Hoping some of you will be able to help with suggestions. I'm now in Melbourne, Australia, after being in Singapore, with our M20. A problem I'd seen occasionally in Singapore was far more apparent when I went on my first big trip this weekend, 21st Feb, with the BSA Motorcycle Owners Association of Victoria, total of about 140miles for the trip, may a bit more, through some lovely roads on route to Ballan for Presidents Day held at the Ballan Vintage rally. There were some reasonably lengthy hills, not that steep, but more work than you'd get in little trips. For the most part I found that I couldn't use full throttle, I'd guess I could get to maybe 3/4 before the power would drop off, and less opening gave better results. Starting off this wasn't apparent, ie I could open up as much as needed, mostly that wouldn't be full throttle though, but sometimes it would be ,or at least close to that.

I'm assuming this is fuel starvation of some kind? I did make a brief attempt to see if partially closing the air slide made a difference, it didn't seem to. Starting was good, better than normal as mostly in Singapore hot starts were tricky, and I'd wondered, and still do, if the magneto has an intermittent breakdown, and may get it checked (a local firm can do that, the lady who does the winding and rebuild gave a talk at the last meeting, very interesting and informative). On the run she started fine on the Sunday run, the only remotely tricky one was starting for the trip home, which was more likely me being impatient and a little too much tickle.

I did manage to lose the carb bell mouth on the trip, it must have worked lose at some point and is now decorating a bit of the Victorian countryside!

So suggestions for what to check and what to rule out?

Thanks

Richard

email (option): dickie.bobbie@hotmail.co.uk

I had similar problem on a 100 mile journey from Cornwall once, and that was the two nuts holding the carb on had come loose and it was sucking in air, it was only when I had struggled home that I noticed the problem.

Rob

email (option): robmiller11(a)yahoo.co.uk

Maybe the mag is getting weak as it gets hot. In effect opening the throttle blows out the weak spark. Try closing the plug gap down to 10 thou and see if it improves. That at least will give you a pointer as to where to look.

Ignition timing set too retarded is a possibility as well...

It may be the mag if you are consistently experiencing trouble starting when hot...That is the usual symptom of the mag failing...(along with a weak, whitish spark when hot)..

Also check you have the correct main jet fitted...(a 170 for an M20)..Ian

email (option): ian@wright52.plus.com

If you are using an air cleaner there can be a variation in which main jet to use but I see you lost your bell mouth type so I take it you are breathing fresh air. If it goes fairly well up a hill it could be ignition timing retarded as Ian says. BSA singles should pull better if you retard it a bit with the lever when timing is correct when going up a hill but not for too long. I'd start with the checks Ian and others suggest and do the tappet clearances while you're at it.

I had this problem getting slower the further I went temporarily solved the problem with putting cold damp flannel on the mag for 10 minutes to cool it down until the bike was off road for the winter sent mag for rebuild

email (option): roger.beck@node6.com

Thanks for all the input, it's given me a plan of action, which hopefully will get me ready for the next big run! I think I'll try the following:

1) check timing, adjust if needed, plus replace and gap plug (may as well do that at the same time)
2) check carb for air leaks, I did a finger check for looseness on Sunday, but a second check will do no harm.
3) check the spark when cold - mainly as a reference, I'm not that good at spotting good from weak and normally just end up cursing when I get zapped.

I'll then need to find a suitable hill, not too far off but long enough to have to work harder to get up, and also devoid of traffic lights or junctions!

Test run up the hill, if the problem shows up then:

4) closeup the plug gap, and repeat the run - things shouldn't have cooled down too much in the plug change.
5) perhaps follow-up with a cold damp cloth - if I remember to plan that part too.

Review the results - if 4 and 5 are needed then it's time to ask Gayle to check-out the magneto.

I'll update with the results - unless I'm still cursing from being zapped....

Cheers

Richard

email (option): dickie.bobbie@hotmail.co.uk

You need to check the spark when cold..and then again when hot.

Usually when the mag is in trouble there will be a good spark when cold but a weak one when hot...

A strong spark is clearly visible and a blue colour...A weak spark is less strong and a whitish colour...

Gap the new (or existing) spark plug to .018"...New plugs are usually gapped to .025" or more...Also use a 'non suppressed' plug cap...

Set the points gap on the mag to the standard .012"..Remember that an incorrect gap here will itself affect the timing...

It would also be an idea to check the tappet clearances and the setting of the valve lifter as mentioned in previous posts.....Ian

email (option): ian@wright52.plus.com

At 3/4 throttle and above you are running on the main jet.
If the main jet has fallen off you et these symptoms.
Bike will run fine at idle and up to 3/4 throttle when it will start to 8 stroke and belch black smoke as it now has a 1/4" main jet which is a wee bit rich.

A failing magneto will generally run bad at all revs.

A leaking carb flange will run way too fast at idle if at all due to lean running conditions and at higher revs will overheat and become apparent to the nose & legs.

email (option): bsansw1@tpg.com.au

A hill. in Melbourne , right, you willbe lcky to find on at all unless you take a trip to the dandnongs.
OTOH westgate bridge after 10 pm when all good country towns folk are safe at home might work for you

email (option): bsansw1@tpg.com.au

We've got plenty of steep hills here in Melb Trevor don't you worry about that.

