{"id":13250,"date":"2014-09-17T08:43:13","date_gmt":"2014-09-17T13:43:13","guid":{"rendered":"http:\/\/www.chinonthetank.com\/?p=13250"},"modified":"2016-05-05T15:16:16","modified_gmt":"2016-05-05T20:16:16","slug":"replace-yamaha-2-stroke-crank-seals","status":"publish","type":"post","link":"https:\/\/www.chinonthetank.com\/2014\/09\/replace-yamaha-2-stroke-crank-seals\/","title":{"rendered":"Replace Yamaha 2 stroke crank seals"},"content":{"rendered":"
Since a lot of friends have been getting 70’s and 80’s Yamaha 2 stroke dirt bikes, and I’ve done this a couple times now on my CT1-175 due to the motor blowing up, I figured I’d do a basic write up on how to change the crank seals.<\/p>\n
First off… Why do you care and what’s the deal?<\/p>\n
On 2 stroke dirt bikes, there is a rubber seal on either side of the crankshaft. Over time these dry out.<\/p>\n
The seal on the magneto side (left side) prevents air from getting into the combustion chamber. If the seal on this side goes bad, you’ll get air leaks. Your idle will hang and\/or the bike will rev erratic randomly. Bike will run lean and trying to tune it will be pointless.<\/p>\n
The seal on the clutch side (right side) prevents crankcase oil from getting into the combustion chamber. If the seal on this side goes bad, you’ll burn a ton of oil and eventually foul plugs and suck the crankcase dry of oil.<\/p>\n
Ok.<\/p>\n
Things you’ll need to change the crank seal which you most likely do not have or own:
\n– air compressor set up and air gun to loosen certain bolts for the first time in 30 years
\n– 26mm \/ 29mm \/ 30mm socket
\n– yamaha magneto puller tool<\/p>\n