CBF125 '14 Refusing to start

ScuttleMonkey · L Plate Warrior Joined: 29 Jan 2017 Karma :

Hello people,

I'm relatively new to riding and am experiencing an issue with my bike. It's a 2014 CBF125 and has done 850 miles. Only had 600 miles when I bought it.

So anyway my problem is this, prior to Christmas I had no issues whatsoever. But now, after not riding it for a few weeks due to weather, I can't get it to start.

A week ago I started it up for the first time and left it idling while I put my gear on, after a few minutes it just cut out. Tried restarting, engine turned over but no start. Shook and rocked the bike, tried again and it fired up fine; got me to work and back with no problem.

Now this week, when I got my bike out for the second time since Christmas, started it up again no problem and then after a couple of minutes it cut out - difference this time is I have been unable to get it going again - engine turns over but no start.

My problem analysis so far:

Battery voltage is reading 12.42V

Yes, there is fuel

Fuel pump is priming on ignition on

No

I don't believe there is any current from HT lead to ground

Can smell fuel in cylinder when cranking with spark plug out

was

I haven't yet monitored the battery voltage during turn over so I might try that tomorrow. But apart from that I am at a complete loss and would appreciate any advice anyone has to offer!

Many Thanks,
Nick

Bozzy · Traffic Copper Joined: 20 Dec 2015 Karma :

Try a new HT lead and plug whilst you're at it. I'd also be tempted to drain the tank if the same fuel has been in it for ages.
____________________
2004 SV650S >>> 2009 Street Triple R

jaffa90 · World Chat Champion Joined: 06 Apr 2016 Karma :

Your bike has done nowt and the battery voltage is low, it should be 12.6v in service the morning after in cold weather 12.8v in mild weather.
What is the voltage when cranking the engine, on tickover/idle and at 3,000rpm with all lights on. I suspect the battery is duff after being discharge with doing nowt, saying that is there an aftermarket alarm fitted?

ScuttleMonkey · L Plate Warrior Joined: 29 Jan 2017 Karma :

Thanks guys. I will try the battery first since that will be the easiest and makes sense to my issues.

There is no aftermarket alarm fitted. The bike is completely stock.

ScuttleMonkey · L Plate Warrior Joined: 29 Jan 2017 Karma :

Okay I have fully recharged the battery and it is in good condition.

Started the bike up this morning no problem and left it idling for a few minutes. Then it began spluttering a little bit, the idle was not smooth. I gave it some revs for 10 seconds then as soon as I rolled off the throttle the thing died.

Tried restarting but no luck. Only difference this time with restarting is I can hear it making a *puh* *puh* sound like it's trying to ignite - i.e. there is now spark at the spark plug and maybe some fuel (maybe not enough??)

I'm going to try changing the spark plug and check the timing as that's cheap and easy - but I really don't think that's the issue.

It's all pointing to the fuel system - what should I check and how do I go about checking it? Components I am aware of: Fuel itself, pump and injector. I think the fuel must be fine otherwise it wouldn't have started this morning. What tools and materials am I going to need?

One thing to note which I forgot in my original post, when turning on the ignition I can hear the pump priming but there is also this other noise like a fast clicking / buzzing - lasts about 2 seconds. It has always done this as far as I am aware so didn't think anything of it, but maybe it was the beginning of a failing component.

Would be nice to know if any other CBF125 owners experience this same noise.

Many Thanks,
Nick

jaffa90 · World Chat Champion Joined: 06 Apr 2016 Karma :

You have come on here for advice and just ignoring it.
As my last post.

ScuttleMonkey · L Plate Warrior Joined: 29 Jan 2017 Karma :

chris-red · Have you considered a TDM? Joined: 21 Sep 2005 Karma :

jaffa90 · World Chat Champion Joined: 06 Apr 2016 Karma :

That`s a good start so the headlight stays bright when it stalls.
Sounds like it`s losing pump pressure after it starts unless the injectors are partly blocked with stale fuel.
so switch off and then back on with fuel cap open to breath.
The noises you here are normal.
Try again and give it some throttle when it starts acting daft and if possible remove the spark plug to see / smells of fuel.

ScuttleMonkey · L Plate Warrior Joined: 29 Jan 2017 Karma :

ScuttleMonkey · L Plate Warrior Joined: 29 Jan 2017 Karma :

Okay, so a little update:

The bike appears to be working again!

What was the problem?: I have no idea.

Thursday night I decided to give the battery another charging up since it was beginning to get a bit low after all the cranking it has been doing. Then on Friday I decided to fit a new spark plug, cranked the engine and let it run - 2 minutes later it stalled just as the original problem. I then decided to stick the charger on it again thinking maybe it is the battery after all despite what the readings were saying. Came back a few hours later, the charger was reading 0amps, turned the engine over and let it run - 2 minutes came and went, 10 minutes later and the thing was still running. Switched it off for a short while and then started it back up, again it ran without stalling. Tried again the following day, same thing no stalling issues. No idea what is going on, could it really be a bad battery?

One thing I have noticed though when idling is that it is quite rough, in that, the rpms are not steady (at any temp), they will constantly fluctuate by a good couple hundred rpm and all of the lights will dim at the same time. Battery voltage is good, when idling voltage is 14.4V and this is maintained at 2k and 5k RPM. When the RPM dips down the voltage drops by 0.1V, although this could be substantially more as my multimeter probably isn't quick enough to respond.

Are these symptoms of a bad battery? I'll happily go and replace the battery if I think it will fix the problem but don't want to needlessly throw money at the bike - I'd rather find the actual issue through checking and testing, just don't know what to test!

jaffa90 · World Chat Champion Joined: 06 Apr 2016 Karma :

What`s the battery voltage the morning after without being on charge?
Your bike charging system sounds ok.

ScuttleMonkey · L Plate Warrior Joined: 29 Jan 2017 Karma :

Sorry for the long delay in replying, have been on holiday Smile

So I left the battery unplugged for 2 days and the reading was 12.6V. Bike started up fine but still 'hunting' revs, they keep dropping down then picking back up.

It also does it if I hold the revs at 2k.

I tried unplugging the MAP sensor just to see what would happen and the bike behaved exactly the same. When I tried unplugging the IAC valve the bike idled much lower ~1k before stalling, I guess that can only be expected and probably doesn't help in any way in diagnosing the problem.

One thing I should add, when the bike is cold it'll idle at around 2k, and is pretty steady, it's only when it starts warming up does the hunting start.

Bozzy · Traffic Copper Joined: 20 Dec 2015 Karma :

I'd definitely be checking out HT leads if it gets worse when it warms up.
____________________
2004 SV650S >>> 2009 Street Triple R

ScuttleMonkey · L Plate Warrior Joined: 29 Jan 2017 Karma :

Okay, I will see what I can do.

What's the best way to test HT lead? am I just looking for resistance? I have a feeling the HT Lead may not be removable from the coil pack, but haven't properly looked.

spottedtango · Trackday Trickster Joined: 04 Dec 2015 Karma :

https://www.youtube.com/watch?v=rRQ45lT2d3c.

Test your coil whilst you're at it. Sometimes when they heat up and cool down you can get funny resistances.

https://www.youtube.com/watch?v=4_EFGAFxi1w

skip to about 4mins for a rough guide on ht lead testing.