ORIGINAL: jmaxey51
ORIGINAL: supertib
Its all in the setup and tune....We dont add shims, we usually remove one...However obviously your able to run it fine with adding a shim...... As for the engines wearing out early its likely some other factor being overlooked.... What may I ask was going wrong with the other ones ? not often I see a JPX in the trash at 4 gallons....heck most of them still have huge pinch at 4 gallons LOL ! out of curiosity what setup do you use on your JPX 21 ? as in clutch/pipe/plug/fuel etc ?
i love these engines ! here is my latest one, heck in this video I remove a shim and show before and after !
http://www.youtube.com/watch?v=569nF90fUSQ
they were loosing all compression and wouldnt hold a tune and ran very very hot, and 2 snapped rods. mine is still not that easy to turn over by hand.
i ran JP3, three shoe clutch (VP pro or Odonnell shoes) with 1.1 springs on truggy and 1.0 on buggy. i ran the ofna turbo medium plug or P4 if i couldnt find an Ofna one. and i ran byrons 20-12 and now 30-11.
my dad ran dynamite 053 or RB 2045 pipe same clutch setup. except he ran 1.0 alot on truggy too. and same plugs and same fuel.
sounds more like lack of tuning knowledge to be honest.... overheating and snapping rods have nothing to do with the head shims I can assure you...The reason your JPX is doing so good and your friends aren't is that you and your dad know how to tune better then they do ! those guys would have killed their JPX no matter what shims they ran.. !