Britbike forum Forums British Motorcycle specific Brands Bsa bulletin board Lighting no start

How worn are your idler bushes?
The idler bushes are quite small and even the slightest amount of wear will throw the timing out by a random amount

The Springs don't have to be the same size ,
You actually get a more complex Advance curve by using different
size springs .
1. A weaker or primary spring , able to hold the advance at idle rpms
and then
2. a slacker secondary spring that only comes on ... after the the primary spring is partially stretched.

... but here , we dont know whats really going on , or if this is even an ignition problem .
so stronger Springs will help hold idle rpms .

which Direction is the points cam advancing ?

Someone earlier brought up the point that you might have a Triumph AAU .
i dont remember if the correct Direction was ever verified.
BSA runs points run on a counter shaft , so the aau spins opposite the engine Direction .
... the points cam advances into its own Direction ... counterclockwise .
.

Looking at the pic it appears to advance the right way.
If its a 4 CA make the toy that Allan suggests, then fit EI.

I know it's confusing but I never had 4C point or AAU in.

And yes, it is a BSA CCW advancing AAU.

Andy Hingham: Idler bushes? That the idler gear runs on that the points are attached to?
All I can say is that all those bushes in the case looked real good. Lowish mileage engine I believe.

Could be the lighting, I only see one points wire. Looks quite unmolested.

I believe I've discovered the issue.
Multiple checks of everything did another compression test with a bit of oil.
No change and a bit below 90 both cylinders.
Leakdown test with my cobbled tool.

Hissing all around head gasket far as I can tell. Went from 100psi to 65psi in one minute.
I used an annealed copper gasket with some spray copper seal but after torquing the head once I took it off
briefly (forget the reason) and remember thinking I should re-anneal - but didn't!
Also torqued the outside bolts by feel. Really should get a tool to put a torque wrench on those.
Slight leak out the left exhaust pipe also.
Let's hope this is my no-start issue!

Comments welcome.

Ok, so I annealed the had gasket carefully and sprayed with copper seal stuff.
Also lapped the exhaust valves.
Now my compression is no better. Leak down test revealed air leaking out all the valves to some degree.
Hard to tell if its leaking at the head gasket.
This is interesting as I tested the head by inverting and filling with kerosene. Held the level for quite a while
but did eventually go down.

So what do I need to do? Remember I'm still fairly new at this.
Have the valve seats done at - a motorcycle shop? Buy new valves too? Springs?
Why didn't my lapping of the exhaust valves work?

Take the head & valve to a motorycle repair shop or a lawnmower repair shop
The kit used for A65's is the same as used for Briggs & Stratton ( plus 1/2 the other stationary engines ) .
Pick a shop that has lots of old machines for sale that they have repaired for resale.
If you have pulled the valves out of the head should be a 20 minute job at whatever they charge per hour.

You can do it yourself withthe Neway gear which is hard to make a mistake with and good enough for a normal street rider.
However the kit is not inexpensive so unless you are intending to this type of work regularly not an economic outlay .

valve lapping is not as easy as many would suggest and if the guides are not as good as they could be then getting an acceptable job is quite difficult.

So obviously the valves are A problem, the question is are they THE problem?
I would have expected that at 90psi there was enough compression to get you something, might run as rough as a bears arse, but i would have thought it would at least make an effort.

Have been watching this thread for a while and cannot get the timing out of my head. Are you absolutely sure that you have timed it at 34 BTDC and not 34 ATDC? i.e. you got the direction of rotation right?
Please don't ask me why this thought will not go away, I was a lot younger then.

Hissing around head? Mix a dish soap- water solution and wipe around to see if bubbling occurs. You will never find this problem if you don't follow exact procedures for each check. If you have precisely followed all steps, I would go back to the start. Do one thing at a time. i have read stories about proper annealing of gaskets and don't think many do it properly anyway. I do not even try, but I definitely use a torque wrench and tighten in proper sequence in steps. I also feel that the valves are good enough to run or at least give signs of life if all else is right. A lot of thing you have checked would keep from running at peak, but imo would not keep it from starting.

These old bikes can be frustrating at times. I feel your pain.

I didn't see here where you took Allen's suggestion to use a piston stop to find tdc for degree wheel. It's the only way to be accurate with timing and should not be overlooked considering the mountain of problems you're having. Also either didnt see or missed how you did your timing side gear alignment.

Thanks for the replies.
I have double checked most things so many times it's ridiculous.
I am well aware of the anomaly of the BSA points rotating clockwise and the rotor traveling CC. Definitely BTDC.
Funny, I have a friend of many years named David Martin who is a mechanic (ten car garage at home full on 60's muscle cars- all mint all running)
who thinks it should start as is too. He has 2 Harley baggers but has seen a lot.

