2016 CBR125R Starting/Stalling Issues

[VigilanteofLight]

Hi All,

 

I bought a 2016 CBR125R last Monday. I'm well versed with cars but this is my first foray into bikes. It had a few issues I knew about, such as leaking fork seals, front brake pads, loose shifter linkage. I've ridden it every day to work and back since buying it, no mechanical issues other than clutch wrongly adjusted. After about a week the bike started struggling to cold start, and stalled at pretty much every opportunity unless keeping the revs above 2k. After two days of that, I had time to have a look and the bike wouldn't even start at all. The tachometer was showing around 5-600RPM while cranking cold. The next day, not a peep from the tachometer needle while cranking. No warning lights on the dash. Before the issues, it had absolutely no sign whatsoever of any issues. it started very suddenly on the first day of stalling.

 

The previous owner seemed pretty genuine when he said he hadn't seen any issues while riding, and he had been using it most days. He gave me his mechanic's number which he said he had taken the bike to once a month - I believe him on that but I don't believe the mechanic did a lot in these instances.

 

Stuff I have checked: 

 

Engine and chassis codes - match V5C. Original.

Battery voltage - happily sat at good voltage >12.6V. Cranking at 11.8V.

Spark plug - sparking happily while outside engine. replaced with new one and tested the new one, still sparking happily. - (this would also indicate to me the crank position sensor is fine, because it knows when to spark?)

Fuel lines - with injector disconnected, had fuel flow out of the supply line. When supply line connected, it visibly pushed itself tight on the connector, showing it had pressure when priming. The fuel pump sounds great when priming too. Just to be sure, sprayed a bit of brake cleaner down the throttle body before/while cranking and no luck. Also had a camera down the throttle body while cranking, saw a spray of fuel from injector.

Compression - 7 bar. Not great, but a car engine would probably start OK with this compression. Should be 11:1.

 

Note- while testing compression this morning, the tachometer needle moved a bit, but I didn't see what it did properly as I was watching the compression dial. I think it sort of flickered but did not stay at a constant RPM as it should while cranking. The engine sounded like it was cranking fine.

 

Coolant - brown. not good. New coolant waiting to go in.

Oil - black, very black, sparkly bits. Oh dear. See photo. That is new oil I put in since I bought, and it has not done a lot on that oil. Pretty sure it's a petrol engine, not diesel... Also there was a lot more sparkle than just what was on my finger. (the drops of red are from taking off the coolant pump)

Clutch-side Engine casing - see photo. WTF are those heat-scarred gouges. Clutch assembly looks untouched though. Clutch exploded and then replaced? Also the gasket is ruined and someone tried to use goo. Oh dear. 

Valve clearances - Checked using Haynes manual procedure. Slightly out, but now adjusted to spec (I'm pretty sure at least). Haven't been able to try cranking it as I need a new gasket for the clutch-side engine cover before putting oil and coolant in. Inside the valve cover in general looked pretty good, no dirt or sparkles.

 

So it has fuel. It has spark. it has air. It has a bit of compression. I don't know if its doing the spark, fuel and air at the right times, but it has them. 

I get the impression this engine has been treated pretty poorly. But that shouldn't stop it from dying so quickly over a couple of days.

So I am a bit stuck. I think it might be an electronics issue, but the lack of warning lights is strange.

 

What else can I try short of taking the engine apart or buying Ebay's finest motor? I don't want this bike to defeat me.

[husoi]

You didn't mention the fuel filter.

Nor the oil filter which will need replacing for the look of that oil.

Those bits of aluminium could be a bit of bad news..

Hopefully you will show the bike who's the boss. After your Mrs obviously

[VigilanteofLight]

I am not too worried about the fuel filter for now as I couldn't get it to start with brake cleaner in the intake. This generation doesn't have an oil filter afaik, just a weird little tray thing at the bottom of the engine, which I've cleaned out... it was also speckled with sparkly bits

[Fender1515]

I think my next check would be cam chain timing,  as I am wondering if the chain has slipped, putting the timing out. It could also be the cause of the swarf in the oil, but lets no go there!! 

[Fozzie]

I've had an older version of this engine apart recently, split the cases. I seem to remember it had a few weird gouge marks in a couple of places, the inside of the clutch cover being one of them. The clutch clears it by a healthy margin so I couldn't tell what did it, but it's weird yours has similar marks. 

 

Firstly, metal fragments in the oil is not good... The picture where it's on your finger, where did this doom glitter come from? Was it from the end of a magnetic sump plug? Did you scrape it out of the filter? How much was in the oil you drained?

