Noise in engine

[alumaline]

Hi, There is odd metal hitting metal noise inside my HT engine. Imagine a vacuum cleaner sucking up a penny. You hear a bang and rattling then silence (normal two cycle noise) then a random bang again. Like something broke loose or was ingested but has no effect on power or performance yet. Motor has maybe ran through 5 gallons of fuel so it is reasonably new.

I did have the RT carb open to fix the choke lock but was careful the lever and small spring did not get free before tightening the cover. The small shaft holding the choke lock lever fell out but it must have fallen outside the engine, it was replaced with small screw. Do needle bearings ever come out of connecting rod? Thanks for ideas. Mark S.

 

[Greg58]

Try pedaling around with the clutch in to see if its clutch related. Do this with the engine off.

 

[Kioshk]

My first thought was a rouge needle from the bearing. If it is, it's only matter of time before it finds its way into the combustion-chamber, and will probably end up damaging the jug. It's an easy check, just pull the jug and disconnect the piston. I HAVE had a lower bearing go on me; its cage fell apart and a chunk fell into the crankcase. The loose needles didn't fall out however, but they did chatter, and would periodically bind up causing the engine to clunk randomly...it's all signs of impending disaster though. I think this might be your problem if you find that the upper bearing's alright.

 

[skitchfish]

Normally I would think left side gear clatter when a member post this. Unfortunately with your most accurate audio account. Impending doom!

 

[skitchfish]

Excuse me Right side gear meshing, mashing! Nope thats internal!

 

[Ono Nadagin]

I say open it up and see if it can be saved before it cant.

would not think it is in the top end but I would pull the plug and look in to see if you can see anything, then pull the jug from the block for a visual inspection and go from there after you know what failed

 

[Theon]

I agree, Pull it down.
Easy to do,
Plenty of help here to put it back together.
Give it some better bearings, and check everything.
you may be able to save it before it's to late.

 

[mapbike]

Pull the head off and you'll know real quick if it something on top of piston.... may be able to save it if it is ....... don run it on turn it over again.........!

 

[2door]

I agree. Pull the cylinder head, check for any damage on the top end and if none, pull the cylinder.
Just be sure you know what's involved putting the piston back into the cylinder. The piston rings must be aligned with their guide pins and compressed before sliding the piston back in.

If you do open it up, let us know what you find.

Tom

 

[skitchfish]

You have been advised, Do not attempt to start again without inspection and expectations.

 

[Ono Nadagin]

being a cheapskate I would not pull the head to save the gasket... I would pull the plug and do a visual then pull the jug from the block.... I think all agree it is gonna be in the bottom end or it would have be catastrophic failure already

IMO gonna be a wrist pin needle bearing or some crap left in the lower end at the factory that worked itself loose from where it was jammed.... might even be a bit of a broken piston ring

 

[rhodeisland]

Sound something like this.
http://www.youtube.com/watch?v=BEemNpznoM0

 

[mapbike]

being a cheapskate I would not pull the head to save the gasket... I would pull the plug and do a visual then pull the jug from the block.... I think all agree it is gonna be in the bottom end or it would have be catastrophic failure already

IMO gonna be a wrist pin needle bearing or some crap left in the lower end at the factory that worked itself loose from where it was jammed.... might even be a bit of a broken piston ring

Judging from what you said here makes me wonder how many of these engines you've been into...., pulling the cylinder head off os the easiest thing to do and will not ruin the gasket, the gasket will not even be remov d and all it os is an aluminum gasket that is somewhere in the range of 0.020-0.025" thick and it can be reused over and over as long as it is put back exactly as it came off so all sealing surfaces remain the same always.

If there isn't anythong on top of piston, I agree that the jug/cylinder should ne pulled next so the wrist pin and upper bearing can be checked for breakage or premature wear, also while I was at thos point I would check to make sure there wasn't any seriouse up and down movement of the con rod, the lower bearing are less common to crap out but I had one do ot and it destroyed the topend of the engine.

