sword70 Posted April 27, 2012 Share Posted April 27, 2012 I need a little help to clear up some confusion, i recently purchased 2 DT50MX's for my son to rebuild prior to a cbt test and one piston cracked whilst kicking it over and the other is badly scored around the ring. I have been trying to size up the pistons / barrels to order a new piston set but sizes are a bit odd or i am missing something. One bike has had a big bore kit fitted that the barrel weighs about half as much as the other and top of the piston has 0.50 stamped on it, as close as i can tell the piston is 44.4mm wide and bore of barrel 44.5mm, only have a set of vernier calipers to measure with and this so as close as i can get in accuracy. Other bike has heavy barrel supposed to have been standard but doesnt look like it to me, piston is about 42.7mm wide and barrel 42.9mm. I had assumed as the stock size is 40mm and big bore usually 43mm, making the heavier one around 5 times oversize and lighter one almost 3 times oversize not the 0.50 the top of the piston says???? Am i missing something or maybe measuring it wrong? i would have thought sizes would go up 40mm, 40.5mm, 41mm, 41.5mm, 42mm, 42.5mm, 43mm, 43.5mm etc give or take a fag paper allowing for wear and tolerances. Wither way its either around £15 per bike for piston if i can get my head round this or £50 per bike for barrel and piston kit so worth a little research and screaming help for advice :-) Thanks in advance for any heads up info on this lot Link to comment Share on other sites More sharing options...
Moderator Cynic Posted April 27, 2012 Moderator Share Posted April 27, 2012 Its good practice to do a bit of an intro on here. There are no silly start up screens and protocols but its generally accepted you pop a few words in the new members bit. Your piston issue, 41mm is the stock size for that bike, has been for the dt 50 since i was riding em in 86. The 0.5 on the piston denotes the oversize, ie it has been rebored and a piston .5mm bigger diameter has been fitted. If you want to replace it then you will need the next oversize up probably 1.0mm The bigbore, who knows. If you can't find out who made it to get replacement parts it may well be junk. Link to comment Share on other sites More sharing options...
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