 

If you've proven fuel/spark, and it's not a weak battery (Honda's often suffer with the generator/regrec/battery) I'd start looking into what is causing the glitter a bit more.

 

Have you checked the condition of the cam shaft and cam followers? Mine was scraped up badly from oil starvation, which moving down the engine, also caused the small end to wear and the piston/rings were eating into the cylinder wall. This could cause some glitter in the oil. Do a compression test as well if you can. 

[VigilanteofLight]

10 minutes ago, Fender1515 said:

I think my next check would be cam chain timing,  as I am wondering if the chain has slipped, putting the timing out. It could also be the cause of the swarf in the oil, but lets no go there!! 

I wasn't sure if this was possible - I guess it is, but one thing that made me think otherwise was that when checking the valve clearances, they were both nicely closed at top dead centre on the compression stroke - if the cam was one tooth out, maybe this would still happen but I don't know. I suppose I might see extra wear on the tensioner/guides perhaps?

[VigilanteofLight]

8 minutes ago, Fozzie said:

I've had an older version of this engine apart recently, split the cases. I seem to remember it had a few weird gouge marks in a couple of places, the inside of the clutch cover being one of them. The clutch clears it by a healthy margin so I couldn't tell what did it, but it's weird yours has similar marks. 

 

Firstly, metal fragments in the oil is not good... The picture where it's on your finger, where did this doom glitter come from? Was it from the end of a magnetic sump plug? Did you scrape it out of the filter? How much was in the oil you drained?

 

If you've proven fuel/spark, and it's not a weak battery (Honda's often suffer with the generator/regrec/battery) I'd start looking into what is causing the glitter a bit more.

 

Have you checked the condition of the cam shaft and cam followers? Mine was scraped up badly from oil starvation, which moving down the engine, also caused the small end to wear and the piston/rings were eating into the cylinder wall. This could cause some glitter in the oil. Do a compression test as well if you can. 

The metal fragments were there when I did my oil change, before I took anything else apart. It was fairly sparse so I thought it wasn't anything to worry about. The oil strainer had about one or two thumbprints worth of bits in it, and the fingerprint (x3 fingerprints) were from a small pool of oil in the bottom of the clutch area, after taking the clutch casing off.

 

This sounds like I might need to take the head off then, the camshaft looked OK visually but it could have been starved of oil. the level was below minimum when I checked it, after having stalling issues. One thing I read in the manual said about doing a compression test, which came out as 7 bar, then doing another after pouring some oil through the spark plug hole - if it increases, then it's the piston/rings. if not, valves. I stupidly didn't read this before draining the oil, but I will do it again once my new casing gaskets arrive.

 

with regards to the clutch cover marks, I have a suspicion my clutch was done at some point, maybe a bearing failed? the ball bearing on the outer face feels brand new on mine.

 

 

[Fozzie]

If the clutch failed due to a bearing failure, that would itself have been a likely result of low oil. Trouble is, if someone replaced just the blown bearing and clutch, there could have been significant damage to the others that wasn't dealt with and something else is now on its way out, causing things to grind as it develops free play. But there's usually a rumbling sound when one of the main bearings goes bad. 

Are you thinking the last owner started having problems and wanted rid?

 

Is the engine in time? Cam chain tensioners are another problem child with these bikes. And even worse, I've known amateur mechanics install them without winding them before they bolt them down. So they get installed at full extension, over tighten the cam chain, which just chews the sprocket and itself up. Another project of mine, an ER5 had this issue, and it caused the engine to run really badly. And it wasn't until I tried to turn it over by hand that I noticed it was extremely tight.  

 

 

[AstronautNinja]

Unfortunately I can be of no assistance but I love your approach. Makes a nice change for logic to be followed as far as possible (before anyone pipes up yes I am referring to my self) 

 

Best of luck

[RideWithStyles]

Low oil can be a killer with these engines as they do burn it and designed to do it, add poor oil choices, lack of checking (properly!! With the dip stick day ontop of the casing -unless its a window model), and some other ignorant ownership. 
 

Car compressions are very low compared to bikes, they run a lot higher and have higher revs.

If you check the Honda manual of any age of these engines Compression should be closer to 185psi / 12/13bar if fully fit….so your is sounding it very poorly….

if you having to put Aload of revs to make it start from cold from what your saying it could be an indication of your using the fuel,oil and heat to try to seal to gain compression.

