This Forum is now CLOSED use the link to get more details viewtopic.php?f=3&t=13924#p102587
By calv
#7890
Hi guys . Just wondering if any body can help. My 1960 constellation when hot is blowing blue smoke from the exhaust. Had barrels homed out and new rings .but hasn't solved the problem. Is this likely to need a rebore and new pistons ? Or could it be something else. Many thank
By Alan R
#72367
Hi Calv------ Have you given the new rings time to bed-in yet ??..........What were the bore readings when you last had the heads off ??.......Are you using the recommended oil ( or a near equivalent ) or a modern semi or fully synthetic oil ??
By calv
#72369
I've done about 150 miles so far. Bore readings / piston had plus 20 on them .but did not do any measuring. Not really mechanical minded I afraid . Still learning
By Alan R
#72373
Hi Calv---- might I respectfully ask you}---- If you're not mechanically minded then how did you know about Honing and in particular what type of hone to use ??....My reason for asking is this}--- Honing is regarded as a surface finishing process which during the process will also remove a very small amount of metal....So when having a re-bore the machine operator will bring the hole diameter to within a small amount of the desired finished size by using a cutting tool, then use the hone to bring the bore to final size AND the required surface finish...........

When your engine started to smoke ie.. before honing, there was already an existing problem.(probably high-milage related normal wear ??...The fact that both cylinders behave the same would seem to indicate this )...When the head and barrel was removed my guess is that the bores were very shiny ( Glazed ) and that "Glaze-busting" was recommended ??.....It's at this stage that micrometer readings of both bore AND piston must be taken to ascertain the whole situation.... When fitting those new rings did you check for "Top" marking and fit accordingly ?.....Did you set the gaps to the appropriate figure ??... then set the three ring gaps at 120 degrees from one another ??.............Finally, is this smoke appearing during normal, steady cruising OR after a throttle closed run then opening up again ?? ( That might indicate worn inlet valve guides / seals ).....
By calv
#72375
Hi Alan you are correct. The barrels seemed very polished . That's why I had them homed out . The pistons had +20 on them so I got new +20 rings . ( probably at this point measuring would have been a good idea) . Fitted rings so the gaps off rings are not in a straight bond.
Seems to smoke on throttle and over run. ...many thanks

Shop for accessories at Hitchcocks Motorcycles