Engine rattle?

[CookMySock]

Bike is Hyosung GT250, 250cc vtwin. I just bought it recently.

I have just reassembled this engine, rods, bearings, everything looked clean and tight when bolting it up. It was dissasembled because someone thought it wasn't fast enough. There was one little blemish on a piston, so I filed the nasty bit smooth and went with it. The bores were mint. The engine has been apart before. Bike has 40,000kms on it.

When I start the engine it gives a very short but quite alarming "rattle-brappp" and then instantly clears up to a very slight chink-chink-chink sound idling at 1500 rpm, which again vanishes completely at over 2500 rpm, and is completely smooth to ride otherwise.

It doesn't sound like bottom end, more like timing chain, and more from the front cylinder than the back. Almost like the chain has tight link in it or something.

Perhaps that little blemish on the piston is polishing itself off.

It seems to be getting better as I ride it (maybe an hour in total so far).

Any suggestions?


may thanks,
Steve

[enigma51]

Get a proper mechanic to look at it.

[SixPackBack]

Hope your quick on the clutch when the fucker seizes, and yeah a mechanic would be the go.

[YellowDog]

As you don't think it is a big end, then I guess it won't be.

I am not a fan of filing cylinder blemishes, though my experience of such disasters goes back to the late 70s. A rebore and larger rings would be my preferred route.

Was the head skimmed before you screwed it back on? Perhaps an earlier than planned re-torqued might help.

[Mom]

Someone already covered the quick clutch action warning. Ride it with caution till you discover what it is. Chances are it will throw a hissy fit and put a valve into the top of a piston or chuck a conrod out the front of the cylinder if you ride it to clear the noises it is making.

[CookMySock]

I am not a fan of filing cylinder blemishes, though my experience of such disasters goes back to the late 70s. A rebore and larger rings would be my preferred route. Yeah I could have slapped a new piston and rings in it for $75. Maybe I will yet.

Time to get a honing tool - I heard the sandpaper ones were better than the stone ones.


Was the head skimmed before you screwed it back on? Perhaps an earlier than planned re-torqued might help.I don't know the history of the engine at all. I found the bike with it's engine in cardboard boxes. I put it together myself. Yeah I will check the head torque before long.

I have another camchain tensioner to try too, although that looked mint when it went on. It sounds a whole lot like a camchain noise, rattle-slap when starting and and at revs under 1400.

What puzzles me, is it runs clean and smooth as soon as there's revs on, and it's slowly getting better and better. I'm tempted to just run it for a week.

It occurs to me, when I was refitting rings to piston after removing that scuff, the rings were quite, er, well, stretched is not the right word hehe. Maybe I would call it re-tensioned.. Anyway, it all slipped back together ok so I ignored it.

Steve

[AllanB]

Drop the oil into a spotless container and check for metal flake ..........

[CookMySock]

Drop the oil into a spotless container and check for metal flake ..........Good idea. Will do before I run it next. Will check the filter over too. Thank you.

Steve

[CookMySock]

Oil drain done, and there are about ten tiny flecks of something softer than steel but harder than paint. About three larger flecks about 3-6mm across.

I remove the stator cover and theres some dark coloured paste in the oil inside the flywheel and a few gritty bits that mash to a black paste between two sockets, and also a piece of shellac off the stator.

Now what I didnt tell you earlier, is the stator appears to have contacted the rotor at some time - perhaps the cover got bashed or something (no marks on it), or the crank bearings gave up and let the shaft move.

I have another stator cover in good nick, so I will slap that on, change filters, refill, and report back.

Steve

[CookMySock]

The flecks came from the stator for sure - swapped it over, no change. Tried a replacement camchain tensioner - no different. Grumble..

Time to take it to the bike shop I think. Oh well - a good try.

Steve

[gwigs]

Good on ya DB for having a go.....hope you can get it sorted.....getting your hands dirty and solving the prob can give you a lot of satisfaction...:niceone:
Sorry I cant offer any advice...

[slimjim]

what where the bearing shells like..as too they can throw noise til rpm takes over.. also throw in some heavier oil and start ..if sound is quieter..yup full strip and replace,,as you have said it was in bit's and 40000km humm that's fuck all ..however a clean motor parts mean nothing , and if no knowledge then you have no knowledge as to how many times its been put back together and still got rattle noise and fillings don't just stop in cases, they enjoy getting into shell casings ,bearings

[CookMySock]

what where the bearing shells like..as too they can throw noise til rpm takes over.. also throw in some heavier oil and start ..if sound is quieter..yup full strip and replace,,as you have said it was in bit's and 40000km humm that's fuck all ..however a clean motor parts mean nothing , and if no knowledge then you have no knowledge as to how many times its been put back together and still got rattle noise and fillings don't just stop in cases, they enjoy getting into shell casings ,bearingsI didn't have the bottom end apart. I bought it with only the cylinders removed. I couldn't detect any play in the rods or roller mains - I wouldn't have bought it if there were signs of wear.

The engine has been apart before, and aside from minor cylinder and piston marks it was clean as. My guess its been done up before.

I took it to the bike shop today, and the mechanic was pretty sure thats just a noisy cam follower, so I'll pull the lid off of it and check some clearances.

Next, rear brakes to rebuild, tyre to replace, and WOF to get.

Steve

[ready4whatever]

dont know sorry but got the same problem with my mazda B2200. lol

[CookMySock]

In an update, the bike shop declared it "probably a worn camchain or something" - its not going to split the engine in half. I've given the bike a good caning for 400km and it's quite stable, so we'll worry about it later.

Steve

[7mmWSM]

Oil drain done, and there are about ten tiny flecks of something softer than steel but harder than paint. About three larger flecks about 3-6mm across.

I remove the stator cover and theres some dark coloured paste in the oil inside the flywheel and a few gritty bits that mash to a black paste between two sockets, and also a piece of shellac off the stator.

Now what I didnt tell you earlier, is the stator appears to have contacted the rotor at some time - perhaps the cover got bashed or something (no marks on it), or the crank bearings gave up and let the shaft move.

I have another stator cover in good nick, so I will slap that on, change filters, refill, and report back.

Steve

Run a magnet over the metal flakes to determine it is metal as opposed to alloy (engine casings) or clutch fibres. If it sticks to the magnet its most probably bearings or gears

[Squid]

Its a Hyo. Ride the tits off it and wear good leathers so if it does blow up or seize and it goes sticky side up you'll be protected.