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My 650L smokes like crazy on cold starts. I just replaced the piston and rings, valve guides and seals and it quit for a while,(5 or 6 rides) now it's back. Runs perfect, just smokes only when cold. Anybody got any ideas on how the oil is getting into the combustion chamber? This is really bumming me out, my neighbors don't like it much either. Thanks..

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Hey!!

Welcome to the club. I just posted the exact same thing. Total rebuild and it smokes like a brush fire when cold. I had two or three cold starts just fine, but today it smokes for a good 4 minutes and fogged the whole neighborhood.

I wonder if they are sucking up oil from the case or something??

Good luck,

Dave

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mine smokes too - when I use the choke on cold starts.

I noticed if I do not use the choke... is dosent smoke.

have you guys tried starting it without the choke?

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I haven't tried without the choke. I don't think my bike will start cold without it. I do turn the choke down to halfway within 15 seconds or so and it makes no difference in regards to the smoke. It is oil smoke for sure. It actually runs for about 5 or 10 seconds clean, then it starts smoking. I'm kind of glad I'm not the only one, sucks that it's happening at all but maybe we will get this message to someone who knows what the problem is.

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Check the ring end gap on the oil rings!! Really,had this happen twice years ago on two separate xr 600s'

And if it's out of spec use the next size up rings and file the end to spec.

First check the oil ring spring make sure it's really end to end and not overlapped.

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It smoked again today on a cold start. Not as bad as yesterday, but still lots of smoke. At least 2 minutes af solid, white smoke. Not condensation, burning oil.

I took it for a ride and got it all warmed up and started to do some tests.

Went up a really long, steep hill and used compression braking to come back down. Very high manifold vacuum. Every 20 seconds or so I would give it WOT. No smoke. If the seals or guides were bad, there should have been a little bit of smoke, but not a trace.

Rode in 2nd or 3rd @ mid rpm for about 30 seconds then WOT, nothing.

Let it sit in N while holding RPM's near the middle for 30s then WOT. Nothing.

Got back to the garage and did a warm leakdown test. About 5% leakdown, very good. Almost all from the rings as to be expeccted.

Compression test with decom, 110 dry 130 wet. Not bad.

I made sure the oil level in the tank was 1/2 up the dip stick, and pulled the check plug on the side of the case and let the extra oil out. Not much, about 1/4L total, so I'm not over filled with oil.

I added about 2 1/2 caps of oil to test the compression wet and the bike smoked for about 5 minutes after. Yesterday on cold start it smoked about 4 minutes, so there is quite a bit of oil getting to the combustion chamber.

Before I left the bike, I tipped it far over to let the extra oil in the head pour down the cam chain opening. I will see if this makes a difference tomorrow.

Other than that, I don't know. Maybe it's normal??

I don't think the rings could so bad to smoke at startup so much, but not any other time. Same with the valve seals.

Any ideas???

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It smoked again today on a cold start. Not as bad as yesterday, but still lots of smoke. At least 2 minutes af solid, white smoke. Not condensation, burning oil.

I took it for a ride and got it all warmed up and started to do some tests.

Went up a really long, steep hill and used compression braking to come back down. Very high manifold vacuum. Every 20 seconds or so I would give it WOT. No smoke. If the seals or guides were bad, there should have been a little bit of smoke, but not a trace.

Rode in 2nd or 3rd @ mid rpm for about 30 seconds then WOT, nothing.

Let it sit in N while holding RPM's near the middle for 30s then WOT. Nothing.

Got back to the garage and did a warm leakdown test. About 5% leakdown, very good. Almost all from the rings as to be expeccted.

Compression test with decom, 110 dry 130 wet. Not bad.

I made sure the oil level in the tank was 1/2 up the dip stick, and pulled the check plug on the side of the case and let the extera oil out. Not much, about 1/4L total, so I'm not over filled with oil.

I added about 2 1/2 caps of oil to test the compression wet and the bike smoked for about 5 minutes after. Yesterday on cold start it smoked about 4 minutes, so there is quite a bit of oil getting to the combustion chamber.

