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Mark Parker
Mark Parker
Bega NSW Australia
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Gold Star valve lifter/decompressor
#794478 12/31/19 6:38 pm
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Recently joined the family of BSA with a DB34 GS. Just going round the bits and have hit upon a problem I need help with. The valve gaps were chronically out. Regapped according to the manual which required rocker spindles to be turned towards cylinder head then turned clockwise/anti clockwise for gap. Valve lifter had been working OK prior to procedure and now no longer works at all. Wondering whether movement of the rocker spindle on the exhaust side has put valve lifter cam out of alignment with the rocker arm. Any idea what has changed and suggestions how to go about rectifying the problem would be appreciated.

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Re: Gold Star valve lifter/decompressor
moto8500 #794491 12/31/19 7:58 pm
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The most likely explanation is you got the clockwise/anticlockwise backwards, possibly assuming it should be done from the timing side of the engine. Are you 100% sure you adjusted the clearances according to the following two descriptions?

[Linked Image]

[Linked Image]

Re: Gold Star valve lifter/decompressor
Magnetoman #794525 01/01/20 2:02 am
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Thank you Magnetoman for the helpful reply.

I never say never - so lets assume I did not set the valve gap in accordance with the correct procedure and that the eccentric portion of the spindle faces away from the valve and so I am getting a false valve clearance reading - why would scenario have the effect of disabling the valve lifter.

Re: Gold Star valve lifter/decompressor
moto8500 #794526 01/01/20 2:23 am
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Originally Posted by moto8500
why would scenario have the effect of disabling the valve lifter.
The valve lifter presses against the rocker, and the rocker moves forward and back as the spindle is rotated. So, if the rocker is in the wrong location the lifter can't reach it.

[Linked Image]


Last edited by Magnetoman; 01/01/20 5:06 pm. Reason: added red arc to show motion of rocker arm as spindle is rotated
Re: Gold Star valve lifter/decompressor
moto8500 #794544 01/01/20 9:57 am
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Five star Magnetoman - you have explained what has happened to disable the lifter. I have obviously got the clockwise/anti clockwise backwards and will have to reset so the lifter can reach the rocker. Just a point of clarity so my understanding is correct - the forward and backward movement of the rocker as the spindle rotates - if that side to side or up and down motion?

Re: Gold Star valve lifter/decompressor
moto8500 #794545 01/01/20 10:50 am
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Quote
if that side to side or up and down motion?


Its an offset circle so its both side to side and up and down, which is why you have the issue as you have to get the right combination as there are 2 potential sideways positions for a particular vertical position and you currently have the wrong one.

Re: Gold Star valve lifter/decompressor
moto8500 #794550 01/01/20 11:59 am
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Thank you Kommando as that clarifies how the rocker moves when the spindle is rotated. I am sure the thread will be of use to another Gold Star owner with a similar issue. Many thanks to you both.

Re: Gold Star valve lifter/decompressor
moto8500 #794889 01/05/20 8:05 pm
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It's not impossible for the lever part to get the wrong side of the rocker if that makes sense. It did on mine despite the correct method used to adjust clearances. I had to remove the rocker box to put it back. Fiddly but straightforward enough, been fine since.


Current bikes:
1959 BSA Goldstar DBD34
1939 Velocette KSS. Mk2
Previous bikes:
1966 Velo Thruxton
1960 Velocette Venom Clubman
1939 Velocette 350 Mac
1959 Velocette Venom
1998 Ducati 916
1978 Norton Commando 850
various other stuff
Re: Gold Star valve lifter/decompressor
Velo-Felo #794905 01/05/20 10:33 pm
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Originally Posted by Velo-Felo
It's not impossible for the lever part to get the wrong side of the rocker if that makes sense. It did on mine despite the correct method used to adjust clearances. I had to remove the rocker box to put it back. Fiddly but straightforward enough, been fine since.




I'm thinking moto8500 is hoping he doesn't have this situation. To remove a Gold Star rockerbox with the engine in situ he would have to remove the cylinder head. This is why some Gold Star owners prefer to replace the rockerbox studs with cap screws, enabling the removal of the rckerbox separately.


