Gouged Cylinder and Piston

Discussion in '2-Stroke Engines' started by superwhite, Dec 5, 2015.

  1. superwhite

    superwhite New Member

    So I'm maybe 100 miles in on my new build and the engine starts knocking. I ran 16:1 for the first gallon, then the second gallon was 20:1. I ran it pretty easy hoping for a proper break in and long engine life. I took the top end apart first and noticed that one of the head bolts had pulled loose and stripped itself slightly. Would this make the cylinder uneven enough to cause scoring? The gear puller didn't come in my kit so I had to order one. I got it yesterday and took the bottom apart. Everything looked fine, the bearings didn't roll very smoothly. I ordered new SKS bearings, surely that's gotta be an upgrade right? I sent pics to bikeberry and they told me this didn't look that bad, so does that mean I'm supposed to reuse this, all gouged up like it is? He wouldn't warranty it and wanted to wait until I got the bottom end apart to see if there were problems in there? I asked hans at bikeberry to meet me in the middle and send me a replacement cylinder and head, I had already ordered a piston kit and a 15mm wide wrist pin bushing, seal kit, new carb, and SKS bearings. I haven't heard back but I do realize its Saturday, maybe they aren't open today. Seems fair to me tho. What do you guys think? Can I reuse this cylinder? NCM_0055-1.jpg NCM_0054-1.jpg NCM_0053-1.jpg NCM_0050.jpg NCM_0057-1.jpg
     

  2. crassius

    crassius Well-Known Member

    top ends aren't that hard to swap out, so I'd try that one before getting a new one

    doesn't look horrible, but needs cleaning up a bit - I'd guess you sucked in some grit when stud loosened or maybe some fine aluminum particles from the stripped threads
     
  3. jaguar

    jaguar Well-Known Member

    probably the aluminum lost from the piston hitting the head caused the scoring.
    or maybe you ran it without an air filter and the ingested dirt particles scored it.

    it's not the suppliers fault if you were the one that put the high compression head on without checking the piston/head clearance.
     
  4. superwhite

    superwhite New Member

    I didn't put on a high compression head, its all stock right out the box. It's always been ran with an air filter.
     
  5. butre

    butre Well-Known Member

    it'll run. if there's not a performance problem let it be. if you're not gonna throw a bunch of money or work at that motor then I wouldn't bother doing anything about it. just make sure there's not anything floating around in the case.

    either way bikeberry isn't going to warranty it. if it makes you feel better to give it a new jug then by all means go for it
     
  6. superwhite

    superwhite New Member

    Thanks for the replies. I'm gonna try the top end, once my bearings come in and I can reassemble the whole thing. I ordered a new piston, rings, wrist pin, and bearing but they really dont look that bad. I ordered a 15mm wide wrist pin bearing, should I swap that out? I dont know if anyone has had better luck with a wider bearing... The piston sure had alot of slop in it. I'll probably reassemble using the old parts to see what happens before I put new parts besides the lower end bearings.

    Thanks a bunch and have a wonderful Sunday!!
     
  7. jaguar

    jaguar Well-Known Member

    but what caused the ring on the top of the piston that looks like it was hitting the head?
     
  8. superwhite

    superwhite New Member

    I'm not sure yet. That isnt where it was hitting when I first took it apart. I saw the head stud had slightly pulled loose so I put it back together the best I could with the bolt going in hard most of the way, didn't have a tap yet. That was when the piston Started hitting the head. I only ran it a minute and shut it off, took the upper cylinder off and saw the additional damage. I'm assuming the torque was uneven due to the bolt and the fact that only one side of the piston had a mark on the top of it. I'm going to tap the hole and locktite the original studs back in so I can use the acorn nuts, hopefully the stud will stay put. I was using the long bolts that came in the upgraded hardware kit. There was alot of fragments in the bottom end, I really couldn't believe all the crap that was in there, I cant tell where it was all coming from tho, maybe just normal break in... It was metallic. I'm kinda on hold tho until the sks bearings and gasket set come in. Are you Jaguar of the Jaguar CDI? I'm looking into upgrading the CDI, it didnt run real great, slow engine rpm build up when i'd give it throttle, and it would 4 stroke at full throttle. I ordered a nt speed carb, I think thats what I got, its got the big black air cleaner on it, and fuel shutoff. I had the speed carb on it with the red airfilter before, I adjusted the needle a couple times, it got better but still wasn't optimal.
     
  9. superwhite

    superwhite New Member

    I saw where my chain was riding on the aluminum cover at the sprocket, I think the extra force it was under played a part in my bearing problems, its dug a pretty good spot out of the cover, i'm going to remove the rest of it with my dremel so it has plenty of clearance... The bearing on the other side of that sprocket doesnt roll smoothly at all, it kinda catches, and was squeaking when I would use pedal power. I'm stoked I found out what that noise was! Also, the magneto magnet had alot of metal shavings stuck to it, right where it is supposed to transfer at the magneto loop, I think this could have definately caused a problem.
     
  10. jaguar

    jaguar Well-Known Member

    when you put it back together put solder on the top of the piston from left to right, put the head on, and crank the engine over slowly.
    then take it apart and measure the squished part of the solder. It shouldn't be any less than .6mm (.024")

    my Jaguar CDI will help with the 4 stroking but you may also have to reduce the main jet size. My CDI is essential for engines with increased compression.
     
  11. crassius

    crassius Well-Known Member

    he means you should just lay a strand on loosly, not solder it down
     
  12. butre

    butre Well-Known Member

    it's not gonna stick anyway
     
  13. jaguar

    jaguar Well-Known Member

    what is not going to "stick"?
     
  14. butre

    butre Well-Known Member

    Referring to Crassius's comment, solder won't stick to aluminum without fancy flux.
     
  15. superwhite

    superwhite New Member

    I got some flux lol. The bearings we don't reach me til the 18th ugh. I ordered sks 6202z and 6202zzs. From what I've read the plastic shielded ones aren't even recommended for high rpm use... So almost all my stuff will be here and the bearings last, its killing me!

    The bike rides awesome tho, I have the tank, motor, throttle and cdi removed. All that vibration didn't hurt the bike at all! I got it at a pawn shop for 30 bucks.

    I want to lighten my fly wheel and piston but don't have a vice and only an electridrill. How strong is the steel the flywheel is made of? The piston I ordered is so light, is there even a point in drilling holes in it? However recommended is it upgrading cdis for the sole purpose of making it run better? It ran great till my bro soldered it. I replaced it with spliced in aircraft wiring which helped a little but it still bogs down when nits wide open. I have to roll back to 3/4 to get it to stop 4 stroking, it didn't do it before all that. I got a new carb tho, as soon as my bearings come in...
     
  16. jaguar

    jaguar Well-Known Member

    the stock ignition system is trash. even the stator coil goes bad often. carry a spare.
     
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