Some of it depends on the climate. You'll do better up there. I have heard of very rare cases where they can go up to 80,000 miles but here in Texas the rubber on the tensioners is cracking by 25,000. Often broke by 35,000. Flex the main tensioner bow and you can see cracking if it has started. The chains last depending on how often they are adjusted, less and they die quicker, the extra whip doing it. Replacement chains can be a whopping problem with many not lasting nearly so long as the OEM ones. Smaller pins used in them. Common to strip aluminum out of threads from a lot of adjustment, if apart a good idea to helicoil the front outside hole.
It has been found that the front run of the crank to cam chain has a guide that comes nowhere near the chain and the chain whips at speed even when adjusted tight, there are new guides that take care of that issue. Instead of dead straight and 3/8" away from the chain they kiss it and run the chain in a bow like the back run does, it makes chain last MUCH longer as it cannot whip at all then.
) how many miles can the primary and cam chains last? On the engine that I am about to start rebuilding they have done about 18000 since new. Thanks.
