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Gold Star Engine Rebuild: Rocker Box
#811324 06/03/20 3:07 pm
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Late-ZB and BB Gold Stars as well as B33s adjust valve lash using variable-length tappets at the crankcase mouth, while CB, DB and DBD Gold Stars use eccentric spindles ("rocker fulcrum pins") for this purpose. Despite this, as the next figure shows, both types of rocker boxes are quite similar.

[Linked Image]

Assembling a rocker box is relatively simple. Although the illustrations in this thread are from a B33 rocker box I note where CB and later Gold Star models differ. The assembly procedure will assume you are starting from completely separate parts, so to disassemble a rocker box you would begin at the last step and work backwards.

Supplies needed:
-- Assembly lube
-- Loctite 262 (red, high strength)

A. Inspect the components to be sure you have the correct ones.

-- The circumference and operating arms on Gold Star rockers are ground to make them lighter than their B33 counterparts. For example, a BB Gold Star Inlet rocker is ~155 g (~165 g for a DBD) vs. ~180–200 g for a B33. However, even without weighing a rocker, if the casting number is still visible it is not from a Gold Star.

-- The exhaust rockers of late-ZB and BB Gold Stars and B33s have a drilled passage at the pushrod end and a hole at the valve end to bring oil to the cap of the pushrod and the valve tip. Both holes are present on Gold Star intake rockers as well, but B33s only have the oil passage at the pushrod end. Starting with CB Gold Stars the ball and sockets were reversed and the oil passage at the pushrod end was eliminated and replaced with a hole directly over the pushrod.

[Linked Image]

-- Ensure the oil holes at both ends of both Gold Star rockers (and only at the pushrod end of a B33 inlet rocker) aren't blocked.

[Linked Image]

-- Rocker spindles ("rocker fulcrum pin") on CB, DB and DBD Gold Stars (bottom) have a hex head at the oil inlet end to operate the eccentric shaft while those on late-ZB and BB Gold Stars and B33s (top) are plain.

[Linked Image]

-- The spindles should have a diameter 0.5605" in order to provide 0.002" clearance in an unworn 9/16" rocker arm. Insert the spindles in the lifters and check that they turn without any feeling of resistance.

-- Clean the inside of the spindles and make sure the exit hole isn't blocked. Not all exit holes are in the same position, but this has no effect on function.

[Linked Image]

-- The banjo bolts for attaching the oil feed manifold to the spindles are not interchangeable. The bolt on the inlet side (65-317) has a much smaller hole than the one on the exhaust side (65-318). Make sure neither one is clogged.

Last edited by Magnetoman; 06/03/20 9:20 pm.
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Re: Gold Star Engine Rebuild: Rocker Box
Magnetoman #811326 06/03/20 3:11 pm
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-- The longitudinal groove brings oil from the hole to the circumferential groove at the left of the next photograph, where it feed the oil passage leading to the pushrod. The groove also leads it to the area of the spring to provide greater flow into the rocker box than otherwise would be the case. Early B33 spindles, such as the ones in the photograph, do not have a second circumferential groove under the hole that is later B33 rockers that feed oil to that hole. Gold Star spindles have both grooves.

[Linked Image]

B. Lay out the parts for the valve lifter mechanism.

[Linked Image]

[Linked Image]

-- Note that part #24 has a hollow end into which the OEM tapered felt washer #25 fits.

[Linked Image]

-- If you can't find an OEM felt washer you can use a set of plug cutters to make one from an appropriate piece of dense industrial felt.

[Linked Image]

Re: Gold Star Engine Rebuild: Rocker Box
Magnetoman #811328 06/03/20 3:16 pm
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C. Assemble the valve lifter mechanism.

C-1. Apply assembly lube, insert the shaft, and place the cam on the shaft such that it lifts as the shaft is rotated CW as viewed from the operating end of the shaft.

[Linked Image]

-- Assembly of the lifter could take place with the exhaust rocker already in place but there is more room without it. Although the split pin will keep the nut from falling off, Loctite will ensure the cam remains solidly locked with no play.

C-2. Continue to attach the other parts on the above diagram in the correct order.

-- A standard split pin is too long for the clearance between the shaft and rocker cover so clip it quite a bit shorter before installing it.

C-3. I may change this later once the engine is together, but by comparing with my other Gold Stars it appears the operating arm should be attached at the ~10:30 or 11:00 position when it first starts moving the lifter.