I spent a long time getting float heights correct. More on this later maybe but don't want to turn this into a float height thread.

I don't know what else it could be but the valves and compression. Was actually a bit under 90 psi and as I said, on leakdown was hissing obviously
out the carbs and exhaust. Dropped from 100 PSI to 65 PSI in a minute.

Beach, when apart I used dial gauge to find my timing point, if you remember I have no usable notch in the flywheel so this is what I had to do.
A few posts back I included a photo of my dial gauge through the plug hole as I was double checking that.

Valve timing was simply lining up marks on the gears. Fine points of adjusting valve timing beyond me but I did check the valves opening and
closing points with degree wheel on rotor side.

Machine shops are rare around here and can be pricey. One gave me an estimate of $400 to do the valves and mentioned he thought maybe
would need new guides. (I don't think so) Only an estimate but in my experience you don't often get a lower price when a vendor puts out
a number. Kind of expensive, yes?

Oh, also, I have a decent torque wrench and now have the 15mm crow foot to do the nuts.

That's a lot for a valve job, imo. Maybe your friend could suggest someone.

Has anyone asked the obvious question?
Are the leads on the correct plugs? if the AAU or points plate have been off the bike it could be timed on the wrong cylinder. Try swapping plug leads

"I don't know what else it could be but the valves and compression. Was actually a bit under 90 psi and as I said, on leakdown was hissing obviously
out the carbs and exhaust. Dropped from 100 PSI to 65 PSI in a minute."

This sounds like you've already identified a major problem, whether it is the only problem who knows. Assuming the head gasket is sealing, and the leakage is not coming from there and being confused with valve leakage, then:
-Whether or not the guides are knackered, some or all the valves are not sealing during the leakdown test.
This could be due to tight valve clearances, bent valves or poor valve/seat contact surfaces.
Do you find the hissing in all the ports, or just some?

Try opening the clearances (silly big) and repeating the leakdown test. If the hissing still comes from the in/ex ports (note which ones) then the valves must come out, no question.

Even with worn guides/stems it is easy to get good sealing of valve/seat surfaces in a static test like leakdown, so you will have to check the guides/stems as a separate matter.
If you find the guides need replacement, that maybe something for an engineer, depending on your confidence/ability.

But getting the valves out, checking them and basic reconditioning is well within most folks scope. No need to spend $400 at this stage, IMHO.
Enough for now.

If the guides are worn it is better to get guide liners fitted. Less chance of developing a loose guide

It sure isn't tappet lash clearance. Leakdown is done at TDC compression. Valves fully shut.

Plugs are sparking on correct cylinder. Ask me again and I'll tell you the same.

Here's something. Valves spring free lengths are way off.
I believe should be

Outer: 2 1/32"
Inner: 1 5/8"

Mine are

Outer: 1 3/4"
Inner: 1 1/2"

Right, or are they??? That is what was being asked... are you certain they are fully closing?

Take a look at my thread here and see if that's what you've got: http://www.britbike.com/forums/ubbthreads.php/topics/776512/a65-progressive-valve-springs

Yes I am certain!!! Valve cover was off.

These outers do look progressive, don't they?
Does that make them OK?

Ordering new anyway.

Whether or not the springs are ok makes no difference to your leakdown observation.

Alright. I thought possibly weak spring could prevent valves from closing tight.
So why should or shouldn't I care about the springs?

You should care about the springs as well as every other part of the motor, but the immediate issue seems to be with valve/seat sealing.

The springs may or may not be ideal, but are unlikely to have much relevance to your leakdown observations.

They are good enough to check the seating of valves. The valves should have gone back in same position.

Well hopefully they will, but while they're out, now is the time for a little wiggling to see how floppy the valves are in the guides ( any more than about 10 thou head shake is worn) but more relevantly now is the time to examine the valve and seat surfaces.

If in any doubt it is time to try a little lapping with fine paste.

Then look at the surface of the valve, if it shows just one patch of grinding, the valve is bent.

If the valve is straight, continue with careful lapping to get a good contact surface, using the finest compound. Don't be tempted to use coarse to speed it up.
You should end up with something like a continuous smooth contact surface between valve/seat at least about 1/16+" wide.

By the sound of it the motor is now in pieces, but when you were trying to start it were you just kicking it or did you try a bump start, preferably down hill where you can get a bit of speed up? I my experience starting like that can get over a load of starting tuning issues (timing, mixture etc.) then at least you will know that the bugger runs, and all you have to do is find out why it wont start!