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"Loose Nut" from Houston, Texas
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Sounds like you might have a small coolant leak when the coolant system is under pressure, the coolant is dripping down on exhaust and causing the smoke. Or the tech spilled some and is on exhaust smoking. You would only notice the smoke when stopped as the wind would blow the smoke away when moving. If you still have a doubt, take to shop and have them run a pressure check in cooling system. They would put a special cap on and pressurized system. Good luck and keep us informed.
 

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Discussion Starter · #22 ·
Sounds like you might have a small coolant leak when the coolant system is under pressure, the coolant is dripping down on exhaust and causing the smoke. Or the tech spilled some and is on exhaust smoking. You would only notice the smoke when stopped as the wind would blow the smoke away when moving. If you still have a doubt, take to shop and have them run a pressure check in cooling system. They would put a special cap on and pressurized system. Good luck and keep us informed.
Okay, if I am honest I don't think the tech spilled anything as it is the exact same smoke when I noticed the other time. I will go for a ride tomorrow and if it still persists I will go over to the garage to check it.
Thanks buddy, have a great weekend!!
 

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2016 Harley-Davidson Street 750 in Sunglo Velocity Red
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I'm thinking another thing that could be red when it hits the garage floor is one particular brand of oil. Bel-Ray Powersports is known for its red oil, but mostly that's transmission and gear oil. Please pull the dipstick and check your engine oil mostly for color but also for fill level since you're there anyway. Let us know if it's red.
 

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Discussion Starter · #24 ·
I'm thinking another thing that could be red when it hits the garage floor is one particular brand of oil. Bel-Ray Powersports is known for its red oil, but mostly that's transmission and gear oil. Please pull the dipstick and check your engine oil mostly for color but also for fill level since you're there anyway. Let us know if it's red.
So the last time I visited the garage the mechanic filled some oil in my engine because for some reason the yellow engine light on the speedometer was on when I bought the bike and I went by for him to check. The oil he filled I believe was the 20W-50. The light was resolved after I read the error code and reset the error using the button on the meter so it never showed up and the bike has been riding all good since then. He didn't fill it up to full but when a checked a week ago the engine oil was okay.

I told the mechanic about the smoke and his response was:
"It may put a tiny amount of coolant out of the overflow from time to time which would smoke a little if gets on somewhere hot.
Check the coolant level when the bike is cold, as in an ideal world it would have been totally cold when we added some but that would take a long time for it to go cold and return back to the little tank under the side panel.
See how it goes over the weekend and if it persists we may have to book it in to take a look up the ramp."


The leak I noticed two weeks ago was kind of a lot, but if I am honest I haven't noticed any leak of such quantity since then. Only the smoke coming out from the bottom of the engine.
 

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2016 Harley-Davidson Street 750 in Sunglo Velocity Red
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Another thing that I forgot was that since the coolant bottle was completely empty when the mechanic filled it you should check it the next time it is cold. When the bottle has any amount of coolant in it you know that the rest of the system is full of coolant. As soon as the bottle has no coolant you have no idea how much of the rest of the cooling system is also dry.
 

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Discussion Starter · #26 ·
Another thing that I forgot was that since the coolant bottle was completely empty when the mechanic filled it you should check it the next time it is cold. When the bottle has any amount of coolant in it you know that the rest of the system is full of coolant. As soon as the bottle has no coolant you have no idea how much of the rest of the cooling system is also dry.
@PugslyCat So I went for a very short ride today to see whether the smoke or leaking is still present. Before riding I noticed that the coolant tank was empty when I checked with the bike cold but it was refilled yesterday. I drove for 5 minutes just to check whether the smoke would come out but it didn't and there was no leaking fluid, but I was hearing the radiator working quite often. As I was going back home - 1 minute before arriving the red temperature lamp turned on for several seconds and just before I stopped it turned off (I understand it is not ideal to drive without coolant as you explained in previous posts.. I just wanted to check for the smoke and leak).
Therefore, the logical explanation is that there is a leak somewhere in the cooling system and yesterday the coolant fluid was leaking from somewhere on a hot surface (engine, exhaust) and that's where the smoke was coming? And since today it was empty there were no leaks so no smoke? I guess if this is the cause I need to have the bike checked at the garage to repair the leak but would you suggest I buy some coolant fluid and refill it by myself before riding again even if it's a ride to the mechanic - what do you believe could be the issue?
 

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2016 Harley-Davidson Street 750 in Sunglo Velocity Red
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I'm guessing that some leak was puffing out steam rather than liquid dripping on a hot surface. The cooling system is pressurized to keep the coolant in a liquid state. When it comes out through a leak it's already hot enough to boil at normal atmospheric pressure.

I would ask the mechanic if he thinks you can limp in after filling the bike with tap water. I don't see the sense in buying coolant that is going to boil off, but your mechanic will complain about following bad advice from the internet.
 

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Discussion Starter · #28 ·
Alright mate. I will speak with the mechanic to go have the bike checked and hopefully after everything will be okay.
Many thanks for your response. Enjoy the weekend!!
 

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In a pinch if you don't have coolant just add water to get it to the shop. Whatever the leak is any repair will drain it all out anyways and then add new coolant when fixed.
 

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2016 Harley-Davidson Street 750 in Sunglo Velocity Red
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That's what I'm thinking but don't want the mechanic to turn around and claim the whole cause of a boil over or anything else was due only to filling up with water.
 

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2017 Street Rod 750
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Any halfway decent mechanic worth anything would fill the radiator up with water and then pressure test it. Trust me, as a former mechanic myself, tap water is cheap, coolant is expensive. If its leaking anyways then for testing purposes water will find the leak just as well as coolant would.

Plus if its gonna leak out anyways put water in it, cheaper. I would never use water as a long term solution, especially tap water. If you ever get the concentrated coolant that you have to mix, always mix with distilled water as to not corrode and destroy internal engine parts. But seeing as any repair made except for a radiator cap will cause all the coolant to leak out once removed, once its fixed put the proper coolant in and call it a day.

It's more likely the mechanic will call him out on not filling it up with water or coolant and riding it in empty, instead of just filling it with water. These are liquid cooled, that air pocket created will just make it boil over and overheat faster.
 

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2016 Harley-Davidson Street 750 in Sunglo Velocity Red
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@Sarge2481 is 100% correct.

My suggestion that you check with the mechanic before filling with tap water instead of mixed coolant for the ride to the shop was unadulterated CYA on my part and probably totally unnecessary.
 
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