 

no point checking the drain plug even with a mag, need to check the filter, if it’s got shite /shiney stuff on the mag plug then the filter will be clogged up to shite as that should have it all as that’s what it’s designed to do, unless it’s the old useless strainer in the older models but your which should have a proper filter.
cut it open and if you find loads of glitter in the pleats that’s your clue… depending on The size and colour of the glitter will let you know WTF has been worn out/killed…rings, bearings, liners, coatings etc.

from the sounds of it at first thought prepare yourself for abit of pain….

Edited September 5, 2024 by RideWithStyles

[VigilanteofLight]

30 minutes ago, Fozzie said:

If the clutch failed due to a bearing failure, that would itself have been a likely result of low oil. Trouble is, if someone replaced just the blown bearing and clutch, there could have been significant damage to the others that wasn't dealt with and something else is now on its way out, causing things to grind as it develops free play. But there's usually a rumbling sound when one of the main bearings goes bad. 

Are you thinking the last owner started having problems and wanted rid?

 

Is the engine in time? Cam chain tensioners are another problem child with these bikes. And even worse, I've known amateur mechanics install them without winding them before they bolt them down. So they get installed at full extension, over tighten the cam chain, which just chews the sprocket and itself up. Another project of mine, an ER5 had this issue, and it caused the engine to run really badly. And it wasn't until I tried to turn it over by hand that I noticed it was extremely tight.  

 

 

I'm not sure how to check if the engine is in time to be honest. It felt completely fine riding the day before, and I didn't notice a lack of power when it was having its stalling issues. But, I only had 5 good days on the bike to get to know it... If you know a way to check timing then I will follow that, but otherwise I might just drop the engine and take the head off?

[Fozzie]

1 hour ago, VigilanteofLight said:

I'm not sure how to check if the engine is in time to be honest. It felt completely fine riding the day before, and I didn't notice a lack of power when it was having its stalling issues. But, I only had 5 good days on the bike to get to know it... If you know a way to check timing then I will follow that, but otherwise I might just drop the engine and take the head off?

Take the valve cover off, and the two inspection caps on the left side of the engine (on the casing).

Get a socket on the nut in the central hole and turn it anti-clockwise. Theres a T mark next to a pair of punched lines on the rotor rim, visible through the higher/smaller inspection hole. When those punched lines just past the T mark line up with the notch in the inspection hole, look at the cam shaft gear at the top of the engine. A horizontal line on the gear should line up flush with the top of the cylinder head. The rockers on top should have some play and not be acting on the valves, if they are, spin the engine 360 degrees and line them up again, and check.

 

If you can’t get the lines on the generator rotor and the camshaft gear, it’s not in time. If you can, it is. Check the condition of all parts while you’re there, look for worn teeth on the gear, or gouge marks on the camshaft/rockers.

[VigilanteofLight]

2 minutes ago, Fozzie said:

Take the valve cover off, and the two inspection caps on the left side of the engine (on the casing).

Get a socket on the nut in the central hole and turn it anti-clockwise. Theres a T mark next to a pair of punched lines on the rotor rim, visible through the higher/smaller inspection hole. When those punched lines just past the T mark line up with the notch in the inspection hole, look at the cam shaft gear at the top of the engine. A horizontal line on the gear should line up flush with the top of the cylinder head. The rockers on top should have some play and not be acting on the valves, if they are, spin the engine 360 degrees and line them up again, and check.

 

If you can’t get the lines on the generator rotor and the camshaft gear, it’s not in time. If you can, it is. Check the condition of all parts while you’re there, look for worn teeth on the gear, or gouge marks on the camshaft/rockers.

It looks like it's in time, so I suspect the head has to come off. I also took some photos of the camshaft and cam gear. To me they all look pretty reasonable - apart from that weird splodge of corrosion or something on the cam gear - it almost looks like chalk. The shoulder screws had washers on and the O-rings in them have disintegrated, so maybe a bit of moisture has got in. I don't think this had ever come off before I took it off today.

 

 

[Fozzie]

Hmmm it looks cleaner than the 20k mile engine I had, which was thrashed. But worse than the 35k mile engine I got to replace it, which seemed to have a mature owner. That said it’s not that much worse. It looks fairly clean from that photo. 
 

The oil seals on the top of the valve cover are fairly cheap, I think it’s about £10 for a full set for the engine. 
 

