Author Topic: GB is not OK!  (Read 11618 times)

Online Greybeard

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Re: GB is not OK!
« Reply #195 on: 07.06. 2018 15:32 »
Is the timing out making your valves touch the pistons ?
Roy, I did wonder about that but I've removed the inner timing cover to check the marks on the gears.
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Offline RogerSB

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Re: GB is not OK!
« Reply #196 on: 07.06. 2018 15:41 »
I'm not sure if the valves *may* have slightly longer stems.
A10SR valves have a different pt no to the other A Group models but I don't know how they differ.

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Re: GB is not OK!
« Reply #197 on: 07.06. 2018 15:47 »
Surely if valves, push rods, followers etc are longer, it would only make a difference if there were no tappet clearance. As there is clearance isn't the problem elswhere?  Or am I missing something ?
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Re: GB is not OK!
« Reply #198 on: 07.06. 2018 16:10 »
G'day GB.
I just went back to page 1 and read for an hour! Beforehand you said with 30 on the tappets she turned over. Now with two head gaskets and 30 on the tappets she doesn't *????* The only thing I can think of is something has dropped into the cam trough and is jamming the cam.  *dunno*
Cheers
edit: or the key is missing on either the crank or cam pinion.
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Re: GB is not OK!
« Reply #199 on: 07.06. 2018 16:14 »
G'day GB.
I just went back to page 1 and read for an hour! Beforehand you said with 30 on the tappets she turned over. Now with two head gaskets and 30 on the tappets she doesn't *????* The only thing I can think of is something has dropped into the cam trough and is jamming the cam.  *dunno*
Cheers
Nope can't be that; the engine turns free without the head on.

I'm so tired of this that I may be making mistakes about tappet clearances. I'll get back to the problem when I've left it for a couple of days. My faculties may have returned by then!
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Re: GB is not OK!
« Reply #200 on: 07.06. 2018 16:18 »
see my edit ^^^
'51 A7 plunger, '57 A7SS racer now a A10CR, '78 XT500, '83 CB1100F, 88 HD FXST, 2000 CBR929RR ex Honda Australia Superbike .
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Re: GB is not OK!
« Reply #201 on: 07.06. 2018 16:18 »
Surely if valves, push rods, followers etc are longer, it would only make a difference if there were no tappet clearance. As there is clearance isn't the problem elswhere?  Or am I missing something ?
Tappet clearance is set when the follower is on the flat area, not when the cam is lifting the follower/tappet/valve.
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Re: GB is not OK!
« Reply #202 on: 07.06. 2018 16:21 »
...or the key is missing on either the crank or cam pinion.

Hmm, I'll have to check them. TDC does seem to coincide with a pair of rockers, 'rocking' though.
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Offline RogerSB

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Re: GB is not OK!
« Reply #203 on: 07.06. 2018 16:26 »
GB, in BSA Twin Restoration book it specifies for:-

356 camshaft:  Inlet open 42, inlet closed 62, exhaust open 67, exhaust closed 37.

334 camshaft: Inlet open 30, inlet closed 70, exhaust open 65, exhaust closed 25.

Are you timing it as before when you had the 334 fitted? Look at timing it as a 356.

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Offline RogerSB

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Re: GB is not OK!
« Reply #204 on: 07.06. 2018 16:34 »
In the same Book valve spring lengths for A7, A7ST, A7SS, A10, 1951 - 1962: Inner 1.531, Outer 1,875.

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Offline RoyC

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Re: GB is not OK!
« Reply #205 on: 07.06. 2018 17:19 »
In the same Book valve spring lengths for A7, A7ST, A7SS, A10, 1951 - 1962: Inner 1.531, Outer 1,875.

Is that the installed length ?
My bike is a 1958 A7SS
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Re: GB is not OK!
« Reply #206 on: 07.06. 2018 17:29 »
Thats the free length Roy in decimal. In inches inner spring 1 17/32" and outer spring 1 7/8".

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Offline chaterlea25

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Re: GB is not OK!
« Reply #207 on: 07.06. 2018 17:34 »
Hi GB,
I think I can see what the problem is??
First though, what shape groove is on the valve stems?
semicircular or a parallel reduced portion?
From your photos there appears to be too much valve stem protruding up from the valve caps
also the collets are not sitting far enough down into the caps
I had a thought earlier that maybe the top collar/collets were hitting the tops of the guides
I came across an A10 head where the components were mixed up and Super rocket valves and collets were fitted to
iron head valve caps, they do not fit correctly
The collets themselves maybe too thick??

If you take a valve cap and collets and assemble them off the engine will the collets hold the cap solidly without "rock"
The taper should hold the cap from falling

I am wondering now if this problem existed and contributed to wearing the reprofiled cam ????

John
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Re: GB is not OK!
« Reply #208 on: 07.06. 2018 18:30 »
Hi GB,
I think I can see what the problem is??
First though, what shape groove is on the valve stems?
semicircular or a parallel reduced portion?
From your photos there appears to be too much valve stem protruding up from the valve caps
also the collets are not sitting far enough down into the caps
I had a thought earlier that maybe the top collar/collets were hitting the tops of the guides
I came across an A10 head where the components were mixed up and Super rocket valves and collets were fitted to
iron head valve caps, they do not fit correctly
The collets themselves maybe too thick??

If you take a valve cap and collets and assemble them off the engine will the collets hold the cap solidly without "rock"
The taper should hold the cap from falling

I am wondering now if this problem existed and contributed to wearing the reprofiled cam ????

John

Wow, you guys are great; while I've been out for a walk with Janet and the dog you've all been scratching your heads on my behalf!.

The collets are something I will be checking.

What about Rogers idea about different cam timing? I guess if that cam requires different timing there must be a camshaft pinion to go with it. I'll check the parts book.
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Re: GB is not OK!
« Reply #209 on: 07.06. 2018 18:41 »
One thing I'll ask GB is if you can measure the length of your pushrods, if it's no trouble ?
Sorry duTch, I forgot about that but I'll be seeing the pushrods again soon and I'll try to remember to measure them.
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