Author Topic: Rocker box  (Read 855 times)

Offline Derek Wrighthouse

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Rocker box
« on: 03.07. 2016 17:23 »
Hello just refitted the rocker box on my 1961 A7SS  I have checked that the push rods are  correctly located in the rockers ( can't see anything have To, go by feel) checked it 6 times all seems ok, but bike will not start.

The valves work fine when turned over by kickstart. Query, is it possible that push rods are not in right place even though valves work fine.

Offline TT John

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Re: Rocker box
« Reply #1 on: 03.07. 2016 18:53 »
I'd check to see if you have a spark first, I really cannot see you getting the push rods in the wrong place, I take it that you readjusted the tappets correctly before trying to start it. *wink2*

Offline bikerboy

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Re: Rocker box
« Reply #2 on: 04.07. 2016 00:26 »
Its effectively impossible for the push rods to go into the wrong cups they just wont physically fit

Online RichardL

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Re: Rocker box
« Reply #3 on: 04.07. 2016 14:21 »
Also, it's possible for the bottom of a pushrod to ride the edge of the cup in a lifter. This shows up as an adjuster that seems too far unscrewed. You can check this after dropping in the pushrods by being sure you feel some suction when trying to pull them up a bit from the oily lifters. As for seeing inside, I use a small-diameter, telescoping-type mirror. A bit fussy to get into position, but gives peace of mind.

All that said, it's pretty hard to guess at the cause of not starting without knowing the full extent of the rebuild and if it was running well before the head/rocker work.

Ricard L.
Plan on signing up for the world-wide 2017 DISTINGUISHED GENTLEMAN'S RIDE on September 30, 2018. Watch website at https://www.gentlemansride.com for details.

Online RichardL

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Re: Rocker box
« Reply #4 on: 04.07. 2016 15:04 »
Have you double-checked plug wires right way around? I think most here (certainly, I) have made this mistake at some point.

Richard L.

Plan on signing up for the world-wide 2017 DISTINGUISHED GENTLEMAN'S RIDE on September 30, 2018. Watch website at https://www.gentlemansride.com for details.

Offline East_Coast_BSA

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Re: Rocker box
« Reply #5 on: 06.07. 2016 05:16 »
You've probably looked already, but have you reset the lash?  When I change out my rocker gaskets or take the box on and off for head re-torque, I'm really careful about the lash.  If mine gets tight, the bike can be a real bastard to start.  It's very finicky about this.  If the lash is correct, first kick every time hot or cold.  If it tightens up, you can kick like crazy and it won't even pop. 

Offline mugwump

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Re: Rocker box
« Reply #6 on: 07.07. 2016 19:50 »
Can somebody explain/translate 'Lash' please.

60'Matchy G12
58 AJS 18s
58 Ariel Huntmaster]

Online muskrat

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Re: Rocker box
« Reply #7 on: 07.07. 2016 20:28 »
Lash = tappet clearance.
I have an A7SS twin carb head on my Cafe. She needs 10 and 12 thou to run right when hot.
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Offline mugwump

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Re: Rocker box
« Reply #8 on: 07.07. 2016 21:03 »
Thanks, never heard the term lash before. I was given an endoscope ( plugs into lap-top ) and like many gadgets, one wonders how we got by before. Yes, I know we did get by but like most things once we get used to new gadgets they become invaluable. I found that it was possible for the pushrod to sit just on the edge of the follower cup on several bikes and the e'scope allows you to see exactly whats going on. Useful for examining cylinder bores and other parts too.

60'Matchy G12
58 AJS 18s
58 Ariel Huntmaster]

Offline duTch

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Re: Rocker box
« Reply #9 on: 08.07. 2016 10:06 »
 Hey Dezza- Derek Wrighthouse, who started this thread;  *welcome*, but I'm surprised that the newbie papparazzi haven't busted you for sneaking in unannounced  *smile* now they maybe do their stuff
Started building in about 1977/8 a on average '52 A10 -built from bits 'n pieces never resto intended -maybe 'personalised'
Have a '74 850T Moto Guzzi since '92-best thing I ever bought doesn't need a kickstart 'cos it bump starts sooooooooo(mostly) easy
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Offline Rocket Racer

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Re: Rocker box
« Reply #10 on: 18.07. 2016 02:31 »
Hello just refitted the rocker box on my 1961 A7SS  I have checked that the push rods are  correctly located in the rockers ( can't see anything have To, go by feel) checked it 6 times all seems ok, but bike will not start.

The valves work fine when turned over by kickstart. Query, is it possible that push rods are not in right place even though valves work fine.

I usually take the plugs out, jack the bike up in 4th gear so I can rotate the motor readily. Usually i can get a finger onto each valve rocker and tell its seated.
If the motor can be rotated and the valves are opening and shutting and have the correct clearances for your cams, then all sounds good and you may have to ponder other options like having the plugs connected to the wrong cylinders
Yes we like photos of bikes and an intro  *welcome*
A good rider periodically checks all nuts and bolts with a spanner to see that they are tight - Instruction Manual for BSA B series, p46, para 2.
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