Ha - now I'd thought of Westgate too, it's very handy as I'm on Southbank. But a trip towards the Dandenongs could be nice, as I'd combine with a look at Puffing Billy :-) The route out to Ballan was perfect, but that's a day trip all on it's own! I'll pull the carby apart and check and clean (apart from the float bowl that is...see above for why), as maybe the main isn't right. I'm looking forward to the weekend now :-)

email (option): dickie.bobbie@hotmail.co.uk

'But a trip towards the Dandenongs could be nice...'...

Keep away from there in the winter...A freezing wind blowing round the Dandenongs can be bloody uncomfortable... ...Ian

email (option): ian@wright52.plus.com

They do say that the wind blows cold around the 'Trossachs'

Ron

email (option): ronpier@talk21.com

Hi Richard,
Your not far from me in Kensington.

Hiya Matt

We'll have to organise a meet at some time in that case. What bike(s) do you run, are you in the BSAMOA, drop me an email

@Ian - we've a little way to go before winter arrives here, so I should be safe

Richard

email (option): dickie.bobbie@hotmail.co.uk

Well my maternal grandmother lived in Harrietville and when she moved to Sydney brought her push bike with her but she almost never rode it because she thought that Sydney was just too hilly.
Last sunday we went for a little 310 mile ride that included a 1 in 3 climb up to Saddleback mountain lookout, now that is a hill.
Unfortunately it was also too good for the M20 cush drive having now fixed the clutch so it no longer slips, the cush skips over the cam lobes

email (option): bsansw1@tpg.com.au

??????
How did you go there ?
Via Myrtleford ?

That M20 of yours must need a lot more work than you are letting on.
You really should swap it fr a faster machine, now I have this nice little C 10 in the shed .
Seriously you need to get in some practice because in April you will have to ride nearly twice that distance to Newstead which from Southport is about 1/2 the distance we ride from Walla Walla in about 2/3 of a day depending how long we stay in the pub the night before.
And I am still hard put to remember any hills on route, perhaps a few along the Campasie river.

Then in October you need to ride up to Bogan Gate, if the chook house boys are going again on their bantams and C 10's they might let you tag along.

You really need to get out of that postage stamp pretending to be a state south o the border

email (option): bsansw1@tpg.com.au

Ha, thanks Trevor,

Yes, I've some practice to do for sure. Bessie will be fine for the ABR, I've a nice Long list of checks, I just need to get them done asap in case they end with "rebuild mag"!

Still it's going to take me a while to get the scale of Aus in my head. The trip back on Sunday was lovely, and as I only had one reasonable hill, even Bessie's current weakness wasn't a hassle. It did remind me I need to think about petrol stops though, the clock had over 130 miles showing when I reached a station on Doherty's Road. Mind I had a can to hand if I had run out :-) the Long open spaces are lovely though, and somehow felt like they were meant for a slow plod :-)

Think I'll practice around our "little" postage stamp before going inter-state :-)

Cheers

Richard

email (option): dickie.bobbie@hotmail.co.uk

I will be looking for you.
My M20 is on the list of members bikes so I should not be hard to find.
We generally camp near the fence between the dunnies & the camping grounds.
If you are partial to fermented grape juice that is red in colour and are going via Heathcote then stop into the cellar shop, very worth while if one perhaps should be that way inclined

email (option): bsansw1@tpg.com.au

Hi Trevor

Thanks for the tip about the red stuff, Amanda will appreciate that, and she’ll most likely be driving over in the car so that would be an attractive put-stop!

I’m just back from a test run, and a film in Yarraville, after working my way down the list of things to check, clean and adjust today. So here’s the report.

