| Author | Message | ||
     Sportyeric |
My riding bud has put 100 miles on a newly re-built engine. Not revved above 3000. It kicks out a puff of blue smoke when the throttle is chopped for a shift. Could that be considered normal and likely go away? | ||
| Sparky |
What all was rebuilt on it? Did he go into the heads? If the only time it smokes like that is when closing the throttle from rpms, what happens is a temporary higher than normal vacuum condition in the intake manifold pulls oil past the valve guides. That could be due to leaky intake valve seals, worn valve stems, worn or improperly resized guides. If any of these are the problem and are not fixed, it will most likely get worse and coat the back side of the intake valves with carbon deposits, foul spark plugs and spread oil into the exhaust pipes. | ||
| Naustin |
oops. | ||
| Sportyeric |
I was thinking rings still seating. Wouldn't that suck oil up from the crankcase? | ||
| Sparky |
Generally speaking, if the rings are letting oil into the combustion chamber while they are seating, it would tend to smoke at other times than between shifts. But as the rings wear in, this smoking should go away. Give it a few more hundred miles and if it doesn't stop smoking by then, maybe a leakdown test would show that the rings are seated and something else is making it smoke. | ||
| Blake |
I agree with Sparky who is well known for his accurate advice concerning much diagnostical Buellishness.  | ||
| Sportyeric |
Thanks for the input. The engine had a crank up rebuild, including dynamic balancing, the installation of XB style (?) oil squirters, a Baker six-speed and probably a few other life-extending up-grades so its very disheartening to see a possible flaw. It was disassembled for two years and the heads may not have had any work done on them so its possible that the valve stem seals dried up. We'll be hoping that it heals itself with a few more miles of break-in. | ||
| Fulgur |
If the engine is being "broken in" why has it not been revved hard? | ||
| Sportyeric |
Because the "revved hard" school of thought may be appropriate for rings but doesn't allow other items to mesh gently, although I'm sure there are other threads which have discussed the concept to death. But mostly because all the major manufacturers advise against. I believe my buddy is actually trying to closely follow recommendations from either S&S or Ron Axtell. Maybe both. | ||
| Fulgur |
I understand. I have always revved hard (building up to in a progressive way and after getting the engine hot) on all my bikes. The Jap bikes handle it great. I did the same with my Buell. To be honest I have had quite a few engine problems. Now that I have taken it apart I see that the rings were bedded real good but maybe that is not the way with these engines. Maybe I was just unlucky and got a bad engine, I have found lots of bits that were not right on the inside. We will see once I rebuild it right. .....Fulgur. |