Before delving deeper into the engine, are you sure it’s not fuel pump or injector related? Or perhaps even a failed ignition coil? I’m not seeing the usual things that usually indicate you need to tear the engine down. Other than the glitter anyway, which does seem excessive, but I’d expect a big engine noise if anything was gone.

[Tinkicker]

Everyone has given entirely reasonable advice and I cannot add anything to what has been said, also I do not have any direct experience to this model.  

However, the elephant in the room is the metallic particles in the oil.  I focus on this.  If it is making metal in the oil, this should be your primary concern.  First port if call is identify the debris.  Will it all stick to a magnet?

 

Compression, if over 85 psi should allow it to run.  Not well, but it should start just about.

Timing.  Yup.  Could affect compression.

Valve clearances were out of adjustment.  Possiby also affect compression if too tight or too slack.

We have a very rapidly deteriorating situation where we have good running, poor running and no running.  And those shavings in the oil...

 

And thanks to google in regards to how the engine is constructed..

 

I would be looking to pull the cam and examine the cam bearings.  Are they seized or worn and spinning in the cam holder? The way the holder is constructed would suggest the bearings are a clearance fit twixt holder and bearing.  If a bearing is getting a sufficiently stiff to turn,  it would spin in the holder rather than spin itself.

Poor oil, lack of maintenance and possibly poor oil flow to the top end will quickly destroy the cam bearings, allowing the cam to float around, not doing cammy things very well.  Only needs a small amount of play.

 

A bit of delving shows a brand new cam holder is around £25 from honda.  This seems to be in almost service item territory.  I was shocked..  Is this showing a very popular replacement item, and or a nod from honda that it can be problematic?

 

Just something to throw in the mix.....

 

Edited September 6, 2024 by Tinkicker

[VigilanteofLight]

So I've done some electrical testing. Resistances on everything I've tested so far have been bang on:

 

Ignition coil - 2.5 Ohm

CKP - 115 Ohm

IACV - 128 Ohm

Bank angle sensor - 3.38V ( a bit low but still has voltage)

 

13 hours ago, Fozzie said:

Before delving deeper into the engine, are you sure it’s not fuel pump or injector related? Or perhaps even a failed ignition coil?

 

I tried to take out the injector this morning and snapped a screw, can't get the bolt out with an extractor set. New throttle body coming on Monday. That's the weird thing though, no big engine noises. And while having stalling issues, no loss of power at high end. The injector, now that it's out, looks pretty good though, no obvious gummed up bits. I can't test the spray though as I can't crank the engine at the mo.

 

4 hours ago, Tinkicker said:

I was shocked..  Is this showing a very popular replacement item, and or a nod from honda that it can be problematic?

 

I think you're right, something has failed in the general head area, and that seems suspiciously priced, yeah.

 

I'm gonna put some new oil and coolant in when gaskets arrive then crank it, if nothing I will take the cam holder off.

 

Cheers for all the support so far, you guys have been really helpful

 

[Fozzie]

@Tinkicker is correct, the holder is a press fit. The cam shaft comes out quite easily. I wish I kept my old scrap engine now, as the old camshaft was toast, absolutely buggered. And my theories on it were that it had either starved of oil, the clearances set *way* too tight, or the bearings had failed. As the original engine I had did have a lot of glitter and more sizeable chunks in the oil, which I assumed came from the cams/rockers. 

 

The holder isn't making me suspicious though, unless the camshaft sits in it loose. That is dirt cheap, but I've never heard of it failing on the other 125cc based forums, which I've read over a lot. But I wouldn't rule it out. 

 

If you do strip it down @VigilanteofLight, you need a couple of special tools. A 40mm long allen head 3mm bolt (removes the oil jet once the head/cylinder have been removed). A tool for removing the generator. And a tool for removing the oil strainer. They are inexpensive, and the engine comes apart quite easily, just make sure to picture everything and note how some bits come apart. 

Then you'll be looking for scorched/failed bearings, and any components that appear to have shed material. If you buy a new engine, you may as well do this first to work out if it's salvageable.

 

But I would try to prove the injector and if check connections around the bike like with the ECU and the earth. Cheap, easier stuff, before doing the open heart surgery. That said, the glitter makes the open heart surgery inevitable, I'm just interested to see if you have 2 problems, rather than 1. As if it can be made to run, it might help hone in on the other issue. 

[Tinkicker]

Fozzie mentioned the generator...  It would be good to see if the crank pickup has collected a fair bit of metallic debris on the tip.  That could cause your starting and tach problems if it cannot see the reluctor on the flywheel.

