonable that enough oil can get by the 2-ring piston to supply the exhaust valve stem with the same oil mixture as seen by the inlet valve. Also, if this amount of oil is critical to the survival of the exhaust guide, having the oil control ring in place for the first 2000 miles would explain why the first guide died.
Conclusion: Assuming the oil in the fuel was responsible for keeping the inlet guide alive for all 3000 miles, and assuming 6% of the new oil flow rate gets past the 2-ring piston (but that much less got by the 3-ring piston), and assuming this amount of "leaked" oil hitting the hot exhaust valve stem has the same effect as when hitting a cool inlet valve, and assuming the Norton guide has the same wear properties as G2 cast iron, and assuming the side thrust from the worn lifter overcame the positive effects of the oil mist, then absent the problem with the lifter the replacement exhaust guide "should" have survived. Also, it means the first exhaust guide "should" have survived the entire trip had I left out the oil control ring from the start.
I like the fact there is a plausible explanation for the failure of the 2nd guide even with the additional oil it received, as well as an easy solution (i.e. leave the oil control ring out), but clearly a lot of assumptions are involved, even if they are reasonable ones. It will take another ~1000 miles to know if the problem is now solved.
I am still unconvinced that we have progressed to the stage yet where we can discount rocker arm/valve geometry as one of the primary causes of the rapid exhaust valve guide wear. Saying that it didn't happen to the inlet valve guide is no real reason as the operating conditions for the two guides are quite different. I keep coming back to those two diagrams you posted showing the arc swept by the tip of the rocker arm and how the tangents varied at different points in the camshaft lift. Engineering is supposed to be about numbers and specifications but my experience over the years in trouble shooting problems has been that gut feel also has a valuable part to play. My gut tells me that to reduce guide wear you need to do something to improve the geometry. Maybe shorter valves and respecced valve springs? Just my two cents worth of course.
My gut tells me that to reduce guide wear you need to do something to improve the geometry. Maybe shorter valves and respecced valve springs?
Originally Posted by gunner
I'm with Tridentman on this one
OK, fair enough, add to my list of assumptions:
...and assume the valves supplied by the AOMCC are the same length as the originals so the geometry is the same, and assume the springs supplied by the AOMCC have the same specs as the originals, and assume the original exhaust guide (when used with the original 2-ring, non-cam-ground piston) had a lifetime >2000 miles, and assume there are no other relevant assumptions I've forgotten to list, and...
The point being, although the current valve geometry might be the source of the problem, there's no reason it stands out more than any of the other possible sources. So, it's difficult to spend the effort to modify the geometry given that it just as well might not be the source of the problem.
However, a longer, not shorter, valve stem would improve the geometry (whether at half-lift or full-lift is the desired result only determines the additional length). But, realistically, looking for a longer exhaust valve that either fits as-is, or that is suitable for modification, isn't going to happen.
The situation is even worse for alternate valve springs that fit even if I knew what weaker spring constants would still keep them from floating, which I don't. However, at least in the case of the springs, the values I've found for somewhat comparable applications leave me pretty convinced the current ones are fine.
OK, back to the valve. Being too lazy to try to look for a longer replacement doesn't mean all is lost. An alternative is for me to make my own Stellite-tipped lash cap to lengthen the stem. Such a cap would have a somewhat larger OD than the existing stem but, in the grander scheme of things, the total weight of the assembly only would be a few grams heavier than that of a valve with a longer stem so valve float near redline wouldn't be much of a concern. Another nice feature of this possibility is it also lets me postpone a decision since such a cap could be added even after the engine is completely assembled.
Addendum: I realized I hadn't described the precise amount of inlet guide wear I measured after the 3000 miles. Without having the original clearances in front of me to influence my measurements I measured the front-to-back and side-to-side clearances at 5 depths from the top to the bottom of the guide. Within an uncertainty of +/-0.0001" there was no measurable wear anywhere in the inlet guide. For example, in the middle of the guide the side-to-side clearance I recorded when new was 0.0026" and the value I measured after 3000 miles was 0.0025" (i.e. the guide became less-worn, if the measurement uncertainty is ignored).
Whether or not Val Page used the wrong geometry in his design, or the current valves supplied by the AOMCC give the wrong geometry, you can't ask for better performance than having zero measured wear of a guide after 3000 miles (note: six of the ten values showed less clearance so the measurements were scattered around an average of 0, i.e. truly consistent with no measurable wear even absent the 0.0001" uncertainty) . Even recognizing that the exhaust valve lives in a harsher environment, these results for the inlet guide make me think factors other than valve train geometry were responsible for the exhaust guide wear (e.g. having 3-rings for the first 2000 miles; and having a worn rocker for the next 1000 miles).
Last edited by Magnetoman; 10/22/187:13 pm. Reason: Addendum:
I just skimmed this, looks like flake graphite wins over spheroidal on the thermal conductivity , that rules out the bottom table in the post above.. One in particular caught my eye, Ni resist 5, it has high nickel 35% giving the lowest thermal expansion, the low chrome content makes it easier to machine .
Last edited by gavin eisler; 10/22/1810:21 pm.
71 Devimead A65 750 56 Norbsa 68 Longstroke A65 Cagiva Raptor 650 MZ TS 250 The poster formerly known as Pod
Given the stellar performance of G2 cast iron in the role of inlet guide I don't have any interest in experimenting with alternatives. However, if John knows the specs of the particular Ni-Resist he uses, and has found that it works significantly better than G2 in an exhaust guide, it would be foolish of me not to order a rod to use for the Ariel.