Discussion
Hi all, recently got my CBT and passed Theory, working to getting full license later in the year. I recently bought a 2021 Keeway TX125, which i like....it feels a bit bigger (and quicker) than the Honda CB125F i've done some lessons on. Honda feels the better built bike though, which is no suprise.
Anyway - there is a problem - the bike revs on it's own. It didn't do it when i got it, typically, but does now, which makes it very difficult to ride as in the lower gears it's pulling by itself and the revs flare when left alone. A quick blip brings them back down but they soon climb again to a high level and stay there.
The throttle itself feels good, doesn't seem to stick in operation - but the revs thing happens by itself. Does anyone have any ideas?
I've looked for anything obvious that stands out as wrong but i can't see anything myself (but i am new to this).
Any ideas or things to try next? I'm wondering if it's something to do with a faulty sensor or ECU but wondering if theres anything " i " can do before i take it somewhere.....
Anyway - there is a problem - the bike revs on it's own. It didn't do it when i got it, typically, but does now, which makes it very difficult to ride as in the lower gears it's pulling by itself and the revs flare when left alone. A quick blip brings them back down but they soon climb again to a high level and stay there.
The throttle itself feels good, doesn't seem to stick in operation - but the revs thing happens by itself. Does anyone have any ideas?
I've looked for anything obvious that stands out as wrong but i can't see anything myself (but i am new to this).
Any ideas or things to try next? I'm wondering if it's something to do with a faulty sensor or ECU but wondering if theres anything " i " can do before i take it somewhere.....
Keeway uses a carbed engine as far as I know and it will have 2 screws on the side of the carb. One is the air fuel mixture, the other is the idle screw.
Start the bike and with a good fitting flathead screwdriver (electricians non tapered 3mm screwdriver would be best) adjust the idle screw 1/8 of a turn at a time untill it is holding a steady idle.
While you are there you could tune your mixture too, youtube will have plenty of instructions for this.
Start the bike and with a good fitting flathead screwdriver (electricians non tapered 3mm screwdriver would be best) adjust the idle screw 1/8 of a turn at a time untill it is holding a steady idle.
While you are there you could tune your mixture too, youtube will have plenty of instructions for this.
I'd have said an air leak or weak mixture too, as above, but as another possible culprit: it's not got a badly routed throttle cable by any chance has it?
On some bikes, turning the bars to one side can cause opening of the throttle if it's got too short a cable, or a badly routed one.
On some bikes, turning the bars to one side can cause opening of the throttle if it's got too short a cable, or a badly routed one.
srob said:
Possibly an air leak (on the inlet side)?
This could well be it, check by letting the bike idle and spray brake cleaner at intake manifold where it joins the carb, and the inlet flange on the head.
There could be some loose clamps or screws, or the chinese rubber might have some unseen cracks,
all leading to too much air getting into the engine, leaning it out, and causing revs to rise.
bongtom said:
A lesson to us all - never buy a cheap Chinese bike.
But to your question, either an air leak or more likely bad routing of the throttle cable and it is getting caught and stretched. You really need to take it to a mechanic.
Not sure that's the lesson at all. Any bike can have faults even if brand new (which this isn't). But to your question, either an air leak or more likely bad routing of the throttle cable and it is getting caught and stretched. You really need to take it to a mechanic.
Thanks everyone for your comments. Some things to try there.
Yeah, having a slight bit of buyers regret as i was choosing between (for my low budget) much older Japanese 125 or much newer Chinese one. Knew the pros and cons of both. Ultimately this one was/is in really good condition, been garaged, honestly doesn't look far away from 'new' condition. Was great for the first few rides but now this (and a couple of lesser issues) have shown up.
So yeah. Expected some potential issues and i'm not convinced an older Japanese bike wouldn't have given me any issues either but yeah.
I think mine is the EFI engine, euro 4. I think this means i don't have the adjustable carb. I have the 3 plugs that go into that area. Sorry for newbie lack of knowdge here.
Yeah, having a slight bit of buyers regret as i was choosing between (for my low budget) much older Japanese 125 or much newer Chinese one. Knew the pros and cons of both. Ultimately this one was/is in really good condition, been garaged, honestly doesn't look far away from 'new' condition. Was great for the first few rides but now this (and a couple of lesser issues) have shown up.
So yeah. Expected some potential issues and i'm not convinced an older Japanese bike wouldn't have given me any issues either but yeah.
I think mine is the EFI engine, euro 4. I think this means i don't have the adjustable carb. I have the 3 plugs that go into that area. Sorry for newbie lack of knowdge here.
Edited by M1C on Tuesday 16th May 09:19
A lesson in cheap Chinese bikes. One thing goes wrong and the rest will soon follow. That being said, their quality has improved massively in the last 10 years and some can be "quite reliable" now it seems.
As others have said, check for air leaks with brake cleaner around the inlet hoses and such. Check for sticky throttle components too. It does sort of sound like the throttle cable. My CBF125 will increase revs if I lightly touch the throttle for a couple of seconds.
