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Just been recomissioning a GP200 and have fitted new gearbox bearings, chain, tensioner and kickstart shaft. I also took the top end off and fitted a new small end bearing and gaskets and whilst I had it apart I cleaned up some light marks on the piston and inside the barrel and cleaned up the cylinder head then lapped them both. When I got it running I noticed a bit of a rattle on tickover and immediately thought it was something to do with the gearbox/chain. Took the side case of and nothing obvious so adjusted the bottom chain guide a little just to make sure the chain wasn't hitting it and checked the chain tension which seemed good. So don't think the rattle is related to that side of things but seems to be coming from the cylinder/flywheel side. Doesn't seem as though it's the flywheel on the cowling and have checked to make sure the head cowling isn't touching the exhaust downpipe or anything obvious like that. The scooter starts fine and ticks over and seems to run ok but when it's ticking over I can still hear this strange rattle? Nothing sounds loose anywhere either. Anyone got any suggestions on where to start, could it be I've over done it with the tidying of the barrel and piston and am getting piston slap or something like that? I only cleaned the marks very lightly and they where still visible when I reassembled?

Is this the kickstart piston teeth making contact with the 1st gear teeth... piston not retracting far enough? This is very common and an easy way to check may be as simple as removing the kickstart rebound buffer from the side casing so that it allows the internal piston to retract further.... does the noise then disappear?

NB: If only just making contact then you can often check this by pulling up on the kickstart lever when the motor is ticking over, with the upwards pressure on the lever squashing the butter enough to be a check too. I did this the last time I heard this on a pal's GP when I pulled up alongside him at traffic lights.

It is a quick check.

Adam

Adam_Winstone wrote:Is this the kickstart piston teeth making contact with the 1st gear teeth... piston not retracting far enough? This is very common and an easy way to check may be as simple as removing the kickstart rebound buffer from the side casing so that it allows the internal piston to retract further.... does the noise then disappear?

NB: If only just making contact then you can often check this by pulling up on the kickstart lever when the motor is ticking over, with the upwards pressure on the lever squashing the butter enough to be a check too. I did this the last time I heard this on a pal's GP when I pulled up alongside him at traffic lights.

It is a quick check.

Adam

Cheers Adam, I'm sure I've checked this but will try again won't hurt. To be honest I know that sound and that's more of a constant grind sound and what I'm hearing is more of a rattle (if that makes sense?). I'll try again though and report back. Cheers.

It could be a gudgeon pin circlip has made a bid for freedom, in which case you’ll end up with an unwanted additional port in the barrel if left unattended.

(I've had engines in the past that have arrived with this 'feature'... )

Otherwise, I don't suppose it could be pinking if all is as before

eadmr04 wrote:

Adam_Winstone wrote:Is this the kickstart piston teeth making contact with the 1st gear teeth... piston not retracting far enough? This is very common and an easy way to check may be as simple as removing the kickstart rebound buffer from the side casing so that it allows the internal piston to retract further.... does the noise then disappear?

NB: If only just making contact then you can often check this by pulling up on the kickstart lever when the motor is ticking over, with the upwards pressure on the lever squashing the butter enough to be a check too. I did this the last time I heard this on a pal's GP when I pulled up alongside him at traffic lights.

It is a quick check.

Adam

Cheers Adam, I'm sure I've checked this but will try again won't hurt. To be honest I know that sound and that's more of a constant grind sound and what I'm hearing is more of a rattle (if that makes sense?). I'll try again though and report back. Cheers.

Not the kickstart

Warkton Tornado No.1 wrote:It could be a gudgeon pin circlip has made a bid for freedom, in which case you’ll end up with an unwanted additional port in the barrel if left unattended.

(I've had engines in the past that have arrived with this 'feature'... )

Otherwise, I don't suppose it could be pinking if all is as before

Think I'm going to have to strip down again . Don't think it's pinking as doing it from cold on start up and at tickover, thought you'd only get pinking if it was getting hot?

Not sure if this will work but have recorded it and think this link will open the video?

http://vid339.photobucket.com/albums/n4 ... 6gp7p6.mp4

Pinking can result from compression/fuel/ignition problems but listening to the video clip, I’d say that is a mechanical rattle.

It could be the retaining clip for the flywheel dust cover or something as simple as a split/loose head cowling/flywheel cover.

I’d look in those areas.

Flywheel fins on cowling? Check the inside of the cowling for witness marks.

I had a strange rattle on a 100% standard 125 Special. Wouldnt do it when cold but was very noticeable when warmed up. I checked everything including all of the above. It turned out to be the fins on the flywheel having come slightly loose from the flywheel itself. They weren't touching the cowling so no marks. Just rattling on the flywheel. Annoyingly couldn't be felt with the flywheel off either. Replaced the flywheel and no more rattle.
Paul

Scooter Paul wrote:I had a strange rattle on a 100% standard 125 Special. Wouldnt do it when cold but was very noticeable when warmed up. I checked everything including all of the above. It turned out to be the fins on the flywheel having come slightly loose from the flywheel itself. They weren't touching the cowling so no marks. Just rattling on the flywheel. Annoyingly couldn't be felt with the flywheel off either. Replaced the flywheel and no more rattle.
Paul

I have a strange rattle coming from my engine and as yours its only noticable when the engine warms up.I have a 12v Indian flywheel,I'll check it to see if the fins of the flywheel have come loose.By the way,if the looseness couldn't be felt with the flywheel off,how did you know that was the problem.

my first port of call when I have a rattle is to empty my tool box I've found about 3/4's of all rattles come from there

Right lads. Took the flywheel cowlin off and no grind marks or signs of scrapping or looseness. I moved the flywheel back and forward and noticed this slight knock, is this normal (see clip 1 and 2):
http://vid339.photobucket.com/albums/n4 ... wx3lgg.mp4
http://vid339.photobucket.com/albums/n4 ... qhhqkc.mp4

Could this point to the crank or crank bearings starting to go and giving the rattle sound?

Ive also noticed it's quite smokey (see clip 3)

http://vid339.photobucket.com/albums/n4 ... 9qfn1h.mp4

I've cleaned the tail pipe and started the scooter and ran for a couple of minutes and noticed this



I'm wondering if the rattle could be the crank and this has made the main oil seal fail explaining the extra smoke and oil in the tail pipe?

Any thoughts would be great.

HxPaul wrote:

Scooter Paul wrote:I had a strange rattle on a 100% standard 125 Special. Wouldnt do it when cold but was very noticeable when warmed up. I checked everything including all of the above. It turned out to be the fins on the flywheel having come slightly loose from the flywheel itself. They weren't touching the cowling so no marks. Just rattling on the flywheel. Annoyingly couldn't be felt with the flywheel off either. Replaced the flywheel and no more rattle.
Paul

I have a strange rattle coming from my engine and as yours its only noticable when the engine warms up.I have a 12v Indian flywheel,I'll check it to see if the fins of the flywheel have come loose.By the way,if the looseness couldn't be felt with the flywheel off,how did you know that was the problem.

Having tried everything else I just replaced the flywheel, I had plenty to hand, and that was the problem solved.

Just tried another flywheel but still got the same noise?