Before I left the bike, I tipped it far over to let the extera oil in the head pour down the cam chain opening. I will see if this makes a difference tomorrow.

Other than that, I don't know. Maybe it's normal??

I don't think the rings could so bad to smoke at startup so much, but not any other time.

Any ideas???

Maybe a leakdown test cold may show different results. As I'm sure you know, rings that are bad/incorrect end gap wont really show oil leakage cold as much as guides/seals. I wonder if somehow any of your vacuum/breather hoses are incorrectly routed.... Possibly sucking oil into the intake?

This whole situation just doesnt make much sense. It has to be something simple........

You replaced the piston. Did you have it bored/honed, did you check the machine shops work? Cyl. bore to piston diameter specs? Did you make sure to offset all the ring gaps?

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Hey,

I was thinking of a cold leakdown too. I will try that tomorrow before I start it.

When I got the bike the piston and rings were shot. You could hear the piston slap over the road noise. It smoked pretty good on decell and coming to a stop, but nothing like this on startup.

It's just for that amout of smoke, the rings would have to be totaly shot.

I honed the cylinder and it specked out at 100.30 mm or so. A little worn with some slight gouges, but not deep enough to feel. I have seen and ridden much worse. I have a new sleeve, but just have to get it bored to the correct size later this week.

All rings were offset. 180 for compression and 120 for the oil. No overlap on the middle oil ring.

All valves/head/ports cleaned from carbon and such.

Valve guides were good, only 7000 original miles. New valve seals. Valves lapped in thier original guide.

Bike runs great except for the jetting I need to do.

I checked the oil hose from the head to the tank thinking that it might be plugged or something, and today when I started it I removed and plugged the case breather hose, but it still smoked.

Is there any other way that hot, thin oil could enter the combustion chamber??

I soaked the UNI air filter in 20w40 oil after I washed it. I got as much excess oil out as I could, but ??? I'll take that off tomorrow for starting too. Only thing is it never smoked like this the first 3 rides.

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Right. The first day I road was Saturday. In the morning it was fine. Road 50 miles then it sat for 3-4 hours, no smoke, then another 50 miles.

Sunday morning, lots of smoke.

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With no change in power or noise?

Somethings got to be sucking oil somewhere. Look in all hoses for oil.

You also keep mentioning liters of oil. Dont confuse that with the qt. capacity.

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With no change in power or noise?

Somethings got to be sucking oil somewhere. Look in all hoses for oil.

You also keep mentioning liters of oil. Dont confuse that with the qt. capacity.

No change in the sound or power.

I mention liters because I'm from Canada. 1 Liter is 1.05 quarts, so the same thing.

The guides are not worn. It would smoke durring operation if they were that worn.

I'll try some things before I start it today.

Thanks,

Dave

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I've done almost all that the others have done with testing with almost identical results. When I did the rebuild I had a local shop do all the cylinder/valve work and fit the piston including end gap in the cyl. This shop does all the work for several dealers in the area BMW and Harley just to mention a few so I trust their work. The bike runs awesome despite the smoke, jetting is on, and I use a K&N. I will go over all the hoses and see if anything is up with them.

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Cold leakdown was 10 - 12%.

I got the same 2-3 minutes of smoke yesterday.

Today, I removed the air filter first, same thing. 2-3 minutes of heavy smoke.

I leaned the bike on it's side toward the cam chain tonight. I will see if that makes a difference.

I will pull the head next. It has to be the seals or something. No other options???? I made sure I put tape on the valves before I put the seals on to avoid damage, but maybe they are messed up?? Doesn't really make sence though.

Only other thing I can think of is that oil is getting forced into the cylinder when all the oil has settled in the case. After 2-3 minutes, the level drops enough (oil to tank) to release the pressure??? Any ideas there??

Maybe tomorrow I will drain the oil to the tank before I start it.

Thanks,

Dave

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I have a 95 650L and when I got it ,it also smoked for a few seconds when started. After a few rides it doesn't do it anymore.

The previous owner told me he didn't use it for months when I bought it.

I have no idea also what that was.

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