Just joined? Please introduce yourself.
Results 1 to 10 of 10

Thread: Does this sound reasonable?

  1. #1
    Registered Member chevynut's Avatar
    Join Date
    Nov 2011

    Member #:115
    Location
    Fort Collins, CO
    Posts
    10,835

    Does this sound reasonable?

    Guys, got the engine pulled from my ATV (Yamaha Grizzly 660) and tore it partway down. I'm not sure which way to go with it from here.

    Here's the deal.....the ATV has 2700 miles on it, which I've been told isn't a lot. My other one doesn't have a speedo/odo so I have no idea how many miles I've ridden it since I got it around 10 years ago.

    The previous owner was riding it on a road at 68 mph (nutty) when it suddenly lost power. He turned around and went back to their mountain cabin and it was knocking when he shut it off. He took it home, started it up and drove it into his garage where he was going to rebuild it. He decided he didn't have the time or the desire to do it so he sold it...I bought it. He concluded that it needed a bottom end rebuild and advertized it as such based on his evaluation.

    Yesterday I tore it down and one of the first things I did was drain the oil. It had about a half a cup in it and the oil capacity is 2 quarts. I saw no metal in the oil but it was pretty black. I connected a battery to the starter to see if it would knock when it turned over...it didn't as far as I could tell and it seemed to turn over smoothly. Using the pull-starter it seemed to have some compression. I tried a compression check but my gauge end wouldn't go far enough down in the deep spark plug well on the head. So I put my thumb over the hole and cranked it over a few times. It had compression but not much.

    I pulled the cylinder head and the piston has a little carbon but it's not bad. The valves all look good...it has 5 valves even though it's a single cylinder engine. Weird.

    Anyhow, I pulled the cylinder and the piston has obvious scoring/galling and the cylinder sleeve is scored pretty bad on the thrust side. The cam looks fine as does everything else in the top end of the engine. The rings are pretty tight in the piston grooves. The rod bearing (roller) seems pretty tight other than having some side play which I believe is normal. It turns over great and the crank is also on roller bearings, which seem to have no wear. I can see no damage looking down into the crankcase and the timing chain and everything looks good and was still covered with oil.

    So I'm concluding that he ran it low on oil and the piston started to seize in the cylinder causing the rapid loss of power. The bottom end seems to be okay since everything there is on roller bearings, and what little oil it had was enough to preserve the bearings. He said the transfer case worked fine as well, and it's all roller bearings too. I'm assuming the knock was from the piston, not the bottom end.

    I'm really hesitant to split the case and get into the engine any further, because I don't think I need to. I think the bottom end is fine and a top end rebuild should take care of it.

    So my plan is to flush the engine with diesel fuel to see if I can find any metal shavings or anything that didn't come out with the oil. I plan to remove the oil filter and split it open to see if there's anything in it. Then if all looks okay I'll buy piston kit and have the cylinder bored and honed and replace it with all the new top-end gaskets. Hopefully once I put it all together it will run fine without the knock. I assume the knock was from the piston, not the bottom end.

    Does this sound reasonable? Or am I wasting time and money. I figure if something IS wrong in the bottom end I haven't wasted anything but gaskets if I have to tear it down again. A bottom end kit is almost $400 and the piston kit with gaskets is $165 plus maybe $75 for boring and honing. I'd have to do the top end in any case. There could be a few odds and ends I need too by the time I'm finished.

    What do you think? I don't want to have to do this again, but I hate to spend the extra $400 or more and the added time if I don't need to.
    56 Nomad, Ramjet 502, Viper 6-speed T56, C4 Corvette front and rear suspension


    Other vehicles:

    56 Chevy 2-door BelAir sedan
    56 Chevy 210 4-door sedan
    57 Chevy 210 4-door sedan
    1962 327/340HP Corvette
    1961 Willys CJ3B Jeep
    2001 Porsche Boxster S
    2003 Chevy Silverado 2500 HD Duramax
    2019 GMC Sierra Denali Duramax

  2. #2
    Registered Member chevynut's Avatar
    Join Date
    Nov 2011

    Member #:115
    Location
    Fort Collins, CO
    Posts
    10,835
    Flushed the crankcase and filtered the diesel through a paper towel, and I found ZERO metal in it. There were a few particles of what looked like tiny sand grains, but it could have been from when I removed the head or just sitting on the bottom from checking oil. Then I removed the oil filter, cut it open with a can opener, and dumped the element and all contents into a glass jar. I poured gas in it and sloshed it around, and again filtered it through a paper towel. There were a few tiny metal particles, probably from the piston, and again just a little more sand particles. The PO must not have been very careful with the dipstick when he checked his oil...which he must not have done very often. I suspect the oil had never been changed on this ATV. It still had what looked like the factory oil filter and with 2700 miles he probably figured it was't due for an oil change yet.

