Honda S-Wing FES-125-7 2008 crankshaft main bearing

marcocambridg... · L Plate Warrior Joined: 09 Mar 2017 Karma :

Hello everyone,

I am about to replace a main left bearing on a Honda S-Wing FES-125-7 2008 crankshaft, because the bike doesn't go faster than 25mph and is making a loud noise over that speed. Drive parts and clutch was checked/replaced, but the problem is still there.
Compared to a good working bike, there was no up and down play on the other scooters crankshaft there is on mine. I am certain now that the noise that occurs is a bearing noise, and when it is cool it operates as it should for a short time, as soon as the engine is above a certain temperature (which is getting lower every time I use it) the power is lost.

Any ideas how to start? I am a handson person, did many mechanical repairs on cars, but never dismantled this bike.

I am happy to share pictures later, would you be able to help with tips and tricks, please?

Best regards,

Marco

Paulf · Nova Slayer Joined: 24 Jan 2017 Karma :

Hi most likely your big end has gone it seems to be a problem that has occurred to me and others on the forum. Firstly your need to take nearly all the plastic fairing off. Get the engine out and strip the engine out. Not sure about your competency. But a good idea if you are looking to do it yourself is get the honda workshop manual. Good luck and note the panels come off in sequence and it is going to take a couple of days to complete.

marcocambridg... · L Plate Warrior Joined: 09 Mar 2017 Karma :

Hi Paul,
Thanks for your tips.
I have ordered a Haynes Manual for the bike, it will arrive next week.
Until that I will take off the fairings, I have done that on another bikes.
What do you mean by big end? Is that the left side of the crankshaft?
I am attaching a photo - it shows that the crankshaft has an up and down movement.

Petemate · Trackday Trickster Joined: 13 Nov 2015 Karma :

marcocambridg... · L Plate Warrior Joined: 09 Mar 2017 Karma :

Thanks for the comment, Pete.
I am attaching a photo of a crankshaft assembly. I guess my end goal is to replace those main bearings, which one? The red or blue arrow? Or both?

Paulf · Nova Slayer Joined: 24 Jan 2017 Karma :

Sorry my initial diagnosis was incorrect but my solution is. The bearing cannot be extracted without splitting the crankcase something I have done recently. As you progress I am happy to help give advice on possible problem e.g. removing stator flywheel and splitting the crankcase. My big end had gone completely no balls or rollers, they where metal flakes in the sump. My solution was to buy a crankshaft assembly with main bearings off Amazon and gasket set. Crankshaft assembly £115, it was cheaper than having the bearing professional changed you might get away with just changing the main bearings. Note I found the bore was scored by the unusual movement associated with the big end gone. That was solved by buying a barrel and piston set £70 approx off ebay or Amazon. You might be lucky. I brought the bike as spares or repair so I am still quids in on a comparable bike price on eBay when finished. Good luck

Petemate · Trackday Trickster Joined: 13 Nov 2015 Karma :

Paulf · Nova Slayer Joined: 24 Jan 2017 Karma :

Sorry to answer your question the red one, it has the timing chain cog, the blue one has the oil pump and starter gear. For good reason honda has captive, ie within the crankcase main bearing. There is a cast lip in the crankcase stopping seating extraction from the drive pulley end, probably get a seal as well, it under the plate on the drive side, oh and remove the plate before you remove the chain tensioner bolt, if you ask me how I know I did not, and nearly rounded the hex socket in the head. And I have the honda workshop manual Embarassed

cb1rocket · World Chat Champion Joined: 30 Jan 2010 Karma :

Just did mine.

https://goo.gl/photos/VURjBgMSzoGE4xEp8
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Petemate · Trackday Trickster Joined: 13 Nov 2015 Karma :

Paulf · Nova Slayer Joined: 24 Jan 2017 Karma :

Yes going on mine as well lots of bearing bit everywhere.

cb1rocket · World Chat Champion Joined: 30 Jan 2010 Karma :

Can be caused by running low too low on oil but just enough that it still keeps going after an oil change etc but the damage is already done.
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Teflon-Mike · tl;dr Joined: 01 Jun 2010 Karma :

Damage is also likely to be far more than one bearing.. that would tend to be more a symptom than a root cause prolem.