[Linked Image]

D. Assemble the rockers

-- Both rockers are assembled the same way.

[Linked Image]

-- Thrust washer #34 on a late ZB.GS, BB.GS or B33 is 0.100" thick.

D-1. Use grease to hold the thrust washer in place, or wait until Step D-6 and use a needle nose pliers to install it once the spindle is mostly in place.

D-2. Spray assembly lube on the inside of the rockers and insert the appropriate rocker in the corresponding cavity in the rocker box. It will require a few twists and turns to insert the rocker but there are no clearance issues even with the exhaust lifter in place.

[Linked Image]

D-3. With the rocker in place, begin to insert the spindle.

[Linked Image]

Re: Gold Star Engine Rebuild: Rocker Box
Magnetoman #811331 06/03/20 3:22 pm
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D-4. With the spindle barely peeking into the cavity, insert the spring and washer, which will hold themselves in position as you begin to insert the spindle through them. Note that if the open end of the spring isn't in the right orientation when you insert the washer (top) it's easy to get the washer trapped between coils (bottom) where it will block the spindle from being inserted.

[Linked Image]

D-5. Once the washer is correctly positioned it still will require manipulation with a small needle-nose pliers to get the washer over the sharp step near the threaded end of the spindle. However, after the spindle is past that point it will be easy to continue inserting the spindle.

[Linked Image]

D-6. If in Step D-1 you attached the thrust washer to the cavity at the other end of the rocker box using grease, and if it didn't fall out and need to be retrieved, continue pushing the spindle until the threaded end emerges from the rocker box. Since it is a light press fit it might require tapping the end with a soft hammer before the threads emerge.

However, at this point in the assembly process an alternative to using grease as mentioned in Step D-1 is to open a gap between the rocker and housing by pulling the rocker against the spring and use a small needle-nose pliers to insert the thrust washer. The washer only needs to be partially in place before you let the spring push the rocker against it. The rocker will keep the thrust washer from falling while you then manipulate it into the cavity, after which you can continue pushing the spindle.

[Linked Image]

-- If the thrust washer is out of position, or the spindle is misaligned and can't be pushed out the exit hole in the rocker box, viewing the spindle from the hole in the housing will allow you to correct the problem.

[Linked Image]

D-7. The spindle is a loose press fit in the rocker box so it will require a few taps from a soft hammer to fully insert it, after which the nut and washer can be attached and tightened.

D-8. The other spindle is installed in the same way.

-- The internal cavity of each rocker assembly has an open volume of 3 mL (6 mL total) that needs to fill before oil can get to where it needs to be. That volume, plus that of the supply line, means the oil pump would have to work for a while fill them, which is why you should prime the lines and cavities before starting the engine for the first time after a rebuild.

[Linked Image]

---------- [End rocker box rebuild] ------------

1 member likes this: Hugh Jorgen
Re: Gold Star Engine Rebuild: Rocker Box
Magnetoman #811374 06/03/20 9:02 pm
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MM: Nice article. It could be mentioned that the special hollow bolts 65-317 and 65-318 that hold the oil banjo onto the ends of the spindles are not interchangeable. 317 has a very small hole for the inlet rocker while 318 has a larger hole for feeding the exhaust rocker. The 317 hole would be easy to clog.

Gordo


The roadside repairs make for the best post ride stories.
Re: Gold Star Engine Rebuild: Rocker Box
Gordo in Comox #811378 06/03/20 9:18 pm
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Originally Posted by Gordo in Comox
It could be mentioned that the special hollow bolts 65-317 and 65-318 that hold the oil banjo onto the ends of the spindles are not interchangeable.
Hmm, that reminds me, I don't have either of those bolts. If I can't get my hands on a set I'll use ones from a Gold Star to get the dimensions for machining my own. As soon as I have a chance to pull them from one of my Gold Stars I'll add a photograph to this thread. Meanwhile, I'll make a note in the appropriate post in this thread as soon as I hit 'send' on this. Thanks for mentioning this very important point.

Re: Gold Star Engine Rebuild: Rocker Box
Magnetoman #811512 06/05/20 2:45 am
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I think you already mention it 6/3/2020 9:20


1951 ZB GS
1953 BB GS
1953 Super Flash
1954 Vincent BS
1963 RGS
1956 Triumph T110

Re: Gold Star Engine Rebuild: Rocker Box
Magnetoman #811734 06/07/20 4:44 am
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and speaking of rocker box studs... I and many others have replaced the OEM studs with SS socket head bolts. Lube the threads with anti seize.
This allows easy fitting of the rocker box on the assembled head on the engine. It's just a few minutes work doing a 'look see' of your valves/springs and fitting and aligning the push rods during assembly.

