The BSA A7-A10 Forum

Technical => A7 & A10 Engine => Topic started by: renos-a10 on 06.03. 2012 07:51

Title: A7 SS 500cc (timing)
Post by: renos-a10 on 06.03. 2012 07:51
 G'day all ,

 What about A7 ss timing ? is the same for a10 ( 33 degrees ) ?
Thanks
Renos
Title: Re: A7 SS 500cc
Post by: beezermacc on 06.03. 2012 08:01
SRM recommend 35 degrees - 5/16" BTDC for alloy head models. This also takes into account the cr4ppy modern fuel combustion properties. This setting seems to work fine on my A7SS.
Title: Re: A7 SS 500cc
Post by: renos-a10 on 06.03. 2012 10:56
Thanks Beezermacc.
Also what about A10?

thanks in advance
Title: Re: A7 SS 500cc
Post by: beezermacc on 06.03. 2012 18:08
All iron heads and low or flat top pistons - 33 degrees - 9/32"
All alloy heads and higher comp pistons - 35 degrees - 5/16"

Taken from technical section of SRM website.  Worth a look.
Title: Re: A7 SS 500cc
Post by: Dunney on 10.04. 2013 18:12
Hiya chaps

Newbie to the forum here.

I don't think I have ever managed to get the timing right on my 60 A7ss.  How do you measure it?  I use a digi vernier gague.  I remove the tank so that vernier can stand on the vertical, get TDC, zero the unit and wind it round (not back) and then set at 5/16th.  I have tried timing it to 1/4 BTDC as well and it still feels sluggish and makes rubbish power as if it is retarded.

What am I am I doing wrong?  The valve timing is correct, just checked it as I had the inner cover off to change the cork breather gasket. 

I have had a love hate relationship with this bike of over 20 years and in that time it has never been the bike I had always hoped it would be.

Suggestions welcome.

Dunney en France
Title: Re: A7 SS 500cc
Post by: bsa-bill on 10.04. 2013 19:20
Hi Dunney and welcome

best to introduce yourself and give us nosey folk a little background about yourself and bike, but you can do that when your ready

Getting timing with a digital vernier is something I hadn't though of, I think most of them are accurate to about 1% which while good for most things for timing 1 degree out in 360 could make a difference when coupled with the same 1 degree out at TDC plus getting TDC itself can be problematic.
You seem to have the method perfect so I would suggest you try to get TDC with a wood stick, mark it when TDC comes around clockwise and again anti clockwise, you may find a difference, split the difference and then time the engine as you did before.
If you happen to have a dial gauge then they are a good bit better for assessing TDC.

Best of luck with it and let us know how you get on, could of course be something other than timing but best try that first
Title: Re: A7 SS 500cc
Post by: chaterlea25 on 10.04. 2013 21:56
Hi Dunney
Welcome  *smile* *smile*

The only "perfect" solution is an accurately set up degree disc and a stroboscope, that way you can also easily see if the timing varies between cylinders
Is you SS manual advance? a work out auto advance will rob a lot of power due to poor advance control

HTH
John
Title: Re: A7 SS 500cc
Post by: muskrat on 11.04. 2013 10:18
G'day Dunney welcome to the forum.
                                                 Do a search for ignition timing, search button next to home, help. Lots of info there.
I do as John suggests. I also made a plug to screw into the plug hole that touches the piston at the desired distance from TDC
See http://www.a7a10.net/forum/index.php?topic=6011.msg41207#msg41207
Go to Bikes, pictures, members and give us an intro.
Cheers
Title: Re: A7 SS 500cc
Post by: Dunney on 11.04. 2013 11:12
Thanks for your thoughts guys.  I should have said that it has a manual A/R facility.  Have never tried to strobe it.  The idea of having to take the primary drive apart as well as the timing side just to set the timing has never appealed to me but perhaps I should.

Can you hear the groan from here!

