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rattle after running at high speed

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czakal
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PostPosted: 22:11 - 27 Jul 2017    Post subject: rattle after running at high speed Reply with quote

Hello people,
Today I rode my Pulsar 125 at high speed (for that bike), near 60mph on a highway for a short stretch. It was near redline and sometimes going right over it. Near the end of the highway stretch, the power suddenly went down a little bit--I was able to bring it back up to speed with the throttle but it seems to have a light rattle/vibrating sound at times (possibly more often at low revs but I didn't test it). There's a small chance I could be imagining problems (I might have closed the throttle without noticing; and also there's a minor rattle from a slightly loose plastic panel, but this rattle sounds like it comes from around the engine). What kind of problem causes intermittent vibrating/rattling sound?
Thanks for all the help again!
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jaffa90
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PostPosted: 00:01 - 28 Jul 2017    Post subject: Reply with quote

Red line means danger of engine failure, try a bigger faster engine/ bike.
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doggone
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PostPosted: 07:32 - 28 Jul 2017    Post subject: Reply with quote

You could put up a short video?
It doesn't sound good Razz if the drop in power was also real.
It is possible to have a partial seizure due to heat which frees off when it cools, so try again cautiously.
Otherwise big end bearings maybe - could be anything.
Perhaps just a bolt coming loose.

Sometimes putting a chunky screwdriver or similar on different parts of the engine, and pressing your ear against the handle helps locate the source of odd noises.
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RhynoCZ
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PostPosted: 09:26 - 28 Jul 2017    Post subject: Reply with quote

From the pictures (Google) it's aircooled, so overheating is a possibility, which leads to a partial/full seizure.

What engine oil do you run?
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lilredmachine
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PostPosted: 13:40 - 28 Jul 2017    Post subject: Reply with quote

Worst case:

Motor probably pinched up a tad. The rattle could be the 'little end' which is the bearing hole the piston gugdeon pin sits in. When these get very hot they can elongate as the metal stretches at high rpm with the weight of the piston acting on it, particularly if it is dragging on the surface of the cylinder. This will allow the piston to move slightly independently of the rod, causing faint rattlling sound. Whilst not immediately fatal, i wouldn't be counting on that motor being around for ever, once the metal has been overheated and the tolerances are borked it's all downhill from there.

Other causes might be valvetrain related, oil starvation in the head causes excessive wear very quickly, if it is OHV could have bent a pushrod slightly, common with high rpm use. I would take the valve cover off, get the motor to TDC and have a fiddle and see if there are any excessive clearances.

Best case:

Of course, something could have just rattled loose. Check the heat guard on the exhaust, i remember those are bolted on the stock pipes.

Have to be careful with modern 125s, they are tuned lean for emissions testing and are often in neglected states. Long periods of over or at redline can kill them whereas an old cg would just take it and ask for more.
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Commuter_Tim
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PostPosted: 00:51 - 29 Jul 2017    Post subject: Reply with quote

Cheap shit chinese copy bike you say?
Engine mount bolts worked loose and rattling? Thinking
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The above post is most likely nonsensical.

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czakal
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PostPosted: 11:26 - 29 Jul 2017    Post subject: Reply with quote

The rattling began after a noticeable loss of power so likelier to be something in the engine. It was probably first caused by low oil. I'm going to refill it, then take it to the shop to check, unfortunately I don't quite have the skills to open up an engine. Will let you know how it goes...
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RhynoCZ
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PostPosted: 11:39 - 29 Jul 2017    Post subject: Reply with quote

czakal wrote:
The rattling began after a noticeable loss of power so likelier to be something in the engine. It was probably first caused by low oil. I'm going to refill it, then take it to the shop to check, unfortunately I don't quite have the skills to open up an engine. Will let you know how it goes...


If it was low on oil, then it's too late to just fill it up. Low on oil means metal on metal grinding, generating heat, speeding up the wearing process. Thumbs Down
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Johnnythefox
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PostPosted: 13:30 - 29 Jul 2017    Post subject: Reply with quote

Maybe OP meant to say, 'My bike was low on oil and I ragged past the red line, it now makes a rattling noise, if I top up the oil will that make it ok'
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czakal
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PostPosted: 18:43 - 29 Jul 2017    Post subject: Reply with quote

Back from the garage. Turns out the oil drained faster than usual because the oil seal was leaking a bit. Unfortunately I was booked in late and there wasn't time to look at the engine in detail but the mechanic said it didn't seem 'that serious'. Have to go back another time to have that checked and fixed for good.
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Wafer_Thin_Ham
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PostPosted: 18:54 - 29 Jul 2017    Post subject: Reply with quote

jaffa90 wrote:
Red line means danger of engine failure,


Depends what you mean by "redline". Do you mean the rev limiter? If so, no it doesn't mean "danger of engine failure".
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czakal
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PostPosted: 19:27 - 29 Jul 2017    Post subject: Reply with quote

No, just the red markings on the tachometer.
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Wafer_Thin_Ham
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PostPosted: 19:33 - 29 Jul 2017    Post subject: Reply with quote

czakal wrote:
No, just the red markings on the tachometer.


If you didn't hit the limiter (or even if you did) then it's not a problem for a welll maintained engine.

It's only if you over rev them (through a poorly executed downshift, or running in gear down a very steep hill) that it can be a problem. Generally the piston ends up whacking a valve.
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