1) Plug – the original, Champion L86C, was gapped a little wide, but was sparking ok. I swapped for a replacement NGK B6HS. The spark seemed a little stronger, but see below also.
2) Carby – starting by checking fuel flow, to the main jet from the float chamber, that was fine, filling more than ¾ of a jam jar in less than 30s. The jets were clear, the main correctly seated, not lose. There was a bit of sediment in the traps under the main jet and at the fuel inlet, but not much.
3) Points – a little pitted and perhaps a little wide. The points assembly wasn’t actually lose, but could be moved back and forth several degrees. I noticed that when I undid the points / spring. I’m not sure if there should be movement, but I made sure when I reassembled that had the points tight and had them position to the anti-clockwise end of this movement, on the basis that and drag would tend to keep it there – not that I think they were lose enough for that, but it means I’m not sure about the timing, see next! Spark seemed nice and strong, maybe a little stronger than the start of the work.
4) Ignition Timing – as noted above, the movement possible from the points assembly and my uncertainty about where they were at the start means I don’t know if the timing was right or not, I made a check before adjusting and that showed the points opening almost at TDC, but that could mostly have been the movement in the points assembly. Anyway, when I’d finished it was at 7/16 BTDC and therefore far more advanced that the initial check. I did a final check on the spark before putting the plug in. It seemed as if the spark with the B6HS was intermittent, I swapped the L86C back and that looked better, but in the interest of experiment I kept the B6HS in. Oh, before I forget I’m glad I bought two of them, the first one you couldn’t undo the top to attach the HT lead (I don’t have a plug-cap, just a nice copper lug) – after several attempts the whole top unscrewed from the plug ceramic! That plug is now in the bin, I don’t think I’d trust it.
Unexpected extra rear wheel – I’d spotted what sounded like a lose chain at the end of the run last weekend, turns out the rear wheel had moved on the nearside and the final drive chain was slack. The wheels had to come out for the road-worthiness inspection, so perhaps it just wasn’t tightened enough after that. I’ll keep an eye on that on the next run. Anyway gave me an excuse to put the correct relined shoes in to replace the temporary slightly narrower ones that were needed for the road-worthiness test.
Test Run
First Start – a very poor start, took about 10 to 20 kicks, I was getting hot and on the verge of pulling the plug out and putting the L86C back. She almost started on the first kick, but didn’t quite catch and then noting until that last kick.
Run-out – I went out over Westgate Bridge, that’s a bit of freeway and a reasonable climb to the top of the bridge. Speed limit on that was 80km/h today. I had to back-off at one point as we were doing 55/60 mph. Bessie pulled cleanly and strongly the whole time, holding 50mph up the bridge. I used full throttle as long and often as possible, and ran on to Williamstown before looping back to Yarraville to meet my Amanda for film and food.
Second Start – second kick, pretty perfect. About 3-hours after the arrival, so cold start like the first one, only with very different results.
Run-back – no issues, this time I took the slower roads to start, coming back through Footscray. The road through the docks is a little faster and has a small bridge before you enter the city. I grabbed full throttle in all gears away from each set of lights, feeling like a teenager and most likely looking like a prat! Bessie didn’t miss a beat and ran very well.
Conclusion – well seems good, but with the first poor start I’m not convinced that there isn’t an issue still with the magneto. Or maybe that was sulking and wants its L86C back. We’re off to the Grampians in a few weeks (me on the bike, Amanda in the car) to join in part of the BSA rally over there. That’s about 260km each way, so I’ll see how she runs. I think I’ll give Gayle at Blue Spark a call to see if she’d be able to check out the magneto and get it back to me before the ABR in April – that way I’ll know for sure if all is well with the sparks!

Thanks for everyone for the input, suggestions, comments, etc.

Cheers Richard

email (option): dickie.bobbie@hotmail.co.uk

I run BP5Hs in my M20 I fing the B6's s little to cold.
Being a side valve piston clearence is not a problem.
Don't know the code for projecting electrodes in Champions is.

Australia is a little different to the rest of the world as we have no specifications dictating what "fuel" is. Any mix of semi flamiable hydrocarbons which contain less than the prescribed maximum amounts of Pb, Cu, Zn & Cd, which burns with less than the prescribed amount of ash and meets the required octane levels can be sold as "fuel".
So tuning can be interesting and I am yet to get the same mileage from any 2 tanks of "fuel".
A lot of what we get out of the pumps is litterally light fuel oil with a hand full of aromatics thrown in so the engine can start.
Much of this is conductive at compression pressures and will coat your nice new plug which if it does not fire first up will go bad right out of the box. Thus the hotter plug.

A thou of gap at the points is 2 deg of advance/ retard at the crank, so being a little out with the points can make a big difference to the timing.
And I do hope you remembered to set the timing, cable tight on full advance.

Some nice riding in the Grampions but not my favourite piece of the postage stamp as 3 of the 5 times we went there the rain was so hard and the wind so strong I fell off because I could not go fast enough into the storm to maintian balance.
Ask the boys about the rally where the bon fire floated away down the creek or the one where the dunny trailer did the same thing, full of people whose tents had washed away ( sunny Australia Har , har, har ).

And it always rains at the ABR so bring some "Pommie riding gear".
A part of the charm of the event and keeps the morons at bay.

email (option): bsansw1@tpg.com.au

Hi Trevor

Ah, that's something I hadn't taken into account. I seem to recall some other discussions on the forum on plug temp ratings. I'll see how the B6HS goes along, but keep in mind a B5.

I may have to cross my fingers for next weekend as I donated my wet wether gear when I left the UK. In Singapore I just put up with getting wet, happened a few times, but you dry out and it's warm. That approach won't work here, if I get time I'll grab a one piece oversuit, but I know how time gets gobbled up! If I believed the forecast I've a 20% chance of rain, those odds aren't too bad :-) I'll have to sort waterproofs for the ABR though, that's late April and I think the odds would be too risky by then ;-)

Cheers

Richard

email (option): Dickie.bobbie@hotmail.co.uk

Forget the standard plugs and go for the P so a
BP5HS
or a
BP6HS

email (option): bsansw1@tpg.com.au

Hi Trevor

Ah, project to be less prone to fouling. Ok, added to list.

How about the fancy iridium jobbies, have you tried one?

Cheers

Richard

email (option): dickie.bobbie@hotmail.co.uk