125 Engine Life

[andrew]

Just wondering if anyone out there can advise. I read in an old copy of Bike magazine that any bike engine under 250cc is very unlikely to last more than 20 thousand miles. Is this the case?

I've just started using the City Fly to commute to and from work and am a bit concerned by what I read. Surely bikes like the CG, SR, City Fly etc... must be built to last longer than that?

Obviously this depends on how you ride them and how well you look after them I'd just like to know if I should expect my bike to blow up some time this year.



Thanks.

[Fire_Eyes]

I'm not really sure about the exact life time. But I think that 2strokes in general last less than 4strokes.
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Kawasaki ZZR 400 | K5 GSX-R 600

[Liverpoolrobb...]

ive got a 2stroke thats lasted 18k so it aint bad

[simon1221]

Ive seen some 2t 125s that have 35,000 miles on, wont last much longer.

If you do the service interval stuff then it will probably last about 30k for a 2stroke at the least.

4stroke (cg125) last forever.
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DNA50 (sorry) ->> TZR125l >> GPZ500S

[andrew]

Guess i'm just a bit worried because the route I take to work is mostly large A Roads which means the engine is close to the limit most of the time it is ridden.

Also in regard to 2-strokes, a 30k + 2 stroke would have been rebuilt a number of times, I just wanted to know how long until my 4 stroke goes bang??

Oh and for the record, Bike suck!

[0ni]

I'm on 37,000 miles on a 23 year old Honda CB125 TDC. 13 previous owners and everyone of them probably abused the bike.

Nothing serious has happened with the bike that wasn't caused by someone arsing up a repair. Parts are dirt, dirt cheap. Check the other thread about the £20 Cylinder head and top cover including delivery.

Change the oil, lube the chain, keep it tightened. Replace consumables when they need to be replaced and it should last forever.

If it doesn't then ebay is your friend and just put a new engine in for £20.

(Oh yeah, matt black paint sprayed on everything apart from the seat, chain, lights and number plate keeps it looking daz fresh )
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Its a lovely day, just wait until some bastard spoils it.

[Kickstart]

Hi

Depends how it is treated. Older ohc single cylinder Honda 125s used to have very short engine lives before the head and cam became a one piece unit (plain cam bearings, no real oil filter and owner abuse really were not a recipe for a long engine life). The twins were not quite as bad.

Modern stuff should last OK, 2 stroke or 4 stroke, in a low commuter state of tune. In such a state the 2 stroke will probably be more able to put up with being thrashed from cold and skipped oil changes (it is not reliant on a high pressure oil system managing to pump cold thick oil round when you start the engine).

However I would not expect either to do much over 20k~30k without needing some work (cam chain, rebore, possibly valve problems), less if being thrashed all the time. Smaller bikes do not exactly have the best build quality (after all, if does not cost that much less to make them than a sports 600 so they save their pennies on component quality and cheap labour to drive the prices down).

UMG says the CG engine lasts 30k~45k, the CB125T is said to be basically reliable up to about 25k. I would expect the City Fly engine (more complex ohc engine) to be closer to the CB125T engine life.

2 strokes are definatly easier to fix when they go wrong. Friend used to do the various 4 corners charity runs in the late 80s. He tells the tale of some old guy who used to do them on an AR125 (yes, 4 corners of the UK on a 2 stroke 125 with luggage and at a fair speed) who was seen smacking a screw driver down the spark plug hole to unseize it before carrying on his way.

All the best

Keith
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[tatters]

it will be intresting in a few years to see how long the CBR125,s have lasted mileage wise.


my 1998 NSR125R had 33,000 miles on it with a untouched engine when l sold it. l put it down to being restrited all its life and being run on TTS.
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Past:NRG50,AF1125(x2),NSR125RR,ZZR250,CX500,VFR400,KR1S,ZZR600(x2),CB400N,YZF1000(x2),KH125,Z200,FX400R,CBR954RR(x2)GPZ500S,GT550,VFR750F(x2),RD350N,XR650R,CBR600F,CB250,KDX250,YZF750R,CRM250,400EXC,KLR650,TTR600RE,DR350S,R100GSPD,RGV250,VMAX1200,DL650,KZ750 Present:G650XC,C12,CRF450X,1190ADV

[Liverpoolrobb...]

my runner hasnt had a rebuild so far!

[andrew]

That's no good at all. I was planning on keeping it for quite a while to commute on aswell. I guess the money you save on petrol and things like tyres will be made up when the thing goes pop.

Keith, any idea on how much a 125cc 4 stroke would cost for a complete engine rebuild?

[Kickstart]

Hi

Depends on what need replacing.

Worst realistic scenario:-
Rebore
New piston
Gasket set
Big end bearing
Main bearings
Cam chain
Tensioner
Regrind valves

Basically nothing too hideously expensive but the labour will cost a bit if you are not prepared to do the work yourself (and the big end / main bearings are not that likely to go if you treat it well). It could get far worse should the cam seize into the head, in which case you might get away with repairs to it (SEP in Kegworth used to do a good business in Honda cylinder heads), or you might need a new head and cam (hideous from Honda, probably not bad 2nd hand). Given that the City Fly is a learner bike it would probably easy to find a good recent engine from one which has been crashed.

Treat it well with regular oil changes (probably every 1k~2k on that engine as there is not much oil in there), give it a chance to get up to temperature, etc, and you will probably just get away with an oocasional rebore and new cam chain which I am sure you are capable of doing yourself.

