Broke Down!

Bugger!!

On my way home from work, travelling up the A3 from near the Tolworth turn off, doing around 50-55mph, and I start to lose power.  Luckily there was a petrol station coming up and I was able to make it onto the sliproad into the station before the engine completely conked.

Checked petrol in tank, and that there was nothing leaking out underneath (oil or water), then fired her up.  She was running, but every time I tried to rev up, or put it in gear and try to pull away, she'd cut out again.

Called out breakdown assistance, and when he checked her over, he said that the left cylinder wasn't firing, but he couldn't take the tank off at the roadside so he recovered the bike back to my home.

He thinks it could be as simple as the spark plug cap coming off, but I'm worried it could be more significant.  Any ideas??

Jim

Yeah, something in the ignition circuit. Unlikely to be anything serious; these bikes are bomb-proof.

Thanks badseeds,

Yeah, here's hoping it is simple (and cheap)!

I'd love to have a go at solving it myself, but with my job taking up so much of my time, and my family the rest of any spare time I have left, I don't think it possible.

Anyway, I haven't had the bike long, and I was meaning for it to have a decent service to check it over, so I'll probably take it along to a local bike mechanics and get it done there whilst fixing the current problem.


Jim

Was it raining? 

Sounds electrical to me.

Not, it wasn't raining, and the roads were dry.

It was fine, cruising along at around 50-55mph, then I had a slow a little for heavier traffic, and as I then went to speed up again I felt like there was no more power from the throttle.  It then got worse pretty quickly so that I was struggling to make it over to the left hand lane and reach the slip road into the petrol station before it conked out.  Luckily no one came flying up fast behind me.

As I wrote, I was able to get it started again several times, but on twisting the throttle, it would be missing quite badly then it would just conk out again. There was certainly not enough power to even pull away again.

My first thought was that I might need to switch to reserve, but I'd only done less than 140 miles since filling up.  Sure enough there was still plenty in the tank, and switching to reserve anyway made no difference.  I then thought it must be the fuel supply to the carbs (this was before the recovery guy pointed out that the left cylinder wasn't firing).  I thought it might be a vacuum hose off, or simply crud blocking the flow of fuel.  But the fact that it is on one side only narrows down the possibilities, I guess.

It suppose it could still be a problem in the left fuel line/carb....  I'll find out when it's been seen properly by the mechanic.  I'll give them a call tomorrow morning.

Jim

Had the bike been standing before you bought it? One of my CBs is a '96 that I bought 2 years ago. It had only covered 7k miles and was spotless. However, there was evidence it had been standing about idle. Amongst the history were invoices for TWO occasions where the carbs had been stripped and cleaned. It also had new stanchions, yet its original front tyre.

Start the engine and wet a bit of kitchen roll; touch it to the downpipes to see which one sizzles.
Once you know which cylinder it is whip out the plug and check its condition for starters, also put the plug into the lead and try earthing it on the engine to see if it is producing spark.

The bike has gone into a local mechanics workshop in Tooting - they collected it from my home address this afternoon and started working on it.

They're going to let me know what is wrong, then repair it and do a service including carb sync.

Jim

It will be interesting to see what they find out Jim.

Hope you get it back without spending too many £s

Good Luck!

I hope you have found a good mechanic... or these things can start to get expensive, even if they
are simple to fix.

As I said, fingers crossed.

OK, I'm embarrassed....!!

They've checked the bike out, done a service and carb sync, and told me that the loss of power and conking out was due to me running out of fuel...!! 

That is odd because I had it on main, according to what the manual states, and when I got to the petrol station I checked and could see fuel in the tank, albeit quite low.  I switched to reserve but it still wouldn't run properly, firing on only one cylinder.  But at least it wasn't an expensive repair.

So, now I realise that I only got around 150miles on a near full tank (I fill up with the bike on side stand so there's no chance of a leak from the filler cap). That works out around 40mpg.   I suppose that's down to mainly using the bike for poottling to and from work in heavy London traffic and using lower gears more often, but still not impressive.

Anyway, lesson learned in terms of keeping an eye on fuel level!! (The workshop is just going to check which way the fuel tap works - up for reserve, down for main, or other way round - to be sure before returning the bike to me, just in case the tap fitted on my bike is non-standard).

Jim

Oh, and a mention for Paul and his colleagues at South London Motorcycles in Tooting SW17.  Very helpful, friendly, and fast in doing the biz to check out and service the bike.

They're even going to return it to my house free of charge, either this evening or tomorrow morning.  (They didn't charge for collection yesterday from my house either).

Seems like an excellent service to me!

Jim

Glad it's sorted Jim.  An easy mistake to make as the tap is not well marked.

I think horizontal is off. Up is on and down is reserve.

Up is reserve, down is on. It is on both my 96's anyway. Glad it's sorted Jim; that is excellent service.

I get about 45mpg in the traffic. 

The only way to really tell is to fill the tank up properly (on the centre stand or, at least, with the bike upright) a few times and do the calculation - if you fill it to the bottom of the filler collar then it won't overflow (you can, in fact, fill it more than this, but probably best not to risk it).

The 'main' tank should be 17 litres, which (at 45mpg) should be good for 160-170 miles, the reserve is 2 litres which is good for another 20 miles (hopefully!).

OK, now I'm confused - happier but still confused.

I got the bike back today and filled up this evening - but it only took 14.2 litres whilst parked on the centre stand!  That means that I got 140+ miles on just 14 litres - about 45mpg, so exactly what you get, eternally_troubled, when riding round most of the time in heavy traffic.

However, it also raises two questions:  14.2 litres is a lot less than the stated volume of 16 litres for the main tank before switching to reserve - so why would that be? Secondly, whatever happened when I broke down occurred as I ran out on the main tank setting, and because I was riding at around 50-55mph it seemed to temporarily mess up the "works" and I couldn't get it going again, even on reserve.  Is that possible?

Could it be that the tube that goes up into the tank from the fuel tap is longer than it should be, meaning reserve is a larger volume relative to the main tank than it should be? 

Could there also be crud in the bottom of the tank affecting the fuel flow when switched on reserve?  It certainly was still unhappy running this evening until I got to fill up and switch back to main, but that could also have been as the engine was still warming up.

Questions, questions....!!  (Any suggested answers gratefully received!)

Jim

Hi,
glad its on the road again, carb balance etc always worth doing.
On my cb5's (had 4 so far) reserve is UP, on is Down, off horizontal. I set the trip counter to 0 and fill up at 160 or so.

I would check the tank breathers. Increasing vacuum in the tank =  less then no fuel being sucked through = stopping, and bike starting again when the fuel cap is opened to see if fuel is in etc, which releases the vacuum.

The two breather hoses on the right side of the tank exit near the swingarm, both should be just cut at the end. However, the engine breather looks similar to the larger of the 2 tank pipes and has a stopper in it. If the stoppers mistakenly gone on the end of the tank breather, there you go.

Also, when you open the fuel cap and there is a hiss, this also indicates vacuum present.
Have a look at the fuel cap to see its not gunked up too.

atb

m1

Live in the west country and mostly go on country rides, well away from traffic. I occasionally use the faster A roads at up to 70mph or so, but mostly the B roads. The bikes runs at normal operating temp for most of my longish rides. My mpg varies between 66-72. I've had a low of 62 when using the motorway at 90, and a high of 78mpg on a 100mile ride on goodish roads here. I'm not a throttle-ripper. I try to be smooth.

Hope this shines a light. Cheers