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    The outside of a motorbike engine seen up close near the exhaust

    500彩票网安全下载 Ren's Biking Blog

    To Fix Or Not To Fix Or How To Fix

    I know I've covered this before but the CBF125's oil consumption is now, well, frankly, alarming. I check it roughly every 150 miles and I'm often putting in 200-300ccs of oil. I'd estimate in those 150 miles I've used say 5 litres of fuel which means it's running on roughly 5% oil. That's more than most 2-stroke's 2-3% oil mix.

    So what do I do?

    I could, maybe should, just leave it alone. The bike runs fine, it starts fine, the fuel economy is fine (save for the oil cost) and as long as I keep on topping it up at present there's no suggestion anything will go wrong. There is no point in fixing things that aren't broken. 

    Ren's CBF in 2013 when it was still quite new and clean
    Cor! I remember when it was new to me with about 6,000 miles on it.

    But. The only real issue is this alarming consumption prevents me from using the 125 for anything other than local runs. It's fine to go to Sharon's, maybe a day out in The Trough of Bowland or even North Wales. Anything more than that will require me to carry a litre of oil with me. If I were to go on a tour I'd have to purchase more oil as I travelled. I'd be worried about drying out the motor if I didn't stop to check it often.

    I have the 500 though. There's no real problem using the 125 for the local stuff then using the 500 for the tours. I'd just like the option. I'd just like the chance. 

    I could fix it up. For the staggeringly stupendous cost of - ready for this - £39 I can get a NEW piston and a NEW barrel/cylinder and a NEW set of rings and a NEW gudgeon pin and a NEW head and base gasket. That's just bleeding ridiculous, I couldn't buy the metal to make it for that price.

    Of course this will not be genuine Honda, this will be a Chinese copy of some description. Whether or not it meets Honda's exacting standards is unknown but at that price it's got to be worth a shot. Sharon's Keeway clearly demonstrates that the Chinese can and do make some good stuff.

    A genuine Honda barrel is prohibitively expensive at £370, 9 times more than the complete kit!! I would do better to buy another engine at that price and throw it in, job done. I could then strip the old motor at my leisure, more out of curiosity rather than need. It will be interesting to see what an 87,000 mile 125 engine is like inside.

    The piston on Ren's CBF125 but way back when it was still quite new
    I wonder what it looks like now inside the engine's top end?

    The problem with a new motor is - is it worth it? While the bike is still sound the rust mites are taking their toll and everything else is quite aged. Would it not be wiser to put that £350 - £400 for a used motor towards a much newer CBF125 or CB125F? I could end up with a 1,500,000 mile 125 rather like "Trigger's Broom" (8 frames, 12 engines, 4 tanks, 6 seats...)

    Then there are various shades in between all this. Used piston and barrel but genuine Honda? New genuine Honda rings? New pattern rings? A rebore and oversize piston is pointless at these prices. I suppose IF IF IF I decide to fix it the first thing is to strip the motor to see what is worn and what needs replacing.

    So the first question is - to strip or not to strip? Keep lobbing oil into it or start the process of fixing it? Remember I am not a retired gentleman of leisure. I can't take an age for this task as I don't fancy commuting on the 500 and leaving it parked outside the office.


    Share you500彩票网安全下载r motorcycling ponderings - click here.

    Reader's Comments

    Upt'North said :-
    I'd leave it alone for now and if and when it goes Caboom! Put the Chinese kit on it.
    I'm guessing you500彩票网安全下载're not using expensive oil and there's no need for oil changes either. Although it may still be prudent.
    If the Chinese kit is made from cheese and lasts one trip, so be it. Then you500彩票网安全下载 can Bury it in the back garden along with all the other bodies.
    Upt'North.
    27/1/2020 2:10:39 PM UTC
    Ren - The Ed^1 said :-
    What makes you500彩票网安全下载 think I'm not using expensive oil? No, but cheap oil ain't cheap these days. I'd struggle to find even the most basic of 10w40 for less than lb15 for 5 litres. Eeeeeeh I recall 20w50, 5 quid for 5 litres.

    Just as a note to anyone reading - don't use 20w50 in the CBF125. The conrod big end bearing has a needle bearing not plain bearing. The suggestion given to me is that the thicker oil can't get out of the way of the needle bearings fast enough causing a pressure wave in front of the needles. This is what eats the crank. I have no science behind this or proof although Honda did set it to 10w40 for a reason.

