Hello all Rev3 guys out there !
My recent experiences and studies....
About last two or three months i have been struggling with my Rev3 (year 2001) engine and carburation.
My first problem was with the left side vent of the Mikuni - fuel came out of the vent when the carb's tank was full....
I read all the MIkuni "tuning" articles, even the hose build to connect two vents.
I made actually a bit funny mistake and closed the flooding vent. Seemed that the engine ran fine, but about few months...
It started to make a bit laboring sound. Like, it didnt got the perfect mixture.
I played a bit with the AIR screw, finally the engine needed it fully closed to run "normal". - it was of course abnormal !
I realised it got to be something more, so i opened the cylinder's head to clean the piston's head. Of course , it was dirty and horrible inside, so i got it very clean.
Now, few days ago i got the engine running, but again....the mysterious laboring sound ....
I realised that its something with the carb, because this bike's engine ran very smootly when i bought it. Actually it was rebuilt by recent owner.
I opened the "flooding" vent of my carb, so two float vents are now opened. Also, i checked the float plate, to get it parallel to the carb's "plane". The left vent doesnt flood anymore !
NOW it runs perfectly, almost like new !
So, my thoughts about all of this ...
Actually, when the flooding vent was closed, the left side float didnt got the atmospheric pressure, so basically it was "stuck". It caused abnormal working of the engine - laboring sound.....
So why the vent started to flood ?
In my theory....
Remeber, I had my piston's head very dirty and usually it makes the engine's pressure to go very high.
So, i assume that some amount of pressure "ran backward" to carburation system. This caused carburation pressure to exceed atmospheric pressure in the float tank.
Basically the atmospheric pressure didnt manage to push the fuel to jets in the float tank of the carb !
The result was that one of the float vent started to flood - fuel in float tank ran backward and out of the left vent
Now, when .......
my piston head is clean and new head gasket is installed,
my carb is checked and cleaned,
my carb's plates are parallel to over all "plane" of the carb and
my carb' two "atmospheric" vents are fully opened without hose tuning..........
The engine runs like new and my Mikuni does not flood anymore !
Model: Rev 3
Engine: 270 cc
Pilot jet: 27,5
Main jet: 145
Sorry about my english and i hope this helps !
Cheers from Estonia !