79 shovel. Posted some issues before about it fouling plugs quickly. Compression is 95 in the front and 85 in the rear. Leak test was 20% in rear and the front was fine. Bike was running real bad fouling plugs. I'd change the plugs and it would run great for 3 hours the run on one cylinder(I think). Anyways I took it to my mechanic and he found some bad o rings in my carb and replaced em. Also tightened some stuff up. Now it blows whitish smoke when warm. I havent ridden enough to see if the plugs foul and do what it did before, but after a hour or so ride, the plugs are black in the rear. Any ideas on what it may be? I'm going back to the mechanic on Thursday to check in.

Thanks in advance.

 

Black plug indicates rich. Sounds like one cylinder is not burning the fuel. White smoke is most likely raw unburnt fuel

 

Sorry I can't call it white smoke, it's not black smoke though . Just went for a ride for about an hour and on the way home while stopped at idle it would idle a couple seconds fine then drop and back fire through the pipe and die.

 

Back fire is caused from excess unburnt fuel in the exhaust igniting. Still sounds like one cylinder not firing properly. I can explain symptoms. Sorry can't tell you what is actually going on. But it has to do with that one cycilnder getting to much fuel. Weather its not firing or firing at the wrong time IDK. But black plug and the smoke plus back fire then die at idle. Is indicating that, that one cycilnder is getting to much or not burning all the fuel and flooding out. Which at idle would make it shut down then back fire. It sounds like at idle fuel is building up and flooding the motor which causes the bike to stall then the hot exhaust is igniting the unburnt fuel and then pop backfire. IMO

 

I've heard that before with this bike, so it make sense. Gonna throw a proven carb on it to see if it helps. It needs a rebuild or top end at least but I'm trying to push it till winter. I tried hotter plugs in the rear and they didn't help at all. I might try em again. It's worth a shot.

Thanks

 

Are you getting a strong spark? Sounds like maybe an ignition issue that is not giving spark to fire the fuel.

 

I'm getting spark. It's got a dyna electronic ignition.

Thanks

 

what i see in this - you had an issue that got much worse - your guy replaced o rings in the carb was said --- must have been intake o rings - now the carb is way over rich -- sooo i think you have the incorrect jets for a sealed intake that you did not have before - cant go by the compression numbers posted every gage is different BUT as seen lots of times you said - quote - 20 percent in the one and the other is ( FINE ) i dont have the words fine on my leak down tester so i cant help with that - but 20 percent is enough to have cause to re do the top end - plan on pistons and rings - valve guides and possible a set of stainless black coated valves i like and only use today cast iron guides with the rubber blue seals - and kibblewhite valves

 

^^^ plus 1 on that I just didn't want to say it. I was trying to beat around the bush about it. Sounds like time for rebuild

 

Yeah I knew it was coming. I'm taking it to him tonight so..,,
Thanks for your help