Weird clanking noise during rides

My motor was clanking an clattering too. Turns out my wrist pin bearing was worn. It didnt grenade or break, but it was worn enough to allow some slop.
 
Kinda sounds like detonation to me...those whiskers in the head can cause hot-spots leading to detonation or "pinging" Might try an extra head gasket or run premium fuel to see if it helps.
 
UPDATE: Turns out it was a busted magneto. Boy that sucker went bad fast. Now, I still have this weird idling issue: whenever I am rolling down a hill with the engine engaged at ~10-15mph and then come to a stop at the bottom and disengage the clutch, the engine's RPM will dip significantly (down to 1300rpm and lower) and will sometimes die as a result. I normally idle around 1700-2100 RPM (using tachhour meter). Speaking of which, I totally forgot that I can just look at the tachhour when turning the engine to check for spark. If there is no current running through the plug wire, then the tachhour will stay at 0 RPM. That way I didn't have to pull the plug out and ground it while trying to turn the engine.

I cleaned away the crud that was forming around the base of the spark plug threads in the cylinder head and made sure piston rings, piston, wrist pin, etc are all in good condition (as shown in the pics from my previous post). No gouges in cylinder wall and compression is still good. Gaskets are still nice and tight with no leaks, as tested by spraying carb cleaner all around.

The weird thing is using a NGK B6HS plug or even a BP8HS plug, the engine is a lot more prone to dying in the above scenario. When I switch to a old Z8C chinese stock plug (single prong), the engine dies a lot less frequently, but the RPM still dips considerably in the above scenario.

It looks like my intake port is the same size as the exhaust port. So I am guessing I have a Grubee engine.
 
vachon644 said:
I doubt a bushing is any more reliable than a good needle bearing since all modern motorcycle engines use them and they're rarely the cause of failures.
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lol

can i interest u in a small wager? :-)

...on the one hand we have a relatively soft metal, more or less matched! up with a hardened piece (the wrist pin).

On the other hand we have the same wrist pin and 10 or so precision(lol) hardened pieces within a brittle metal cage.

then we're gonna heat the assembly while hammering on it...

also gotta consider that the 'guiding assembly' for the hammer strikes will be prone to vary, as well as the amount of heat and lubrication applied.

Fun, huh?

:-)
rc
 
I just rode the bike again yesterday and it was running ok for 1.5hr or so, then during normal cruising around 30mph on flat land, it started losing power until it wouldn't start anymore. It felt extremely hard to turn over the engine and just wouldn't start at all.

There is still a spark going to the spark plug. I got home and opened up the top end of the engine to find some weird build up on the cylinder head, as shown in the pictures. This happened over that course of yesterday's riding, as I had clean all the previous crap out of the cylinder head before riding yesterday.

The piston rings looks okay, but I do notice the piston head itself seems to have a lot of blowby. The crankshaft and lower crankbody still move freely and nothing is jamming it and the piston head itself still moves and rotates freely on the wrist pin and wrist pin bearing. The previous problem of it dying after going up a hill at moderate speeds (~15mph) WOT and then releasing the throttle happened almost all the time after 1hr of riding. Still no leaks around the gaskets before it died, so I am clueless as to what is happening to this fairly new engine. I have never seen this weird type of build up in my previous two engines.

Does it mean the engine is running to lean/rich, too hot? The plug, as you can partially see, is still the brown tan color, although it has some of that same weird buildup seen on the cylinder head. I seriously have no idea what the heell is wrong with this engine and it's driving me nuts. Every ride I had so far with this engine has had something go wrong.
 

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On any of the pictures, I didn't see a fuel filter. I know that these gas tanks can have some dirt inside right off the factory. If that dirt got down and clogged either the carburetor or the fuel filter (which may have been installed in the wrong direction thus you couldn't see the dirt building up), it may have reduced the fuel flow to a point where you leaned out the engine. That would explain the black color and ring failure. Can you open up your carb and check the fuel filter in the hole where the gas enters it?
 
vachon644 said:
On any of the pictures, I didn't see a fuel filter. I know that these gas tanks can have some dirt inside right off the factory. If that dirt got down and clogged either the carburetor or the fuel filter (which may have been installed in the wrong direction thus you couldn't see the dirt building up), it may have reduced the fuel flow to a point where you leaned out the engine. That would explain the black color and ring failure. Can you open up your carb and check the fuel filter in the hole where the gas enters it?
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I do have a fuel filter, sorry, didn't show it in any pics. When I opened the carb two days ago, it was fairly clean, no large debris or particles. So what is that gunk around the spark plug and on head cylinder wall?

I placed new piston rings on the piston and made sure the cylinder walls are still in good shape. No gouges or scratches anywhere. I attempted to ride the bike and it still has the problem of dying on idle. Compression is still good. The weird thing is it dies abruptly. And the power is still weak (can't go up the same hill like I could when it was brand new). It doesn't gradually lose RPM till it stalls, but rather it idles fine and then for no apparent reason, it cuts out. Tried a new spark plug and different CDI and still have the same problem. Another thing, the engine now sounds extremely loud at higher RPMs. It's almost like I didn't have a muffler on it. The muffler is not broken and all other parts are the same as before putting on new piston rings. It only get super loud after a certain RPM. Below that threshold, it sounds normal, but once it goes past it, it's extremely loud. Again, I checked the exhaust intake, head gaskets for leaks and found none. I even tried a brand new muffler I had lying around and it still had the same extreme loudness at higher RPMs.


