Non-starting Classic

[MikeBristol]

Hello all,
Was out on my Classic a few days ago, seemed pretty normal though perhaps not quite as smooth and even as usual. At next start attempt (full choke at first), it started and revved to about 3,000, but when the choke was pushed in a bit slowed down and faltered before stopping. Same at next attempt, then next time not starting at all. Has fresh fuel, and my spark tester shows sparks at both sides, though a bit weak on the left-hand side. No spitting banging or any other sign of life. It's a low mileage bike with excellent compression. I will change the plugs tomorrow but doubt this is the issue.
What to check next? How could choke or other carb adjustment have suddenly changed to produce this effect?
Not used to SU carbs, and not wanting to fiddle and make anything worse!
Anyone in Shropshire area fancy a look? Considering sending it to Andover for other work, but there's perhaps a lack of expertise there now?
Thanks for any ideas, Mike

[Dekave294]

I have no experience of SU carbs, yet the problem you describe sounds similar what happens to Keihin CV carbs om my KTM if not used regualarly?
Where the pilot air jets block because of modern fuel and the diaphragms/slides don't function properly. If left for up to 6 weeks the pilot fuel jets can block too.
Perhaps worth considering?

[johnbirchjar]

Hi Mike,
SU carbs are pretty stable once they are set up,so a bit more info please,has the bike stood for any length of time?try checking the diaframs on the fuel tap,(the dreaded E fuel just loves them,I did away with the vac:fuel tap on my Classic,re-placed it with a conventional "Gravity Tap" after fitting THREE diaframs in one year! )another check is take the plugs out,turn the engine over and listen for the chambers to "Chuff",the old memory isn't what it was so not quite sure if the "Chuffing"is good news or bad,doubtless someone will tell,J.B.

[Anthony Duffield]

Mike,

I have a Commander, which may be different from your Classic, if my bike had the same symptoms it would suggest to me lack of fuel.

You said:

seemed pretty normal though perhaps not quite as smooth and even as usual. At next start attempt (full choke at first), it started and revved to about 3,000, but when the choke was pushed in a bit slowed down and faltered before stopping. Same at next attempt, then next time not starting at all. Has fresh fuel, and my spark tester shows sparks at both sides,

It ran on full choke then stopped, then no starting at all. This suggests your were starting to run out of fuel, using full choke provided enough fuel to get it started then it would not start at all.

If you have a vacuum pipe to the fuel tap, pull it off at the engine end, disconnect the fuel line to the RH carb, suck on the vacuum pipe to check that you have fuel, if you do suspect a stuck float.

Good luck.

[MikeBristol]

Thanks Anthony. I'll check this out tomorrow and report back, Mike

[johnbirchjar]

The lack of fuel?hence my suggestion to check the fuel tap diafram,J.B.

[MikeBristol]

The vacuum pipe from the petrol tap disappears behind a cover which I can't yet see how to remove, so at the moment I can't check for fuel in the carbs. What's the best method to see if the tap itself is faulty, to eliminate that before going further? Mike

[johnbirchjar]

Hi Mike,if your Classic is as per all Classics, the panel is only held on by two deutz screws,then you can get at the bottom of the fuel pipe where it runs into the carb:(I think,the old memory aint what was)take it off and with a descent battery turning the engine over you will know if fuel is getting at least to the carbs,if not it's an odds on bet that the fuel tap diafram is knackered(unless the fuel filter is all bunged up)It's a simple job,and if this isn't the problem, then a process of elimination begins,J.B.

[MikeBristol]

I'll take a closer look!

[MikeBristol]

Had a few minutes today and checked that the petrol tap appears to be working correctly - fuel flows when engine cranked. So next to check the carb end. Is that possible without removing the panel mentioned above, which at the moment I haven't been able to shift? Can I just undo the unions at each side, held in place by retaining plates 50-0616?

[MikeBristol]

Should read retaining plates part no. 50-0617 !

[Joe]

Hello,
Yes, just loosen the screws and rotate the retaining plate out of the way and you will be able to pull the fuel feed unions off to see if you have fuel.
If you still have the original fuel filter fitted check the end hasn’t reduced in size due to modern fuel by pulling off the fuel hose and checking the internal diameter of the filter. If this has reduced you won’t have sufficient fuel for both carbs and the bike will only run on one chamber, the left hand side as this is supplied first with fuel.
Good luck,
Joe.