I hope all of you are using composite rocker box gaskets vs those POS OEM paper gaskets.

Beware of the oil banjo bolts supplied by some unknowing parts sellers with the 'huge' oil holes. I'm not aware of what engine they were made for.

Last edited by Dave - NV; 06/07/20 4:49 am.

Dave - NV
Re: Gold Star Engine Rebuild: Rocker Box
Magnetoman #811747 06/07/20 10:45 am
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The banjo bolts with the huge holes are B31/B33 etc (one piece head) drain tube bolts


BSA B31 500 "Stargazer"
Greeves 200 "Blue Meanie"
Greeves 350
Greeves 360
Suzuki GSX1100 EFE "Sorcerers Apprentice"
GM500 sprint/LSR bike "Deofol"
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Re: Gold Star Engine Rebuild: Rocker Box
Dave - NV #811763 06/07/20 4:51 pm
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Originally Posted by Dave - NV
I and many others have replaced the OEM studs with SS socket head bolts.
I thought I had posted the following photograph with this thread, but apparently not.

[Linked Image]

The socket head cap screws are 5/16"-18 NC, with the three longer ones 3"-long and the six shorter ones 2¼"-long. The original spacer for one of the longer studs was likely lost decades ago. Although it isn't necessary, I have a lathe so it was easy enough to make one. It's the same ~⅛" thickness as the plate. Although the holes are tapped for Whitworth studs, "American" NC bolts fit without problem.

Re: Gold Star Engine Rebuild: Rocker Box
Magnetoman #811861 06/08/20 1:42 pm
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Could you please tell the diameters of the the oil feed bolt holes?

Thanks, Rico

Re: Gold Star Engine Rebuild: Rocker Box
vintagebike #811889 06/08/20 5:46 pm
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Originally Posted by vintagebike
Could you please tell the diameters of the the oil feed bolt holes?
They're 5/16" and threaded 26 tpi

Re: Gold Star Engine Rebuild: Rocker Box
Magnetoman #811890 06/08/20 5:52 pm
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Thanks, but i mean the tiny holes in the bolts..

Re: Gold Star Engine Rebuild: Rocker Box
vintagebike #811891 06/08/20 5:56 pm
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Originally Posted by vintagebike
Thanks, but i mean the tiny holes in the bolts..
Ah, sorry, I misread your post. Someone else will have to answer your question because I haven't yet removed the bolts from one of my working Gold Stars to make the measurements myself.

Re: Gold Star Engine Rebuild: Rocker Box
Magnetoman #811900 06/08/20 7:16 pm
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I found in the internet, that the smaller hole 65-317 has a 3/64" hole, the larger 65-318 a 3/32". Can anybody confirm this?

Re: Gold Star Engine Rebuild: Rocker Box
Magnetoman #811920 06/08/20 10:04 pm
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They are interchangeable, when racing we would use the larger 65-318 on both sides to assure ample oiling.


Bill B...


Boomer
Re: Gold Star Engine Rebuild: Rocker Box
Magnetoman #811938 06/09/20 12:16 am
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It's an approximation, but assume the flow is simply proportional to the square of the hole diameter. Converting the diameter of the bolts to mm because that way I don't have to write so many zeros:

Inlet bolt dia.2 = 1.425 mm2
Exhaust bolt dia.2 = 5.701 mm2
Rocker outlet hole dia.2 = 3.726 mm2 × 2 holes = 7.453 mm2

This approximation shows that the two holes in the rocker can flow somewhat more oil out of the rocker than the constriction in the bolt can supply, so the bolt constriction is the limiting factor. The smaller constriction in the inlet bolt is much more of a limitation for the flow through the inlet rocker.

Carrying this approximation further, if the inlet bolt is replaced by an outlet bolt, it will be capable of flowing ~5.701/1.425 = 4× more oil than before (if the pump can supply it), with the sum of the oil flowing through both bolts increasing by a factor of 1.6×. I can't see anything wrong with pushing additional oil through the inlet rocker as long as the supply line can deliver the increased flow. Otherwise, the oil that the pump does supply will get divided evenly between the two rockers and, while the inlet rocker will get more than it previously did, it will come at the expense of the exhaust rocker getting less.

