Author Topic: JP3 Change Over Valves.  (Read 62 times)


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JP3 Change Over Valves.
« on: May 27, 2023, 02:06:08 PM »
I am running a JP3 in my narrowboat and was recently pushing against a strong flow coming up the Thames. As I was working the engine I used the low compression option for the first time.  After the initial experience of the hissing and barking while going from high to low, I found that the engine ran very cleanly (after the engine was at running temp) in low.  I am now on a canal which doesn’t require the effort so have been leaving them set to high comp.  My problem is that I now have a slight leak in number two (although its seems to have had no effect on the performance).  It seems to be hissing through the nut holding the wheel in place.  I assume there is a bit of carbon build up - does anyone have a clever trick for getting a better seal? 

Note: I stopped reading the manual for removal when it was suggesting that I hammer chunks of wood into the block!



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Re: JP3 Change Over Valves.
« Reply #1 on: May 28, 2023, 11:31:29 PM »
Hi Papster, the best way to decarbonise an engine is to inject water into the inlet manifold when the engine is hot. A household squirty bottle is ideal for this. Squirt the water in at a rate that just starts the RPMs to fall. You will need to do this once with the compression valves open and once with them closed, should clear the carbon.
There are proprietary products like Seafoam that will do the same thing.