"loose"front main...

[SDgray-HT]

was running my 1500 today and noticed the crank pulley seemed to be "jumping"slightly at a low RPM idle-took the side guard off and with engine stopped,pried up and down on the crank pulley and found about 1/16" or slightly more of up and down play...Are two cyl yanmars known to wear the front main to this degree or do you think it may have been run out of oil at some time in it's life and caused this?BTW engine runs good and when i changed the oil a couple weeks back,the drained oil and the filter were carefully examined and no metal particles were found.Looks like i am going to have get off and get under to pull the crankcase plate for a look...This little problem could lead to a restoration of this tractor LOL -it's in very decent cosmetic shape for ~37 yrs.

 

[4x4_Welder-HT]

Have you checked to make sure the pulley is tight to the crank?

 

[SDgray-HT]

it is tight-when i first saw the movement i was thinking the pulley casting was irregular or something,so i looked from the front under the radiator while idling and the crank snout could be seen"jumping"with the pulley.

 

[winston-HT]

Wow, those are 1 piece main bearings. Pretty sure that is an engine pull job to change those mains.

 

[SDgray-HT]

Yep,kinda curious what will be found when i get into this-hopefully a main journal regrind and new mains will cure the problem(will check everything else too,repair/replace as needed) and get my little 1500 back to 100% health. Will check the clutch and driveshaft coupler when apart too.

 

[winston-HT]

Hoping you might take a few pictures for us along the way. <E>:wink:</E>

 

[SDgray-HT]

will take plenty of pics of the process-will see if i can sucessfully video the "jumping"of the crank before the repair too.Meanwhile,the non-engine related "small"projects and spiff-ups will continue.

 

[4x4_Welder-HT]

I wouldn't run it again until it's fixed. That crank only has two bearings, that means that your flywheel is moving at an angle, and the rods are being subjected to an angle as well. This could lead to a cracked rear main bearing housing, bent/broken rods, or even a broken crank.

 

[SDgray-HT]

indeed considered "out of commision" until repaired -i initially thought it might have broken crank but could tell it wasn't once i got my hands on the pulley,didn't have the clank and rattle of a broken crank either-had to fix an onan"performer 18"opposed twin with broken crank once,it had taken a big hit to the flywheel-clunked and rattled at idle real bad LOL

 

[SDgray-HT]

Got it in the shop and getting it apart-got the sump plate off and nothing looks too bad yet,just a light film of very fine metallic"dust"on top of the plate-no particles.Rod bearing clearance feels good and big ends are shiny-no burnt oil blackening.Wow,that is one stout crank for such a small engine!-looks like the journals are heat-treated too,"Old skool"overbuilt quality <E></E>

 

[SDgray-HT]

pretty much stripped down to the basic short block now-still hanging off the front of the tractor,will seperate and complete disassembly tomorrow or next few days-these old yanmars are super easy to work on;almost as easy as a lawnmower LOL. Anyway no serious problems yet besides the oil pump was in bad shape-badly worn from downward pressure of crank gear displaced downward by worn mains.
-gears and governor in good shape
-valvetrain looks good
-sleeves showed a little"dusting"evidence,but no ridge,scoring or major wear-probably will do a light hone and a re-ring job.
-valve and valve seat condition will be checked.

 

[SDgray-HT]

short block is off and will soon be disassembled-the clutch was in good shape(not sure if the original or not)but the coupler between the clutch shaft and the tranny input shaft was pretty bad-just about ready to strip out...The splines of the shafts were good.

 

[SDgray-HT]

the mains were totally shot-front worn past the copper down to the steel ring,rear had large chunks of copper flaking off.The main journals were badly worn too,abt. .010-will see if they cleanup at .010 under.Rod bearings and journals were pretty good on the other hand-amazing since they get oil via the mains and the oil pump was in bad shape...Will be dropping the crank off at my fave crank grinder shortly.Have been getting pics of any interesting wear/damage-may post up later.

 

[Norm-HT]

I would get get appropriately undersized bearings, (.010/.025), for machine shop before dropping off.

 

[SDgray-HT]

I was thinking about that too-Also,cleaning parts,i realized the flywheel is centered on the crank by the 70mm std flange diameter;once that is turned undersize i will have to make a ring to compensate for removed diameter and insure flywheel is properly centered...

 

[Norm-HT]

<QUOTE author="SDgray"><s>

</s>I was thinking about that too-Also,cleaning parts,i realized the flywheel is centered on the crank by the 70mm std flange diameter;once that is turned undersize i will have to make a ring to compensate for removed diameter and insure flywheel is properly centered...<e>

/e></QUOTE>

<E>:?:</E> They are not going to mess with that flange, (main bearing housing). The only change will be the OD of the crank journal and the ID of the main bearing.

 

[SDgray-HT]

Yeah,kinda worded that wrong-it is the the reduced diameter of the (soon to be)reground undersize rear journal that i will have to make a centering ring for as it will then be too undersize to properly locate the flywheel on center.Good thing i have a lathe to make that ring-if journal "cleans up"at .010,could make the ring from a .005 thk.strip of sheet metal

 

[4x4_Welder-HT]

Maybe you can have the machine shop leave the step on the end. There should be a staining line and a seal line to work from there. This would be best, as a shim in that pocket could come out and cut the seal.
Also, on the diagrams it shows a "parallel pin" that looks like a dowel pin for centering.

 

[SDgray-HT]

1 pc rear main wouldn't fit over a step on end of journal-2 pc rear main would be nice in this case-oh well,ring will be easy to make.Meanwhile,i have finished cleaning/inspection of the block and found it has two freeze cracks i have to repair:between the liners top and bottom-i have a few methods in mind for the repair,have had to fix broken cast iron before.Someone had"fixed"the problem before by pouring some gray epoxy like material into the water jacket to a depth of about 3/8"-this repair actually held,but i am going to do a better repair...This explains what took out the mains-damaged by operating with water in the oil-damaged mains not repaired,tractor put back into use after the crack "repair"...

 

[SDgray-HT]

The cracks have been fixed and the crank was dropped off at the machine shop last week,so proceeding along with repair-for the crack repair,made some 1/8"thick steel pieces-one on each side of crack-secured with M6 bolts,once all the parts had been test fitted and tweaked as needed,the block was"sprung"ever so slightly with a portapower so the cracks could be cleaned,locktite applied into cracks(mostly as a sealer)repair hardware quickly installed(bolts for bottom repair sealed with high temp silicone)and finally a good hot weld bead was applied to the four steel pieces so they would cinch the cracks good and closed after the weld beads cooled and contracted.

 

[SDgray-HT]

got the crank back from the machine shop today-took a while because the usuall guy had a heart attack and was on light duty for a while,but they did a nice job and fit is good <E>:wink:</E> as soon as i finish engine repair on my Z28(water got in,bent a con rod-had 200,000 mi.anyway...)i'll roll the yanmar back in and get it back together-i attached a handle and wooden peg leg to the bellhousing to move the tractor around-nice that it is small LOL.