Touchy Feely

[Mosin]

I realise that I am probably out on a limb here asking a load of grizzled old bikers, mechanics, engineers and the like to discuss feelings, but here goes....

I am pretty new to the whole classic bike scene but have recently done a lot of work on my A7ss and it now starts and runs pretty well. Or so I thought. Because I have been running it in after an rebuild I have not really been using much throttle or taking the bike over about 40mph. This has been fine. However, now that I have covered nearly 1000 miles, I am thinking about gradually opening it up a little and this is where my question lies.

The bike seems to be running sluggishly, particularly at the lower end of the rev range, and does not seem very willing to accelerate much past about 55mph (although I must admit I have not pushed it very hard). It also seems to be running quite hot - although it has never shown any sign of siezing on me. During the rebuild, I converted to Pazon electronic ignition and I am very pleased with that, but I am concerned that I may not have got it set quite right.

I have read dozens of threads where people talk about their bikes runing "slightly advanced" or running "excessively retarded" or whatever. My question is, how can you tell this by riding them? What does advanced or retarded ignition actually FEEL like when you are riding the bike? There is a certain amount of advance/retard adjustment on the pazon unit (I think about 20 degrees) and I have currently got it set in the middle of this, but I could do with knowing which way to rotate it in order to fix things, but I will only know this if I can establish whether I am (or more specifically, the bike is) excessively advanced or excessively retarded at the moment.

[MG]

Don't worry, we all have an emotional side when it comes to our bikes.  

IMHO the best way of telling whether ignition is set up properly is getting a cheapo timing strobe gun (25-30 Euros here). Mark one teeth on the crankshaft sprocket and make some marks on the inner primary cover with the degrees from TDC to maybe 40 deg BTDC accordingly and you can really see what the igntion system is doing at different revs and whether your setup is correct.

This is what I'm using:
http://cgi.ebay.co.uk/NEW-DRAPER-PISTOL-GRIP-XENON-STROBE-TIMING-LIGHT-52616-/290416446574?cmd=ViewItem&pt=UK_Diagnostic_Tools_Equipment&hash=item439e2b4c6e

Cheap and no means of adjusting the strobe timing, so nothing to go wrong

Ref feeling: Retarded ignition feels very much like you described it. Lack of power and an increase in exhaust temperature (ex pipes turning blue rather quickly).
Over-advanced ignition on the other hand causes premature detonation (pinging), which imposes extremely high stresses on all the engine components (rods, crank, pistons, bearings), finally leading to serious damage (worn bearings, holed pistons, broken rods/crank etc.). The pinging noise sounds like someone hitting a bell with a small hammer and occurs when accelerating and/or at high revs. At lower/middle revs the engine goes very well, but when you demand higher power at high revs (going flat out or accelerating uphill) it will start pinging.

HTH, Markus

[Mosin]

Thanks for the tips Markus. I have got a timing disk, but no strobe so it looks as though one of those is going to have to be my next purchase. However in the mean time I think I will try just advancing the ignition by rotating the Pazon unit a little... say 5 degrees or so, to see if there is a marked improvement in performance. It's a relatively easy job to do this and I can always shift it back again if necessary.

Simon

[groily]

Think that's a v good idea Mosin. Because frankly, where it's possible easily to fine tune by ear and experiment - which it is with an adjustable backplate like on  most electronic units - it's often the only way to get it just how you want, regardless of what the degree disc says. It's certainly how I played with the Boyer system on my Enfield twin (it just remains for me to strobe it to see what I actually ended up at next time I have the primary outer off). There are so many variables, but if it starts right, sounds right, pulls right, doesn't detonate or ping and doesn't overheat etc etc, it probably darn well IS right or pretty close.
Is also why I think Orabanda's slotted mag mod is one of the best ideas out there!

[Mosin]

I was so excited by all of this that I decided to finish work early to give it a go! I initially advanced the timing by five degrees according to the increments on the slotted backplate. I then took it up the road, but there was little recogniseable difference. I advanced it a further five degrees and though slightly harder to start, it the gave me a small improvement when taken out up the road. Finally I advanced it yet another five degrees (total 15). It kicked back more than usual on starting but once running seemed to be running much better. I am not sure if it is any cooler, but there was a perceivable improvement in performance and as far as I am aware no "pinking" even when I ran it up the local hill in top gear. I have now reached the limit of adjustment on the slots and any further adjustment is going to have to be obtained by re-setting the whole timing.

I'm going to have to get a strobe aren't I?

[muskrat]

G'day Mosin,
                 5 degrees are very large incriments when it comes to timing, and 15 from where you started is heaps. Yes, get a strobe. You should be looking at about 34 degrees full advance at about 4000 rpm.
Cheers

[mike667]

I was so excited by all of this that I decided to finish work early to give it a go! I initially advanced the timing by five degrees according to the increments on the slotted backplate. I then took it up the road, but there was little recogniseable difference. I advanced it a further five degrees and though slightly harder to start, it the gave me a small improvement when taken out up the road. Finally I advanced it yet another five degrees (total 15). It kicked back more than usual on starting but once running seemed to be running much better. I am not sure if it is any cooler, but there was a perceivable improvement in performance and as far as I am aware no "pinking" even when I ran it up the local hill in top gear. I have now reached the limit of adjustment on the slots and any further adjustment is going to have to be obtained by re-setting the whole timing.

I'm going to have to get a strobe aren't I?

yes - kickback is almost always a sign that your to advanced - as muskrat says 15 degrees from the start is a huge change - i bet you'll find that you won't need to pull out the unit and readjust the magnetic rotor - it will be somewhere between where you started and have ended up...

i have a pazon unit on my commando -  and find that a very small amount of movement on the plate makes a dramatic change in the timing by strobe....

also remember no matter how "on the mark" your timing is -  if the valves are not set correct and the plug gap too its all for squat!