[MikeBristol]

Thanks Joe. I've removed the unions in turn and fuel flows to both sides when cranking. I don't see a fuel filter in the parts book, and there's no mention in the manual. Do all Classics have them? When I next get out to the shed I'll whip out the plugs and check for fuel there, Mike

[Joe]

Hello Mike,
apologies I was thinking of my Commander which does have a fuel filter.
It sounds like your fuel system is good and I don’t think a carburettor fault would have given you your symptoms so I think it is an Electrical problem.
Electrical connections can be a problem on motorcycles and we expect a lot from them but we never service them. It could easily be as simple as oxidisation of the battery terminals. I think you need to inspect all the electrical connections. Disconnect the battery and start with the ignition box, ignition pick up and the two 9 way plugs/sockets under the instruments. Do one at a time so no confusion with location. Also remove and inspect/replace two fuses, Main fuse 30A and Ignition fuse 10A just in case slight corrosion has struck. it is also worth applying some switch cleaner to the kill switch on the handlebar controls ( sorry, I can’t remember which side it’s on RH I think) WD4O is good for this. Also check the electrical connection of the plug and socket on the RH switch gear which is down by the headlamp. You can unplug the two wires to the side stand cut out switch to eliminate it. It only shorts down to Earth to cut the engine out so disconnecting will do.
Sometimes my Classic is a bit hard to start turning over slowly and not firing if I’ve left it standing for ages. When I connect my jump pack it bursts into life. Can you get access to a starter pack? This may spin the engine over faster and put a bit more volts into the system indicating poor electrical connections.
You’ll get there and you’ll certainly know your bike better at the end.
Good luck, Joe.

[MikeBristol]

Thanks for taking trouble over this Joe. At the weekend I removed the fuel unions on both carbs and fuel flowed at each when cranking. I do wonder if ethanol has affected components in the carbs, like the O rings at each union? But strange if all fuel was blocked and not even a cough or splutter. Bike was recommissioned at Andover last Summer and was then running well (excellent compression too), but I don't know that the carbs were stripped. After reconnecting the unions I removed a plug, which was quite dry, and couldn't detect petrol in the chamber when cranking. The plug didn't show a spark when held against the engine fins, which I put down to low voltage affecting the electronic ignition. Battery was new last summer and bike has been run regularly, or connected to a charger for a day or two if unused for more than a couple of weeks. Battey now charged up, and my inline spark tester between the plug and cap shows a spark - which I suppose could be failing under compression. I will check fuses, terminals and connections next. And maybe new plugs. Also the side-stand switch.
The starter button may have a poor connection, as it doesn't always spin on first press (and a spare handlebar switch came with the bike, suggesting PO had suspected an issue) - but if the engine turns could any other fault in the switchgear prevent starting? It always does spin if held down for a few seconds. Kill switch seems reliable. Mike

[Anthony Duffield]

Mike,

This is a suggestion that I would do and perhaps not others, it will be your choice.

If you have a good spark and from what you say no fuel. If not done already renew the plugs so you can rule out plug issues, buy yourself a tin of easy start, get a good charge into your battery and check if it will fire on the easy start. If it fires the problem is lack of fuel, if does not fire it will be ignition problems.

Tony

[MikeBristol]

Thanks Anthony. In fact I've had some success today - firing on one side though not very happily and I doubt it will stay alive very long with the choke off. Tomorrow I will fit new plugs and see if it will fire on both, and keep running. No real fault found yet, though one battery terminal was slightly loose. So far I haven't disconnected the sidestand switch -is the warning light going on and off when folded proof enough there is no problem there?
The bike came with some spare surface discharge plugs, but has the AN recommended ones fitted now. What's the ideal gap?

[Anthony Duffield]

Mike,

My Commander does not have a light for the side stand, as yours does and the light is working I would say the side stand interlock is OK.

I use NGK C7E 5096 spark plugs, my bike works better with a hotter plug, standard is C8E 7471.

Spark plug gap for a Commander is 0.6mm/24 thou.

Tony

[johnbirchjar]

I used C8E plugs the whole 30 years and 71,000,+ miles in my Classic(except for the VARY rare occasions when I tried other types, but invariably returned to C8E's)J.B.

