NSR125 Engine noise

[deputy]

Have just noticed this week that the engine on my 1989 NSR125F has started to make a funny noise at about 4K rpm. Other than the noise the bike seems to running OK, revs to 10.5K rpm OK. Does feel slightly sluggish though.

Any ideas?

[alains]

how long since the top has been de-carbonised , it's may do this when the valves begin to stock , also did you check your exhaust , may be a protection is rattling .
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the worst day fishing is better than the best day working

[deputy]

top end hasn't had a decoke while I have had the bike (about 9 months). Is this a job I can do or is it a garage job?

[alains]

i would say , if you know mecanics , you can do it . but what you should do is : go to your local honda and ask him for an estimate with piston rings change and eventually the piston itself . if you are going to DIY ask TIM at https://www.davidsilverspares.co.uk the spares needed with price . i can tell some prices (ex VAT) :
barrel+piston kit £85 , piston rings £22 , head gasket+base cylinder seal+valves axel seal £15
i do not know how much is the piston alone but it's necessary to know which letter is on your barrel (the problem is : this letter is near the water pipe & underneath) , so you can see it really after taking off the barrel . about the work time , i would say minimum 3H and 4-5 H for you . i recommand you download the workshop manual which is on the forum . if you want further infos , send me a pm
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the worst day fishing is better than the best day working