Bill B...


Boomer
Re: Gold Star valve lifter/decompressor
Boomer #794909 01/05/20 11:07 pm
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Originally Posted by Boomer
Originally Posted by Velo-Felo
It's not impossible for the lever part to get the wrong side of the rocker if that makes sense. It did on mine despite the correct method used to adjust clearances. I had to remove the rocker box to put it back. Fiddly but straightforward enough, been fine since.




I'm thinking moto8500 is hoping he doesn't have this situation. To remove a Gold Star rockerbox with the engine in situ he would have to remove the cylinder head. This is why some Gold Star owners prefer to replace the rockerbox studs with cap screws, enabling the removal of the rckerbox separately.


Bill B...




Managed to leave my head in situ and remove just the rocker box by taking the studs out. While they were out I cut a screwdriver slot in the top with a hacksaw to make it easier. I'm not keen on the idea of putting Allen bolts/screws in.


Current bikes:
1959 BSA Goldstar DBD34
1939 Velocette KSS. Mk2
Previous bikes:
1966 Velo Thruxton
1960 Velocette Venom Clubman
1939 Velocette 350 Mac
1959 Velocette Venom
1998 Ducati 916
1978 Norton Commando 850
various other stuff
Re: Gold Star valve lifter/decompressor
moto8500 #794961 01/06/20 11:43 am
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The valve lifter can be be returned to it's correct orientation without removing the rocker-box.
Remove the spark plug, engage top gear to rotate the engine using the rear wheel. (you will not have sufficient control with the kick starter) Looking through the plug hole with a bright light, rotate the engine until the edge of the exhaust can be seen, and set the valve to max lift. It will then be possible to return the lifter cam to it's correct position.
If you have a problem seeing the valve through the plug hole, it can be easily seen by removing the exhaust pipe.
As to removing the rocker-box with the engine in situ, without removing the cylinder head, the studs can usually be removed by using a half nut as one nut, and double locking two nuts on the protruding thread.


Brian

Made In England
Re: Gold Star valve lifter/decompressor
Velo-Felo #795054 01/07/20 5:43 am
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Originally Posted by Velo-Felo


Managed to leave my head in situ and remove just the rocker box by taking the studs out. While they were out I cut a screwdriver slot in the top with a hacksaw to make it easier. I'm not keen on the idea of putting Allen bolts/screws in.



Okay, so you are good with removing and replacing the stud with a compromised slot sawn into the top. Tell me how that's a better situation.


Bill B...


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Re: Gold Star valve lifter/decompressor
Boomer #795057 01/07/20 7:07 am
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Not sure I'm understanding your question Bill? Better than what? If it's about not having to disturb the head I would have thought that obvious. If you are asking about cutting a slot in the stud end rather than using bolts then I believe its better to keep the threads in alloy via a stuf than bolts that can potentially have to come in and out a few times.
It's an easy job, the studs can be removed with slim or half nuts and via the slot can be screwed back in with a screwdriver. Seems a perfectly good way to do it to me and I see no compromise.


Current bikes:
1959 BSA Goldstar DBD34
1939 Velocette KSS. Mk2
Previous bikes:
1966 Velo Thruxton
1960 Velocette Venom Clubman
1939 Velocette 350 Mac
1959 Velocette Venom
1998 Ducati 916
1978 Norton Commando 850
various other stuff
Re: Gold Star valve lifter/decompressor
Velo-Felo #795059 01/07/20 9:01 am
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Originally Posted by Velo-Felo
. I believe its better to keep the threads in alloy via a stuf than bolts that can potentially have to come in and out a few times.
It's an easy job, the studs can be removed with slim or half nuts and via the slot can be screwed back in with a screwdriver. Seems a perfectly good way to do it to me and I see no compromise.




What is the difference of removing and replacing the stud versus removing the stud and replacing with a cap screw? Is not removing and replacing the stud disturbing the head? It's not like just because there's a cap screw you're going to take your rockerbox off every Saturaday night. I would think that obvious. I'm not sure I'm persuaded by the "not keen idea".


