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Latest post Sun, Apr 8 2018 5:30 PM by andy2175m4. 35 replies.
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  • Mon, Jan 22 2018 10:36 AM In reply to

    • FX
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    Re: where is this loud noise in sporster engine ?

    Andy, don't just refresh one cyl. Do the whole top end, heads too, you'll be glad you did...I'm surprised you didn't do that when you had it apart the first time. Pay me now, or pay me later....And, once used rings are removed, they will not seat again unless near new, and you hone the cyl...

    FX

    Don't force it, get a bigger hammer.

  • Tue, Jan 23 2018 7:59 PM In reply to

    • andy2175m4
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    Re: where is this loud noise in sporster engine ?

    I pulled the noisy jug again and got .015 to .018 piston to cylinder clearance,  the piston and bore look ok, no major damage, so that would explain the noise. 

    By the way that .018" clearance is the gap on one side, with the piston pushed all the way over to the other side,  I had to remind myself how piston clearance is defined.  I have not discussed boring a bike jug with a machine shop in about 35 years.

    The spec is .003 to .004 clearance, so there you go....noise.

    A perfect candidate for a bore and a pair of .020 over pistons.

  • Wed, Jan 24 2018 5:48 AM In reply to

    • FX
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    Re: where is this loud noise in sporster engine ?

    Hmmm, If piston slap was the noise you should be able to see score marks on the skirt, and cyl. wall...Let us know how you're doing Andy. This is interesting to all...

    FX

    Don't force it, get a bigger hammer.

  • Sat, Feb 3 2018 9:38 AM In reply to

    • andy2175m4
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    Re: where is this loud noise in sporster engine ?

    I took the piston and cylinder to the machine shop and they measured the clearance at  .0042"  which is not too far off spec  (.003-.004)   but having exhausted all other possibilities the noise must be that piston and the best cure would be new pistons and bore to .020 or .030 (depending on how the bores clean up).  

    I thought about knurlinjg the piston but that would cost almost as much as a new piston.

    the engine has .010 over pistoins now so its been bored once, but with the unlimited supply of new pistons and jugs out there a new top end will always be an option.  (unlike some of my more rare projects, sportster parts are always available, as available as for my ford mustang).

    well, the piston looks pretty good, given the noise, so I  will put it back together,  ride it for a while, and live with the noise for now.

    by the way thanks for the help from the Forum guys !

     

  • Tue, Feb 6 2018 12:57 PM In reply to

    • FX
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    Re: where is this loud noise in sporster engine ?

    New rings, and hone the cyls. Andy...Turn the heads upside down on your bench, valves in, and fill the chambers with lacquer thinner to check for leaks in the seats/valves...You can lap the valves in if leaking, and not too bad on the surfaces...

    FX

    Don't force it, get a bigger hammer.

  • Sun, Mar 25 2018 3:16 PM In reply to

    • andy2175m4
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    Re: where is this loud noise in sporster engine ?

    • so picking up where I left off, I took the jug and the piston to the same machine shop the HD dealer uses, 
    • he mic'd the bore and piston and came up with  3.200" bore / 3.196" skirt and measured a clearance of 0.0042"   that is almost in spec,  I beleive the spec for a cast sportster pison is .003  to .004" clearance, .0035 preferred, so that does not seem like enough clearance to account for the piston slap,

    but then maybe it is ?   about 1 mil of extral clearance does not seem like much, any ideas out there on what .001" of extra piston clearance would sound like ?    I just seems to me that is should not be so noisy if it just .001 oversize.

    by the way there is very little scuffing on the piston, it looks ok, 

     

     

  • Mon, Mar 26 2018 5:39 AM In reply to

    • FX
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    Re: where is this loud noise in sporster engine ?

    Andy, that is not excessive clearance, and should not be causing a piston slap noise, that would be a tinny echo type sound. Try to explaine the noise to us again, and when it occures. Are you sure you checked for up and down movement of the rods? Here's a long long shot. I had a guy come to me once with a noise, that turned out to be a too far advanced timing, and causing, not the usual pinging, but an actual knock type sound only on accelleration in the higher gears...

    I read you're original post again about the noise, but see if you can get more precise about the actual sound...What ignition is in it, and how did you time it?

    FX

    Don't force it, get a bigger hammer.

