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Sand in engine.

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  • Sand in engine.

    So, Finally got my YZ125 (dirtbike) engine apart. And its as I feared, Sand in the engine (Cylinder side). Damn seller. Damn me for not noticing the sand in the intake tract and running for the hills.

    So, Already got a new piston and new cylinder because the old one was screwed royally from the power valve kissing the piston goodnight.

    But now that I have the crankcase apart, I noticed the main rod bearing is a little.. sandy too...

    I sprayed lots of air and penetrating oil through it.. likely going to follow up by alternating carb cleaner/air/way oil/air (Way oil 'grabs' things out of nooks and crannies with its thickness/stickyness and low stiction, carb cleaner flushes out the sticky oil)

    Its a roller bearing if anyone is wondering, with little slits in the rod and notches in the side of the rod to allow 2 stroke oil in/out. Disassembling the crank for cleaning is not really an option as I would need a new pin and would likely end up just buying new bearings/rod/etc.

    Anyone have any other suggestions on cleaning the lower rod bearing? There seems to be very little play in the main rod bearing and a new rod bearing kit is $150+70 to install so I would rather not go that route if I don't have to.

    Already have a replacement crank bearing kit, so not going to be reusing those bearings.

    Or am I just crazy to reuse the lower rod bearing after its been exposed to sand? I don't see evidence of damage to the bearing rollers I can see and the play seems low enough. Its a 12000RPM racing motor that I will likely be babying since I am nowhere near skilled enough to use its full power and won't be racing, More just taking it on trails and such..

    I will likely be able to check for increasing rod play at regular intervals since the top end on this bike needs constant tear downs (Every 10 to 20 hours recommended) and the bottom end itself is only rated for 80 to 160 hours or something silly.
    Play Brutal Nature, Black Moons free to play highly realistic voxel sandbox game.

  • #2
    When I was into 2-strokes and got the beach inside them, we'd pull the cranks and just used the parts washer (kero or diesel in it) to flush it till we were sure no sand was left in it. Then air hose to clear it out and make vertain.


    • #3
      I've had a couple sandy motors. Either the parts washer like mentioned or a small container of kerosene and a brush and work the rollers round and round and round while submerged until you feel no more crusties.


      • #4
        Put it in a dish washer and let it run. Us Cascade. Put everything that will fit except electrical. Run for a full cycle on "pot and pans"
        Bob Scott


        • #5
          The Dishwasher trick.

          Years ago at a parents night where I taught, a mother was going on and on about how "Little Bobby" was growing up. She mentioned that when she got home from work Bobby had run the dishwasher and quite often wiped down the counters as well.

          Two days before Bobby had told me how he cleaned his motorcycle engine parts in the dishwasher. He then followed with the breakfast dishes to get the last of the grunge out of the dishwasher.

          I did not "spill the beans". Mom's need all the dreams they can get.

          Being these were the "Shop Kids" they were a rough and tumble lot.


          • #6
            rofl dishwasher. Well id put em in the sink but I think they would rust before I got around to washing em, being I am the dishwasher around here.

            Thanks for giving me hope though. I'll figure out a container for the crank and clean it with that kerosene I got kicking around yet never seem to find a use for. (Yea I should use more kerosene and less carb cleaner before that stuff kills me.. Or cleans the skin right off my hand)
            Play Brutal Nature, Black Moons free to play highly realistic voxel sandbox game.


            • #7
              After a few washes in the parts washer and hitting the bearings with air I would get a can of WD40 and give it a few shots and then hit it with air again. Repeat as many times as you want. If there is any grit left in there you should be able to feel it. The only real way to tell what the crank pin and needle bearing surfaces look like it to press the crank halves apart and at that point you might as well replace them. It's a PIA to press those apart and a bit tricky to press them back together and keep the two halves aligned.



              • #8
                I race a 2 stroke, if this was mine , I would shout it a new rod kit and small end bearing as well. Probably only $50 or so, not hard to fit if you have a press. If its got any pitting on the pin or big end of the rod its as good as finished now, save yourself the grief and fix it properly
                My neighbours diary says I have boundary issues


                • #9
                  I agree with the post above...