[MikeBristol]

Thanks John, and others who have contributed. I put a new (NGK iridium) plug in the non-running side and it started up on both. Running is a bit lumpy and the choke doesn't seem to be doing much, so I needed the throttle to keep it at 3,000 rpm to warm up. Would not idle, but maybe needs a bit more time. Not sure how to read the plug I took out, but perhaps I have been using the choke too much when starting, and not giving it enough revs on the fairly gentle runs I have taken it during my ownership. Up to now I have warmed it up on at least three-quarters choke for a few minutes before setting off. Failure to do that often meant rough running, a serious stumble within the first mile, and careful use of the throttle to keep it running. No fun in traffic.
Not sure how this fits the initial symptoms, which seemed much more like a fuelling issue. Tomorrow, if I get time, I'll change the other plug and warm it up for a bit longer - not sure I trust it out on the road yet. Don't want to be pushing it home! Mike

[BlackIP2]

On my IP2, and I would therefore think it's the same with the Classic, the side stand warning light is simply to tell you the side stand is down. I'm pretty sure there is no interlock involved which cuts out the ignition - happy to be corrected if that's not the case?

[MikeBristol]

The Owners Manual fault finding chart under 'Engine turns but does not start' lists 'Side stand down' as a possible cause, though I haven't tested this.

[johnbirchjar]

My Classic would definitely NOT start with the side stand down.
Little tip re;starting from cold,full choke,fire up,push choke in when engine starts to "hunt",push the choke in until the engine evens out(12/1500revs?) then clip a clothes peg , round the choke cable and push in a bit at a time as the engine warms up.
,(depends on the bike and how cold the weather is)you should now be able to ride the bike(even in traffic)until the engine as reached running temp:80c+?
It took me a fair while to work out this method 'cos the factory setting for carbs were way off and the choke couldnt be pushed in a bit at a time it was all or nothing,most frustrating, it was an absolute pig in traffic until the engine had warmed up (and I new nothing about Rotory engines)and I had to re-tune the carbs first.
(I wouldnt mind a pound for every time someone asked what the clothes peg was for) ,ride safe,J.B.

[Ian Mc]

I've had the problem with my Commander. Turned out to be a float needle sticking closed. If you do not want to dismantle the carbs, try to loosen the 4 screws on the bottom of the float chamber to see if fuel is present. Remove the fuel pipe & squirt carb cleaner or Redex into the carb & tap the carb to see if it loosens the needle. Try starting, be prepared for smoke. Use Valvemaster or similar when you fill up, especially if the bike sits for more than a week. E10 is not good for for Rotaries. A faulty sparking plug is usually accompanied by loud backfires.

[MikeBristol]

Thanks for this Ian, which I will try next. Some progress today though. Changed left hand plug and she started up easily, responded to the choke, but clearly right hand chamber not working properly - hot, strong pulses from other exhaust but cold and then at best lukewarm on the right. No backfires though. Exhaust on that side only warmish after a few minutes, but she idled at 1,000 with a little choke. Kept on good terms with the neighbours by not waiting for it to get fully up to temp before turning off! Possibly a good blast would wake things up, but I'll check the right hand carb for fuel as you suggest first. Mike

[Ian Mc]

The exhauast has a ballancer pipe on the manifold, this means the non running side eventually warms up and gives the appearance of running on both chambers. The cold side is the faulty one which helps to narrow it down.

[MikeBristol]

Thanks Ian. I guessed it was probably just heat transference, but was clutching at straws. Busy for a few days now, but then I'll follow your suggestion about the carb and report back.

[MikeBristol]

After a bit of a delay, today I tried Ian's advice to open up the carb by removing the four screws at the bottom, but one is completely inaccessible while the carb is in situ. So I removed the union and pumped a bit of carb cleaner in and will see in a while if that helps.
Should the float needles be viton tipped for ethanol fuel? I see a previous owner had work done by Richard Negus in 2013, which included rebuilding the carbs. The invoice shows two Burlen overhaul kits, but were viton needles standard then? Not sure when E5 fuel first appeared.
I only use the lowest level Ethanol fuel.

[MikeBristol]

Well, following the steps in my last post, today it started and ran normally - after a bit of hesitation on the left hand side. Perhaps it was just a sticking float needle? A pity we have had a lot of localised flooding and the nearest roads are covered in mud and gravel, but I'll try a brief road test when things improve. Before the council get the gritters out anyway! Thanks for all the advice on this one. Mike

[Ian Mc]

Good news. If you are going to leave the bike idle for a while, try the old two stroke method of turning the fuel tap off a quarter mile from home. That way the float will be open with fresh petrol when you turn it back on.