    Bury it in the back garden? Look, right ok, we know Mrs North made you500彩票网安全下载 put fence posts into you500彩票网安全下载r back garden so she could spend the savings on shoes, but we common folks don't have GARDENS! We have a small back yards covered in concrete flags, beneath that will be sewers, gas pipes, mains wires, water pipes and the mortal remains of my hopes and my dreams. There's no space here for motorcycles or bodies.

    Sharon on the other hand - poor poor Sharon does have a garden. If I ever vanish from the blog would someone be kind enough to check Sharon's garden for "fresh" diggings.
    27/1/2020 2:28:44 PM UTC
    John Scotcher said :-
    Be careful about using Chinese aftermarket pistons. I bought one from Wemoto for my Yamaha Serow, fitted it and the engine seized after about 5 miles. On examination by an engineer, he said the piston was not even barrel shaped as a piston should be. Basically, it was tube shaped which does not allow for different expansion rates on the piston. Needless to say, Wemoto didn't want to know, saying that they had never had any problems with them but they stopped selling them on their website after that!
    27/1/2020 2:51:07 PM UTC
    Ren - The Ed^1 said :-
    It's a tough call John Scotcher. I am aware there is some really rather nasty poop out there, but then Sharon's Chinese Keeway has 24000 miles on it with no issues and the quality is excellent. I have absolutely no way of working out those which are good and those which are bad.

    I could take the philosophy that "it's cheap, worth a shot eh", equally valid is "buy cheap, buy twice" which also translates to "buy cheap fit it remove it buy expensive fit it all again bike off the road for ages...".

    Maybe I just keep throwing oil in it eh.
    27/1/2020 4:25:04 PM UTC
    Snod said :-
    If it were me I'd scour ebay for a cheap, low mileage Honda barrel and piston. If there are none which are cheap enough then set up a saved search and keep checking.

    Alternatively if the gearbox is giving any bother then I'd be looking for another motor.. On the cheap of course.

    ~250ml of oil every 150 miles is so bad that even I, a TRX850 owner, would find it strange! Does it smoke? Does it make Sharon feel sick if she follows you500彩票网安全下载 for more than a few miles?
    27/1/2020 7:57:17 PM UTC
    ROD said :-
    I think I would go the all or nothing approach.
    Just keep topping it up with oil until something needs fixing, and hope it is not serious, or take the engine out and do a complete rebuild which will then last many miles.
    If you500彩票网安全下载 just replace the top end, surely you500彩票网安全下载 will be wondering what state the rest of the engine is in after 87,000 miles.
    The logical question must be 'Do you500彩票网安全下载 want to keep the bike, or do you500彩票网安全下载 fancy a change?'. If you500彩票网安全下载 want to keep the bike and a rebuild is viable, do a full rebuild.
    27/1/2020 9:20:23 PM UTC
    nab301 said :-
    Ren, maybe a set of oversize rings in a std bore , maybe the valve guides and or stem seals are worn.... Looking aparts lists it looks like the L/h main bearing isn't replaceable ( crankshaft replacement only )so maybe ride until it stops, maybe a new((to you500彩票网安全下载) bike would be cheaper.....
    Nigel

    27/1/2020 10:51:34 PM UTC
    Ren - The Ed^1 said :-
    Snod - what surprises me is that I'd expect to be followed by a cloud of blue smoke and a collection of environmentalists at this rate of burning oil. And yet no, it runs clean, no smoke on startup, no visible smoke when running. It's as though it has a leak. There is a minor weep at the cylinder head but nothing more. It's as though someone is just taking oil out the motor at night. CONSPIRACY!!

    The problem folks with a major or even minor rebuild is time. Top end, bottom end, rings, valves, whichever I do will take time. Presently the bike is in use 5 days a week for commuting. I dare not use the 500 as it's still too new to leave parked outside the office. The 125, being a dog, is unlikely to attract the attention of professional thieves.

    It's not like I could use Sharon's 125 while I work on my own as there's not enough space to move if there's 3 bikes in my shed. Anyhow Sharon would kill me if I got her bike nicked. I could use Sharon's bike and leave my 125 at hers where there's space. Bit of a long drag to go and work on it though.

    Hmmmmmm. listening to myself I know what's going to happen I suppose. I guess as ROD suggests just keep riding it till something goes pop then cross all these bridges at that time. Will I get a new (to me) bike, a replacement motor, a replacement motor then rebuild the old one, take up cycling, quite work and live in poverty?

