thanks to all the help i recieved with my last post regarding my timing issues
i now have the bike back together after a rebuild
it fired today but with lots and lots o white smoke and acrid smell
wouldnt rev out and spluttering form exhaust
also exhaust got really hot, am used to it running hot but this was abnomally hot
not entirely sure this isnt my atempts at timing it
1.8mm BTDC with dial guage for points to open
i am presuming the issue could be to do with RH crank seal perhaps but would that cause it to run hot and white smoke?
i was under impression white was water?
anyone encountered this before?
many thanks
D



 

I am encountering it right now, and have ordered new crank seals. My bike instantly went from running great to blubbering and spewing more white smoke than I thought would ever be possible. I typically change the crank seals on all of my bikes because you just don’t know when they are gonna fail. Actually I do all the seals. Usually all the seals thru Yamaha run about $125, which includes the fork seals and wheel bearing seals.

When I first got mine running, before replacing any seals. it ran well the first time around the block. The second time, it began sputtering with tons of white smoke, and stalling. It was the RH seal letting trans oil into the crankcase. Both crank seals were hard, with cracked rubber.

thanks yes have since found vid of the exact issue am having, defintatley RH crank seals, all just replaced after rebuild so must have missed something or something isnt sat right
apart it comes again, hopefully no need to split the cases this time

The exhaust will probably smoke for ages so don't expect it to instantly stop after replacing seal. Good idea to burn the exhaust out regardless including the tail muffler with the spark arrestor built in deep down in there-- if i'm thinking of the right model.
Look for other reasons oil might be gettin past the seal as they usualy go in ok & not easy to make a mistake.
There should be an Oring on the shaft to stop oil creaping under the spacer, but if the crank nut was tight it'd be difficult for oil to get by regardless--as it all pulls up against the bearing & crank.
Sorry keep editing. There "might be" epoxy filled holes around your bearing housing. Look at this pic of a "75 i found & can see the three holes. I'm sure i've heard of those letting go so oil coild get drawn in.
If it is like that i'd think the crank woild have up & down movement as the ring the bearing fits in would probably move giving the impression of a worn bearing.
Regarding running hot, if the oil is smouldering in the exhaust i guess it'd add to heat--something i've never thought about.
But if the timing is set at 1.8 then can't blame that. If set retarded like back at 1mm it would make it run hot & struggle to perform.
Full of joy aren't i.
photos.app.goo.gl/jdbKv1aTNUZr553NA
 

i didnt use ultrablack on the seal and i have the o ring on order i remeber seeing it but i didnt change it
i wont vouch for the timing being bob on as have found it a blighter to time, its sparking, it ran and it didnt kick back not sure timing would cause that much smoke?
i dont think the exahaust is the issue it hasnt been apart for so long and was fine before it all went to pot and i do clear it out with a heat gun failry regularily
the amount of white acrid smoke was truly remarkable so its burning oil somewhere
i will check the holes you refer to
seems illogical to have holes in the casing but it was the 70s i suppose
i am hoping i can get to that seal without clutch basket coming off again as it must be the crank seal rather than one behind the clutch

Hi Digger65, 
 I’ve experienced something similar after a rebuild . An alarming amount of exhaust smoke / turned out it was not transmission fluid burning / in this case it was all the assembly oil lubing things up
( and running premix in the gasoline ) plus pipe getting hot and smoking off the oil in there. 
 After some miles it all cleared out .

 If it was me and had given it some long runs “ hot suppers “  dad used to say to clear things out ,,, next step would be doing a pressure test , find the leak before going in to fix it

Generally the crank gear won't clear the basket so clutch would have to come off.
Hope that's not the case though.
Is there a possibility you put some fuel in out of a can that has something unusual left over in the fuel can like diesel.
Those 3 holes i mentioned are plugged with something like arraldite i think, but i've had no experience with that so others could chime in with info i hope incase i'm talking rubbish.

Ha that happened to me RT , filled the lawn mower with Diesel & finally gave up where all this smoke coming from ?  Took it in to repair shop.  Kicker was he found my mistake pretty quick 

yeah just thinking 'white' smoke OP said.