Guest nwr161282 Posted November 3, 2006 I have just suffered the much talked about and dreaded Oil Starvation problem with an mi. Having stipped the engine down the found a bit of damage. The crank aint too badly scored but still gonna need a regrind. The trouble is that there is a bit of colouring differance with the con rod end caps. Do you think they will have been ovaled? Dont really wanna start removing pistons on less i have too. Some pics below for you to comment on. Share this post Link to post Share on other sites
crf450 0 1 Cars Posted November 3, 2006 (edited) The crank will almost certainly be bent and scrap as will your rod. Edited November 3, 2006 by crf450 Share this post Link to post Share on other sites
Guest nwr161282 Posted November 3, 2006 so it'll be a total strip down then you recon? The pic of the damaged crank is for the number 2 piston. Surprise surprise eh! Share this post Link to post Share on other sites
Beastie 1 Posted November 3, 2006 20 years in the trade and I've seen a few bent cranks. None of them have been caused by oil starvation like that. I'll bet you a pint that if your's was straight before that happened then it's still straight now I saw a big end shell so hammered so badly last year that it was wafer thin and the crank (although still beyond further service) wasn't bent. The rod may be scrap if you are unlucky - the only way that you're going to know for sure is by proper inspection and by careful measuring. Share this post Link to post Share on other sites
nick 3 Posted November 3, 2006 Mine was bent after the exact same thing (oil starvation, spun a shell) luckily it was only by a tiny amount and came out in the grind. Mind you I did do a full lap of Donington with it knocking which probably didn't help matters! I've heard of loads of Mi cranks bending due to this (mine was an 8v crank, so not just the Mi) Nick Share this post Link to post Share on other sites
Guest nwr161282 Posted November 3, 2006 whats the limit for ovality on these is it 0.3mm? Seems alot if it is as i'm used to working to limits of 0.001" - 0.002" (0.03mm-0.06mm). Share this post Link to post Share on other sites
crf450 0 1 Cars Posted November 3, 2006 whats the limit for ovality on these is it 0.3mm? Seems alot if it is as i'm used to working to limits of 0.001" - 0.002" (0.03mm-0.06mm). You may be lucky with your crank but all I can say is that every Mi engine I've seen spin a shell through oil starvation has been bent the crank and wrecked the rod. When I spun a shell through oil starvation the journal was only about 0.05 down but the crank was bent by about 3mm, funnily enough when cool the engine sounded almost perfect running with a 3mm bent crank. If you've got a access to a hydraulic press and a good eye you may be able to bend it straight enough so it will clean up with a grind. Looking at your shells, I think you'll be able to measure how oval you rod is with a tape messure. Share this post Link to post Share on other sites
Guest nwr161282 Posted November 3, 2006 Just measured the crank diameters. The engine had spun the shell on number four piston. Measuring 1,2 and 3 everything seemed fine. The sizes were all within 0.05mm of the 50mm O/D. But on number 4 the O/D is down to 49.65mm. So looks like it'll b a new crank needed. Will get the depth mic out and try and check the conrods. Any one got a good crank for sale? Share this post Link to post Share on other sites
nick 3 Posted November 4, 2006 Just stick an 8v crank in it, should be able to get a good 'un for about a tenner. Nick Share this post Link to post Share on other sites
