YM336D - Started knocking loud while tilling

[tcartwri]

I am saying there are 2 bent rods.

Then you would have witness marks on the upper shell as well, on the opposite side of the rod bore.

The other posibility is that the thrust bearing is marginal. I don't beleive that has been looked at.

 

[Car Doc]

Then you would have witness marks on the upper shell as well, on the opposite side of the rod bore.

The other posibility is that the thrust bearing is marginal. I don't beleive that has been looked at.

The uppers are what I am referring to and are the part that wears.

Also I said parallel and what I meant is "at right angles" and my point being they run at acute angles not fractions of acute angles. We are talking human hair tolerances a very very slight deviation off of an acute 90 degree angle will show up in the bearings and is the exact reason I asked Domush to post them if he could.

Just for conversation but drag race engine builders tune engines by reading bearings it is a science nothing to it but to understand the dynamics.

 

[grainger12002]

Domush
You are going to get this, dont give up.....you will be tilling in no time. Plus think how nice it will sound when its done

 

[bruce1966us]

Domush
You are going to get this, dont give up.....you will be tilling in no time. Plus think how nice it will sound when its done

I still think the engine sounds fine when running. You may work on this thing forever and never quieten it down. Good temp and oil pressure... Run it

 

[Car Doc]

If he runs it with the shim in that cap or the new bearing @ .0005 clearance he will be posting next how it is now a ventilated block and then what will he have???

You guys are not following this close enough or are just talking to be talking so think about what you say please.

 

[Domush]

I didn't think of it when I did it, but obviously adding a shim will cause an oval instead of a perfect circle. So, only one half of the rotation will be gapped properly.

I'm beginning to wonder if a spec of dirt got under one section (or both) of bearing. That would explain why the ends of the lower bearing surface is untouched but the middle area is worn already. We'll see in a couple of hours

I'll take pics of the new bearing surface of #3 when I pop it out. Any other pics which will help diagnosis?

now a ventilated block and then what will he have

An air-cooled two-cylinder

 

[Car Doc]

Here is some info for those who want to argue with me over what I see in the old bearings and you all can make up your own minds. :thumbsup:

Engine bearing failure [SubsTech]

 

[284 International]

Domush, I know you said you checked the rods for straightness by eye, but I think you should look into that again/more. Car Doc and others besides me think that is the problem, too. It won't take much of a bend to screw up the alignment, and it would be easy to miss by eye. The pistons should come off the rod pretty easily, and the trick about a piece of glass or granite counter section as a flat surface would work well here.

In my view, if you put it back together and try to run it, it can't last very long. The tight bearing is worrisome, and clearly indicates a real problem. It used to be fairly common to have machine shops recondition rods; I haven't had that done recently, so don't know what it costs. You could at least find out if the rods are straight, and then see if a shop can fix them. That would save the engine if that's the trouble. There's not anything else that could have reasonably caused that wear pattern, either. It seems probable the motor had water in it, too, so it seems likely that it could have been cranked with some moisture in the cylinder.

This is not the recommended procedure, but worked for me in a pinch to pull the injectors: Just loosen up the retainers a couple turns, until there is a bit of clearance under the nuts. Then crank the engine with the compression release activated. Simultaneously, I stopped cranking and closed the compression release. The injectors, one by one, nicely popped up the little bit to the retainers, and were removable by hand afterward.

 

[Car Doc]

Amen 284. :thumbsup:

This time I would check the pistons @ tdc for bent rods before tear down is the prilim check (we will go over the procedure again at the appropriate time ) and once the head is off and if he hasn't gotten the injectors loose.

Knock them out from the bottom like I mentioned the last time there are seals and washers under there that need replaced also plus if one is not working it can be replaced etc and a compression test could be done later if necessary.

Here is the facts if it has equal compression and has equal fuel it will run fine something is out of that order and that is all assuming it has a good bottom end where there are no other failures eminent.

All the parts can be re-used except the head gasket and even arguably the bearings that are tight lets cross that bridge when/if we get there.

NOTE: I want to make one more comment of caps on backwards uhhum... upon close inspection of the pics of the old bearings I see a wear mark on the lower shell off on one side, a line coming off the edge of where the tab is bent out of the shell that corresponds with a similar mark (as expected) on the upper shell.

Now here is my point how could any of those bearings be installed with tabs on opposite sides???????????????? they came out with tabs on the same side as I suspected it should be so if Domush installed them with the tabs opposite there is one problem. Please someone prove me wrong plus you can see the spot the tab is touching the other bearing shell also on the same side.

 

[grainger12002]

thats interesting Cardoc, I wonder if they actually came off in that order or just placed that way once they were removed from the rod