  • Sat, Mar 31 2018 10:54 AM In reply to

    • andy2175m4
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    Re: where is this loud noise in sporster engine ?

     the noise sounds like piston slap, but is audible only at a fast idle,  not at a slow, warmed up idle, and not when revving the engine, just at that one rpm point,   I dont have a tach but  if the standard idle was 700 rpm,  the noise would be at at 1200  to 1500 rpm.    I checked the rod, and the rod is rock solid, both the upper rod end in the piston, wrist pin are perfect,  and the lower end of the rod in the crank is rock solid, like new. 

    also I checked the cams, no end play in the cams. 

    Timing:  I installed a new dyna tech dual fire ignition and coil, which is a direct replacment for stock, and statically timed it on the 2nd timing mark on the crank.... where first mark is TDC,  2nd mark is timing mark at idle, 3rd mark is fully advanced.    I also checked the top end rockers and rods are all good,  so ?????

     

     

     

     

  • Sat, Mar 31 2018 4:22 PM In reply to

    • FX
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    Re: where is this loud noise in sporster engine ?

    Andy, you have to make sure everything is at par when checking an engine problem. If you timed it at the second mark thinking that is timing at idle, there is no such mark. Two marks on the crank are TDC for each cyl. the third is advanced timeing for the front cyl, where you should have timed it. with ignition at full advanced.

    The Dynatech is an excellent ignition, I've used many of them, and never had one fail. You can static time those by putting the timing mark in the hole on the advanced timing mark, I don't know if on your bike it's the line, or a dot, your manual should tell you. Then manualy turn the cintrifugal advance all the way to advance, and adjust the backing plate till your test light just comes on. It's best to use a strobe though. they have clear timing hole plugs here at J&P. Using the strobe you would hold the throttle at about 2k rpm...Sounds like you may have it timed way wrong... Did you do anything to the engine just before the noise started (ignition)?

    Let us know how you're doing, this is interesting to all...

    FX

    Don't force it, get a bigger hammer.

  • Sat, Mar 31 2018 8:42 PM In reply to

    • andy2175m4
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    Re: where is this loud noise in sporster engine ?

    I did not do anything to the engine before installing the new igntion.  the lower end has not been apart, so the cam timing is probably OK,  but your point about the static timing is quite true, I did not advance the centrifugal advance when dialing in the advance plate, 

    I guess I dont understand the timing procedure, but now I see i need to study up on that.  i  will definitely re-set the timing,  it is way off the way you descdribe it,  thanks for the tip,  all else is original and ok,

     

  • Sun, Apr 1 2018 12:04 AM In reply to

    • andy2175m4
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    Re: where is this loud noise in sporster engine ?

    I just re-read the dyna ignition install sheet, and saw there was a step to advance the centrifugal all the way while finding the fire point,  I missed that when I installed the dyna,

  • Sun, Apr 1 2018 6:16 AM In reply to

    • FX
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    Re: where is this loud noise in sporster engine ?

    Yes, check the timing out, and let us know how it runs. If you didn't have the cam chest apart, you can't be sure the lobes are alright...There might be a flat spot on one of the rear cams. Also are you sure you had the lifters adjusted right?

    FX

    Don't force it, get a bigger hammer.

  • Sun, Apr 1 2018 5:17 PM In reply to

    • andy2175m4
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    Re: where is this loud noise in sporster engine ?

    I re-did the timing per the dyna instructions and it all made sense,  started reight up but the noise is still there.  loud mechanical noise right in the cylinder .

    the only thing I can figure is that the shop that checked it out made a mistake checking bore and clearance.  the noise is loud and only from the rear cylinder,  right  in the middle.  I think a rebore is the only answer now.

     

     

     

     

  • Mon, Apr 2 2018 6:27 AM In reply to

    • FX
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    Re: where is this loud noise in sporster engine ?

    I still think that piston clearence is ok. Did you take the heads apart and check everything out, especially  the rocker shaft bushings?

    FX

    Don't force it, get a bigger hammer.

  • Wed, Apr 4 2018 3:26 PM In reply to

    • andy2175m4
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    Re: where is this loud noise in sporster engine ?

    I pulled the head and the rocker box, and carefully checked the entire valve train,  found nothing wrong there. The rockers and rocker shafts are very tight, end play is good, end play springs on the rocker shafts are all ok, 

    it still sounds like its coming from the cylinder but the piston is not very sloppy so its still a mystery.   I checked the thrust side clearance of the piston skirt and it was about .008 (all on one side) so about .004 all round (in spec)  and 90 deg to the thrust skirt,  ie. near the wrist pin ends, the skirt clearance was about .015, which for the non-thrust skirts of the piston is about right.

    if you can send me a PM, I can send you a MP3 file of the engine noise,

     

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