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Thread: Big end banging

  1. #31
    apriliaforum prov-nov
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    https://youtu.be/5KclvV9RrFs
    please check around time 0:35 where I push hard piston.
    Is this acceptable?

  2. #32
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    If there is oil getting past the rings then its moot. With the piston all the way down you need to use an outside caliper to determine if the cylinder is out of round or worn beyond spec however it would be better to remove the cylinder completely to do this check. If your fortunate the rings will simply be stuck from the aluminum paste in the oil however piston slap did not appear to be the source of the banging in your video so stuck rings or piston/cylinder scuffing would only be a side effect or collateral damage. Now that you have the head off check how far you can rotate the crankshaft before the piston itself moves and this will tell a lot as there should be just a touch more than zero play. Also check for side to side movement in the crankshaft by pushing and pulling on it.

    Wish you were closer to me so I could stop by and lend some support however even Athens Georgia is too far for me to travel.

  3. #33
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    There is still a possibility that the head gasket is the problem behind all this.
    Head gasket fix proved wrong. Correct head gasket on way.
    By the way, the rod has no vertical play.
    Only side play:
    https://www.youtube.com/watch?v=nds7...ature=youtu.be
    Is this acceptable?

  4. #34
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    That play is acceptable at the piston pin however not at the crank pin. How is side to side play between the crankshaft and the engine case?

    Did you change the cylinder base gasket also? If you have a base gasket that is too thin that can cause some interference and excessive blowby from high compression.
    Last edited by Rockynv; 10-25-2018 at 05:33 AM.

  5. #35
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    I dont see any side play between crankshaft and engine case; I grab with force the alternator bell and it doesnt move at all sideways.

  6. #36

  7. #37
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    The main bearings do not look that healthy either and the crankshaft looks like its been scored. Ground metal circulating in the engine never ends up very well.

    How does the crank shaft feel when you drag the edge of your fingernail across the scored areas?

    You will really need to clean all the oil passages very thoroughly to ensure that any and all blockages from the metal paste and burrs that circulated through the engine are removed if you decide to rebuild it. Are the replacement main and cam bearings available for that Rotax?

  8. #38
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    On one side of shaft the scoring has a tiny "step" feel when drag the edge of your fingernail across the scored area.
    I will need to lightly sand it with emery paper?
    Bearing shells (4 halfs) are available and cost 63 euros all.
    BTW below more pics
    https://drive.google.com/file/d/128g...w?usp=drivesdk
    https://drive.google.com/file/d/11zL...w?usp=drivesdk

  9. #39
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    It depends on what your intentions are for the bike. Just barely running for an occasional low speed run at low throttle or fully capable of high speed full throttle use.

    If you intend to use it regularly to its full potential then its time for a new crankshaft with connecting rod and piston pin along with the new main bearings. The oil pump is also suspect and should be replaced if you intend to use the bike and need it running reliably. Those crankshaft main bearing journals were micro-polished and to correct them will require turning down in a machine shop to the next smaller bearing size or have repair sleeves pressed on in the original size. Most times it will be cheaper to replace the crankshaft assembly or possibly to purchase a wrecked scooter from a salvage yard that has a good engine in it.

  10. #40
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    I am not pressing the engines. Smooth throttle and never exceeding 80 kmh when other owners of same model easily report 110-130 kmh achieved.
    This bad outcome was probably a result of gasket maker blocking some oil passage because I had for some time oil light flickering at idle.
    Excuse me for my incompetency, but the term " crankshaft main bearing journals " is a bit confusing to me; I googled it too but not clear if you mean the bearings shells located in the crank or the crankshaft itself.
    Because these bearing shells are available as spares and already have ordered.
    Last edited by aware; 11-01-2018 at 02:56 PM.

  11. #41
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    Quote Originally Posted by aware View Post
    I am not pressing the engines. Smooth throttle and never exceeding 80 kmh when other owners of same model easily report 110-130 kmh achieved.
    This bad outcome was probably a result of gasket maker blocking some oil passage because I had for some time oil light flickering at idle.
    Excuse me for my incompetency, but the term " crankshaft main bearing journals " is a bit confusing to me; I googled it too but not clear if you mean the bearings shells located in the crank or the crankshaft itself.
    Because these bearing shells are available as spares and already have ordered.
    The crankshaft itself will likely need replacing or the bearing surfaces on it machining for sleeves to be pressed over the scored areas to bring it back to the original diameter to fit properly in the bearing shells and shaft seals pressed into the crankcase.

    Removing the ridges with emery cloth will usually make the crankshaft undersized and out of round so its not a long term solution.

    If it was a lawn edger of some other piece of equipment that you run for a few minutes per session a few times a year you might get away with doctoring up the crankshaft with emery cloth but not on a bike that you intend to ride regularly.

    That Bertone C1 design really pushes the engine to its limits even 80 kph and its amazing that there are many still in running condition. That roof system with the weight of all that additional structure was a bit much for those small Rotax engines that were problematic even on lighter more traditional scooters. Nice idea to have the more rainproof cockpit with a windshield wiper, roof, easy chair drivers seat and rear window but it needed to be built on a more appropriately powered scooter.
    Last edited by Rockynv; 11-01-2018 at 08:50 PM.

  12. #42
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    I will then try to locate a shop that can arrange such a sleeve as you say.

  13. #43
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    Quote Originally Posted by aware View Post
    I will then try to locate a shop that can arrange such a sleeve as you say.
    It may cost less to just order a new crankshaft assembly. It depends on what the labor rates are like in your area. You may get lucky and find a shop that is experienced with doing this type of repair on small engines and can do the work at low cost.

  14. #44
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    New assembly costs 700 euro!

  15. #45
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    Quote Originally Posted by aware View Post
    New assembly costs 700 euro!
    Is that for the 125 or the 200. I don't recall which one you have.

    I did a quick search last week and thought I saw some new crankshaft assemblies for the 125 listed in England, Spain and few other countries at around 300 to 400 euro. Is there an import tax in Greece that greatly increases the cost if you purchase from England, Spain, etc?

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