Engine noise

[804]

I have a 3MM TOC 53 with approximately 50 hrs. I had noticed a few flights ago when starting it, it seemed to have some rotational play when coming up to compression, that is when the piston hit resistance, you could move the prop back and forth quite a bit. The last flight, upon landing at idle, it was making a definite clanking, mechanical noise I'd never heard.
I took it apart, expecting to see either top-end or bottom-end bearing damage.
The upper bearing seems fine. My question is about the lower one.
It is a caged needle type. The bearing is a bit wider than the conn rod, and I can move the bearing far enough to the side to see the bearings, and I can see them thru the oil holes in the rod. The bearing appears intact, and moves freely.
But, it seems to be a very loose fit. I can move the rod vertically up and down more than I would expect, and rock it fore and aft, between the counter-balancers, again more than I would expect.
I apologize for the vague description of the play, but I don't have any way or knowledge to measure this. My only reference is that I have replaced several top ends on 2-stroke dirt bikes, but don't remember any of them having this much play.
Does this seem normal?
Thanks in advance.

[octanehuffer]

THERE MUST BE NO PLAY IN THE CON ROD BEARINGS WHILE MOVING UP OR DOWN. Get a new connecting rod. Also make sure the other bearings spin freely without the crankshaft installed. Make sure they dont make any "notchy" sounds when they are cleaned.
edit. You will always have some fore and aft con rod play. Even when it is brand new.

[jack strickland]

According to the Machinery Handbook, there must be .0003 to .0004 lateral clearance, or slop if you prefer, between the roller (torington type) bearings, and the crank pin. So a little clicking is a must. If they are installed with less than the min. clearance, they will gall and distruct. How much clearance is in your rod bearing? A machine shop can measure it for you. If the bearing is marked China, there is your problem. They have not as yet made acceptable ball or roller bearings. IMO. Have run into this problem before. Bearings from U.S.A., Germany Canada, Japan, are very good. If you replace the bearing with one of these, you will be good to go.

[2walla]

You sure that it isn't the pin on the crankshaft is worn? Either way something is shot and will need replaced. Either way if you have to take the crankshaft apart to replace the rod and bearing it may cost more than the motors worth to fix.

[octanehuffer]

If he is able to feel the play vertically, it needs replacement. There is no way he can feel the 3-4 ten thousandths. Amen to the Machinists Handbook Jack.

[804]

Thanks for the replies, guys.
According to two sellers of this engine, the rod/bearing/crank only are available as a unit. Don't know the price yet.
I suppose I could have a shop take it apart, and try to match a quality bearing, but if the crank pin is worn, I'm hosed anyway.
I agree about the cost to fix may be not worth it. Tom at Wildhare says he might have one from a returned engine he'd sell me cheap.
Looks like my "cheap" engine just got expensive. A shame too, 'cause it ran so well for about 300 flights.
Zero problems 'til now.

[jack strickland]

Run the thing till it blows--What do you have to loose- It may be ok-- they can be very noisy, and be ok-- AND ONE SHOULD BE ABLE TO HEAR CLICKING ON ANY TYPE TORRINGTON BEARING wheather caged or open!!!!!!!!!!!!

[jack strickland]

	Quote: Originally Posted by octanehuffer
	If he is able to feel the play vertically, it needs replacement. There is no way he can feel the 3-4 ten thousandths. Amen to the Machinists Handbook Jack.

Yes you can feel 3-4 tenths. And amen to the Machienry Handbook is certainly corrsct.

[Al Lewis]

There are a number of bearing houses where you can order new rod bearings. Any small engine repair can install them for you. It's a very simple process. The bearings you want are drawn cup needle roller bearings and INA/FAG are a very good brand. Torrington is another but has been bought up by Timken so you will probably have a better chance of finding the INA bearings. Here's a link for you to start. If the crank journal is damaged you can buy a sleeve to go over it to refurbish it.

http://medias.ina.de/medias/en!hp.ec.br.pr/HK*HK1212

[octanehuffer]

	Quote: Originally Posted by jack strickland
	Yes you can feel 3-4 tenths. And amen to the Machienry Handbook is certainly corrsct.

I certainly hope someone could feel 3-4 tenths. Thats over 1/4". Or .300-.400. In your reply from the Machinists Handbook, the bearing would have .0003" - .0004". As in ten thousandths. Something that cannot be felt.

[804]

Again, thanks for the replies.
Using a very crude technique, which I would be embarrassed to describe, I am sure there is a lot more than .0003 to .0004 clearance, more like .005 or more.
There really is a lot of play, and while my first description of the noise was a clunking, a loud hammering noise is probably a better way to describe it.
I am going to take Al's advice, and take the engine to a repair shop I've used before to compare price of replacing the bearing/sleeving the crank, to replacing the crank/rod/bearing unit.
At any rate, this engine will be repaired before flying again. Really no other option right now.

[cacctus]

Maybe the engine is still covered under warranty? I have the same engine and mine is covered under a 1 year warranty. Perhaps a call to the dealer you purchased from could go a long way toward a resolution.

Ken

	Quote: Originally Posted by 804
	Again, thanks for the replies. Using a very crude technique, which I would be embarrassed to describe, I am sure there is a lot more than .0003 to .0004 clearance, more like .005 or more. There really is a lot of play, and while my first description of the noise was a clunking, a loud hammering noise is probably a better way to describe it. I am going to take Al's advice, and take the engine to a repair shop I've used before to compare price of replacing the bearing/sleeving the crank, to replacing the crank/rod/bearing unit. At any rate, this engine will be repaired before flying again. Really no other option right now.

[jack strickland]

	Quote: Originally Posted by octanehuffer
	I certainly hope someone could feel 3-4 tenths. Thats over 1/4". Or .300-.400. In your reply from the Machinists Handbook, the bearing would have .0003" - .0004". As in ten thousandths. Something that cannot be felt.

Tenths is refered to in machinest terms as a tenth of a thousandth, and one certainly can feel 3-4 tenths. The tearm tenths is understood by any machinest, why don't you ask one instead of argueing about it?

[Al Lewis]

	Quote: Originally Posted by octanehuffer
	I certainly hope someone could feel 3-4 tenths. Thats over 1/4". Or .300-.400. In your reply from the Machinists Handbook, the bearing would have .0003" - .0004". As in ten thousandths. Something that cannot be felt.

LMAO

[octanehuffer]

	Quote: Originally Posted by jack strickland
	Tenths is refered to in machinest terms as a tenth of a thousandth, and one certainly can feel 3-4 tenths. The tearm tenths is understood by any machinest, why don't you ask one instead of argueing about it?

So you bring in a crank or what ever to machine something, you tell the guy to take off a tenth and he removes one hundred thousanths. .100" Not .0001". Here is a very simple link for you to understand. I run a mill and lathe for the USAF as well as all of my engine blueprinting. Maybe you civilians call it cool people terms, but a ten thousanth is a ten thousanth. Only abbreviated term I have heard is thou. Short for thousanth. If you are calling a ten thousanth, a tenth, it is the wrong definition that could mean something totally different. Maybe it is the different states we live in. WOW
http://wiki.answers.com/Q/What_is_th...al_for_1_tenth