Crank Seals

Do the cases need to be split to rplace crank seals. I just bought a 1979 CR250. It won't start (good spark/new carb). He said that someone told him the crank seals were probably bad.

Any help would be appreciated.

seals

yep you can get one out but not the other

l would be supprised if leaking crank seals would stop you from starting the bike, unless they where so bad you had oil pouring in from the clutch side.

Before you go tearing stuff apart this is what i would do in your shoes.

1, get the bike running.

2, remove stator cover and spray some starter fluid behind the flywheel while the bike is running, if the revs climb due to the fuild getting past the seal and into the barrel (fueled by the starter fluid) you have a duff seal.

3, put a clear hose on your crankcase breather, run the bike half a mile, if you see oily residue climbing up the pipe you have a duff seal (caused by pressure building in the gearhox due to a duff seal) .

...................and take it from there.


you can replace the flywheel side seal without splitting the cases, for the clutch side seal you will have to split the cases.

Thanks!

If the crankcase seals are gone on a twostroke it will not usually tick over, indeed you would be lucky to rev less than half max revs with the throttle firmly shut, so if it runs ok once you get it started it is almost certainly something else,. A good spark in the open does not always mean the same under compression, blocked pilot jet, check timing etc