    Here's an idea just popped into my head. Buy a replacement motor but store it ready to be fitted as and when this current one goes pop. That way swapping the motor won't take the bike off the road for too long, I'll have the old motor to strip down, play with and possibly recondition. If the cycle parts let me down before I get to fit the fresh motor I can always sell the fresh motor again.

    Hmmmmmmmm. You know I used to be very indecisive, I'm not so sure these days.
    28/1/2020 10:12:28 AM UTC
    Bill said :-
    Have you500彩票网安全下载 done a compression check dry then oiled to establish it is bore/ring wear before deciding. Valve guides usually shows as smoke on overrun. When the crf was using oil any one riding behind could smell it even when they could not see the smoke.
    28/1/2020 6:59:03 PM UTC
    Ren - The Ed^1 said :-
    Good call on the oiled/not oiled compression test Bill. Easy to do and may help with grasping what in particular is worn. I've never done valve guides before. From what I can tell it's a job for the engineer's workshop, apparently you500彩票网安全下载 can't just tap out the old ones and tap in the new ones?
    29/1/2020 9:27:03 AM UTC
    Upt'North said :-
    Ed of the yard, the back yard, yes you500彩票网安全下载 Ren.
    Valve guides, I haven't changed many and none on a bike but I seem to remember on Gardner diesels that's exactly what you500彩票网安全下载 did; number 2 hammer and drift of some sort to whack the bejesus out of em.
    May not have been best engineering practice though.
    Upt'North.
    29/1/2020 12:53:37 PM UTC
    Ian Soady said :-
    Valve guides on the kind of bikes I ride are easy enough - warm the head up and use a stepped drift to knock out the old ones and knock in the new. However, I suspect that the alloy in you500彩票网安全下载r head is not the most robust and it probably doesn't have the meat around the guides to support this method.

    Whenever you500彩票网安全下载 fit new guides you500彩票网安全下载 "should" recut the valve and seat although I'vew got away without.....
    29/1/2020 12:55:37 PM UTC
    Bill said :-
    The 230 which is a very similar motor has valve guide seals, it can be done without removing the head, piston at tdc compress spring and valve will not drop much. Rubber band on valve to hold it fully up on assembly, easily removed afterwards Cheap trial fix. I found more economic to buy a 2nd hand low mileage (comparitively) head rather than changing guides.The company who rebored the barrel had an accident and broke it and very kindly replaced it with a new genuine Honda with piston so should last many more years.
    29/1/2020 4:07:03 PM UTC
    nab301 said :-
    Presumably, looking at the cost of an OE replacement exhaust the CBF has a catalytic converter somewhere in the system which would probably explain the lack of smoke although if it's burning as much as you500彩票网安全下载 suggest the cat is probably well on the way to being damaged. If it's burning two stroke amounts of oil (even 50:1 like my EM Zed)it (oil) would be dripping out of the exhaust at this stage like any other two stroke I've owned. ... I have tapped valve guides out of alloy car cylinder heads and replaced them by cooling the new guides and heating the cylinder head but as Ian suggests I always required the use of a valve seat cutter afterwards which meant a trip to the engineering shop.
    Also , on my recently mentioned race imp I used to routinely do compression tests after each event to preempt any loss of performance , so when I detected loss of compression I carried out the text book wet compression test that Bill suggests and it ( cured ) the loss of compression, but in my case the loss of compression was valves and seats. I guess at slow cranking speeds the oil will seal these too. Hopefully it may just be the Stem seals . Maybe a cheap borescope would allow invstigation without too much stripping?
    Nigel
    29/1/2020 9:36:40 PM UTC
    Ren - The Ed^1 said :-
    Whenever I see, read or hear of someone replacing the valve guides there's thing thing where you500彩票网安全下载 are supposed to "ream" them to size. From what I've just researched the utterly correct thing to do is fit the guides which should be oh-so-slightly tight, rig the head up under a drill press at the right angles etc etc and use the reaming tool to ream the guide to the exact tolerance and precise perpendicularity.

    But most in the forums say "it'll be reet", "it'll ream itself in", "just stick the reamer in a hand drill for a few seconds" and so on. So er, I'm non the wiser.

