YM336D - Started knocking loud while tilling

[grainger12002]

Hello Domush,
How are you doing with the tractor ?

 

[Domush]

Sorry for the slow updates, everyone. Work.. and some play, has gotten in the way of continuing the diagnosis. It doesn't help I ordered the wrong pump timing shims, so those are in the mail today.

I am still wondering how much fuel is coming out of #2 at the injector?

I'll be testing for this today. I'll finagle something up as a J pipe.

I would definitely do a compression test (remember the hitch?) and dont worry if the pan is off there is plenty of oil on everything. Do this before plastigage if there is no side movement in that tight rod otherwise there wont be enough oil plastigage needs dry crank/bearing so make sure to oil it after checking it.

I have no means to compression test it. Plus, I can't seem to get the injectors off (tried when the head was off). I'd really like to avoid this if at all possible.

And you are 100 thousand % sure the caps are on right.

I made decent notes as to piston orientation when I removed them. I was lucky, as a number was stamped into each connecting rod, and they all faced towards the injector pump, so there was no messing them up upon reassembly. And I checked my notes, the pistons are back where each started out.

All things considered I almost never miss on my diagnosis when its hands on this is fairly difficult online.

I realize this slightly resembles walking Helen Keller through a driving lesson over the phone, but I do appreciate the fact you (and everyone here) is continuing to help me through it.

The timing is and I have not done one yet just researched it because I am 95% my timing is fast also.

I'll be checking the timing shortly, here.

For now, here are the rod bearing photos:

The order is #1, #2, #3 (left to right)

Let me know if these tell you anything.

Also, what should I do about the #3 rod being tight? Should I loosen the rod cap bolts until it is as loose as the other two or will it loosen on its own without damage? I get concerned when one of these things is not like the others.

 

[grainger12002]

is the rod tighter than the others, I would get some plastigage,tighten it down and see what that tells you.

 

[Car Doc]

Domush,

Thanks for the info and pics etc! They are flat worn out and had considerable amount of clearance as well.

I am going to guess with new bearings they will gage somewhere at or above .003" just guessing? That will work dont worry its not ideal but wont hurt anything just making a prediction is all see how smart I am.

The upper shells (the ones that are shiny) is where we see that.

To radically illustrate this take a 1/2" smooth rod and lay it in a 2" tube and see how wide the bearing surface is that actually touches the rod/tube to give you an idea what I am looking at.

(A 1.985" rod inside a 2" tube is what we are looking for as an example of proper load transfer and oil clearance.) :thumbsup:

"Also, what should I do about the #1 rod being tight? Should I loosen the rod cap bolts until it is as loose as the other two or will it loosen on its own without damage? I get concerned when one of these things is not like the others."

I am concerned about 2 of the bearings actually. See #3 and #5 shell how the one side is worn wider and off to one side more so than #1 shell which is just worn (out) "normally"?

I was sure hoping they would have knocked the injectors out from the bottom for you that would have been the easiest way because I knew we may be wanting them out later but thats water under the bridge now. We sure do need the injectors out I hate to say it but we really do in more ways than one my friend.

Like has been mentioned on the bearings I would pull the caps one at a time while the journal is down, clean the bearing and crank with brakeclean spray and go ahead and plastigage them note that and lets see what the tight rod is doing. Put oil or white lube back on before moving to the next one. If the #1 rod is bent bad enough the bearing could conceivably be tight simply as a matter of the bearing being new so lets keep that in mind also!

The rods will not get looser because they are run in they need to fit properly to start or they will fail there isn't a break in as such on bearings, they just work or they dont. If it is tight there is something wrong like I mentioned maybe bent maybe cap turned around???

I am wondering if you have that rod cap on backwards its easy to do. For instance on 99% of all the engines I know of the tabs go on the same side. I dont know on this one simply because I dont remember 100% sure on mine but "think" it was that way.

Post some of the findings and we may be able to help further nothing so far has damaged it I am pretty sure even if a cap was on backward it will warp it some but probably will work again flip it around as long as the crank isn't scored take pics easier to give educated guesses.

 

[bruce1966us]

Sorry for the slow updates, everyone. Work.. and some play, has gotten in the way of continuing the diagnosis. It doesn't help I ordered the wrong pump timing shims, so those are in the mail today.

I'll be testing for this today. I'll finagle something up as a J pipe.

I have no means to compression test it. Plus, I can't seem to get the injectors off (tried when the head was off). I'd really like to avoid this if at all possible.

I made decent notes as to piston orientation when I removed them. I was lucky, as a number was stamped into each connecting rod, and they all faced towards the injector pump, so there was no messing them up upon reassembly. And I checked my notes, the pistons are back where each started out.

I realize this slightly resembles walking Helen Keller through a driving lesson over the phone, but I do appreciate the fact you (and everyone here) is continuing to help me through it.

I'll be checking the timing shortly, here.

For now, here are the rod bearing photos:

The order is #1, #2, #3 (left to right)

Let me know if these tell you anything.

Also, what should I do about the #1 rod being tight? Should I loosen the rod cap bolts until it is as loose as the other two or will it loosen on its own without damage? I get concerned when one of these things is not like the others.

