BonKunU Posted October 14, 2011 Share Posted October 14, 2011 Ok, I have a Crankshaft upgrade query. Im in the process of installing a an ARIAS 856 big bore kit into my '96 YZF750R. I have all the piston side of things sorted now but Im a little worried about the extra power being put through the crank and rods. When I pulled the engine down it was already about to spin a big end and that was with stock ponies. I have sourced another engine to install the upgraded pistons/cylinders which has good bearing surfaces but still Im wondering if I should send the crank away to be cleaned up in some way. Nitrided again? polished? balanced? lightened? Rods also, should I get these polished and balanced and nitrided and all that or what? What do you think? Im pretty hard on engines. lotsa revs and plenty of wheelies which may have been the reason for nearly spinning the big end through lack of oil pick up. Should I mod the pick up somehow too??? Link to comment Share on other sites More sharing options...
Paulwhite Posted October 14, 2011 Share Posted October 14, 2011 well can u aford to re-do the engine if it goes pop? if not then u better be safer than sorry. if you have the money to spend then why not? also look into new bearings, and defo make sure that you have good oil flow! Link to comment Share on other sites More sharing options...
BonKunU Posted October 16, 2011 Author Share Posted October 16, 2011 Already got the new sleeves, pistons, bearings etc all ready to go together. Just dont know what options I have for upgrading conrods and cranks. Never had any experience with getting it done. Whats going to be the best option??? Link to comment Share on other sites More sharing options...
2 Wheels Posted October 16, 2011 Share Posted October 16, 2011 Unless the engine you have found, too put your new top-end on, is a more powerfull engine, eg. more cc,,,,,,and allready has a stronger crank Then forget about upgrading the origional crank,,,,,, Polished,,,,,,,,,yes Ballanced,,,,,,,get it checked for straightness, profesional job Lightened,,,,,,,no Conrods,,,,,,,get them checked for straightness and wear Mabey now that you will have more Torque you wont have to be so sore on the engine throught the revs Link to comment Share on other sites More sharing options...
BonKunU Posted October 18, 2011 Author Share Posted October 18, 2011 I dont want to sound like a know it all as I dont but that was a little contradictory. You say dont upgrade the crank but then say to polish it and get it checked for straightness and balanced. Conrods, checked for straightness and wear but where do they actually wear as the big end has a bearing shell that takes the wear and the small end has a press fitted gudgeon pin... The engine that I have as a replacement is a '94 model I think but is pretty well identical to the '96 apart from different jetting as mine was sold in Australia and the replacement motor in Canada. It also had quite a few kilometers on it but seems to be in far better condition than the original motor. The valves are still warn badly to the point that it wont start as was my own original motor. Seems they all had very soft metal that should have been run with lead to make them last. Guess Yamaha forgot to consider this when they were put in an unleaded engine. Hopefully the new ones are much harder. Still wanting some more info on benefits of doing any possible work on the crank and rods. Preferable from well informed people. Link to comment Share on other sites More sharing options...
BonKunU Posted October 18, 2011 Author Share Posted October 18, 2011 http://www.facebook.com/photo.php?fbid=10150127433436233&set=a.129230696232.131398.570286232&type=3&theater Link to comment Share on other sites More sharing options...
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