Blue exhaust smoke and running like on one cylinder - Honda RC51 Forum : RC51 Motorcycle Forums
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post #1 of 3 (permalink) Old 05-14-2019, 06:56 PM Thread Starter
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Blue exhaust smoke and running like on one cylinder

Hi fella’s.
I’m after some info or anyone’s experience with a issue I had with my SP1 on the way home tonight.
I just gone round 2nd gear corner and just started to open the throttle when the bike all of a sudden lost power and sounded like I’d lost a cylinder ( just like someone had pulled the HT lead off). I pulled in once I’d got a safe place about a mile down the road and the bike stalled. I had a good look around to find nothing. I restarted the bike after 2 attempts and it ran fine and revved normally but was pushing out a lot blue’ish smoke from the exhaust.
Today was the first ride out this year but the bike is ran every month through winter and fully warmed up with no problems.
At first thought, I thought it would be Piston rings as it’s blue smoke but I’ve read on the forum here that people have had blue smoke and it’s been the fuel pres’ regulator, can anyone confirm this?
The bike isn’t high mileage at only 22k on the clock.
I’ll pull the spark plugs to see if oily wet or just blackened from possible over fuelling.
Any suggestions appreciated.
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post #2 of 3 (permalink) Old 05-28-2019, 12:29 AM
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I'd take a look at the spark plugs, my 01 had a similar fault and new plugs resolved the issue.
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post #3 of 3 (permalink) Old 05-29-2019, 07:52 PM
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Did you notice if the engine's fuel consumption suddenly increased?

A faulty fuel pressure regulator that has suddenly become stuck closed will cause the fuel pressure in the fuel rails of the fuel injection system to sky rocket. The increased fuel pressure will in turn cause the cylinders to eventually flood resulting in the engine stalling. But before stalling, the bike will consume a considerable amount of fuel. This occurs because the ECU does not monitor fuel pressure and, as a result, continues to pulse the fuel injectors at the same duration as if the fuel pressure was within its expected range.

Another indication of a faulty fuel pressure regulator is that once the bike is allowed to stand over night, after stalling the previous day, it will start up immediately the next morning. This is because the excess fuel that flooded the engine has had an opportunity to evaporate. Once restarted, it should stall again after being allowed to idle for several minutes.

The blue smoke that you speak of is a byproduct of the evaporated fuel. When the engine begins to flood the interior of the exhaust system is coated with raw fuel that passes from the combustion chambers unburned. When the fuel eventually evaporates, an oily residue is left behind. Once the engine is restarted and the exhaust system approaches operating temperature, the oily residue begins to burn away emitting a blue smoke. After the proper fuel pressure is restored to the fuel injection system by replacing the fuel pressure regulator and a proper fuel/air mixture is achieved, the oily residue will eventually burn away completely and the blue smoke will cease.

If your bike is experiencing the above symptoms, it may be worth changing the fuel pressure regulator.
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Last edited by Enxss; 06-01-2019 at 11:46 PM.
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