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Thread: Aprilia SXV full engine rebuild video - support me if you can :)

  1. #16
    apriliaforum expert SXVINWA's Avatar
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    Quote Originally Posted by SXV_Jack View Post
    Stronger Cylinderhead Bolts and 60 NM instead of 40 NM for them
    is this a Aprilia Factoty innovation ?
    I'll admit that I'm not a motor guy, but even I would think that going to 150% on head bolt torque would most likely lead to warping the heads and not be a wise idea.

  2. #17
    apriliaforum Junkie riot's Avatar
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    Quote Originally Posted by SXVINWA View Post
    I'll admit that I'm not a motor guy, but even I would think that going to 150% on head bolt torque would most likely lead to warping the heads and not be a wise idea.
    It is impossible to say without a detailed analysis of the cylinder head casting stress distribution.

    But in general - if we had a even metal shape (like a plate), and we bolted in a perfectly circular pattern - then more clamping force would be better for sealing the 'pressure vessel' regardless of gasket type. More clamping force will resist expansion of the cylinders and in general all movement of the various parts. This will be true right up until we hit some stress limit of a component. In my mind, the most likely first failure would be the threads on the head bolts, but it also might be the heads (warping) themselves.

    So provided we are not stripping out threads, we would probably be OK with a little more torque - which is not to say that I recommend this. Without a detailed analysis, you could toque down the heads only to have the bolts strip out under hot or overheating conditions. However with thread inserts, the torque could be increased safely. All I am saying is that there is a decent rationale to this theory.

    Protrusion is also (and I think obviously) critical to ensuring proper clamping force. I think it is easy to imagine if the cylinder is sub-flush of the case deck, then clearly you will not generate any clamping force on the pressure vessel seal.

    Making sure that the system is flat will aid in the distribution of force, to ensure equal clamping force all the way around. Where you can run into trouble, and the likely cause of most gasket failures is when the force becomes locally low. This could be caused by uneven surfaces, or when the stress gets so high that the head or cylinder sealing surface warps. As SXVINWA have points out, this could occur if you go crazy with the cylinder torque.

  3. #18
    apriliaforum prov-nov
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    I was seaching for more information about this.
    i found a thread somewere in a german forum about this.
    they told that the orig. oem head bold is only 10.9 and only suitable for one way use , the quallity is also not so good.
    they made stronger head bolts in 12.9 and nuts in 12. they can hold more torgue and do not stretch like the oem“s.
    this seems the primary issue for head gasket problems .... strechting bolts.
    i dont know - i am no technican or sxv engine spezialist but it sounds possible.

  4. #19
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    No...

    The primary issue for head gasket problems is really only related to the 550...

    This is due to less sealing area between combustion chamber and coolant gallery...

    A 550 is just a bored and stroked 450, so in creating a bigger bore they had to remove sealing area...

    The other issue is Quality control...

    If the cylinder, most likely not, or crank case, more likely, are not machined and matched correctly then you can get a cylinder sitting flush with the crankcase, not ideal, or sitting below the crankcase, completely wrong, then you have potential for sealing issues...

    I have done a number of XV engines and always set liners up with 0.02-0.03mm of protrusion...

    I have never had a head gasket failure after doing so even using the same head bolts numerous times...

  5. #20
    apriliaforum expert levisik's Avatar
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    Btw - I just sold sxv 450 with 550 engine. Now I am sorting out my garage space and need to but head mount for GoPro, to video document my rebuild. Hopefully it will be usefull for others
    2006 Aprilia SXV 450
    Tuneboy Cable available in Poland

  6. #21
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    Quote Originally Posted by S4R View Post
    No...


    A 550 is just a bored and stroked 450, so in creating a bigger bore they had to remove sealing area...
    Okay ... first was the 450 Engine btw thats the base for the 550 ?

    Is the RXV frame and swingarm the identical parts like SXV ?

  7. #22
    apriliaforum expert SXVINWA's Avatar
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    Stating that the 550 is just a bored and stroked 450 is a little oversimplified; the "stroking" portion of that change required more space for the crank, so the 450 and 550 do not share the same engine case halves. They share the cylinder head assemblies, but that is about all for each cylinder. IMO they would have had better results and less issues if they hadn't tried to reuse the cylinder heads. With the bore of the 550, there isn't much surface area left for the head gasket to seal against (as S4R stated).

    The sxv 450 and 550 share the same frame and swingarm. The rxv 450 and 550 share the same frame and swingarm. The sxv and rxv frame and swingarm can not be interchanged.

  8. #23
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    Thanks sxvinwa

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