Re: Gold Star Engine Rebuild: Rocker Box
Magnetoman #811988 06/09/20 2:13 pm
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Hi MM,
The Physicist in you is taking over and running amok (again) laughing

Your post above caused me to go and search out all the rocker feed bolts I could find in my possession without dismantling any from running bikes
I also looked through the 49/53 parts book and the later 58 DBD book
65-317 is shown as the bolt for inlet and exhaust on the iron engine B31/33 but is also shown as fitted to the BB inlet and exhaust for 53
65-318 is the exhaust side bolt for the DBD
The bolt you have with the large hole c5mm. is either a B31/33 head drain bolt or has been drilled out
I measured the oil restricting holes as best I could with small drills and a gas nozzle cleaning set +micrometer

B33 iron head with its original looking bolts, measure 1.1mm - 0.044in. so presuming ? 3/64in.

New DBD bolts from Autocycle measure, inlet 1.1mm. exh 1.6mm - 1/16in.

Webco "Gold Star" oil feed manifold and bolts measure, inlet 1.1mm. exh 2.4mm. 3/32in.

A10 "Dow" bolts both measure 1.1mm.

John

Re: Gold Star Engine Rebuild: Rocker Box
Magnetoman #811996 06/09/20 4:04 pm
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The whole GS engine history is one of evolution and I would expect that each change had a reason. Most changes I would think were for improved performance but I am sure that a few were for reliability. It the factory thought that the later engines needed more oil to the exhaust rocker then I am going to use the two sizes in the ZB and BB engines. To use the larger hole for both rockers would most likely reduce the amount of oil going to the exhaust rocker and thus reduce the advantage of going to the larger hole for the exhaust.

However given the little wear I have seen on any of the rocker spindles and rockers I suspect that the little extra oil could have been more for cooling than lubrication.

Does an oscillating part need the same amount of lubrication as a part that is rotating?

Gordo


The roadside repairs make for the best post ride stories.
Re: Gold Star Engine Rebuild: Rocker Box
Magnetoman #812000 06/09/20 5:11 pm
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Fitting a bolt with a larger hole in the inlet would mean less oil going back to the tank possibility of oil building up in the crankcase.
I agree that the larger oil feed for the exhaust rocker has more to do with cooling


BSA B31 500 "Stargazer"
Greeves 200 "Blue Meanie"
Greeves 350
Greeves 360
Suzuki GSX1100 EFE "Sorcerers Apprentice"
GM500 sprint/LSR bike "Deofol"
Jawa 500 "Llareggub"
Aprilia RSV Mille "Lo Stregone"
'35 & '36 OK Supreme
Kawasaki ZZR1400 "Kuro no senshi"
Re: Gold Star Engine Rebuild: Rocker Box
Magnetoman #812025 06/09/20 8:13 pm
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Originally Posted by Gordo in Comox
I suspect that the little extra oil could have been more for cooling than lubrication.
Does an oscillating part need the same amount of lubrication as a part that is rotating?

The heat capacity of oil is less than half that of water (1.7–2 vs. 4.2 kJ/kg℃) so it isn't a very good coolant. As you pointed out elsewhere the earliest rockers didn't have any holes, which then changed to holes to send oil to the pushrod ends, which then changed to send oil to the valve tips as well. Together with the poor heat capacity of oil, this evolution suggests to me that the oil was for lubrication, not cooling. The hot tips of the exhaust valves must have done better when supplied with more lubrication than required for the cool tips of the inlet valves.

As for lubricating the oscillating rockers on their spindles, irrespective of the size of the banjo bolt the insides always are filled with oil. Although oil flows at a slower rate on the inlet side, there always is a film of oil between both rockers and their spindles. There couldn't be much of a difference in temperature between the inlet and exhaust rockers themselves, so my conclusion is the extra flow rate aided keeping a lubricating film between the hot exhaust valve tip and rocker.

Golland's 'Goldie' makes it clear that all the development work was done with the Isle of Man in mind. The new models were introduced mid-year in time for mechanics to prepare the machines for the next IoM race. While a Gold Star in an AMA mile flat track race at the time would have run flat out for 25 miles, it would have done ~10 times that at the IoM (as well as Daytona). This suggests to me that a feature like the oil hole for the exhaust valve (and larger banjo bolt) was added as a result of observing scuffing under the extreme conditions of the IoM, whereas it might not have happened under lesser conditions like an AMA mile.


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