                  • #10
                    Originally posted by Yow Ling View Post
                    I race a 2 stroke, if this was mine , I would shout it a new rod kit and small end bearing as well. Probably only $50 or so, not hard to fit if you have a press. If its got any pitting on the pin or big end of the rod its as good as finished now, save yourself the grief and fix it properly
                    If you find me a rod kit for a YZ125 1985 for $50 I will love you forever.
                    Cheapest I could find was $80 + $30S/H = $110USD and that comes to $140CAD, same as local price, Then its $60CAD labor to install min, if I drive 40 minutes to the cheapest shop. I don't have a press or any experience with one. Other places had cheaper S/H but much more expensive kit. Its some stupid 'couple year only design that nobody liked' and is 2x as expensive as later years.

                    Finding a replacement crank for this bike is VERY hard, only 1 listed on ebay and its got buggered bearings, bad flywheel side thread and they still want $44+44 S/H for it. So I don't want to potentially screw it up either.

                    Definitely giving it a new small end bearing as that is only $25 locally and easy to replace. Just kinda hoping I can get some more time out of the crank before another rebuild.

                    I'll double check the small end of the rod for wear, that is a good tip. I seem to recall the small end bearing looked fine, I just didn't want to trust it being it was easy and cheap to replace.

                    I am not going to race this bike. I value my life too much to push this thing that hard. Just wanted something with more ompf and suspension for cheap. Got the bike for $500, Starting to think I paid too much for it...
                    Last edited by Black_Moons; 02-26-2015, 09:33 PM.
                    Play Brutal Nature, Black Moons free to play highly realistic voxel sandbox game.


                    • #11
                      Liquid Tide is your friend for getting sand out- much better than petroleum-based cleaners because Tide has surfactants that 'float' debris out. Pro engine builders use Tide to get after leftover casting sand and post-machining chips.


                      • #12
                        Do not put the crank in the dishwasher as you will accomplish nothing with parts that are stagnant...

                        place the crank on some V-blocks and run it through the motions of running (pumping the rod up and down) whilst using your varying sprays - your smart to mix different types of solvent like your doing and you can even use some brake clean as second from last step - dry out with compressed air and then use a diluted liquid detergent with water as the final stage...

                        If you have no real detectable excessive play you may be fine if the surfaces are still fairly smooth - roller bearings will take some abuse when it comes to eating "hash" but do have their limits

                        also keep this in mind - a bearings "running position" can be crucial when introducing "foreign objects" into it's environment

                        point being is a lower end bearing as in connecting rod is not in a stagnant positions and may help to "clear" it's running path because after all sand has mass ---------- possibly not so much so for the cranks "stagnant" side bearings that will just accumulate and do not have the ability to clear themselves

                        moral of story is it fully possible to have semi hashed side crank support bearings whilst the lower end connecting rod bearing is fairing much better,,,

                        get it all cleared out and don't just go by tolerance as you may be riding on a series of plumped up hills and valleys, also go by feel and sight as in a good powered magnifying instrument...

                        it would be great if you could get a peak at the power side of the cranks journal pin but highly unlikely you have that kind of viewing space, next best thing however is to remember to check your free run tolerance with both the rod and the crank in identical "power position" that it goes through when all installed...

                        as you can tell by my post --- been at this awhile - the devil is in the details...


                        • #13
                          I invested $200 at Oshkosh several years ago in a good bore scope & it's payed for itself over & over. I'd advise a quality one you look thru not the one with the screen & don't buy the horror fright one. Mine has a 45% & 90% mirror & you can turn on 1 or 2 leds and I'm sure your going to change the crank seals in the rebuild. Good luck!


                          • #14
                            Why would you need a bore scope on a 2 stroke, You can pop the head off with 4 bolts and the head gasket is 98% of the time reusable.

                            New Crank seals came with Crank Bearing kit yes. I was warned within an inch of my life to replace them at the bike shop, especially on a racing motor as an air leak will eat a piston real quick.
                            Play Brutal Nature, Black Moons free to play highly realistic voxel sandbox game.


                            • #15
                              Out a the night came a terrible scream--WHO PUT THE SAND IN THE VASELINE???
                              Brian Rupnow