    I can do the valve stem seals no problem, I have a valve spring compressor.
    29/1/2020 9:49:46 PM UTC
    nab301 said :-
    All of what you500彩票网安全下载 say is true which is why I generally leave it to professionals. As to "reaming itself" , I stripped a head off a car engine which had been running nicely ( to cure an oil leak ) and discovered a previously bent valve ( presumably a cam belt broke ) Everything will bed itself in if you500彩票网安全下载 leave it long enough I guess!
    The problem I've had locally in recently years is the demise of engineering shops and especially the demise of shops willing / able to tackle bike engines . I left an Enfield Bullet barrel in for rebore and a cylinder head in for new guides and exhaust seat but it took nearly a month for them to complete the job and it felt like they wanted to bill me for the entire months labour too...
    Nigel
    29/1/2020 10:31:08 PM UTC
    Ren - The Ed^1 said :-
    In all my time spannering I was about 20 when I last used an engineer's workshop to skim the head from my mother's Cavalier. As such I can't speak of how many engineering places there are these days. I do know there's a place just around the corner from where I work that does car engine stuff, I've never asked about bike stuff.

    I suppose we live in a time where engines are in fact quite reliable and cars are considered more of a consumable than back in the day. Things have changed, when did you500彩票网安全下载 last see a TV repair man and washing machine fixers are few and far between. The engineering shops that remain will likely do work for enthusiasts with vintage or racing or performance machinery.
    30/1/2020 8:57:38 AM UTC
    Ian Soady said :-
    There are still plenty of those engineering places around, at least in the Midlands. In my new leafy abode of Redditch there is an excellent place called Nametab which will tackle any sort of job. They do specialise in 2 strokes but don't hold that against them....
    30/1/2020 10:25:45 AM UTC
    Pocketpete said :-
    Hmm all that work for a bit of oil loss. I knew you500彩票网安全下载 were tight but its only oil ren.
    30/1/2020 11:14:10 AM UTC
    Ren - The Ed^1 said :-
    Have you500彩票网安全下载 moved Ian?
    BIT of oil loss Pocketpete? BIT?!?! My concern is drying out the sump.
    30/1/2020 11:33:12 AM UTC
    RobEll said :-
    Hi Ren, just a thought but when my old off road, long-toothed XL250 farted it's last it was haemorrhaging oil via the final drive output shaft oil seal. Maybe worth a looksee bit likely already on you500彩票网安全下载r have-checked list. In other news: My little Keeway RKV 125 is banging away better than ever at 15000 miles in 17 months and only a few minor fixes for rear caliper dragging (clean piston/caliper every quarter and done), and shield (duct tape) some wearing wiring sheathing. Love that little bike, and much of it is way over engineered e.g. massive upside down forks and frame from the previous RKV200, only the thin paintwork or electronics are unknowns so far. Much cheaper to fix than my ageing car which costs at least lb300 every visit to the mechanic...with ever more alarming frequency.
    5/2/2020 9:30:35 AM UTC
    Ren - The Ed^1 said :-
    There's no oil on the floor around the bike and no serious oil leaks. There's a weep from the head gasket but the oil dries out before it even starts to dribble it's that slow.

    I'm glad to hear the RKV is doing well! Do you500彩票网安全下载 use it in all weathers? At just shy of 1,000 miles a months I'd guess you500彩票网安全下载 do. And find me a bike that's used regularly and doesn't require the brakes servicing all the time. I used to own a CLR125 City Fly fitted with an supposedly "cheap" Grimeca brake. It was loose, rattly, the pistons weren't so tight and the paint flaked off. But BECAUSE it was built to low tolerances it never seized up and worked a treat. Here's to slack brakes.
    5/2/2020 12:46:54 PM UTC
    RobEll said :-
    Ah, I thought you500彩票网安全下载'd have considered it, the oil leak on that old Honda was
    much increased with the engine running but had more than one oil leak! And yes in all weathers getting to and from Bristol 3 days a week from South Wales for work, a salty business in Winter. I'm a little lazy with the daily (read weekly), bike rinse and it's faring very well on rust front but it is garaged. I've been swapping some parts across from RKS bits which seem a bit easier to find & cheaper, sprockets and the like - these bikes are just SO cheap to buy and run, and everyone likes a bargain! The cheap transport sector of the bike market has been well and truly revived by the recent influx of Chinese commuters, they could teach the big Jap 4 a thing or two, looking at the new super cub for around lb3k...
    6/2/2020 6:17:08 PM UTC

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