I dont think the knock is from the rod bearings. Did you replace them with the rings..?

 

[Domush]

I am going to guess with new bearings they will gauge somewhere at or above .003" just guessing?

I did the plastigauge:

#1 .002"
#2 .002"
#3 .0005" (it pretty well smoshed it.. it was slightly wider than the .001" indicator)

I made a .001" 'spacer' of sorts for the #3 rod cap and it began acting like the other two at 42ft/lbs (spec) torque. I'll probably catch **** for it, but it seems to work. Now I can just barely shimmy it side to side like the other two.

We sure do need the injectors out I hate to say it but we really do in more ways than one my friend.

I was hoping simply adjusting the timing would be enough to try it again.

I am wondering if you have that rod cap on backwards its easy to do.

They are stamped from the factory, so unless someone is texting while rebuilding it is pretty fool proof.

For instance on 99% of all the engines I know of the tabs go on the same side.

These are the 1% if I recall correctly (which I probably don't.. been a long day)

as long as the crank isn't scored

Crank looks fine. The #3 cap was already showing wear pretty much all along the face of it. Nothing deep enough to show copper, but enough I could feel it with my nails (but not my fingertip). Sorry, no pic.. I was in work mode just trying to get 'er done.

I dont think the knock is from the rod bearings. Did you replace them with the rings..?

Yeah, all new rod bearings. I ordered up some new pump timing shims today (ordered the wrong ones initially - doh! ), so hopefully retarding the timing may get rid of the knock. That is my long term hope.. though Car Doc seems intent on finding the real problem and shattering my pump timing dreams :laughing:

 

[clemsonfor]

They are stamped from the factory, so unless someone is texting while rebuilding it is pretty fool proof.


:

This almost got me when i was putting y Stihl Saw backtogeather saturday. The decompression valve fell apart inside the CYL and locked the piston on the upstroke. No damage really but a dinged piston. Anyway upon rebuild it had no compression and i heard and air leak. Was hoping the cyl mated tight to the crankcase and that that was not the problem, came to find out my welding up the old decomp valve to make a plug was not successful the first time. Anyway i was texting while rebuilding and was worried i screwed it up.

 

[Car Doc]

Domush,

Seriously those 2 bearings worry me they are not worn right anyone can see that. I have trained eyes and that stands out screams out should say LOOK AT ME.


Shimming a cap is suicide absolute guarantee to detonate the motor. The fit of the cap is what keeps the bearing from turning in the rod for 1 thing....There is something serious wrong with something to do with the tight rod...

Btw I am stoked about the plastigage up to the .0005.

 

[Domush]

I'm at a loss, now. I have no idea why that cap is so tight without the spacer (which is a piece of fiber material smooshed between the top and bottom rod pieces). Too bad it will grenade it.. it seems to have worked really well

When I removed the pistons I noted which direction was the front of the tractor, so there is no way I confused which piston # is what and which goes where, so that possibility is out. Also, I was careful to never handle more than one piston at a time, so I couldn't mistake which piston returned to which spot in the layout. #3 is one of which the bearing was worn to the side a little, but the new one seems to be wearing pretty evenly (a little concentrated in the center). This rebuild just became complicated.

I did figure out I had the compression release adjusted too much (about double @ .006") on #2 and #3 and maybe too little (.001-.002") on #1. I adjusted them properly (.003") and I notice that 1 cylinder "swoosh" sound, which you can hear when I'm cranking it in my start-up video, is now gone when cranking it in decompressed mode. All three sound the same, now. Serves me right for hurrying through the adjustments, as I originally skipped the #1 adjustment and guestimated the other two (didn't know there was a spec for them until today).

For anyone who is curious, you adjust them by bringing each cyl to TDC, making the set screw barely touch the valve stem, then turning 1 full turn more. That makes the valve .003" open. Repeat for other two cyls.

I spent so much time making that shim and messing with the rod bearings, I still haven't checked the timing out. I wasn't able to turn the crankshaft with the pulley nut (it just kept tightening) while that rod bearing was so tight against #3. Tomorrow I'll be able to test it, now that everything is spinning nicely again. Hopefully someone can chime in and offer some theories as to what to do about #3, as I'm just lost, now. Should I be reinstalling the old bearings and seeing if everything spins as normal? Would it even matter? :sigh: .. I just want my garden tilled.

I'm as sure as can be about which cap goes on which rod, as I scribed the piston # onto each cap and rod match as I removed each set. #3 still has "3" scribed on the cap and rod. I don't know what to do - This rebuild has already cost me plenty of time and money.. I'm losing hope. This rabbit hole just keeps getting deeper and just turned into a maze to boot.

 

[JimRB]

It matters when this shim fails, which it will. Remove rod, rotate crankshaft. Assemble rod cap with no bearings to make sure that it assembled correctly. I believe they bolt the rod cap on rod, machine it while bolted together. Orientation is important or reassembly. I do believe that reconditioned rods happend when they mill a tiny bit off the rod or the cap, bolt them together and resize. Connecting Rod Reconditioning: More to it than you might think: Engine Builder