GT 380 J strange engine sound

[isetta]

Mike thanks. I did check that. Sound is definitely coming from the engine.

[gt-keith]

Any chance of a video clip ? or a clue as to which area or side of the engine the noise is coming from.

[isetta]

Ok I will upload a video clip later today.

[isetta]

https://www.youtube.com/watch?v=0n29GjLcgFU" onclick="window.open(this.href);return false;

here are 3 clips on youtube.

[tz375]

Sounds almost like a broken ring. What is compression like on each of the three cylinders?

[isetta]

i dont have a compression tester. but ya it does not sound good.

Is there another way to test?

[yeadon_m]

Lubrication failure in the top end?? Afraid I would definitely be taking the top end off if it were mine - not a nice sound! Good luck with what's in there, Mike

[sportston]

Yes it could be a broken ring but it sounds like a leak somewhere to me. In order of likelihood; Spark plug loose, head gasket leak, inlet rubber leak, barrel base gasket leak, exhaust leak, crank case leak.
1st thing to do, check the plugs are not leaking, then check for leaks elsewhere using a long piece of vaccuum tubing. Insert tubing into your ear then with other end place it in possible leak areas. Once you find the noise get louder then you have found the source of your leak.
Good luck

[Ivan]

When I first got my 380, it had a noise like that... it was the plastic points drive gear.... had a crack in it.


Ivan

[isetta]

Yes not a good sound. I will do a few more tests before pulling the head. Thanks for all the input everyone!

BTW...is it possible to pull the head off and service without having to pull the whole engine?

[Alan H]

yes.

[Craig380]

I'd echo Sportston: I'm fairly certain that the noise is a compression leak. Get a bright torch and look very carefully all around the cylinder head gasket join, you're looking for any signs of oily / dirty smears coming from the joins (you'll spot them easily if there are any).

If there are any traces, try retorquing the head nuts to spec (26 ft-lb) to see if that fixes it. If it doesn't, you'll need to lift the head to replace the gaskets.

[isetta]

Ok thanks again will take your advice to practice this week and report back.
Cheers.

[isetta]

I have decided to take the top end off and replace the gaskets. I am having a hard time getting the middle four nuts off the front of the cylinder heads. Is there a trick to this? I certainly do not have to take the engine out??!! Any suggestions would be greatly appreciated.
Thanks,
Paul

[Craig380]

If it's the cylinder head nuts, they're probably corroded with the spray from the front wheel. Get some releasing fluid (Plus-Gas or similar) and soak the nuts for a couple days.

Or do you mean the 4 front cylinder base nuts that hold the cylinders to the crankcase, and hide behind the frame tubes?

They are absolute bastards to remove - the only trick is to have a couple of different makes of 14mm ring spanner. Different makes have different offsets, so you can move the nut a few degrees with one spanner, then use the other to move it another few degrees, which will then enable you to get the first spanner back onto the nut, and so on.

Oh, and lots of profanities, obscenities and skinned knuckles