Edited September 6, 2024 by Tinkicker

[VigilanteofLight]

@Tinkicker So the crank pickup - I assumed it was the little sensor inside the flywheel casing - was pretty clean. the flywheel, sensor, and stator all had some very fine metal dust on them but nothing to impede function. 

 

@Fozzie I can't see any issues on the wiring, but I naturally don't have the tools to read the ECM or test it.

I wanted to ask whether it's any chance of an electrical issue still? or whether I should just try an engine rebuild without buying a new ECM.

[VigilanteofLight]

Right. So I managed to get the new throttle body yesterday, and the gasket set. Engine back together with oil and coolant in. 

 

Testing - now that the injector is happily out, I could properly see the jets - happy as anything, fuel system is all good.

First crank over having drained more oil than just the usual amount - 4 bar. Compression is definitely the issue.

Second crank - 7 bar, back to where we were. 

Third crank - oil down spark plug hole - 10 bar. It's the piston/cylinder/rings... why didn't I test this before I took the clutch cover off

 

I think the reason it wasn't cranking was because the oil around the piston was masking the true issue, and it's been drinking oil like no tomorrow. I wonder if the previous owner thought you had to fill up on oil every time you filled up on fuel...

 

 

Anyway, Engine is out and has been disassembled. The piston wobbled a lot and more so in the axis of the crank pin, so cylinder is not circular. Here's some photos of the piston and cylinder wall...

 

 

I've ordered a new cylinder barrel and piston kit, so we shall see how that goes

 Also, yes that's an  RX7 rotor, they make great paperweights

[RideWithStyles]

Did suggest and state the compression is compromised first time round…Rather than go around the electrical which you went down beforehand and finally twice on a merry go round? .

 

anyway- Looking at the marks on the bore and piston skirt, id be checking the pin,the crank and journals for wear and damage now, while you’ve got it striped / you’re at it.

Then after all the new gubbins fitted properly checked out carb lines/jets, rebalance the carbs and see if it runs ok after that? if not then by all means recheck all the other suggestions if your “checks” were proper beforehand.

Edited September 8, 2024 by RideWithStyles

[VigilanteofLight]

48 minutes ago, RideWithStyles said:

Did suggest and state the compression is compromised first time round…Rather than go around the electrical which you went down beforehand and finally twice on a merry go round? .

 

anyway- Looking at the marks on the bore and piston skirt, id be checking the pin,the crank and journals for wear and damage now, while you’ve got it striped / you’re at it.

Then after all the new gubbins fitted properly checked out carb lines/jets, rebalance the carbs and see if it runs ok after that? if not then by all means recheck all the other suggestions if your “checks” were proper beforehand.

This version of the CBR125R is EFI, not carbed - hence why I was so convinced of an electrical issue. I couldn't check the injector because one of the screws felt like it was about to snap, so I didn't take it out. But yeah, I should've tested the compression more thoroughly before I took the sides off the engine... I am hoping the bottom end is fine as I really don't wanna rebuild it... the pics in the Haynes manual look like a nightmare. I'll put another comment in the thread when the engine is together. At the end of the day, it's probably gonna get passed on through another 10 teenagers who will forget to do their oil changes and run it into the ground, so I'm not that bothered if the bottom end craps out in 10k miles or so.

[RideWithStyles]

Apologies, I had thought/convinced myself it was a carbed version? Think I had another thread on my mind.

 

but id definitely check the lower end too just because it would silly to do all this checking and work only for to miss the bottom side had damaged if self and properly destroy a core a short time later while in your hands, prevention is better than…plus if you pass on this bike it looks better to a buyer if it’s had work done so it can go the same/more miles again.

[VigilanteofLight]

So I finished rebuilding the engine last wednesday, I figured I'd wait a week before putting an update to see if it would survive the first few hundred miles.

 

It started first time which was a good sign  it took a few 15 min runs before it would idle nicely, then I changed the oil and have done about 250 miles so far with not a single issue. I've only been keeping it under half throttle as much as possible, and I'll keep that pace for another week before changing the oil again and having a bit more fun from there.

 

Here are some pics - it was definitely starved of oil is my opinion, those scratches on the bore and piston wouldn't happen otherwise. The bore was not circular any more, the piston rocked a lot more in the axis of the pin than it should have. I replaced the cylinder sleeve, piston and rings and put it back together, did a couple coolant flushes and here we are!

[AstronautNinja]

Cool update nice to see / read a thread go from broken to out and about again.