D14 rebuilt engine burns gearbox oil?

[Tav]

Hi all I wonder if anyone can help me with this issue. So d14 rebored new piston and rings all new bearings and seals. Starts and runs lovely. But creates a smoke screen. Have traced this to definitely drawing in oil from gearbox. Cases were sealed with three bond. And seals in correctly. I'm at a loss. Any help appreciated.

[rhyatt]

If you have definitively proved that is is burning gearbox oil then there are 2 routes only.
Firstly , how did you prove it was gearbox oil ? Oil level correct, then a good run of 10 miles minimum, then allow to stand and dip the gearbox level again?
If this has been done and assuming bike was on a centre stand in the same level attitude as at the start.
Gearbox oil can get into the crankcase by a bad sealing of the 2 crankcase halves, I use Wellseal.
Or
Through the crankshaft seals , either or both worn or incorrectly fitted
When you say they were fitted correctly, was the spring in the seal pointing inwards  towards the big end? So that the primary compression pushed seal lips tightly against the crank shoulders
I'm ignoring cracks in casings and ring of screws around the  crankcase not done up tightly

[cdsdorset2]

Are you using the correct 3 bond. The standard one is melted by modern fuel allowing the crankcase to suck in air/oil.Rex caunt sells the correct version for 2 strokes.

[Tav]

Many thanks for the replies. I have obviously missed something. So will strip it again.my feeling is cases not sealing correctly. As when gearbox oil was filled to correct level.engine smokes terribly. No oil smoke dies off to what you would expect. I will post to let you know. And thanks again

[rhyatt]

Hope you find something

[Tav]

Hi all. Just to follow up on the problem I had. After stripping the engine to bare bones I suddenly remembered I had not previously cleaned all the threads out in the crankcase. My fault entirely. The muck and crud that came out of them. Now back together and I'm glad to say running lovely. I hope this may help someone else that has a senior moment. Take care all and thanks

[rhyatt]

Just got to run those new bits in
Enjoy

[rhyatt]

The D7 also, 2 drilling into and out of the mains.
Hence care on crank seals for 2 reasons, pri are compression  and gearbox oil retention

[rhyatt]

Primary compression