Map

 

[Greg58]

A complete gasket set is about $10 on eBay.

http://www.ebay.com/itm/Motorized-B...Parts_Accessories&hash=item4862501d7a&vxp=mtr

 

[Ono Nadagin]

Your right Map I have not been into a China girl yet... but I have been into dozens of 2 stroke motors of all diff types and even more 4 stroke engines, having said that I have found most head gaskets on most engines have to be replaced once a head has been pulled off.

And the point I was trying to make was that when a inspection of the top end can be done with out removing the head, why remove it?.. pull the plug look in maybe grab your air hose and shoot some air into the spark plug hole and listen for something movin around.


A very wise man once told me

"Son... Two things you don't want to reuse gaskets and condoms, if they leak you got problems!"

 

[mapbike]

Your right Map I have not been into a China girl yet... but I have been into dozens of 2 stroke motors of all diff types and even more 4 stroke engines, having said that I have found most head gaskets on most engines have to be replaced once a head has been pulled off.

And the point I was trying to make was that when a inspection of the top end can be done with out removing the head, why remove it?.. pull the plug look in maybe grab your air hose and shoot some air into the spark plug hole and listen for something movin around.


A very wise man once told me

"Son... Two things you don't want to reuse gaskets and condoms, if they leak you got problems!"

Lol.... these head gaskets aren't multi layer or coated so the soft aluminum wil reseal no problem when the head is retorqued properly, sometimes Ill spray a thin coat of copper koat gasket dope on them or a light coat of silver spray paint, never had one leak yet if head is torqued down good.

Wasn't trying to come acroos as being a jerk in my comment, so I hope it wasn't offensive, but also you wont be able to see anything through plug hole and if there is something on piston and it is sitting at BDC you sure dont want to blow air into plug hole because you could easily blow it into transfer port and down into case, pulling the head is a quick simple way to see what the piston looks like and what the cylinder wall looks like, if piston and head has dings in it that is a sure sign that something has been hammmering away in there and may be in the case now or could have gone out exhaust, either way the jug would need to be pulled and a thorough inspection done to see what broke and why.

Map

 

[Toadmund]

I HAVE had a lower bearing go on me; its cage fell apart and a chunk fell into the crankcase. The loose needles didn't fall out however, but they did chatter, and would periodically bind up causing the engine to clunk randomly...it's all signs of impending disaster though. I think this might be your problem if you find that the upper bearing's alright.

That happened to me, but my needle bearings did come out, into my combustion chamber destroying my piston and cylinder, I have a thread on this, or a post, whatever.

And OP, I also have an RT carb, seal of that damn choke lever hole with rubber cement or sealant of some kind, it will disable your ability to use your choke, but at least dirt and other grit won't get into your motor through the choke lever slit.
My RT carb was full of grit and it's possible that that, as well as a vibraty engine, did it in.

 

[Theon]

As Greg said $10 for a complete gasket set...
When you put it back together use a 15mm wrist pin bearing this time.
Get some Japanese Main bearings.
Clean up the ports.
Match port what you can.
Check you port timing and adjust if necessary
Throw away your angle fire head.
Set your squish.
Match port your exhaust manifold.
Get a speed carb, not RT.
And you will have a motor that will impress.

 

[mapbike]

As Greg said $10 for a complete gasket set...
When you put it back together use a 15mm wrist pin bearing this time.
Get some Japanese Main bearings.
Clean up the ports.
Match port what you can.
Check you port timing and adjust if necessary
Throw away your angle fire head.
Set your squish.
Match port your exhaust manifold.
Get a speed carb, not RT.
And you will have a motor that will impress.

Dang Theon the dude is just trying to figure out what is causing a knocking noise in his engine not asking how to . Put a higher performance build together........lol!



Map

 

[Theon]

Sorry, I thought all those things were mandatory.