Knocking noises

[rattler1014]

Hi, need some help please. Had aknocking from under my T25, or so I thought, but ive started him up this evening and it sounds like the noise is coming from either the right side Carb or around that area, no noise on idle but any accelleration an it knocks, only way to describe it is like a machine gun and obviously goes faster when I accelerate. There is also an oil leak but not losing oil, checked the dipstick and the level is fine. HELP!!!!

Its a 1981, 2l Aircooled petrol engine. Thanks.

[CovKid]

Developed while driving or after it was stood?

[marlinowner]

Is it when you you are driving and is road speed dependent, or is it when you rev the engine in neutral? If the first it is likely to be loose bolts where the driveshafts attach to the gearbox. If it's the second then maybe nastiness in the engine.

[rattler1014]

Driving, been stood before I had it and drove it home over a few hundred miles and fine. Drove it the following day and it started then!!

[CovKid]

Change the oil and filter then give it a good run. Sounds like drained tappet and who knows what oil is in it.

[rattler1014]

Cheers, a mechanic friend of mine has listened and seems to think it may be stuck valve, so the piston is knocking it. Oil change this weekend I think, provably do it my self, first time, easy job? Any tips on the oil refill?

[CovKid]

Just make sure its warm to drain it properly - change the filter too.

[Ralf85]

Hi, need some help please. Had aknocking from under my T25, or so I thought, but ive started him up this evening and it sounds like the noise is coming from either the right side Carb or around that area, no noise on idle but any accelleration an it knocks, only way to describe it is like a machine gun and obviously goes faster when I accelerate.

Its a 1981, 2l Aircooled petrol engine. Thanks.

How long have you owned it? How long has it sat still? When was the oil last changed?

It does sound like the oil has drained from hydraulic tappet(s) - a common issue covered in the Haynes manual. It happened to mine just after I bought it. It can take a trip of 15-20 minutes for the noise to go away driving along at about 50mph. If the noise remains Hayes recommends changing the oil to a recommended one for your engine - this is covered in the wiki and previous discussions on here. Good luck.

[CovKid]

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[rattler1014]

Cheers for all your replies, the oil marks on the road are getting bigger under my engine but she I check my dipstick the level is spot on. Oil looks good too, nice clear not thick and black. I've not driven it for a while mainly because my exhaust is blowing, and when the engine runs there's quite a bit of smoke, but I think that's where the oil has leaked on to the exchangers as its not coming from the exhaust itself. My fear is if I go on a tidy drive will I cause more damage!!!!

[CovKid]

degunk the exchangers, pressure wash them, and fit new gaskets under rocker covers. If you can move rocker clips easily, change those too. It sounds like you need to do some maintenance ahead of winter.