Dunney
Title: Re: A7 SS 500cc
Post by: Topdad on 11.04. 2013 12:06
Hi Dunney, everything you and others have said is spot on but can I ask the obvious but sometimes forgotten bit ,thats the points. I always take the points plate out and strip clean and flatten the contact area then check the keyway and clean it finally set it accurately to 12 thou ( i think , see perfect recall !! however I'm confident someone on the forum will correct me) . Now the technical bit after you've set the timing and locked the auto advance ,  insert the ubiquious fag paper between the points turn mag until the paper just starts to move and put the advance cog on and tighten, I can honestly say that by using the stick as per Bills post ( I use a pencil ) I've never had an issue with timing ,my present A10 starts and runs cleanly even when left for months , as mine was last year and came to her last sunday and she started 3rd kick after 6 wks of total inactivity, to sum it up wheather you use the tech method or old way just go slow and steady ,recheck after you've finished and continue until you are happy ,the very best of luck, regards BobH
Title: Re: A7 SS 500cc
Post by: Zen Up 67 on 28.04. 2013 00:04
I used a precision knitting needle through the plug 'ole on my A7SS.

It honestly started first kick after a 30 year rest in pieces and ran like a dream from then on!

I know...... what a *~~##" miracle!

Big Dave never got over it!! (He swears by Triumphs)
Title: Re: A7 SS 500cc
Post by: bikerboy on 01.05. 2013 00:39
Talking of checking timing a mate of mine has just bought one of these and says it is the bees knees

http://www.ebay.co.uk/itm/Top-Dead-Centre-Indicator-Indian-Harley-Norton-BMW-Honda-Suzuki-Yamaha-Kawasaki-/171022692334?pt=Motorcycles_Parts_Accessories&hash=item27d1bf2fee

I was tempted but dont need to now he has bought one  *smile*
Title: Re: A7 SS 500cc
Post by: bsa-bill on 01.05. 2013 12:13
Quote
I was tempted but dont need to now he has bought one  smile

Berkshire's a bit distant from Northumberland Bikerboy or I would have joined the Queue,  *smiley4*
It's brilliant though it's a dial gauge on a plug thread, think I'm swayed
Title: Re: A7 SS 500cc
Post by: Topdad on 01.05. 2013 13:01
Hi Bikerboy, looks very nice ,has your mate tried it yet and if so how did screw in , compactable thread with our old iron /alloy heads.
Going to show my ignorance now by adding  I've never thought about plugs ie threads etc they were.....well just plugs ,so what thread are they ,i'm sure someone will put me out of my misery regards BobH
Title: Re: A7 SS 500cc
Post by: muskrat on 01.05. 2013 14:17
M14 x 1.25 mm Bob.
Trouble with the TDC tool is it's for finding TDC! If you use it to find 5/16" before TDC it will be wrong due to the angle of the plug hole. Too late at night to do trig calcs now, but I think someone has posted the results, and that would only work with flat top pistons.
Cheers
Title: Re: A7 SS 500cc
Post by: Topdad on 01.05. 2013 14:34
Thanks Musky, that confirms it I'm sticking with my high tech pencil !! cost 25 p regards Bob
Title: Re: A7 SS 500cc
Post by: bsa-bill on 01.05. 2013 18:20
Quote
and that would only work with flat top pistons.
Hi Musky - do you mean by those words that the tool would not work because the shape of the head would jam the rod in the tool I wonder.
I reckon as long as the thing goes up and down then the shape of the piston is irrelevant, take your point re the angle but that is calculable (  and probable well within the tolerance of my eyes and a pencil mark  *smiley4*).
I have used a dial gauge on pistons and the big advantage is that it will show movement right upto TDC and down again as opposed to my experience where my to eyes it appears the pistons don't move for a short period before and after TDC, hence the primary chain method of marking the travel at this point and dividing it.
Title: Re: A7 SS 500cc
Post by: muskrat on 01.05. 2013 20:35
 G'day Bill. With high tops (like I use *grins*) it adds another angle. As the piston moves up the tool point will move outward and also down the crown. You can imagine if the angles are a particular way the piston movement would not register on the dial.
Cheers
Title: Re: A7 SS 500cc
Post by: a10gf on 01.05. 2013 20:53
^^^ see my anti-angle tool (http://www.a7a10.net/forum/index.php?topic=368.msg10533#msg10533)  *smile*  at least works good on flat piston.
Title: Re: A7 SS 500cc (timing)
Post by: muskrat on 02.05. 2013 05:10
As long as the "tool/measuring device" is vertical it would work on any piston.
Cheers