Cafe Racer Forum banner

1 - 5 of 5 Posts

·
Registered
Joined
·
133 Posts
Discussion Starter #1
Just thought I would throw in my experience on this site, because it has helped me in the past.

I bought a 1981 CB400t as a fix and sell, knowing there were a couple issues with it out of the gate. One of which was the drain plug had been overtightened, stripping the threads and causing a leak. I wanted to give the TimeSert fix a try, which is a steel thread insert kit. Expensive, at $100, but comes with 6 plugs. So I got it, equipment was great, worked as per directions, and the bike still leaks oil. Its possible that user error caused the failure, but I doubt it. The kit is made for cars and such not bikes. My suspicion is that the insert is longer/thicker than the aluminum case, so oil sneaks in behind the threads and leaks through between the threads and the aluminum case.

So, my advice is for $100 to buy a used engine that has blown top end bits and scalp the lower case half. Then you come away with some spare parts rather than just a pair of thread cutters.
 

·
Registered
Joined
·
1,717 Posts
most of the time I've seen when the oil drain plug is over tightened, there is a crack along the case. you can check using some dye penetrant.
 

·
Registered
Joined
·
133 Posts
Discussion Starter #4
Duh, next bolt size up! Ah. It might have been a crack too, the aluminum is so thin there, it would have been an easier fix in the end to just buy new case. They sell used engines for those CB400s all over on ebay here.
 

·
Registered
Joined
·
1,684 Posts
If it is a crack I would see if widening the surface with a Dremel and filling it with a liquid metal would hold. Or maybe a touch of weld.
 
1 - 5 of 5 Posts
Top