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Discussion Starter #1
Beautiful day for February, so I take my 2004 V Star 650 Classic out. It has had a pop on decel on the rear cylinder, that I haven't been able to get rid of but it's been running pretty good. I have a stock air filter and cobra slash cuts. My pilots are 22.5, mains 100, 3.5 turns out on PMS, pin on #4 (close to taper).
Since it was nice (50+) I took it out and ran it on a two lane for about two hours total at about 55-60 Mph. I could hear a "blip" sound every now and then when at 3/4+ throttle, but not consistent. I pulled back in after a few hours to the garage and I notice white smoke from the rear exhaust (upper) and from the exhaust connection.

Below YouTube video is what I have now.

Any ideas on where to start?

https://youtu.be/C02YFIBsYvA
 

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a tappet cover leak might explain a bit of smoke coming off the head exhaust port area, but not the smoke coming out the tail pipe.

How many miles are on the bike?

Did you have the bike hanging upside down all winter like the photo in your garage? (Sorry, could not resist)

I would not expect the rings or valves to be leaking oil into the combustion chamber until you were getting close to 100k miles on the odo. Maybe a head gasket leak?
 

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Discussion Starter #4
Thanks, I'll check that out first. I did see a oil spot on the black casing (near the serial stamp) below the exhaust pipe connection. One other question, When I did my oil change and filter, it called for 2.96 qt., I probably put 3 in it- overfill wouldn't be an issue would it?
 

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a tappet cover leak might explain a bit of smoke coming off the head exhaust area, but not the smoke coming out the tail pipe.
If the exhaust gasket is not sealing 100% the oil will weep in and burn thru exhaust, I've seen it several times. Would be first place I would check. Also it was mentioned exhaust pop, a leaky exhaust gasket will cause a lean pop.
 

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3 qts is perfect with a new filter

Im wondering if the rear cylinder could be flooding or running very rich for some reason (stuck float?)

pull the spark plug and see what it tells you
 

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Discussion Starter #7
9200+- miles on the bike. Didn't notice that "Upside down thing" I see if I can get that upright for sure. :)
 

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If the exhaust gasket is not sealing 100% the oil will weep in and burn thru exhaust, ... Would be first place I would check. ....
did not think of a weepy tappet cover getting oil into the exhaust port.

how would you check that, quickly hold a rag over the exhaust/muffler tail pipe while idling, and see if exhaust is coming off the connection between the exhaust pipe and the head?

check that both nuts and studs are there on the head too...
 

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did not think of a weepy tappet cover getting oil into the exhaust port.

how would you check that, quickly hold a rag over the exhaust/muffler tail pipe while idling, and see if exhaust is coming off the connection between the exhaust pipe and the head?

check that both nuts and studs are there on the head too...
You can normally here a slight puff, puff sound at the header pipe. I've got an automotive stethoscope I use to trace sounds, hearing ain't as good as it used to be. Sometimes the leak is so small you really don't here it. But oil will weep into the smallest openings. I second the recommendation to check tightness of nuts.
 

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Discussion Starter #10
Ok, I've got a few hours before I have to be back for the ball game, I'm going back out to the warehouse and check tightness of exhaust, and tappet. I'll pull the rear plug while I'm out and see what it looks like. I'll let you know what I find.
 

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9000 miles on a 15 year old bike...

I would not suspect rings, valve seals, exhaust gaskets, head gasket on that bike

but o rings dry out and leak over time. In the video that does look like exhaust blowing out of the exhaust gasket though, not just smoke rising on its own...
 

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Discussion Starter #12
One more post today before guests arrive. My rear plug pictures. Looks a little oily. I tightened the rear exhaust, and checked the tappit bolts. Everything is tight. I saw oil on the bottom bolt on the exhaust bolt. Road it again and once it warms up it starts smoking. definitely smells like burning oil. I'm not having good thoughts about this...
 

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Run a compression test. Here's a good article :
https://www.howtomotorcyclerepair.com/how-to-motorcycle-compression-test/

That will answer if rings are good or possibly valve issue. Oil could also be leaking past the valve guides, no easy test for that.

If it was mine, if tappet cover is leaking replace the oring. Clean everything really, really good. Check if exhaust gasket is good, replace if needed. Install new plugs, some of the color could be from working on carbs. Go for a ride until engine is at full operating temperature. Cut bike off as soon as you get home. Idle the least amount you can before killing the engine. Pull plug as soon as things cool down a bit. How does it look? How does it smell? Post pictures. I'm trying to see if it's a major rich running issue. You stated before you make the rear cylinder rich to eliminate backfire. Sometimes it hard to determine rich fouling verses oil fouling. Keep us informed.

Rich foul


Oil foul
 

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Just reread you post again. You said it stated smoking after it warmed up. If you were burning oil in combustion chamber it would smoke the second you started it. If it's smoking after it gets hot you are most likely burning the oil that has leaked from tappet cover, past exhaust gasket, into exhaust pipe. It will burn once exhaust gets hot enough. Just trying to think it out, it's hard sometimes when you can't see it.
 

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There's been a lot of new members here since you joined in September, Ive lost track of the history of your 650 (unless I go back and search all the threads you posted to)

How much have you rode the bike since you got it? The video shows only the rear muffler spewing smoke, and the smoke at the head connection continues after you stop the engine.

So there is either oil or gas in the muffler, and oil on the head connection point burning off.

Have you recently worked on the exhaust, maybe spraying PB blaster on the studs and nuts to take it off or torque it down?

If this is the first good long ride you have been able to put on the bike yourself, I wonder if the rear cylinder could have been running rich before, or if oil got into the exhaust some other way.

Another thing to check out, make sure the choke on the bike has not gone wonky on the rear carb, keeping it choked while you are riding.

Time for some good news: if your rear cylinder tappet cover is leaking oil and causing all this, it is the only one of the 4 tappet covers you can get off without taking the carbs off the bike. You will have to remove the tool compartment plastic cover, and maybe the battery compartment cover, but you can get a 10mm box or open end wrench on both bolts, take the tappet cover off and replace that one Oring.

Dont go nuts torquing it back down, its an o-ring so its either going to seal or its not, and then you will crush the tappet cover if you keep wrenching on it.
 

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Discussion Starter #18
Going to stop by my local dealer and see if he has tappet gasket and exhaust gasket. I'll start there. I had the breather box off last week changing the pilots from 25's down to 22.5's (resynched also) so I'll also check the crankcase breather. With the 25's you almost didn't need a choke. Was trying different pilots to see if I could get rid of the decel pop and the backfire I was getting on rear cylinder when I increased throttle slowly (usually at 1/8th to 1/4 throttle).

This was the first extended ride at 55-60 Mph I have done on this bike. Most of the other rides were backroad 25-35 Mph with curves and shifting and some short runs at 55 at colder outside temps. Maybe a gasket or metal heated up and shifted with the 60+ degrees today and the longer higher speed ride.
 

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If the crankcase breather hose is not connected to the intake air box (popped off when the engine backfired?) it could be dripping oil anywhere on the top of the engine, depending on where the end landed.
 
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