CB125F 2017 tickover issues

[Tonibe63]

Have you tried owners forums or Facebook owners groups? Always lots of model specific info on there, you may even find a knowledgeable local to advise.

[Snaf MKII]

After further digging, no air leaks having sprayed all over the throttle body and air box etc, fiddle with the throttle cable and adjusted it slightly to tighten it and open the throttle very slightly and sat and ticked over quite merrily for about 15 mins blipping the throttle etc and would always drop back to around 1300 revs nicely. Turned it off and started it again and it wouldn't tick over at all, just die

That sounds like throttle position sensor to me, you've adjusted the throttle so that the TPS sees the throttle open when you turn it back on again some ecu's will not deal with that very well. My BMW for instance will not run properly if you open the throttle before the ecu has done it's pre start checks.
So you probably need to go back and set the TPS and throttle cables correctly, idle speed shouldn't be set by throttle position. The good news is that you got it to run something like it should which points to there being nothing else wrong.

[Hoggyf]

That sounds like throttle position sensor to me, you've adjusted the throttle so that the TPS sees the throttle open when you turn it back on again some ecu's will not deal with that very well. My BMW for instance will not run properly if you open the throttle before the ecu has done it's pre start checks.
So you probably need to go back and set the TPS and throttle cables correctly, idle speed shouldn't be set by throttle position. The good news is that you got it to run something like it should which points to there being nothing else wrong.

I've hunted high and low all over the internet to find out how to reset the TPS or fully reset the ECO but can't find anything or find a workshop manual unless I buy a Haynes one (and I'm a tight wad!) waiting to speak to local Honda dealer for advise and possibly book it in for a look at. I'm fairly sure that it is ECU based, i.e. sensor, TPS or ECU itself thats the issue as it will run fine at one point then switch it off and back on and it goes tits up

[Snaf MKII]

Take a look at the owners manual regarding starting the engine, there appears to be some sort of reset using full throttle for 5 seconds and pushing the starter button. It says the engine will not start if full throttle is applied so I guess it must be doing something of a reset or maybe just clearing a flooded engine.
Pg29-30
https://2rom-prd-data.hondamotopub.com/ ... NB11_0.pdf

[Hoggyf]

Take a look at the owners manual regarding starting the engine, there appears to be some sort of reset using full throttle for 5 seconds and pushing the starter button. It says the engine will not start if full throttle is applied so I guess it must be doing something of a reset or maybe just clearing a flooded engine.

I'll give that a try, hadn't read it that way as a possible reset - cheers

[bowber]

You've probably upset the throttle position sensor since it doesn't run on restart.
My son's 125f had similar problems but it would sometimes also not rev, fitted an new (from a breakers) fuel pump and that sorted it.
It then went on to burn out the alternator but that was a cheap easy fix, took longer to travel 20 miles to collect him from collage.
My 701 has a problem on idle after warming up and I'm reasonably certain it's the lambda sensor again (replacement from a breakers), they have a heater in them and it can fail, the result is an erratic idle as the sensor is sending false readings to the ecu.
There's a few videos on YouTube on how to test them.

[Hoggyf]

Well a replacement throttle body didn't solve the issues, spoke to the local Honda dealer prior to ordering the throttle body from eBay, there service guy said that unless the engine management light was on there would be no fault codes to read and they would just throw parts at it so better to save money and do that myself was his recommendation, hence replacing the throttle body. Off to source a fuel pump now then, was always a toss up which to do first.

[Hoggyf]

And a replacement fuel pump did nothing either, wonder if a box of matches would solve it?
I suppose the next bit is air and oil temp sensor, surely can't be the lambda sensor

[bill_qaz]

Did your new throttle body include a replacement IACV

[Hoggyf]

What's an IACV ? Edit - (Googled it now and found out its an idle air control valve, that's a know issue on the cbf125, not the cb125f that I'm working on, don't think as far as I can find out that the cb125f has an idle air control valve)

It came with the injector etc and the sensors on the throttle body, solenoid etc, after I replaced that I then bought a fuel pump and replaced that, I've now tried it with the replacement throttle body and with the original throttle body wi no change, ok when cold then dies after ticking over for around 3-4 mins which to me now suggests maybe the oil temp sensor?? Giving a wrong reading? As the air temp shouldn't change so the sensor would read the same??
I've tried it previously with the air sensor disconnected and then with the oil temp sensor disconnected, didn't resolve it.