[MrChris500]

Hi All,

I'm new to the forum, I've owned a 2010 classic 500 with 27,000 miles on the clock for seven months now. Lovely bike, really enjoy cruising on it.

Recently it's developed a fault where it won't start though. It still turns over and has no warning light. I've checked and I have a good spark and what appears to me to be good fuel flow from the injector when I removed it from the inlet but still connected to the fuel line but the bike just won't fire. I've ordered a compression tester, but could low compression cause it to not start? Any ideas of things I could check next? Crank position sensor perhaps? Before cutting out entirely the bike would sometimes bog down previously when cold and weirdly I found the old K&N air filter was entirely covered in mould. That's changed now but can't have helped! Any ideas appreciated! Chris.

[Monkee]

There was a pretty long discussion about the sidestand and the sidestand switch on some models. You could take a look at that since theres a relay there that interrupts the ECU so it wont fire but it'll still let the starter and everything else run.

[MrChris500]

Thanks Monkee,

I did check that while testing the bike on the centre stand. On mine swinging the side stand down stopped the bike turning over. I think it wants to start as I've got spark and fuel.

[MrChris500]

Think I'll get another injector in case the spray isn't good enough. Compression reading with a tool that screws into the spark plug shows 152 psi with the throttle wide open 🤷‍♂️

[axman88]

I'd still try a new sparkplug, if you haven't already.  It's easier to make spark in atmospheric pressure air, than in compressed fuel vapor mix.

And, I'd dismount the air cleaner, and put a shot of starter fluid up into the throttle body, to see what happens.  Buying a tank full of dubious fuel isn't impossible.

[MrChris500]

Thanks axman,

I changed the coil, sparkplug and cap over the winter. I've still got the old ones so can investigate with all of that.

Will also try a fuel swap and get some starter fluid into the throttle body too. If it does catch with the starter fluid and it still won't start with new fuel I'll try a new injector 👌

[axman88]

You didn't mention battery condition.  Like most ECUs and ICUs, the Keihins will refuse to produce spark when voltage drops below the programmed threshold.  I think that is around 10-10.5 Vdc.  If spinning against compression pulls the voltage down below that, no spark.

You might have better luck with the kicker, or try a jumped car battery.  But not with the engine running, as this can overwhelm the bike's regulator.

[MrChris500]

It's got one of those gel batteries on the bike. it seems to be ok, I've done loads of engine cranking recently without the battery running out of puff. I'll measure the voltage while it's cranking to see if above 10.5v but it's well above that when at rest, 13 point something I think. I've been trickle charging it over night while this problem has stopped the bike running. Unfortunately my bike is one of the classic 500s without a kicker. Wish I had that!

My 'try stuff until it works' list is currently injector, fuel pump and crank sensor, just in case the injector is being told to operate with the wrong timing. The fuel pump is the most expensive of those so may try that last.

I did recently add an in-line fuel filter between the tank and the injector. I haven't taken that off the bike yet but if that's the cause I think either the pump must be weak or the injector partially blocked/ineffective too.

[Haggis]

Fuel is at 40 psi between the pump and injector.  You sure your filter can take that? You already have a micron filter on the pump plus there is a small even finer filter in the top of the injector.

[MrChris500]

Not sure at all, job for this evening then! I'll take it out and see what happens. Will let you know.

[MrChris500]

Still didn't start, but at least it's ruled out.

Battery only 12.5v at rest today and was 10.8v while cranking. Giving it another charge now.

[Monkee]

Still didn't start, but at least it's ruled out.

Battery only 12.5v at rest today and was 10.8v while cranking. Giving it another charge now.

I'd change out that battery thats a pretty big voltage drop. At least in my experience I like to keep my batteries at 12.8 at rest and a drop no greater than 11-11.5

[MrChris500]

Finally got this bike running. It was the crank position sensor (pulsar) in the end. Mine had a resistance of 330 ohms but it should have been 200 +/- 20 ohms.

Unfortunately taking the RH cover off to change it I found some hidden history. In the past the chain had snapped and smashed though the engine casing .It was repaired with JB weld type stuff and wasn't leaking but I found loads of swarf in the.oil. I've flushed some new oil through now and drained it before refilling again. The seller did say it recently had a new chain and sprocket but didn't say any more than that 🙄 At least it's back on the road now.

[MrChris500]

In case anyone finds this thread if they have the same issue I thought I'd update it. The bike failed to start again so it wasn't the crank position sensor.

When I got the bike there was some oil in the air box. As oil overfilling can cause this through the crank case breather pipe I didn't worry too much but the oil has come back and currently the breather pipe isn't connected to the airbox. Looks like the oil is coming from the head through the throttle body to the airbox. Maybe a valve guide seal or something, will need to take the head off to see. My theory now is the oil interferes with the MAP sensor in the throttle body causing the poor running and if left longer leads to non-starting. I took the throttle body off and cleaned it all up and the bike then ran really well, as it did when I 1st got it, but  a few days later is starting to splutter again.

[Haggis]

Can't see how any oil getting down the valve guides would be able to make its way backwards to the throttle body.? Any oil getting by would be sucked straight into the combustion chamber. You need to be very careful when cleaning the throttle body. I took the map sensor and tps sensor off to clean mine. I wouldn't spray any type of cleaner on the map sensor for fear of damage.
Also noted your compression figures?  Workshop manual states,
 In case compression pressure is more
than 110 PSI then engine requires
Decarbonisation of cylinder head /
piston (combustion chamber).