As others have said, check for air leaks with brake cleaner around the inlet hoses and such. Check for sticky throttle components too. It does sort of sound like the throttle cable. My CBF125 will increase revs if I lightly touch the throttle for a couple of seconds.
rlw said:
Biker's Nemesis said:
I try to avoid anything Chinese other than a beef curry with fried rice.
Which doesn't sound very Chinese at all.................https://www.youtube.com/watch?v=dXdWGDS8wts&t=...
Assuming it's got a carburettor, fiddling with the screws is usually a bad first move.
Unless the 'carburettor fairy' has visited in the night and changed things, it's usually not going to help.
A good first move is to check the throttle is closing fully, to the limit set by the adjustment screw.
Details depend on the type of carb, but often you can either see the slide or butterfly sticking, or you can feel the cable goes slack because the sticking is in the carb, or stays under tension at the carb end because the cable has friction or is adjusted wrong or routed wrong.
Check whatever choke/cold start system you've got works and isn't stuck on all the time
If that's all correct, then removing the float bowl and cleaning the carb often works, dirt or water or corrosion partially blocking a jet or airway is a common problem.
It's possible that the carb has been adjusted to counter-act a fault which has now cleared. A bit of petrol gum which has dissolved now or a drop of water that's finally been sucked through a jet. A lot of adjustments are relative to 'fully screwed in' on air screws etc. If you can get the 'factory settings' from a manual, then counting turns to 'fully in' to A) see if your settings are wildly different and B) try the factory settings is a useful baseline test.
It's worth identify the adjustments and sussing out what they actually do. Most are only slow running/idle and have negligible effect once the throttle is open a bit.
Unless the 'carburettor fairy' has visited in the night and changed things, it's usually not going to help.
A good first move is to check the throttle is closing fully, to the limit set by the adjustment screw.
Details depend on the type of carb, but often you can either see the slide or butterfly sticking, or you can feel the cable goes slack because the sticking is in the carb, or stays under tension at the carb end because the cable has friction or is adjusted wrong or routed wrong.
Check whatever choke/cold start system you've got works and isn't stuck on all the time
If that's all correct, then removing the float bowl and cleaning the carb often works, dirt or water or corrosion partially blocking a jet or airway is a common problem.
It's possible that the carb has been adjusted to counter-act a fault which has now cleared. A bit of petrol gum which has dissolved now or a drop of water that's finally been sucked through a jet. A lot of adjustments are relative to 'fully screwed in' on air screws etc. If you can get the 'factory settings' from a manual, then counting turns to 'fully in' to A) see if your settings are wildly different and B) try the factory settings is a useful baseline test.
It's worth identify the adjustments and sussing out what they actually do. Most are only slow running/idle and have negligible effect once the throttle is open a bit.
Perhaps a silly question, but has the OP got any manuals for the bike?
This looks like the owners manual, with idle adjustment shown on page 21: https://www.speedwaymotorcycles.co.uk/uploads/Keew...
This looks like the owners manual, with idle adjustment shown on page 21: https://www.speedwaymotorcycles.co.uk/uploads/Keew...
Hi again, thanks all. Yes, i have printed that manual off previously but thank you for suggesting it 
Mine is the 2021 EFI model and doesn't have an adjustable carb, just the 3 electrical plug connectors. So we have had a look and done some trial and error and we think it's the throttle position sensor that has failed. We've adjusted it as far as it would let us but it didn't make a difference so we're going to try a new one of those to see if it improves matters.
Mine is the 2021 EFI model and doesn't have an adjustable carb, just the 3 electrical plug connectors. So we have had a look and done some trial and error and we think it's the throttle position sensor that has failed. We've adjusted it as far as it would let us but it didn't make a difference so we're going to try a new one of those to see if it improves matters.
If the TPS is just a 'position sensor', it cannot, in itself make the bike self rev.
Depending on what flavour of EFI you have, it can screw up the mixture and make the bike run badly at small throttle settings.
If, like certain cars, the TPS incorporates a motor to set the idle throttle opening, then yes it can cause the bike to rev, and what's more the engine will pull strongly.
Being an EFI bike doesn't change the basic point that the throttle needs to flow more air for the bike to run faster. The air throttling is simpler, no tiny bypass passages etc usually, so the basic point of making sure the throttle is closing to the stop generally applies.
But with an EFI with closed loop, any air leak between the throttle and the engine will matter.
Intake rubbers.
Take-off points for sensors or gauges? If there's a small hose/tube running to a 'manifold' pressure sensor that's worth checking.
Electrical connections are often worth checking, clean dry and a squirt of lube as needed. A certain ECU I got to know has about 3 dozen connections on two big connecters, but none of them is 'chassis earth' or DC Zero or whatever. It relies on the fixing bolts for that.
I'd start by eyeballing the electrics and checking the throttle closes consistently and positively. There's maybe a reference setting for how nearly closed it should be when it's on the stop. On my bike you can set that with a small drill bit to check the gap (just using it as a measure like a feeler gauge not drilling anything! a bit of 1.5mm(?) wire would do)
Depending on what flavour of EFI you have, it can screw up the mixture and make the bike run badly at small throttle settings.
