CB125F 2017 tickover issues

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Richard Simpson Mark II
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Re: CB125F 2017 tickover issues

Post by Richard Simpson Mark II » Wed Dec 16, 2020 7:49 pm

Sounds like it's leaning the mix too much when warm.

Either it thinks it's hotter than it is, or is sucking in air downstream of the injector.

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Hoggyf
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Re: CB125F 2017 tickover issues

Post by Hoggyf » Wed Dec 16, 2020 8:13 pm

Can I try just disconnecting the air sensor in the air Box? Any way of testing the sensor?
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Re: CB125F 2017 tickover issues

Post by Snaf MKII » Thu Dec 17, 2020 8:42 am

There will be a temperature sensor somewhere, probably on the radiator. If it's faulty it can fool the ecu in to thinking its to hot or to cold and either under/over fuel it. Simple to test if it makes any difference and cheap to change if you think it's suspect or test for resistance change if you can find data on it.
Do you know what the sensor in the airbox is? Looking at parts diagrams I can't see one and the air temp sensor is on the throttle body.

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Re: CB125F 2017 tickover issues

Post by Hoggyf » Thu Dec 17, 2020 5:57 pm

Definitely no sensor on the radiator, coz there isn't a radiator :mrgreen:
Dunno what the air box sensor is, I was assuming it was air temp??? What's the sensor you saw on the throttle body?
Then:
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Re: CB125F 2017 tickover issues

Post by Snaf MKII » Thu Dec 17, 2020 6:28 pm

Uh yeh, trick question :-). Try the rear of the cylinder head there's one there.

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Re: CB125F 2017 tickover issues

Post by Hoggyf » Fri Dec 18, 2020 4:40 pm

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 :oops:
Been digging through parts lists and found that there is an air temp sensor in the air box, and an oil temp sensor on the head, plus oxygen sensor in the exhaust port, there's also a bank angle sensor somewhere but can't find that nay where, on the 4rt trials bikes the bank sensor is a common issue and you usually link it out to stop it being a problem so need to find that.
Still can't find the tps, I'm assuming it's below the solenoid on the throttle body, but what's the solenoid on the throttle body for?? Shutting fuel flow off? Can't think of a reason why there is one tbh.
Then:
Honda MB5, Honda MBX125, 350LC, RGV250, MTX125, GasGas JTX250, CM 644 DS, BMW R1100S, Beta Rev3 250, Beta Rev4T, Honda XL700V Transalp, BMW F800 GS, Kawasaki Super Sherpa
Now:
Montesa 4RT, Triumph Tiger 800, Beta Alp, Montesa 315

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Re: CB125F 2017 tickover issues

Post by Richard Simpson Mark II » Fri Dec 18, 2020 5:22 pm

Jeeez....I feel old just reading that!

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Re: CB125F 2017 tickover issues

Post by Hugh » Fri Dec 18, 2020 9:36 pm

Greetings again,

Here is another link, similar to the one found earlier by Bill;

https://bikesandtravels.com/biker.aspx?ride=750

TTFN

Hugh.

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Re: CB125F 2017 tickover issues

Post by Thedktor » Sat Dec 19, 2020 7:51 am

Sorry missed your PM.

As has been mentioned the ECU will adjust the mixture depending on the air and engine temperature, so assuming you have no air leaks it is quite likely one of these is faulty - a diagnostic computer will show straightaway if these are incorrect.

Has this been done?
- Steve



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Re: CB125F 2017 tickover issues

Post by Hoggyf » Sat Dec 19, 2020 11:07 am

Greetings again,

Here is another link, similar to the one found earlier by Bill;

https://bikesandtravels.com/biker.aspx?ride=750

TTFN

Hugh.
Unfortunately thats a CBF125 and not the CB125F - different bikes, there's loads of info on the CBF but not much on the CB125F sadly but cheers anyway
As has been mentioned the ECU will adjust the mixture depending on the air and engine temperature, so assuming you have no air leaks it is quite likely one of these is faulty - a diagnostic computer will show straightaway if these are incorrect.

Has this been done?
no hasn't been on the computer as my local bike shop doesn't have the ability to connect to this?? so means going to a main dealer and as she's selling it we were trying to keep the cost down but looks like it might be the best way as we're both loathe to sell a bike with a known fault and selling it with an advised fault will drop the price massively.
Then:
Honda MB5, Honda MBX125, 350LC, RGV250, MTX125, GasGas JTX250, CM 644 DS, BMW R1100S, Beta Rev3 250, Beta Rev4T, Honda XL700V Transalp, BMW F800 GS, Kawasaki Super Sherpa
Now:
Montesa 4RT, Triumph Tiger 800, Beta Alp, Montesa 315

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