Sorry, not really a good answer but it is a bit of a "how long is a piece of string" question.

If you are doing that kind of mileage something like a CB500 might be best. At least this would be far from stressed at the same kind of speeds, although servicing costs would be about the same.

All the best

Keith
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Traxpics, track day and racing photographs - Bimota Forum - Bike performance / thrust graphs for choosing gearing

[pipnet11]

Sounds like they are on about 2T engines. 125 4T engines seem to go forever even when getting thrashed all the time. My GS was sold with just over 51,000 miles on the clock. The clutch plates were the only real thing that was wrong with it, and this was only because it had sat in a scrap yard for 3 years!! Other than that all it needed was a bit of tinkering to get everything moving again and it was fine. Lasted 5,000 miles with me on it.
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I love the girls that do, I hate the girls that dont, I hate the girls who say they will and then they say they wont, but the girl I like most of all and I think youll say Im right, is the girl who says she never has but looks as though she might. - Max Bygraves

[DynaMight]

I dont think you can say x engine will last x miles, Some go on and on and on, Some dont.
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My bikes are at https://www.bikepics.com/members/dynamight/

[mchaggis]

My Mum's CG125 got knackered bearings after 33k miles. We've no idea how it was treated before we got hold of it, but the horrific instant gasket goop leaking oil out of the head can't have helped. The gasket was knackered anyway, but the bike started losing power and the footpeg vibrating after about 500 miles of getting the bike.

So, I'd say it depends mainly on luck and regular servicing, as well as obviously the style of riding. The engines were built to be thrashed after all.
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Discovering the delights of Hammerite and a 3/4" brush.

[mrchips]

The AR had 20k when I bought it, and now it's up to 27k. By July when I sell it will probably be up to 29 anyway. I look after it and all but in the last 7 miles at least, it hasn't had a rebuild so hoping to get another 3 or so out of it. It's rarely taken over 60 and I've only had it flat out about 4 times so I'd be disapointed if it went bang.
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Northern Irish? www.nibikers.com

[Frost]

My CB125 was on 48,000 and still going.

[Kickstart]

Hi

Problem with stories of high mileage is that we have no idea of how many rebuilds they have had prior to their online owners getting them.

All the best

Keith
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Traxpics, track day and racing photographs - Bimota Forum - Bike performance / thrust graphs for choosing gearing

[nwbiker]

i have seen a CG125 with 60,000 miles was a bit looked after and probably would still be going if he didnt decide to turn it into a field bike for messing about on!
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[stevo as b4]

Well my mate had a CG125 that had 26k when he brought it, and it lasted until 37k when a main bearing decided to give up. I stripped that motor, and apart from 1 broken up bearing, (clutch side) everything else looked fine! He fitted a secondhand engine, of unknown history and that lasted him another 5k until he had the bike nicked by local scumbags. He didn't change the oil quite as often as he should have really, as the CG only holds a litre and does without a proper oil filter. If you change it every 1000mile, you shouldnt have any problems, though and thats what i did with mine, but that had only done 14k, so it was hardly run in compared to his!
We both used to ride the CG's flat out everywhere, and neither of us had a problem. They are tough engines that go on and on, if you keep changing the oil regulary.

My KMX200 has 19600m on the clock, and its shattered the piston at the front, which has kind of broke off at the bottom ring, and taken most of the rings out with it, and spat all the bits down the exhaust. I haven't stripped it yet, but ive got a feeling that my Nikosil bore is cactus, and also after it went pop, transmission oil started leaking from the bottom of the engine, so im wondering if some bit of piston has found its way into the cases and damaged the sealed part of the cases that the crank fits into?

It's always a bit of a lottery with a high mileage 2nd hand 2stroke, and if you dont have a history with receipt's and old parts to prove it then it can be like a ticking time bomb, in that you just don't know when it will go bang? My engine was quite noisy, and it sounded like it had a bit of piston slap, but there was no other indication that it was about to go pop. the nuts at the head and barrel were slightly chewed, so it must have been apart at least once or more times. It doesnt make any difference how you ride the bike either sometimes, if a 2stroke engine is worn out, it could expire without much warning at any time!
My advice to anyone with a 2stroke thats got say 10-15K on clock, is that your always better to do a preventative re-build, while it's running well, as if you do let a stroker wear the piston and rings severely, then it can do alot of damage to the rest of the motor if it blows up, which could then cost you 2-3 times or more, the cost of a top end re-build to repair!

[Kickstart]

[jimster]

[mchaggis]

[Flip]

[RickyP88]

Got my Cityfly last July, she'd been sat rusting for 5 years in someone's leaky garage untouched, spent 4 weeks with a wire brush, rust converter and black paint getting her looking somewhat better, new battery, fresh spark plug, new battery, new pads, new chain and sprockets and a full tank of fresh petrol and she fired up straight away.

She came with 11,250 miles on the clock and 12 months on the road she now has 21,600 miles under her belt, since then all I've had to buy is a new back tyre, new set of sprockets and chain and a couple of bulbs.

The exhaust is a bit of a bodge job as I can't find a new one but nothing a good amount of pigeon shit welding and plenty of high temp silicone sealant hasn't kept it working.

I'm hoping to get another 10k miles out of her yet.

[Pol Anorl]