Giving a day to get the engine out, and another to strip it and assess daage and TOTAL extent of possible damage, which will almost certainly be more than one £5 bearing, and likely the entire £150 crank, and could even have taken out the bearng boss the crank-case, cam, cam bearings and or head, and rockers, cylinder and piston rngs, probably even effected the oil pump.... the bill could all told be very very big ideed.

I do mechanics for fun... so I dont cost my time... but I am mad.

If that time, to JUST find out the extent of damage was costed at NMW of aprox £6 ph, you have best part of £100's wrth of labour just to find out how much is really wrong... add another two days of faffing to put t right, plus the parts, even if just crank gaskets and sundres, then another two days to put it back in the frame and de-iggle... with a fair few hours in etween cleaning and inspecting, ordering bts, finding tools you ed etc etc etc....

Even DIY this is likely a £250-£300 job in parts alone, an £300's worth, a weeks worth of holiday, JUST to get it back i service.... how much do you earn on over-time? How d you preffer to spend your week-ends and holiday? That IS lkely threshold cost of getting another bike, that already works, rather than one that 'might' if you have been careful enough.

THAT is the bottom line.... investing a day or so to find out, may be worth the loss.. much more you need be sure just what you have to contend with, as shortcuts are far to often a easy way to a lot more work and hassle and expense.

Can be fun, of course.... BUT you do have to be not just 'mad' but a peculiarly perverse sort of mad.... especially f this s your sole transport and work hours and lack of transport making going and gettng bts and tools that much more hassle.

My advice on where to start, is to stop! Back up, DONT spend a penny.. wait for the book, and start stipping, cleaning and inspectng, very slowly, carfully and diligently, listing ALL the things that possibly need attension or replacement n a rebuild, and costing them up. Rushng be fast way to hurt on two wheels... ecconomic as well as phyical... while accidents happen when confidence out strips competace, and again, works off the bike, and even more whe you have spaners i yoru hand, as a twist grip on t.

Whle, whre you are at the moment, not sure of the dfference between a big end and a man bearing, or how crank-cases split, it does suggest a rather steep learning curve, a lot ore than 'average' time to do any job, checking the book, fgiuring it out, dong reseach etc.... are you REALLY up for this?
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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?'

Petemate · Trackday Trickster Joined: 13 Nov 2015 Karma :

Good post Tef. From my own case, I totally agree with all your points. On reflection, my little LA simply was not worth all the efforts which I have out into it so far, from the aspect of 'getting back what one lays out'. However, it was a good exercise in terms of what the best course of action is and I have enjoyed working on it. From the start, instead of spending approx. 170 quid for the pair of 3rd gears, I should have just gone for a second-hand cluster, which in the end is what I did when the 4th gear joined the queue and cried enough. Even at the tender age of 80, I am still finding that hindsight is a wonderful thing.
Also food for thought is that I could have got myself a nice condition CB500 when I got the LA; once my OH sanctioned the purchase of a bike to keep me busy in retirement I jumped straight on the first thing that came up within a purchase budget of about 400. Now I realise that I could have got a CB500 for the same dosh.
Sorry mods, I digressed.
OP - I hope you get the scoot sorted and for not too much money. A shame that it may have clouded your opinion of Hondas - it could happen to any bike. I was lucky - the main components of mine had been looked after and I can wring its neck whenever I go out on it safe in the knowledge that all is well.
Look after the oil level!!!
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82 not out....1983 Honda LA250 Custom
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Teflon-Mike · tl;dr Joined: 01 Jun 2010 Karma :

Paulf · Nova Slayer Joined: 24 Jan 2017 Karma :

On my fes 125 , bought spares or repairs, had the big end gone. I can see how this happened to mine the sump plug had rounded hex head. Needed a nut extractor on a 3 ft extension and all my effort to get it off it was at that stage were you get either it shifts or the crankcase goes bang and shatters before it started to go. The oil was black. So mine was due to lack of maintenance. Mine is a project if I sell it for what I spent all's good, it something to do and I must be mad as well I enjoy it. EBay and Amazon is your friend and I have 4 wheels to get about. And I did not buy all the specialist tools to remove flywheel, split crankcase, now strippiedhand built front forks.