    Anyhow, it looks like I lucked out on this one. I called a local shop and they will bore and hone the cylinder for me for $45. I may have this thing running for under $300.
    56 Nomad, Ramjet 502, Viper 6-speed T56, C4 Corvette front and rear suspension


    Other vehicles:

    56 Chevy 2-door BelAir sedan
    56 Chevy 210 4-door sedan
    57 Chevy 210 4-door sedan
    1962 327/340HP Corvette
    1961 Willys CJ3B Jeep
    2001 Porsche Boxster S
    2003 Chevy Silverado 2500 HD Duramax
    2019 GMC Sierra Denali Duramax

  3. #3
    Registered Member JT56's Avatar
    Join Date
    Mar 2013

    Member #:1608
    Location
    DFW Texas
    Posts
    1,209
    If I was the one on top of the mountain, I would make sure I covered all the bases.

  4. #4
    Registered Member chevynut's Avatar
    Join Date
    Nov 2011

    Member #:115
    Location
    Fort Collins, CO
    Posts
    10,835
    Joey, I feel pretty confident that the bottom end is okay after looking at the oil and the filter. If this was a car engine without roller bearings, I would be a lot more concerned. Even the rod small end bore still has honing hatch marks and the piston pin looks good with minimal wear.

    I probably won't have the time to get this one running before my hunt starts, so I'll be taking my Big Bear with me. One of the reasons I wanted two ATVs was in case one broke down while riding way back in the woods somewhere. Plus it's a lot more fun and comfortable to ride single on them.
    56 Nomad, Ramjet 502, Viper 6-speed T56, C4 Corvette front and rear suspension


    Other vehicles:

    56 Chevy 2-door BelAir sedan
    56 Chevy 210 4-door sedan
    57 Chevy 210 4-door sedan
    1962 327/340HP Corvette
    1961 Willys CJ3B Jeep
    2001 Porsche Boxster S
    2003 Chevy Silverado 2500 HD Duramax
    2019 GMC Sierra Denali Duramax

  5. #5
    Registered Member JT56's Avatar
    Join Date
    Mar 2013

    Member #:1608
    Location
    DFW Texas
    Posts
    1,209
    I am looking into buying one, just to take on trails. I have rode Polaris, Honda and CanAm. What are your opinions on a good trail riding one? I am not doing the deep mud and such.

  6. #6
    Registered Member chevynut's Avatar
    Join Date
    Nov 2011

    Member #:115
    Location
    Fort Collins, CO
    Posts
    10,835
    Joey, I think there are a lot of good ones. I'm not all that familiar with the different makes and models. I don't like the really big ones, however, as they're hard to maneuver and they're heavy. The Griz 660 isn't that much bigger than my Big Bear 400 as far as frame size...but it won't fit in the back of my truck with the tailgate up like my BB does. The 660 should have a lot more power, but I really don't need it. I just bought it because it was a good deal. IMO I'd be looking for something in the 400-600 cc range....I think a 450 or 550 is perfect. EFI would be nice, as would power steering and IRS. You can really wear yourself out steering one of these things all day.
    56 Nomad, Ramjet 502, Viper 6-speed T56, C4 Corvette front and rear suspension


    Other vehicles:

    56 Chevy 2-door BelAir sedan
    56 Chevy 210 4-door sedan
    57 Chevy 210 4-door sedan
    1962 327/340HP Corvette
    1961 Willys CJ3B Jeep
    2001 Porsche Boxster S
    2003 Chevy Silverado 2500 HD Duramax
    2019 GMC Sierra Denali Duramax

  7. #7
    Registered Member JT56's Avatar
    Join Date
    Mar 2013

    Member #:1608
    Location
    DFW Texas
    Posts
    1,209
    I was leaning towards the Polaris 550 with power steering.

  8. #8
    Registered Member smooth 56's Avatar
    Join Date
    Mar 2012

    Member #:436
    Location
    Lenoir city tennessee
    Posts
    845
    I have the Big Bear 400 myself and love it, like chevy said the big ones have a lot of power but they are harder to maneuver. Mine is only 2 wheel drive with Titan 589 tires tractor grip style and has went every where a 4 wheel drive went in fact I pulled 2, 4 wheel drives out of a hole that I had just went threw lol the look on there faces was priceless. Have a polaris 500 at my in laws love the ride and power hate the steering, arctic cat don't like them they feel like your top heavy and turn over easy. A friend of mine has a suzuki 500 I like that one its comfortable to ride and lots of power.

  9. #9
    Registered Member JT56's Avatar
    Join Date
    Mar 2013

    Member #:1608
    Location
    DFW Texas
    Posts
    1,209
    I haven't tried the suzuki but will see if there is a dealer close. Thanks

  10. #10
    Registered Member
    Join Date
    Jan 2013

    Member #:1485
    Location
    Brodhead, Ky
    Posts
    55
    Since the connector rod didn't break I say your are good. Even then I have rebuilt them. People abuse the hell out of their 4wheelers. I pulled a dirt bike out of a creek, bored it and put it back together and it was good as gold. I have a 2005 Foreman that looked like it was never serviced. It runs great as of today, still can't get the electronic dash board to work right but it is just a tools to me.
    Josh

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •