front cylinder not firing properly?

Just bought a replacement engine for my rocket.. long story.. but the background info is that the engine came from a flood damaged TRIKE in the USA..

I was told by the seller that the Oil had been drained and filter changed, very little water in the oil, fresh oil put in and engine run for 5 min, engine oil and filter changed again.. no signs of water at all and engine seemed to run fine.. had been used for about 20miles and then removed from bike to be sold to me..
Upon arrival and fitting new filter and oil again.. engine seems to run ok, and have taken it out for a run and it pulls good...

I have straight through single exhausts on the beast and have noticed what may be a problem with front cylinder.. should also say I have single pod filters on it,,,

The problem....
The heat/pressure of the exhaust from the rear and middle cylinder are the same, but the front one is not as hot, nor does it come out with the same pressure.. when I put my hand near the end of the exhaust, the front one sounds different too...

Any ideas on what could cause this?.. I'm hoping it may just be a fouled plug and therefore not firing fully,

Any comments welcome...

Is it running rough too?

My first guess would be to check for spark and clean the coil low tension leads on #1 Cylinder. Then see if it changes. I if so you had a erratic spark on Number one. You should do all coils and re-crimp the low tension connectors so they are tight on the coil.

If as you say it seems to run ok and pulls good there doesn't seem to be much problem. Do a compression test on no. 1 to be sure. Those straight pipes will need some serious retuning to run as it should.

Ok.. so clean plug, and the 2 wires on the coil pack... might as well do a compression test while I have plug out..

Would a fouled plug / failed spark give incomplete combustion?

Would it sound different if not firing properly??

ECU had already been remapped, although it was on a 3 into 1 straight through with pod filters.. done the 12 minute tune, but will get it on a dyno as soon as I can, but here in spain they are few and far between

As Scott says check spark, that is the easy bit.
Personally I would want to see a compression test & endoscope inlet/exhaustports & plug holes.
I have seen water mix with combustion carbon the result is disastrous to aluminium.

what is the result of water and carbon on aluminium.. wasn't aware of consequences?

I have seen flooded engine combustion chambers where the cylinderhead has been eaten leaving deep pits
steel valve seats not bad but head a mess.

Remove check /install new plugs, check compression on all three cylinders, make sure throttle body's are balanced correctly, plus check all the little stuff -loose wires ,cracked spark plug wires etc etc and good luck