Engine - strange tapping noise

Have acquired a noticeable tapping sound on the honda cbf125 engine. Makes the loud tapping sound when idle and increases with revs. Im wondering if this could be something to do with the cam chain tensioner (bike is at 33k miles) or if it could be the bearing roller on crankshaft?

I have a haynes manual for the bike and this would be my first attempt ever at looking inside an engine.

Any help would be greatly appreciated and was wondering what are the simple things i should check first before getting the engine out.

Thanks, Phil.

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Originally Posted by Killer Rat

Have acquired a noticeable tapping sound on the honda cbf125 engine. Makes the loud tapping sound when idle and increases with revs. Im wondering if this could be something to do with the cam chain tensioner (bike is at 33k miles) or if it could be the bearing roller on crankshaft?

I have a haynes manual for the bike and this would be my first attempt ever at looking inside an engine.

Any help would be greatly appreciated and was wondering what are the simple things i should check first before getting the engine out.

Thanks, Phil.

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Valve clearances may need re-setting (on some bikes that's done at 3k intervals). If you service yourself this may not have been done, workshop manual or Haynes guide should tell you what you need to do

Will be checking these today, my main concern was that the oil level was extremely low (last checked a fortnight ago) which is my own stupid fault.

Running low on oil is not the end of the world but if it has run dry then this will almost certainly done some damage.
Did you have an oil pressure warning lamp?
If you ran it for even a short time without oil pressure you will have damaged the engine.

No oil lamp im afraid. It would appear that most probable cause of this knocking would be the big end bearing failing. Haven't looked properly yet but have decided to take the plunge and buy a whole crankshaft off fleabay for £50 (compared to £481 direct from honda :eek:). Had to buy it before someone else did and that price it's worth the gamble if that is the problem or not.

cbf same engine as the xl, different gearing. probably valve clearance as has been said but check out the push rods prone to wear especially at higher revs. we had one with 3mm worn off the end nearest the rockers, finally ran out of adjustment.
yes, they do drink oil so keep it topped up. crank may well be ok check the push rods first

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Originally Posted by wheelers

cbf same engine as the xl, different gearing. probably valve clearance as has been said but check out the push rods prone to wear especially at higher revs. we had one with 3mm worn off the end nearest the rockers, finally ran out of adjustment.
yes, they do drink oil so keep it topped up. crank may well be ok check the push rods first

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Sorry for my noobness, but what is a push rod?

Is it in this diagram somewhere:

http://www.bike-parts-honda.com/moto...25M9-2103.html

ah, depends if you have OHV or OHC!! OHV overhead valves use a low cam and push rods to open valves, OHC overhead cam uses a chain to drive a cam over head which pushes the valves open if you have the one in parts you have OHC, they do do both engine variants

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Originally Posted by wheelers

ah, depends if you have OHV or OHC!! OHV overhead valves use a low cam and push rods to open valves, OHC overhead cam uses a chain to drive a cam over head which pushes the valves open if you have the one in parts you have OHC, they do do both engine variants

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I phoned a friend about this. SOHC no push rods present.

Either Tappet clearances or cam chain (if you have one). Whip the rocker cover off with the engine cold and check the clearances.

I had my clearances checked at 30k - and bugger me they were still perfect.
Jap engines are hard to beat (14 years old!!!) Suzuki GSXR
£150 - but hey cheaper than a new engine.

Not a single shim has been added ever - I was going to do it myself but, didn't have time to do it.

Have stripped the engine and the crankshaft was slightly warped, new shaft fitted. Piston and barrel are fine with no scoring damage, changed clutch plates and springs at the same time. Had to angle grind an old socket to take the locknut off the oil sump just to split the crankcase :mad: very odd shaped nut!

Not bad for my first time stripping an engine even if it is a tiny hairdryer. Will fit it back into frame tmw morning and fingers crossed should be ok to run.

Good for you Buddy.. It harks back to the good old days of biking when you learnt from jumping in at the deep end and stripped things down and fixing it. Great way to learn too.
I hope that it cures your problems and the bikes back on the road again..