Valve timing

[woody123]

Hi my name is woody I am doing a 1954 Bsa a7 just putting the engine back together and put all the timing marks back points set the head is still off I have the push rods sat in position as I rotate the engine to just before tdc the left hand ( clutch side ) push rod is just coming up is this right it’s bugging me I read somewhere all push rods should be down hope you can help

[bsa-bill]

no I think your fine, see pic of camshaft, there's no point where all the lobes are flat together

[Greybeard]

Hi Woody. Welcome.
Please do not take offence but your post would be easier to read with some full stops

[Swarfcut]

 

 Woody... It depends whether the cylinder is on compression at TDC.  Here both valves will be closed, followers on the back of the cam. Both push rods down.   As long as the camshaft is located to the drive gear with the key in place and the timing gears are correct for your engine with the timing marks lined up OK, the job's a good 'un.    Crank pinion also locates with a key so is fixed in relation to the crank.

 Recheck the magneto timing while the head is still off....easy to measure piston height before TDC.

 Now tell us a little bit about how you came to our forum, over in the Introductions Section.

 Swarfy.

[chaterlea25]

Hi Woody,
The cylinder that is not on the firing stroke will have the inlet opening a touch before TDC and the exhaust closing
about the same amount after TDC

The only way to get it wrong (if my memory is correct) is if you have a mix of gears from long stroke and later engine type
??

John

[woody123]

Thanks for your help. I was just unsure about it. The bike was runner when i got it. I just stripped it to clean it. The frame has all been away for powder coating.I have starting to put it back together now. But before i put the inner and outer timing cases on i thought just ask.
ps sorry about the full stops

[Swarfcut]

Chaterlea John... Precisely what I meant that the timing gears are correct for the model. Early A7 Longstroke Idler Gear marks are 15 teeth apart,  the more familiar A10/A7 are 21. Or thereabouts...... like you, from memory. Crank pinion and cam gear are marked the same for early and later engines.

 Woody..... That ain't an  ordinary A7.  Looks to have alloy head.  Tell us more.

 Swarfy.

 Additional... View later posts for more accurate interpretation of timing gear markings.

[Greybeard]

ps sorry about the full stops

Thank you for not getting upset about my comment :)

[chaterlea25]

Hi All,
Swarfy, Thanks for reminding us about which gear is different 

Woody,
Are you sure about your bikes dating?
It looks like it has the cross over brake shaft swing arm pivot ?
54 would have the Gold star / B31 type single sided rear hub and rod brake

John

[woody123]

hi John well spotted.Just looked at the log book its 1955 CA12741 ENGINE CA2377. It might not be all correct but i will finish it of ok. One more thing did you notice the rocker cover just sat there. As i lower that down the springs slightly touch the case. Any tips on that i have'nt had the springs out

[chaterlea25]

Hi Woody
Usually the rocker box is threaded over one pair of valves and will then drop down over the other pair
I cannot see which and what studs are fitted to the rocker box?? that might make a difference
On Super Rocket 650's the castings are relieved as these have different springs, top caps and so on

John

[trevinoz]

Swarfy, better give that memory a bit of a shake.
The three L/S timing pinions are different to the later type.

[trevinoz]

Interestingly the inner primary case is the long chain shroud type.

[Swarfcut]

Trev... That's me screwed. My Longstroke basket case gears look the same as the later type, except for the idler gear. Do you happen to know the finer details so I can check if the pinon and cam gear are correct?

 Swarfy.

[trevinoz]

Yes, I have the details in front of me, they are probably on the Forum somewhere and I think that the info came from the Cheshire club.
The crank pinion has the mark one tooth left of the keyway instead of two.
The idler is 17 teeth instead of 21.
The cam pinion has the breather peg at 12 o'clock in line with the keyway and the mark is 14 teeth from the top instead of 15.
Good luck.
Trevor.