Hello and good day,
I recently picked up a 2005 Honda CRF 450 R dirtbike. Seller said the bottom end was most likely the issue for it not running. Not a problem for me as I could buy one of eBay for a fair price and rebuild it. He had the top end rebuilt as preventative maintenance and installed an engine hour after that and it only has 48 hours of riding after that.
Last year he was out riding and the bike died on him. He kicked it over and ran for about 5 minutes and died again after that. So he though it was over heating and let it cool down for a goo half hour at least. He kick it over again and it fired up and about 15 seconds or so later it died. (No clunking or other various engine failure noises). After that he was not able to kick it over at all.
Forward to today (Nov 6th 2018), the engine is currently disassembled and trying to find the root cause of the failure. When my buddy and I drained the oil we found a slight hint of coolant in it, plus when we split the bottom end open there was a fair bit of metal chunks at the bottom. However we cant see anything wrong on the gears/transmission and all the bearings seem to be in good working order. The crank and the piston work as intended as well and do not have any rough patches when we did the stroke. The piston and the piston chamber have very slight wear from the metal chunks, but it is just surface damage and easily fixable.
Before we took everything apart (engine out) everything turned and looked in good operational order. So my buddy and I are stumped as to what could be wrong. The seller also gave me a maintenance manual as well and from the pictures the parts all seem to look good.
If anyone as any ideas where to look/what typically goes in the bottom end of this bike that would be great.
Sorry for the long post, will provide pictures if necessary.
Regards,
Skyevodka