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      JUST IN!   04/24/2018

      HOW TO: 4-STROKE PISTON REPLACEMENT DONE RIGHT!

frankdecrosser

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About frankdecrosser

  • Rank
    TT Silver Member

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  • Gender
    Male
  • Location
    Netherlands
  • Interests
    Motocross, Street&track racing on my Yamaha R1, Mountainbiking
  1. Yes when I get back on the track after bike has cooled down it is good again, for about 10mins. Also depends on the track, in loam wet sand it is more noticeable then on hardpack like conditions, seems when bike must pull harder power drops sooner
  2. My new 2018 KXF450 loses power after a few laps (on a sandy mx track) I logged about 6 hrs on it so far. What is the most probable cause for this? Theoretically it can be anything from a defective sensor to..?? but it's a brand new bike! Any suggestions are welcome
  3. How do you check clearance between valves and piston in such case? I might have had a similar issue with a previous bike were 0,1mm was milled off the head. I turned motor by hand first (of course) and motor ran ok for several hrs before some strange knocking occured when cold. I then took top end off but everything looked like new??
  4. I was concerned about that, but cylinder head has no signs of detonation anymore. So the RON98 and richer mapping solved this issue. I also tried RON 100 but bike did not run as well compared to 98. Always used 95 in my CRF450 without any problems.
  5. In summertime my bike pinged. Due to a loud chain clatter on a TM designworks chainguide I did not notice this, until small part of piston chipped off causing piston to lock against cylinder head. Cylinder head showed a clear pattern of detonation. Valves surprisingly seemed undamaged and did not leak so I only replaced piston, checked cranckshaft etc. Bike ran very well thereafter using 98 octane fuel (not 95 anymore ) and richer mapping (mandatory acc my dealer and even Kawa importer!) for approx 8-10 hrs, until one of the exhaust valves stems broke and slammed through piston upside down. This time I welded cylinder head, machined it flat (-0,05mm) and installed new piston, valves and seats. Cylinder had minor score marks but not too bad. (no smoke whatsoever) To keep costs within limits I used a PROX piston, wich -I assume- caused an annoying nocking after about 5 hrs when engine was cold. After warming up this sound went away. I am not 100% sure if this Prox piston caused this but I took complete top end off and I encountered no issues, everything looked like new, valves within spec etc. Big question mark for me, and I have taken apart hundreds of engines.
  6. I splitted and reassembled cases (pitting in 4th gear and exhaust broken valve) of my 2017 kxf450 using a 2014 manual. I double checked most important torque values with my local dealer. Also got some info from a fellow TT-er
  7. What specific info do you need?
  8. Can be lots of things. Take off cilinder but also re-inspect head/valves, if metal particles were from low end/piston damage I assume they should be catched in oil filter.
  9. How did this happen?
  10. So if I understand correctly; if you remove the dirty airfilter debris can fall directly in the intake on this screen? I assume if you try to wipe sand away from the screen you push some through? (like earlier Kawasaki's) Reason I ask is I am considering a new YZF450 and this does not sound ok.
  11. For mx racing season 2017 I shifted from Honda's (Owned most CR500 and later CRF450 types since 1993) to Kawasaki (KXF450 2017) This because my recent Honda's suffered from issues like misshifts/false neutrals/broken gear dogs, fuel in oil, and burned clutch plates. Other than that it was a good bike. LOL Since I find the Kawasaki very dissapointing w.r.t. reliability, a piston cracked and later a valve broke within 30 hrs, in both cases damaging cilinder head I am considering switching back to Honda for 2018. Are aforementioned issues solved in 2017? Any new issues I should know of? (I heard about cracked damping rubbers in clutch causing problems)
  12. Or use the Honda Gear blocking tool. It is a small toothed piece with a holder pin. In above case clutch cover must be removed but at least you can torque with correct spec.
  13. I rode CRF450's from 2003 up to 2014, most of them 100-120hrs MX racing and never suffered any problems with timing chain or tensioner. I did wreck several transmissions and clutches though.
  14. I would appreciate that very much, thank you!
  15. Where can I get such 16> service manual? I cannot find any specs for 16> bikes on the internet and 70nm for this flywheel just didn't feel right to me.