[wilko]

You'd better pull off timing cover and check cam timing if nothing else works!

[Mosin]

A development... although not a good one....

This evening I bit the bullet and ordered myself a strobe off ebay as suggested. In readiness for its arrival, I figured I'd pull off the primary cover and fasten my timing disk to the crank using my SRM cush drive nut.

When I took the primary case off, I was surprised to see a couple of small bits of metal drop out. It turns out that they were formerly one of the rollers of a link of the primary drive chain. On close inspection, I also discovered that one of the other rollers was badly cracked and about to drop off too. I have never known this to happen to a chain before.

I removed the cush drive nut and spring and with the bike in neutral span the clutch. To my surprise the crank shaft sprocket immediately slid about 1/2" out along the crankshaft and sat there spinning perfectly. This suggests to me that the two sprockets are not in alignment and the excess pressure caused by this has caused the damage to the primary chain. It also might go some way to explaining the relatively poor performance of the bike....

To cap it all, I can't for the life of me find my parts book. Can anyone enlighten me as to whether there should be any shims behind this sprocket to keep the chain running true or something else that I am missing? 

[muskrat]

G'day Mosin,
                 yes there are shims to adjust the engine sprocker 67-2056/7/8 but these will not take up that much. I think you will find the g/box is scew-if (out of line with the motor). This often happens if the bolts have not been loosened enough when adjusting the primary chain. Back off the adjuster and loosen the bolts now push the box forward and back a couple of times then tighten them. Now spin it again and see where it ends up. Use a new chain.
Cheers

[bsa-bill]

I think there is also a spacer on the crank with a internal chamfer prt no 67-1138, is this in there ?

apologies if this is a bit obvious

All the best - Bill

[chaterlea25]

Hi Mosin,
I remember back to when you were dismantling the bike after the blow up and you had trouble with
removing the clutch centre!! so presmably you had to go and buy a new one???
There are a lot of absolute "shite" ones about
Some of them have even the scroll on the back for the sliding plate running in the wrong direction
Also the depth of the tapered hole for the shaft varies quite a bit
I know that BSA made different centres for different models to accomodate chain alignment
It can be a tricky problem to solve sometimes,

I normally trial assemble the primary drive without the inner casing fitted to ensure the sprockets are aligned using a straight edge, also check the fit of the clutch centre on the gearbox shaft, It has to be a 90% contact over the taper
If the centre is a poor fit and relying on the key for drive it will soon wreck the gearbox shaft
They are not that hard and can be turned or ground internally to move the clutch inwards a bit.

Next you have to check that the chain will not  rub off the back of the inner case, there is not normally room for a heavy duty chain there,and beware of industrial chain will self destruct in short order

If there is not enough clearance for the chain, the plate sandwiched between the crankcase and primary case can be thinned down or a new one made, or even use thinner or no gaskets just sealer!
Next, you MUST make a spacer or suitable washers to bolt the rear of the case to the frame without stressing it.

Let us know what you find as the work goes on
Regards
John O R

[Mosin]

I think I've got this one sorted. Firstly, the spacer which sits behind the cush drive and the shims which are used to adjust it were missing. (I've ordered replacement parts from Draganfly). To make matters worse, I then removed the clutch (after my problems with my past clutch I splashed out and bought a brand new four spring one from JB restorations which seems to fit and work very well. When I removed the clutch, I discovered quite a lot of scoring towards the back of the primary inner where the chain had obvioulsy been catching. I removed the primary inner and noticed that there is a sizeable gap between the rear mounting on the primary inner and the lug on the frame which it bolts to. When I assembled the inner I remember this and figured that since there had been no spacer there to begin with I would just use the bolt to tug everything into line. I have now looked at the parts book and realised that there should be a spacer (as mentioned by John O R) to fill this gap without twisting the primary inner whichis what had happened.

I originally bought the bike as a 'complete non-runner' and am now starting to realise that the P.O. had obviously cobbled it together as much as possible to make it look like it had been done, without paying too much attention to putting things back as they were supposed to be. Frankly I wish he hadn't bothered. Never again will I assume that just because something is set up as it was when I bought the bike that that is how it should be. Luckily I discovered the error before too much damage was done.

And to think that this started off as a thread about ignition timing... It's funny how one thing leads to another... Nothing is ever simple is it?

[chaterlea25]

Hi Mosin,
if the crank spacer was missing, I think I would be right in saying that the cush drive inner sleeve would have been rubbing up against the crankcase??
This obviously is not a good situation and could have ground ally away and into the main bearing??
The shims involved here are only for minor adjustments, I dont like the shims and make new spacers to the correct size
You cannot assume that parts supplied will fit and make everything work!

Assumptions are the mother of all f**k ups!!!!

Going back to my previous reply the only way to ensure correct alignmant is with a straight edge, I do this along the rear of the sprockets with no cases fitted, today out of curiosity I tried out 3 centre adaptors I bought at Stafford
last month, an original BSA 6 spring and 4 spring and one of the shite pattern ones that I bought for less than £20 to experiment on!! They all sat on the taper in different positions, about 3/16 difference in total, one fitting roughly halfway between the other 2

HTH
John o R

[Mosin]

Hi John

Thanks for the suggestions. I've just checked the back of the main bearing and amazingly it does not even appear to be marked! That's obviously a massive relief. I will certainly take your advice about lining up the sprockets with a straight edge. As regards where the clutch centre sits on the gearbox shaft, I suppose that it doesn't really matter wheter the two sprockets are a couple of thou one way or the other just so long as they line up and don't cause the chain to foul the chain case?

Cheers,

Simon