Bill B...


Boomer
Re: Gold Star valve lifter/decompressor
moto8500 #795062 01/07/20 10:50 am
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(What is the difference of removing and replacing the stud versus removing the stud and replacing with a cap screw? )

Studs and bolts are fundamentally different their installation and operation, especially into aluminium.
It is considered good engineering practice to use a course thread into alloy, when a stud is inserted it is not under load, and therefore there is no high friction forces on the thread.
The load is then applied with a steel nut, onto the steel stud, which in most cases is a fine thread.
Another advantage, a stud can use the entire thread available, whereas a bolt needs clearance, to avoid bottoming out.

The cylinder head retaining threads would soon fail without the bronze inserts.


Brian

Made In England
Re: Gold Star valve lifter/decompressor
moto8500 #795082 01/07/20 5:37 pm
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If mechanical issues were the only consideration, studs would be better than bolts. The clamping force of the nut pulls the threads of the stud against the Al without any rotational friction which is why wear doesn't occur with a stud. Also, more accurate torque values can be obtained because there is only the stretch of the stud plus the friction of the nut against the washer, whereas with a bolt there is also the friction of the threads against the Al.

However, the convenience of being able to (rarely) remove the rocker box without removing the head is an additional consideration. Although bolts do cause wear of the Al, remember that primary covers are removed and replaced much more frequently than a rocker box ever will be and the resulting wear on those Al threads typically isn't an issue.

As far as I can tell from reading what seem to be authoritative sources in books and manuals, studs only should be finger tight in the head. "Preloading" the studs in the Al, which many people commonly do by "double-nutting" them during assembly, does nothing to help. Given this, if the studs are installed finger tight they should be easy to remove even if in the course of tightening the nut the studs rotate slightly to jam them somewhat tighter into the Al. However, the amount of protrusion of the studs above the rocker box might require making a pair of thin "jam nuts" for their removal. While cutting slots to allow removal with a screwdriver instead of double nuts would work, it strikes me as a pretty crude thing to do to a Gold Star engine.

Anyway, it seems to me that either replacing the studs with cap screws, or installing the studs finger tight so they can be easily removed, are equally good solutions to the problem of removing the rocker box without disturbing the head. If I ever have to remove the rocker boxes from my Gold Stars I have to hope the rebuilder (me, in one case) was aware of the 'finger-tight' rule.

Re: Gold Star valve lifter/decompressor
Magnetoman #795154 01/08/20 11:05 am
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Originally Posted by Magnetoman
While cutting slots to allow removal with a screwdriver instead of double nuts would work, it strikes me as a pretty crude thing to do to a Gold Star engine.


Have to disagree.. a small slot accurately cut in the top of the studs so that the 'engineering integrity' of the engine can be maintained by retaining the original studs is in my book a lot less crude that fitting non standard bolts with the subsequent risk to the alloy head. Unless you particularly like having to take the head off at the same time. I do believe in keeping things as close to what the factory intended, they managed to get it mostly right! My Velocettes have very 'quirky' engineering in places but it does work. But each to their own.. the fact that these things are used on the road at all is the priority. I'm not sure how much longer we will be able to enjoy classic cars and bikes, make the most of it!


Current bikes:
1959 BSA Goldstar DBD34
1939 Velocette KSS. Mk2
Previous bikes:
1966 Velo Thruxton
1960 Velocette Venom Clubman
1939 Velocette 350 Mac
1959 Velocette Venom
1998 Ducati 916
1978 Norton Commando 850
various other stuff
Re: Gold Star valve lifter/decompressor
moto8500 #795173 01/08/20 3:53 pm
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cheers there are always ideas to overcome short falls . on a 66 matchless G80 that I had . matchless used a sleeve nut on the rocker box .It uses shorter studs in the head so that it could be lifted over the studs to remove. this should work well on the goldstar rocker box with studs in the head and nuts on the top of the rocker box. the only but is that the rocker box needs to drilled for the sleeve nuts or the use of step studs in the head. on a race bike this saves a lot of time in pits just saying hunter


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