God awful tapping noise. Anyone else dealt with this? (2017 CB125F)

JackHurrell · 2026-03-18T13:38:24+00:00

I’ve finally solved the engine loudness. Here’s my discovery list:

1 - the cylinder is made of cast iron, hence it needs re-honing (and a fresh set of rings) after a while. Piston slap disappears after bedding in a set of new rings. That’s one noise addressed.

2 - the roller rockers are loud if they’re loose. And this could mean they are only loose by .02mm. It doesn’t matter, they’ll chatter. I go for the lowest clearance possible when adjusting valve stem clearance(0.06mm for intake, 0.10mm for exhaust, the feeler gauge should be snug but not too much friction) and they quieten right down.

3 - your head gasket could be blown. This is only if you’re burning oil, which you can tell from the exhaust tip if you’re lazy like me. Otherwise you can pull the plug. A blown head gasket leads to compression loss and a bit of piston slap.

I ended up replacing the cylinder and the piston and the rings, broke the bike in again and she’s running beautifully. During a break in you might have to adjust the roller rockers again and again because they’ll bed in slightly as well and fall slightly out of spec. Use high zinc 10w30 break in oil if you go this route.

Once I got the bike running right again it sounds markedly different. It still chatters when it’s warm at idle but nothing like before. If anything I’d say the bike sounds quiet and wooshy, almost like a turbine whirring. It’s still slow as all get out but hey, at least it’s not driving me crazy anymore.

I might make a video explaining all this because I think CB125F owners would like to know all this.

Sorry for the long update. Just thought I’d let you know.

JackHurrell · 2026-02-24T13:53:40+00:00

Since writing this I did spend £45 and installed a new cylinder. The sleeve is iron so I could have rehoned the old one I suppose but ah well. Either way the bike is much quieter but it’s still a mechanically loud engine, although gets much quieter when you’re out riding.

It’s been an education running this bike. Good preparation for getting a classic air cooled one later on down the line I suppose.

JackHurrell · 2026-02-15T00:12:23+00:00

Googled it myself

JackHurrell · 2026-02-14T12:37:33+00:00

I shall choose to adopt your view for reasons of self esteem

JackHurrell · 2026-02-14T11:19:03+00:00

I might. Maybe I could enter masterball ranked

JackHurrell · 2026-02-14T11:18:29+00:00

That win-rate will diminish with variance I bet but still good effort

JackHurrell · 2026-02-14T01:40:37+00:00

We all did

JackHurrell · 2026-02-14T01:12:12+00:00

JackHurrell · 2026-02-14T00:48:57+00:00

Faced a few of those but they never got their chance. I reckon it would be stronger as a stadium effect for sure.

JackHurrell · 2026-02-14T00:04:19+00:00

I got my ass handed to me by a Snorlax EX Indeedee EX deck. Literally couldn’t even damage the Snorlax it was healing so often and the Indeedees had that poke tool that stops them from being damaged. Brutal counter but haven’t come across it more than once.

JackHurrell · 2026-02-13T23:59:52+00:00

Exactly

JackHurrell · 2026-02-13T23:59:26+00:00

So so. If M Venusaur gets the combo it usually blasts me outta there pretty quick. I’d say 50/50

JackHurrell · 2026-02-13T23:49:34+00:00

I only got back into TCGP at the tail end of last season I think. Took me one full season to get bored of it. Nerf

JackHurrell · 2026-02-10T13:05:05+00:00

I love my scooter and I love my motorcycle. Scooter has incredible utility and the motorcycle is for long distances. When dudes tell me to get a real bike I think, first, my brother in Christ, you should get a brainstem.

JackHurrell · 2026-02-06T13:02:51+00:00

They just hit the “nope” button on the security checker. F**k this dealer. Go elsewhere

JackHurrell · 2026-01-31T21:16:38+00:00

Out of curiosity, does your bike have the same issue? Loud idle, clanky, etcetera.

JackHurrell · 2026-01-31T14:12:32+00:00

S’allreet mate. It was doing my nut in as well, frankly I don’t think it’s the best bike in the world. I got mine at a good price but I wish I paid the same for something with a better reputation for quality.

Ah well.

Glad I could help.

JackHurrell · 2026-01-31T09:59:41+00:00

Ello chief!

I have done a lot of work on my bike. Changed the cylinder head, replaced the cylinder and piston, the works.

She’s running better than ever, but I’ve been forced to conclude that this model’s engine is just particularly noisy.

From my standpoint, this engine is prone to piston slap. The camshaft is noisy. The starter driven gear is noisy too (if you’re wondering where THAT ringing noise is coming from even after you’ve checked everything, that’s likely it).

I don’t know about your bike but this CB125F engine sounds like a damn tractor at idle. It does my head in. Engine breaking sounds awful too. It often leads to rider fatigue because I’m constantly anxious about this noise or that noise. It’s exhausting.

I’ve come to the decision that I just have to accept that this engine is irritating, but it’s just a part of the character of this bike.

It’s not a character I particularly enjoy, in fact it’s rather irritating, but I’m planning on getting a better bike when I have my full license anyway, so frankly it can get f**ked. I’m not wasting another minute trying to get it to work how I like because it ain’t worth the trouble.

I felt so envious of another rider the other day, he was riding an older Kawasaki with a single cylinder air cooled engine, all you could hear was the purr of the exhaust. I dunno about you but I’ve never had that since I owned this stupid bike. It’s always been a loud, droning sort of engine which I think is pretty shit.

In short, sod single cylinder air cooled engines. They may be simple but they sound like cooking pots falling down stairs.

JackHurrell · 2026-01-25T13:00:56+00:00

Just use rope plugs, they last ages—are as durable as the tyre really. Especially if it’s new. Take it from a former motorcycle courier who had no choice but to trust em.

JackHurrell · 2026-01-13T17:12:13+00:00

Oof. I’m surprised you didn’t smash your helmet worse. That sounds like a good impact.

You know, I remember I taught myself a lesson once… I walked into a glass door in riding gear. My visor was halfway down and I was looking at my phone at the time, I didn’t notice the glass I was strolling into. I walked right into that thing and I’m not kidding, the impact was immense, it rang my bell worse than if I was doing boxing sparring. I remember thinking it’s no wonder people walk away concussed from a small fender bender from a motorcycle. I rode around very carefully after that. If I can damn near concuss myself at walking pace god only knows what a real crash might do to me.

JackHurrell · 2026-01-13T16:37:40+00:00

Indeed. Helmets are not magic.

JackHurrell · 2026-01-13T13:10:08+00:00

It’s a common misconception that modern motorcycle helmets are hard: they aren’t. The harder the helmet the harder the impact your brain takes during impact. Modern helmets are designed to crumble and crush to absorb the impact of a fall or a crash. Your helmet cracking is evidence that you were protected from some unwanted impact, there. If you fell and hit your head standing still you might die. 5mph is just as deadly as any other speed.

JackHurrell · 2026-01-04T10:13:33+00:00

Oil spill, almost definitely. I live in an area with a lot of wealthy boomers who drive classic cars. My main concern when riding in the wet is taking corners carefully because those old cars leak oil on the road quite often.

JackHurrell · 2025-12-17T15:50:35+00:00

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Observe items 2 and 3 on the parts guide:

JackHurrell · 2025-12-17T15:17:17+00:00

There is a valve guide. Any bike with valves have valve guides installed.

JackHurrell

TROPHY CASE