If, like certain cars, the TPS incorporates a motor to set the idle throttle opening, then yes it can cause the bike to rev, and what's more the engine will pull strongly.
Being an EFI bike doesn't change the basic point that the throttle needs to flow more air for the bike to run faster. The air throttling is simpler, no tiny bypass passages etc usually, so the basic point of making sure the throttle is closing to the stop generally applies.
But with an EFI with closed loop, any air leak between the throttle and the engine will matter.
Intake rubbers.
Take-off points for sensors or gauges? If there's a small hose/tube running to a 'manifold' pressure sensor that's worth checking.
Electrical connections are often worth checking, clean dry and a squirt of lube as needed. A certain ECU I got to know has about 3 dozen connections on two big connecters, but none of them is 'chassis earth' or DC Zero or whatever. It relies on the fixing bolts for that.
I'd start by eyeballing the electrics and checking the throttle closes consistently and positively. There's maybe a reference setting for how nearly closed it should be when it's on the stop. On my bike you can set that with a small drill bit to check the gap (just using it as a measure like a feeler gauge not drilling anything! a bit of 1.5mm(?) wire would do)
I wouldn't start fiddling with things yourself if you don't understand how they work, take it to your local independent bike shop and ask them to service it and sort out the problems. If it's been stood for a while and not ridden there could be issues, same as any bike, just needs somebody who knows what they're doing to twiddle with it.
Chinese bikes are very good these days, WK which is CF Moto is very good, as is Hero (Indian but sells all over Asia) which makes over 8m motorbikes and scooters a year. Keyway is owned by Geely which owns Volvo and Polestar and makes a lot of motorbikes ! Times are changing and Chinese and Indian manufacturers which often we've never heard of, are massive businesses making millions of bikes a year.
Chinese bikes are very good these days, WK which is CF Moto is very good, as is Hero (Indian but sells all over Asia) which makes over 8m motorbikes and scooters a year. Keyway is owned by Geely which owns Volvo and Polestar and makes a lot of motorbikes ! Times are changing and Chinese and Indian manufacturers which often we've never heard of, are massive businesses making millions of bikes a year.
SteveKTMer said:
I wouldn't start fiddling with things yourself if you don't understand how they work, take it to your local independent bike shop and ask them to service it and sort out the problems. If it's been stood for a while and not ridden there could be issues, same as any bike, just needs somebody who knows what they're doing to twiddle with it.
Chinese bikes are very good these days, WK which is CF Moto is very good, as is Hero (Indian but sells all over Asia) which makes over 8m motorbikes and scooters a year. Keyway is owned by Geely which owns Volvo and Polestar and makes a lot of motorbikes ! Times are changing and Chinese and Indian manufacturers which often we've never heard of, are massive businesses making millions of bikes a year.
Sort of agree with that, but you have to start learning somewhere, and checking the basics like throttle cables and bits fallen off is a start.Chinese bikes are very good these days, WK which is CF Moto is very good, as is Hero (Indian but sells all over Asia) which makes over 8m motorbikes and scooters a year. Keyway is owned by Geely which owns Volvo and Polestar and makes a lot of motorbikes ! Times are changing and Chinese and Indian manufacturers which often we've never heard of, are massive businesses making millions of bikes a year.
While these bikes are good, they are cheap, so they don't get looked after, as mechanic time is expensive, people don't want to take a bike to a garage and get a £500 bill. It's not a Ducati.
OutInTheShed said:
SteveKTMer said:
I wouldn't start fiddling with things yourself if you don't understand how they work, take it to your local independent bike shop and ask them to service it and sort out the problems. If it's been stood for a while and not ridden there could be issues, same as any bike, just needs somebody who knows what they're doing to twiddle with it.
Chinese bikes are very good these days, WK which is CF Moto is very good, as is Hero (Indian but sells all over Asia) which makes over 8m motorbikes and scooters a year. Keyway is owned by Geely which owns Volvo and Polestar and makes a lot of motorbikes ! Times are changing and Chinese and Indian manufacturers which often we've never heard of, are massive businesses making millions of bikes a year.
Sort of agree with that, but you have to start learning somewhere, and checking the basics like throttle cables and bits fallen off is a start.Chinese bikes are very good these days, WK which is CF Moto is very good, as is Hero (Indian but sells all over Asia) which makes over 8m motorbikes and scooters a year. Keyway is owned by Geely which owns Volvo and Polestar and makes a lot of motorbikes ! Times are changing and Chinese and Indian manufacturers which often we've never heard of, are massive businesses making millions of bikes a year.
While these bikes are good, they are cheap, so they don't get looked after, as mechanic time is expensive, people don't want to take a bike to a garage and get a £500 bill. It's not a Ducati.
I won't be taking the bike to pieces as you are quite right, i don't really know what i'm going but i do have an experienced pair of hands (my stepdad) who is a long time biker and is very handy and a great help. We have been through the steps listed above and checked the 'usual suspects'. I'll update with what happens next in a few days.
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