Afterward, I attempted to place a brand new cylinder head gasket and torqued the head bolts down to 120 in/lb , but the new gasket still leaks, as evidenced by extremely loud popping noises not normally heard with the old gasket. By the way, this is not related to the extremely loud engine problem mentioned previously. The new gasket was placed after the above incident. Both mating surfaces are clean and smooth, no signs of divots or damage otherwise. The new head gasket is also in pristine, new condition. It seems the old gasket forms a better seal and is made from a more pliable type of soft metal that is able to deform to the exact contours of both mating surfaces. The new gasket I got it stiffer and probably doesn't deform enough to make a perfect seal. What should I torque the head bolts at? I stripped out head studs last time when I was trying to get a new head gasket to seal.

I seriously have no idea what is wrong.
 
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Have you tried replacing your magneto? Mine was causing hard starts and rough idle after it got wet the first time. It got wet last friday and now its toast.
 
moonerdizzle said:
Have you tried replacing your magneto? Mine was causing hard starts and rough idle after it got wet the first time. It got wet last friday and now its toast.
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Yeah, the magneto went out a few days before and I am using a brand new magneto right now. I have a trailtech tachhour RPM device that measures current through the spark plug wire. So if the TTO device shows RPMs, that means there is a current present and thus the magneto is working, or else the TTO will show 0 rpm when I turn the engine over. Like I said in my previous post, it starts up fine and seem to idle fine, it just stops abruptly at random. No drop in RPM, just idling happily and out of nowhere, it stops dead after less than a minute.
 
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Well for starters, your engine is "4-stroking" when you WOT. The clanging sounds like the slop between the small 20 tooth beveled drive gear and large 82 tooth flywheel gear. If your engine was firing on every stroke like it was supposed to, that slop wouldn't be there and the clanging wouldn't happen. It's prolly time to replace both of those gears anyways.
 
Cavi Mike said:
Well for starters, your engine is "4-stroking" when you WOT. The clanging sounds like the slop between the small 20 tooth beveled drive gear and large 82 tooth flywheel gear. If your engine was firing on every stroke like it was supposed to, that slop wouldn't be there and the clanging wouldn't happen. It's prolly time to replace both of those gears anyways.
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Now that I have re-ringed the piston and changed the spark plug to a B6HS, it doesn't seem to 4-stroke anymore, but now it's the issue of being super loud pass a certain RPM as well as dying randomly at idle, as mentioned in my previous post. Do you have any idea what is and is causing the weird buildup on my cylinder head, around the spark plug?
 
userix said:
Now that I have re-ringed the piston and changed the spark plug to a B6HS, it doesn't seem to 4-stroke anymore, but now it's the issue of being super loud pass a certain RPM as well as dying randomly at idle, as mentioned in my previous post. Do you have any idea what is and is causing the weird buildup on my cylinder head, around the spark plug?
Click to expand...

Did you say you were running 32-1? I wonder if maybe you just got a bad batch of 2 stroke oil??
 
IMO

the clutch mechanisms on these little chinagirls were not really designed to be dis-engaged for any period longer than momentarily.

I kill my engine and re-pedal start at a stoplight. and never pedal, with the clutch dis-engaged, any longer than it would take to turn the motor over easily as I slipped the clutch to start it.

I suspect you have induced considerable wear on the bucking bar release mechanism and it's ball bearing, it sounds like the clutch friction disk bearings are way too loose, and there is also a lot of noise from the primary gear engagement.

Replace the clutch hub/bearing/friction disk assembly and the pinion for the crank, grease the bucking bar bearing well if they do not need replacement also, and try a new method of operation in which you 'pretend' this mab does not really have a neutral position for the drive train.

There's NOT really any time when it should sit there, with the motor being revved for a photo op, except perhaps for some rare tuning event.

IMO

Oh... other than that stuff, it sounds pretty much like a rattley little chinagirl ! :-)


Best
rc
 
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Interesting theory. I normally didn't have issues like this with my previous engines. But I don't see how bad bucking bar and bearing, which are fine in my case, can cause engine to die after a hard climb and then putting the clutch in.
 
engine dying after hard climb when pulling the clutch in is probably because carb is adjusted improperly for the excess heat build up from that workout.

They are just not the best quality engines, or carbs!

it ain't a perfect world

:-)
rc
 
Here's a video of the super loud revving. This happened after I placed new piston rings on the piston. And it still dies randomly on normal idle. New gaskets on both end of the cylinder.

Loudness - YouTube
 
Could be a loose (worn out) crank bearing. My last engine made a similar sound when it died. When I took it apart, I could feel slop on the bottom end bearing. You shouldn't be able to feel any.

You can check it with the cylinder off. Grab the rod and see if you can feel any up and down movement with the crank at TDC. Side to side doesn't matter. If the bottom end feels alright check the wrist pin and bearing

You could also have a crank bearing going out.
 
Have you tried a fresh fuel mix and different two stroke oil since this problem started? Just a thought, as I haven’t seen a carbon build up like that on any newish motor .
 
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