GB is not OK, again!

[Greybeard]

As I said before, an ispiration.

Perspiration more like!

[Greybeard]

I am so infrequently right when it comes to these long-distance diagnosis guessing games, could I be forgiven for beaming just a little? (Hmm? What was that thing they said comes just before the fall?)

Well, minimally, the rocker covers need to come off for a look-see. I know this is nearly impossible after all the chatter about it, and I don't want to offend by even thinking to mention it, but could it be the sound made after a lip-riding pushrod finds home 10 miles in?

Richard L.

Give the man a cigar!

[chaterlea25]

Hi GB and All,

Glad to hear the BSA is running again,
I am still confused as to why the tappet adjusters sit like the are??

On loose guide's 
A few weeks ago I was asked to look at a cast iron A10 head, it had been fitted with phosphor bronze guides 
The valves were very tight in the guides! I got out a 5/16in. reamer and went to wind it through the guide
the guide moved as I pushed in the reamer 
The PB would have expanded more than iron causing the guide to squeeze in on the valve stem
New CI guides and valve seats plus some new fins added and its back in service

While I was reassembling the cases with the new camshaft I noticed there was about a 1/16", 2mm of endfloat. I found a thin washer to put behind the pinion but removed it when I read that the breather cork controls endfloat.

I took a minute today (away from the HD marathon  )to go and check the spare crankcase and cam/gear that's fitted
I poked some feelers between the cam shoulder and the timing side bush, a .4mm feeler (16 thou) fitted in
by sliding the cam pinion in and out this seemed a lot (click ,clack)
From memory when I built other A10 engines camshaft endfloat is negligible

John

[chaterlea25]

Hi GB

Give the man a cigar!

  and all I got was the offer of a kiss 

John

[RichardL]

Give the man a cigar!

I'd love to have a cigar with you, and happy to buy. Regarding your offer to John, you're on your own.

Richard L.

[duTch]

 

Quote

    ..... whats with these hole up the middle all about ....


 Fairly sure my old ones that were in the engine when I bought it in ~'77/8 were like that- maybe they're a Plunger era thing

 Found my old Pushrods and they don't have holes in the ends- must've been thinking of something else, maybe an old Holden engine with hydraulic lfters

 GB- I hope that all works and the Pushrod Gremlins have found another home (or even better to have become extinct)

[Greybeard]

and all I got was the offer of a kiss 

Here you go. Pucker up!

[RoyC]

Just a thought on your adjusters screwed out too far. Are your gaskets on the thick side ?

[Greybeard]

Are your gaskets on the thick side ?

They are not Roy. I have the normal paper gasket under the cylinder block and a solid copper head gasket.
The exhaust tappets are adjusted normally. It's only the inlets that are odd.

If both inlet push-rods are bent that could explain the problem, but, while I was last holding the pushrods they were straight and I don't see how they could have been bent while the bike was on the bench. Also, as both inlet tappets are screwed down to the same level, it seems unlikely that both pushrods would bend to the same amount.

Another possibility is that the inlet cam followers are slightly shorter than the exhaust ones; unlikely, as they are high quality SRM items.

What else? A problem with the camshaft? Seems unlikely.

I've just gone to the shed to check that I didn't put two of the duff followers back in again! Come on, I bet you'd considered that as a possibility!

[RichardL]

Maybe SRM made the intake pushrods a tiny bit shorter than original. Why, no clue. Wild-*ss guesses: by accident; accommodate higher intake lift cam without hitting the rocker cover; (out of ideas).

Richard L.

[Greybeard]

Maybe SRM made the intake pushrods a tiny bit shorter than original. Why, no clue. Wild-*ss guesses: by accident; accommodate higher intake lift cam without hitting the rocker cover; (out of ideas).

Richard L.

But I've been using those push-rods for years! Admittedly, all tappets needed to be screwed well in but I put that down to the reprofiled camshaft that I had.

[Greybeard]

I've had an epiphany.  Due to the wrong valve collets jamming the engine I reckon I've managed to bend both Inlet rocker arms  ; it's the only likely explanation of the extreme tappet adjusting issue.

Thoughts?

When I can face another strip I'll be investigating.

[RoyC]

I've had an epiphany.  Due to the wrong valve collets jamming the engine I reckon I've managed to bend both Inlet rocker arms  ; it's the only likely explanation of the extreme tappet adjusting issue.

Thoughts?

When I can face another strip I'll be investigating.

However unlikely, it does look like the most plausible explanation, having ruled out the push rods, cam followers and gasket thickness.
With the high lift cam, the adjusters should be further out, not in.

[duTch]

 

.....With the high lift cam, the adjusters should be further out, not in.

 I know I'm a bit mechanically dyslexic as well, but as the valve-lash is adjusted when the lifter is on the base circle (fully closed), I'd expect no change unless the base circle is different 

[RoyC]

.....With the high lift cam, the adjusters should be further out, not in.

 I know I'm a bit mechanically dyslexic as well, but as the valve-lash is adjusted when the lifter is on the base circle (fully closed), I'd expect no change unless the base circle is different 

Of course, you are quite correct duTch.
If you are mechanically dyslexic, I am mechanically confused. 
That poses another question. Is the base circle on the new cam the same as the old cam ?

Edit - Could a std. cam become a high lift cam just by reducing the diameter of the base circle ?