Honda CB125

Honda CB125E - 40 000km Report

So it is now just over six years since I bought my trusty Honda CB125E. How time has flown by! I've had my full licence for over four years and as I write this there are four motorcycles parked in the garage, three Hondas and one Yamaha. Of course one of those Hondas is my CB125E. Other bikes have come and gone over the last few years but my CB is a permanent resident. I don't think I'll ever sell it. It's just too perfect to let go. It is still the bike that gets the most use and despite the company it keeps in my garage it is still my favourite machine. If I had to sell all but one of them you can guess which one I would keep.

The interval between this report and the previous report was quite lengthy as my personal circumstances have changed. We have moved house and my commute to work has become much shorter. I no longer ride to work as my work machine (a truck) is kept in my front yard. My commute is now a short walk of about twenty or so steps. The little Honda has become my personal transport and around town machine but still gets almost daily use. My other motorcycles have mixed uses, two of them are historic Hondas from the 1980's stored for future generations to enjoy and the Yamaha is my weekend escape from the city machine. The time taken to clock up the next 10,000km was a lot longer as a result. And for those who are wondering, I still have my trusty Holden Ute. It has been unregistered for a long time!

The bike has had very little in the way of changes up to this point however the 40,000km mark was a goal I had set when I started this website all those years ago and this report will be a little special in that I have taken the step of tearing the motor down so that we can have a look inside and examine how worn the engine has become. I chose the 40,000km mark as this is an interesting point in the life of a small motor. Postie bikes like the CT110 and the NBC110 as used by Australia Post are often due for a rebuild at around this mark. Most scooters are the same. Consider that to travel at 90km/h the CB125E has to spin at around 7500rpm whereas a Suzuki SV650S I had up until recently chugged along at barely half that, 3900rpm. Small engines do not have an easy life! I have acquired another engine from a motorcycle wrecker for us to make a comparison with as well but lets not get ahead of ourselves. Lets look at the bike itself and then the state of the engine.

Issues and Problems

So my little Honda had its first and only break down of a sort. I got up for work one morning at the 35,050km mark and turned the fuel tap on to start it up. I never let any bike sit over night with the fuel tap on by the way, when I'm finished with it off it goes. Anyway, when I turned the fuel tap on my fingers were wet with fuel. The fuel tap had started to leak from behind the fuel cock itself. Just a drip but a constant one, you can't ride around with a fuel leak so off to work on a different bike I went.

A replacement fuel tap assembly was purchased from Western Motorcycles in Penrith. They have the Honda parts fiche online making it very easy to pick out what you want and order it regardless of the time of day. Very convenient and very cool. I bought the whole assembly part no. 16950-KYA-601 for a very reasonable $38.09 plus postage (about $10 from memory) as it made the swap over easy and included new O-rings and such. It arrived in about a week and I was back in business.

Wear and Tear

The bike itself has become slightly weathered as it is ridden rain, hail or shine and is now over six years old. Corrosion is limited to the mirrors for the most part and not particularly badly I must add. Surface rust has appeared on the frame in places where it has been stone chipped but once again surface rust with no pitting. I have to boast that it has never been laid down or even so much as fallen off its stand in all of the time that I've owned it. It has a couple of light scratches on the tank from a cockatoo that settled on it (and got sent on its way quickly) but other than that the paintwork is all original, very much intact and presentable despite the all weather riding.

At 37500km the rear tyre once again required replacement. Unlike the early days of owning this bike where the unusual tyre size made finding tyres of the right size challenging I found a Pirelli City Demon at a good price right on the shelf at Trooper Lu's in Moorebank. The market has really stepped up to the plate and the Pirelli wasn't the only available choice. So that is the fourth rear tyre for the bike while still on the second front tyre.

Oils Ain't Oils?

Engine Tear Down Comparison I've bought myself a couple of spare motors for my Honda as I want to start playing with big bore kits and other good wholesome activities while keeping the original engine intact. There is a company called High Octane Commuting that has started to stock a range of affordable spare parts and even big bore kits for the Honda CB125E. Their 200cc conversion looks interesting indeed though it involves replacing a large number of parts in the engine and is priced accordingly. I wanted to see how my original engine had travelled over the last six years and, seeing how I have removed it from the bike anyway to make room for a project engine, it wasn't hard to pull it down and have a look. One of the engines I've bought for project came from a wrecker and was dirt cheap on account of the fact that when they tried to start it the motor made a pretty impressive rattle. It came from a bike with 29,000km on it. If you take a look at the above picture you see a comparison between the wrecker engine on the left which I've nicknamed BOB (as in Bucket of Bolts) and my bikes original engine on the right after 40,000km. And wow what a difference!!

Total Piston FailureJust looking at the accumulated varnish on BOB and comparing it to my original engine we can see a significant difference. BOB was not well treated and failed prematurely as you can see by this close up of the piston. I would say that BOB's oil changes were very few and far between resulting in significant piston ring wear. When the piston rings wore out the piston skirt gouged the cylinder wall and disintegrated. By the way, if your piston looks like this you need to completely strip the motor down and remove every bit of shrapnel. You can see some of the shrapnel I collected out of BOB under the piston in the photo.

My engine on the other hand is clean inside despite having over 10,000km more on the clock! You can see the scuffing on the piston skirt from normal contact and although this piston is far from new it is still quite servicable. Measuring the rings showed wear but once again still very servicable and within specification. This engine would have continued to run for some time though how much longer is hard to say. At least another 20,000km or 30,000km. Perhaps more, perhaps much much more.

The difference is of course how the bike was treated. BOB rarely saw fresh oil but my Honda had an oil change every 2500km without fail. I warm my bikes a little before riding them, I doubt BOB ever had such kindness. Some food for thought maybe?