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Discussion Starter #1
We've all heard the saying, "treated like a rented mule..."

After watching equipment auctions looking at Polaris Rangers, I ran across an ad for a 2018 Yanmar Bull. It was an rental unit that had been rode very hard and was partially disassembled. Looking at the pictures I thought to myself, "How difficult could it be to repair?" After all its just a Yamaha Viking. Parts are available, repair manuals are available, and there is a lot of good information online. What was I thinking?
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I placed a ridiculously low bid and I was the only bidder. Lucky me! It cost me more to have it shipped from Louisiana to Delaware than I paid for it. After getting it here I started the cleaning and removal of literally 180 lbs of dirt. Seriously, I weighed it!
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After removing the dirt I hit it with the pressure washer to see what I was dealing with.
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Since I am not completely comfortable with rebuilding the engine on my own. I contacted one of my friends who rebuilds motorcycles for a living. We discussed this machine and he agreed to work on the engine. Going in I expected to have to put a cylinder, piston, gaskets, etc. Well after he tore the engine down we discovered the piston had broken as there were aluminum bits in the case. He also said the main case bearings were gritty. The rod bearing didn't sound too good either. Soooo.... it got a new crank, rod, all the bearings, cylinder, piston, valves, and thoroughly cleaned. Cha-ching!!

We also discovered the rental company was nice enough to swipe the speed sensor, power steering control box, swap out the key switch, and loose the right side bed panel. So off to eBay and Craigslist I go. Some say I have too much free time...

The best price I could find for a used power steering control was from PSN. I had already planned on changing the plastics/color so the missing panel wasn't a big deal. The other panels were pretty well beat and broken anyway. I found a blue front fender/cowl on eBay for a steal. He also had the left side bed panel in blue. Both were new parts. And they were within diving distance Sweet! No shipping charges!! The right side panel also came from the Bay.
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After waiting for what seemed like forever, my friend called and said the engine was done. So I rushed over, picked it up, and prepared to drop it back in. It went in without a hitch. I replaced a the rear driveshaft boots while it was apart. Everything seemed to go well.

Then the fun started. As I poured the water in (I thought I'd fill it with water to clean out the coolant system then swap it out for coolant later) it starts coming out the water pump weep hose. No big deal I thought. It just needs to run and it will stop. Nope... But not knowing better and being too excited to have a running machine, I ran it for awhile. Mistake number 1. I probably didn't bleed the coolant system correctly either. So it ran hot, and filled the crankcase with water. Water in the crankcase means one of two things. Either the water pump seals are bad or the cylinder/head is really cracked. Since it would still run I went after the water pump seal. Took off the side cover with the water pump and sure enough, very bad water pump seal. Why it wasn't changed I dunno. Ordered a new water pump seal kit. Got that changed and figured it would be ok. Nope.
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Apparently when I ran it hot I blew the head gasket. Ordered a new head gasket. Took it all apart again and replaced the head gasket. After going though all this, I figured I better do a better job of bleeding the coolant. I also checked the head for warpage and really didn't find any. Put it all back together and fill it up with coolant again. I did notice a small leak from the hose between the water pump pipe and the head. No big deal I thought... again... Wrong...
 

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Apparently it lost enough coolant to run hot again. I figured no problem, just go get a small piece of hose to replace the bad one. No body has 22mm ID hose. Anywhere. Yamaha said the part was on back order and it would take about three weeks to get it. So back to eBay again, ordered a piece of 22mm ID blue silicon hose. While waiting for it to arrive, I was searching Craigslist and ran across new 28" MongreIs and 14" Tusk beadlock wheels. So of course I had to buy them... IMG_0331.JPG
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So after the hose arrived, I put it on, bled the system like has been discussed many times. Fill it with the front elevated, bleed the water pump, bleed the thermostat housing, wait, top off. Sounds easy enough. I did that and ran it long enough for the fan to come on and off. Recheck, it's low again, refill, run, recheck, refill, run,... Something is still wrong. Look in the coolant reservoir, little bubbles while its running. Bad sign...

So I now have another head gasket on order. Along with a new thermosensor. And the proper center caps for the wheels...
 

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keep at it!
 

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Amazing efforts! At least it is sitting on nice wheels while it waits to be done!

Sent from my SAMSUNG-SM-G890A using Tapatalk
 

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Wow awesome work! Make sure the head is dead flat before you re-gasket it, run an engineers steel ruler over it or sit it on a dead flat surface with fine emery paper, swirl it around and make sure that the fresh scuff marks are even all over. Keep us updated!
 

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Discussion Starter #6
That's the plan. Rechecking the head and the cylinder top surfaces. Can you guys think of any thing else that I should check while I'm in there? I got the email today the parts shipped today. Of course I'm planning on going out of town for a while before the parts get here. So I have time to pregame my plan of attack.

I do have my eye on a few more parts. Maybe I search Craigslist too much... lol
 

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Can you guys think of any thing else that I should check while I'm in there?
I'd be checking the thermostat, it has to start opening at 71+-2C, has to be fully open at 85C, and has to open 7mm.
 

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It should be right then, maybe just leave it out for now until you sort the issues.
 

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Discussion Starter #10
Not much has changed on the Bull. The head gasket and thermosensor arrived last week. The center caps also arrived. However they showed up and I literally walked out the door to go on a road trip.

I did pick up a few more parts in my travels: a front windshield, rear window, another plastic roof, and a rear view mirror. All from a barely used machine that the owner put a hard cab on. He also had a set of almost brand new stock tires/wheels. I just don’t need those. Lol.

Now just waiting to get back home so the work can continue.
 

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On the rebuild did you do the bolts on the middle gear ,30 Ft Pds torque and red loctite.
 
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Discussion Starter #13
Progress!! I pulled the head off and found where the head gasket was blown. Now I'm going to check and recheck the head and cylinder surfaces to be sure they are true.
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Head side of gasket:
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Cylinder side of gasket:
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If you look close at the left side you can see where the seal is missing. The first head gasket I changed blew out the head side, this one is the cylinder side. I resurfaced the head last time, that's why I pulled the cylinder to check/resurface. Better safe than pull it apart again later. The good news is I'm getting better at taking it apart....🤣
 

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Head side of gasket:
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If you look close at the left side you can see where the seal is missing. The first head gasket I changed blew out the head side, this one is the cylinder side. I resurfaced the head last time, that's why I pulled the cylinder to check/resurface. Better safe than pull it apart again later. The good news is I'm getting better at taking it apart....🤣
That's blown across the two coolant holes, what about to compression? If you look closely at the cylinder sealing ring at the bottom just above the left hand coolant hole, maybe there? You can see it better on post 13 if you open the thumbnail.
 

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The pictures make them worse they really are.
Oh ok, still it might be worth getting a 600 grit wet paper and polishing them out in a 8 pattern. I wouldn't be giving it any excuses lol
 
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