bad noise, please help

[ocatoro]

so after doing my cbt today, i was hiding from the rain all evening. then the weather come right tonight, so i thought i'd take the h100 up and down the farm track a few times for something to do...

seemed ok at first, like it has been during the days since i've had it. only difference being that i put a 5litres of petrol in there earlier thisevening.

it started making this bad noise on idle, but revved freely and accelerated fine still. but i brought it back to the house anyway.

here is noise 1
https://www.youtube.com/watch?v=HTWY1GCRb1A&feature=youtu.be

then after a few minutes of head scratching trying to work out what on earth has happened, it got worse and ended up sounding like this.....
https://www.youtube.com/watch?v=AX8sweSsO3Y&feature=youtu.be

it now won't idle, the 2nd video i had to hold the throttle open a little to keep it running.

this noise sounds like death to me. what on earth is happening to it?

anyone offer any help?
____________________
CBT - 17/09/12 * Theory - 23/10/12 * Mod1 - 05/03/13 * Mod2 - 25/03/13 * BOSH!
Current - None but shed project H100 (first bike )
Past - ER5, '93 ZZR600, '92 CB400 SF, ZZR600 (again), yellow Monster 620, Blackbird - black Monster 620ie - '96 ZZR600

[Joenitro]

Is your spark plug loose?

[ocatoro]

[dungbug]

Did you add any 2 stroke oil????
____________________
CBT: Pass 25/06/2011 Theory Test: Pass12/06/2012 Mod 1: Fail 08/07/2012
Mod 1 Retest: Pass 15/0702012 Mod 2: Pass 03/08/2012
Suzuki GN125 (Sold) ~ Current bike: Yamaha YZF 600R Thundercat

[ocatoro]

[cb1rocket]

you haven't empty the gearbox oil by chance and not filled it up?

They do run rough at first when warming up thou, although I can't tell. Is the choke off? That will cause it to run bad, they literally like only the best part of 5 secs of being on!

[ocatoro]

[dungbug]

What's the condition of the spark plug? 2 smoke plugs will foul over time.
____________________
CBT: Pass 25/06/2011 Theory Test: Pass12/06/2012 Mod 1: Fail 08/07/2012
Mod 1 Retest: Pass 15/0702012 Mod 2: Pass 03/08/2012
Suzuki GN125 (Sold) ~ Current bike: Yamaha YZF 600R Thundercat

[RichieZX6R]

[ocatoro]

[Speed]

For the cost of a plug (£5 or so) i'd just replace it and see if that does the trick.

[Speed]

Forgot to mention, you don't have a hole/crack in your exhaust do you? Run it and have a listen/feel of the exhaust for any blowing

[Vincent]

I'm not sure how poor spark plug condition would make the engine rattle

The little ends are definitely rattling but they usually do on two strokes anyway. Are you sure the exhaust isn't leaking anywhere? If not, it'll be rings, big end or mains I would have thought. What's the mileage and do you know if it's had a top end strip down at all?
____________________
Space Is Deep

[ocatoro]

ok, so head and barrel off. piston looks brand new, as do the bearings at either end of the conrod... like they've just come out of the packet new.

barrel is very very smooth all round, has honing marks on though can't feel them.

so it's probably safe to say it's had the work done that was claimed.


however, i ran the engine with the left hand cover off for a few seconds, the side the chain and generator are on... and when it drops in revs and/or to idle, when the knocking noise can be heard.... the cylindrical unit (coil?) rattles back and forth. so something is loose in the bottom end. i just don't know what's in there to know what could be loose


(ps... i now can't seem to get the piston back in the barrel... is there a nack to this?)
____________________
CBT - 17/09/12 * Theory - 23/10/12 * Mod1 - 05/03/13 * Mod2 - 25/03/13 * BOSH!
Current - None but shed project H100 (first bike )
Past - ER5, '93 ZZR600, '92 CB400 SF, ZZR600 (again), yellow Monster 620, Blackbird - black Monster 620ie - '96 ZZR600

[ocatoro]

[Vincent]

I think it's top end tear down time Not a massive or expensive job unless you find something major in there.
____________________
Space Is Deep

[ocatoro]

do you mean bottom end?

yeah i agree, i don't think anything in there is expensive. it's just a job i'm unsure of
____________________
CBT - 17/09/12 * Theory - 23/10/12 * Mod1 - 05/03/13 * Mod2 - 25/03/13 * BOSH!
Current - None but shed project H100 (first bike )
Past - ER5, '93 ZZR600, '92 CB400 SF, ZZR600 (again), yellow Monster 620, Blackbird - black Monster 620ie - '96 ZZR600

[Vincent]

Take the barrel off first, it may just be a ring gone awol or a dropped circlip. Once the barrel's off, you'll be able to tell if it's the bottom end or not then take it from there.
____________________
Space Is Deep

[ocatoro]

yes, i'd already had the top end off... the rings are spanking new with no damage at all. as is the piston etc...


however, whilst putting it all back together, i've noticed that the exhaust front pipe has been forced on with some oversized bolts and ripped all the threads out, so they won't go back in properly i dunno how they were holding to be honest.

so with that in mind, i started it without the exhaust bolted up... same noise, louder/worse.

could that make the engine make a bad knocking noise? or will that have caused something else to break and make a knocking?
____________________
CBT - 17/09/12 * Theory - 23/10/12 * Mod1 - 05/03/13 * Mod2 - 25/03/13 * BOSH!
Current - None but shed project H100 (first bike )
Past - ER5, '93 ZZR600, '92 CB400 SF, ZZR600 (again), yellow Monster 620, Blackbird - black Monster 620ie - '96 ZZR600

[Beamexican]

If you took the cover off and the flywheel/magneto is loose check the nut holding it on if you haven't already, if its bolted onto the crank properly I would say its probably the main bearing, if you grab the magneto can you move it up/down side to side?

Can't really tell what the noise sounds like on my phone but if the magneto is loose moved the timing could be hugely out which could make it run bad, sound odd I think.

Not sure if your bike has points or whether this would make any difference but someone else will know more about this bike than I do.

[ocatoro]

[Beamexican]

Magneto should rotate smoothly without going up or down etc,.mains and big end are different big end is the bearing in the conrod sandwiched in the crank then you have a bearing in each side of the case that the crank sits in.

Sounds like there might be an issue with your crank, did the bike vibrate a lot when running?

[ocatoro]

yeah the magneto does that, and no movement at all except when the bike is dropping off revs. when the knocking is apparent. by hand, i cannot move it in any way it shouldn't move.

ok thanks for clearing that up... so if it is not just the exhaust it'll be the main bearings most likely and can get them swapped out. just checked, theyre £8 for one side, and £5 for the other side. never met such a hilariously cheap engine before.

the bike doesn't vibrate, no. not really even a great deal when the knocking is in progress as the engine comes off revs back to idle. so perhaps the main bearings are not too bad?
____________________
CBT - 17/09/12 * Theory - 23/10/12 * Mod1 - 05/03/13 * Mod2 - 25/03/13 * BOSH!
Current - None but shed project H100 (first bike )
Past - ER5, '93 ZZR600, '92 CB400 SF, ZZR600 (again), yellow Monster 620, Blackbird - black Monster 620ie - '96 ZZR600

[karthead]

Just wondering, I would've thought that things such as bearings or rings would fail over time, not suddenly as the OP has described it..

[cb1rocket]

if the main bearings have gone it would look something like this and the flywheel going all over the place suggest this.

https://cdn.bikechatforums.com/files/swarf_left_behind_from_damage_bearing.jpg