Honda CB125 TD Engine Issue

[ajordan9]

Hey,

So I have an issue with my bike after riding it 100 odd miles to Portsmouth and back over the weekend.

For some reason its started making this really high pitched spluttery noise: https://youtu.be/XGnKIBBrq2E

And also I noticed when pushing the bike into the higher rev ranges it jutters slightly. But getting it moving fast is hard in London where everywhere near me is 20.

The idle or engine never sounds this high pitched, its almost like im riding a 50cc.

I did check the oil level too and it was between the markings but on the lower end. I might replace it although I only did this last month.

Would be great to know if you have any solutions.

Thanks,

[WD Forte]

I'd hold my hand near (but not touching)
around where the downpipes connect to the head and around the head gasket area to see if I could detect any leaks

Engine running of course
____________________
bikers smell of wee

[Teflon-Mike]

Well, for starters, it shouldn't be blue.
Next up your cam-chain is making a heck of a racket.
The tappets are noisy
It sounds like you have a hole in the exhaust or a missing exhaust gasket.
It's missing intermittently on one pot... quite a common issue, at low revs or on a knackered motor.

Start by servicing it; adjust cam-chain tension, its NOT automatic, and the adjuster is awkward to get at between the carbs. Adjust tappts; I recommend buying the proper tappet key from Dave-Silvers, maybe even the lock-nut spanner that goes with it; pair cost about £15 the lock-nut spanner the expensive bit, but since job needs doing every two oil changes, and they should be done every 1000-miles, they will pay for themselves pretty quick. Also oft advocate ordering new tappets at the same time... reason I advocate the tool, is how many I have opened to find the tappets chewed top feckery by folk trying to adjust them with a pair of mole-grips or pliers rather than proper tappet tap.

HINT: give it a good 15 minute 'hard' run before service to get it hot; makes oil come out easier; renew spark-plugs at the same time, and check the colour of the plugs when you remove them, before fitting new against pictures in the Haynes.

Probably wirth sticking a pair of exhaust gaskets on the parts list too; they may not be shot, but good chance some muppet has removed one in belief its the magic 'restriction'... no, they make about 12bhp in good fettle, 'cos that's what they make! Earlier T-shock examples and rare 'other-market' Super-Dreams had the more powerful, 17bhp motor, that had larger carbs and the rare as rocking horse 309 cam-shaft; they were de-tuned, NOT restricted.

On the exhaust headers; I have never come accross one that hasn't got either dents, dings scrapes and or holes, in the lowest part of the headers as they bend under the engine; whether OE twin-pipes Motad or Micron 2-1, they all suffer there as it IS the lowest part of the exhaust where water collects to rust the metal from the inside if it only ever does short runs and never gets hot enough to boil off the condensation; also where the pipes get kerbed, going up and down pavement kerbs, and where metal stretched thinnest when formed.

Otherwise; I have a little fleet of these things, and I REALLY cant diagnose everything with 100% accuracy from vague sound track of the thing ticking over in a U-Tube vid taken with a smurphone! So, be prepared to buy the book, and do a bit of popper diagnostics, IF anything persists after servicing it, and eliminating the obvious variables.
____________________
My Webby'Tef's-tQ, loads of stuff about my bikes, my Land-Rovers, and the stuff I do with them!
Current Bikes:'Honda VF1000F' ;'CB750F2N' ;'CB125TD ( 6 3 of em!)'; 'Montesa Cota 248'. Learner FAQ's:= 'U want to Ride a Motorbike! Where Do U start?'

[ajordan9]

[Teflon-Mike]

You still need top tension the cam-chain, and do a service.

The exhaust flange has come off. You will need to new nuts to put it back on; you will also need the two collets (pt No. 18233KB4000, £4.38 each at DSS) that should sit behind it and press the exhaust into the exhaust port, that will also have fallen off, and not stayed around the exhaust pipe; you will also need to remove that header completely, so that you can get into the exhaust port, pries out the old, and now crushed and useless old exhaust gasket and replace with new.

Replace old parts, then put the flange over the studs just far enough to get the new nuts aprox 2 threads.. then tighten evenly 1/2 turn on each nut until firm.. do NOT over tighten. Ride till warm; check exhaust flange for leaks, and do up a final 1/4 turn each stud... then if there is room on the stud.. lock with a double nut so that they wont shake loose again.... then check periodically that they aren't loosening off.

Add-on-Edd: - Just spotted the 'root cause'.. the collets of both headers appear to have been fitted inside out. Hence flange puilled so far up the studs leaving so little room for nuts, hence nuts shook off the LH header.

Buy two new gaskets, and refit exhaust both side, with collets the right way round, and you should be able to double-nut so that they wont fall off like these did.

[ajordan9]

[WD Forte]

I wouldn't quite call it dangerous, just the that bike will run as rough as a bears ass like that.
While you're sorting the exhaust out it may be worth checking over the rest of the bike to see if anything else is working loose.
Preventative maintenance and all that.
____________________
bikers smell of wee

[ajordan9]

So I've managed to sort out where the pipe goes into the engine and seal that up again with new parts. Thanks for the help on that!

However when I took the exhaust off on one side I had to remove a clamp from underneath which seemed to hold the two exhausts together.

Heres a pic: https://ibb.co/eSOtAK

When I put it back on I noticed there was quite a bit of air coming out of pipes where they slot in. Do you guys know if there is a gasket in this section that might need replacing? it seemed to have something but think over time its broken off or maybe even not been replaced when taken off in the past.

This is what it looks like without the clamp.
https://ibb.co/jWhycz


Thanks so much!