Wanna play... GUESS THIS NOISE?

Ok, I'm on a 2001 LX. I just put in an Airsal head and piston and wearing an old Bi-Turbo. I just put on 2 new sprockets and a chain. I also just changed the tranny oil. All in the last couple days.

Ok -- the new sound: it sounds like it is coming from the cylinder area (it runs in time with the engine, not the tranny). It sounds like the noise you get when you put a baseball card on a bicycle, a bit lower in tone, but the same flippy metallic type sound. Again, as the throttle revs, it increases in time.

I'm already paranoid the oil pump isn't working so I put in more oil into the tank (that's why the Airsal went in, I burnt my last cylinder/piston on a no oil condition). I pulled the head and it doesn't appear like anything is scratched.

What could it be and how can I diagnose it properly? Can the reed valve make that much noise? The intake came loose during the time (and I heard it and correctly guessed a loose intake) -- can the reed become damaged getting loose?

Is it something externally rattling (it is fairly noisy at low RPM, can't hear it at speed, exhaust too loud). Tell me what I sound pull and how to inspect and I'll give it a whirl.

If you correctly guess this sound -- I'll send you the wrist-pin from my damaged piston/cylinder combo! Good luck!

Tks,

Ben

Re: Wanna play... GUESS THIS NOISE?

Vacuum leak, around gaskets.

Re: Wanna play... GUESS THIS NOISE?

low tone.. hmm.. sounds to me like an intake leak.. a muffled, mild pulsating intake 'roar'

Re: Wanna play... GUESS THIS NOISE?

I have the exact same noise. but it dont seem to affect anything

Re: Wanna play... GUESS THIS NOISE?

I have a 95 and had a sound that i think is simmilar to yours. It sounded like a radeling metalic noise. I believe mine was my crank bearings were worn out, cause what happens when they do is make that sound, so i just orered 2 and new seals for like 30 bucks total from mopedwarehouse.com.

Re: Wanna play... GUESS THIS NOISE?

I pulled the head and cylinder off today and rechecked all the gaskets. All seems fine. I checked the piston and wrist-pin and the bearing that sits in the there and it seems okay, as well.

The noise is driving me nuts. It is like someone is tapping the cylinder with a ball peen hammer.

Is there any info online about cracking the A35 and replacing the crank bearing Terry? I'd love to give it a whirl but would like to know if I need any special tools or techniques to get inside the motor.

Ben

Re: Wanna play... GUESS THIS NOISE?

ball peen hammer? Thats quite different than your original description.. Sounds more like preignition (pinging).

Check your points timing.. If thats OK then maybe the compression ratio was jacked up with these mods.

Also put a brand new plug in there and do a plug chop.. but be careful. If it's preignition you can hole that piston in a hurry.

Maybe that piston is hitting the head.. Do a clearance check. Remove the plug and put a piece of thin soft solder in there. Turn the crank over, past TDC, remove the solder and measure it where it's flattened out.. should be at least about 0.5mm thick.

Whatever the hell it is, find it and fix it.. All of a sudden this sound don't sound good at all.

Re: Wanna play... GUESS THIS NOISE?

btw.. does that kit come with cylinder base gaskets of different thicknesses? If so they must have provided directions on how to determine which one(s) to install. Raising/lowering the cylinder with gaskets adjusts piston/head clearance.

If the problem is lack of clearance, this might be the solution.

A thicker head gasket will also do it but that lowers the compression ratio, which may or may not be desirable.

Re: Wanna play... GUESS THIS NOISE?

If u get the problem Fixed Ben Let me Know I seem to hear the same sound.

Re: Wanna play... GUESS THIS NOISE?

You might be 4-stroking, what's your jet size?

Re: Wanna play... GUESS THIS NOISE?

I'm running a #56 jet at the moment. Going to try a #58 shortly.

The sound has become more obvious over the last couple days. It is definately a fast pinging sound from idle at no load to strong throttle. There is no lack of performance, I'm doing 47mph on flats.

I tore down the entire top-end yesterday to check everything and put in a new cylinder gasket. The new gasket is thinner, but the sound was evident with the stock gasket, which I didn't replace initially.

I carefully checked the cylinder, head, piston, wrist pin, clips and upper rod bearing and everything appears to be okay. Both the intake and exhaust are tightened down properly.

I've tried different plugs and am getting the same sound. I'm running high octane fuel.

I don't think the LX has points (correct me if I'm mistaken) -- and I don't think it would ping at idle, especially a cold idle where nothing in the cylinder would have time to heat up and start a pinging condition.

I'm curious about head clearance, although I'd be the first one with this problem, I think. Joe -- I'm not clear on how your clearance technique works, can you explain again?

What kind of lateral movement should the connecting rod have? I can wiggle it a couple of millimeters side-to-side when the top end is off. Is this normal?

Does anyone know what sound you get when the main or connecting rod bearings start to screw up? Keep in mind, before I put this kit on, I screwed up my cylinder/piston with a no oil job. Maybe some garbage slid down into some bearings.

Thanks for the input thus far -- I hope we can help someone else when we figure this out.

Ben

Re: Wanna play... GUESS THIS NOISE?

i can't imagine anything that has preignition at idle..

To check piston clearance, get a piece of thin electrical solder wire about 6 inches long. Remove the spark plug and stick the wire into the hole. Hold one end of the wire and get the other end to touch the side of the cylinder in there.

Use whatever means to turn the flywheel. You want the piston to go up, squish the solder wire and to keep going past top dead center.

Remove the solder and the end should look flattened. (if not use thicker solder) Measure how thick that flattened part is. This is how close the piston comes to the cylinder head near the edge of the combustion chamber. When things get hot, that clearance decreases..

Side clearance on the lower connecting rod is critical and specs are mentioned in every manual i ever seen.. Don't just wiggle the little end of the rod.. All rods wiggle a little. Use a feeler gauge to measure the clearance between the connecting rod's side and the crankshaft .. down at the bearing.

Another check is up-and-down clearance. This is more likely to cause the noise you describe. I forget the proper method to measure this.. it takes some careful setup.. it's probably on the Net if you do a search.

I didn't know you toasted that motor.. bearings often go away when a cylinder/piston go. I like the sound of this less and less as this thread progresses..

Re: Wanna play... GUESS THIS NOISE?

here's a tip from a Honda manual..

"Check the condition of the big-end rod bearing by grasping the rod in one hand and lifting up on it. With the heel of your other hand, rap sharply on the top of the rod. A sharp metalic sound, such as a click, is an indication that the bearing or crankpin or both are worn and the crankshaft assembly should be replaced."

This test was done on a crankshaft removed from the engine but the crank is still attached. This way there's no mistaking a main bearing or a wrist pin problem for the big end problem.. The only thing that could "click" if the crank is removed is that big end..

In your case, try this.. just remove the head, turn the crank until the piston starts on it's down-stroke. Now the rod and bearings are "stretched" out .. Hit the piston's top with something soft that won't make a noise.. maybe the heel of your hand is enough.

The only wrong with this method is that the wrist pin could make the clicking noise, or perhaps the main bearings.. But its six of one and half a dozen of the other.. ANY clicking noise is gonna be bad newws.

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