Jota Carbs

GT

GT

Full member
Hi All, as you can see, Newbie. Just getting to grips with my 180 series 2. lumpy to start with but now running ok. However, it seems to run out of breath at high RPM sometimes. Running cleanly, but no oomph. I can see that there is a jet inside the carb bell mouth that squirts fuel when the throttle is opened. It only squirts on the ledft hand cyclinder, middle and right nothing. What jet is this? I assume all 3 should be squirting fuel as the throttles are opened?

Regards
Glenn

 
those jets are the accelerator pumps

have a look at your air filter, see what color it is
if it is a Uni-Filter remove it and go for a run and see what happens

HTH
Red
 
howdy glenn,

those are the accelerator pump jets/nozzles
the diaphragm is located above carb inlet and operated by ramp on carb slide
all three should be functioning

probably has nothing to do with running out of breath at the top end
but would make a difference in roll on throttle changes

the nozzles are located by the large brass screw to the side of the inlet
there's a flat for nozzle orientation to the airflow and an O ring seal

cheers,
scott
 
Hi Glen

assuming your air filter is not restricting air flow (see Red's suggestions).......

the relevant piece of information required to diagnose the issue of "running out of breath" at high rpm is firstly what position the throttle is in?

if the throttle is being held wound wide open, then the carbs will be operating on the main jet size alone. Main jet may be too big or too small

if the throttle is half open, then the carbs will be operating on a combination of main jet but mostly jet needle and jet needle clip height. So, would need to know what jet needle is in there, there are 28 different profiles of the Dellorrtto needle, most people here seem to be using the K1 needle.

the squirt of fuel you are seeing from the one carb is from a mechanical pump that is actuated by an arm and a liitle bump on the side of the round slide which actuates the pump arm as the slide rises. It is to give a shot of raw fuel when the slide is opened quickly, but doesn't keep pumping once the slide is fully open as at full throttle. Yes, all three accelerator pump jets should be squirting fuel at the same time as the slides go up. The accelerator pumps are adjustable on each individual carb, and there is an adjustment/calibration procedure to be followed once basic issues like possible blocakges/linkages disconnected or missing/etc are checked first.

where are you located?

Paul LeClair
 
Thanks Paul and others,

I am located in London. Have has discussions with Keith over the weeks and I think it needs to go up t'north for remedial treatment. Once the (probable) multiple isues are diagonosed (still on orginal ignition, sometimes leaving no2 plug wet with fuel, sometimes runs fine, sediment collecting in fuel lines after clearing etc) then I can start to manage myself, but with so little knowledge of the moving parts, i'd like to take on some experienced feedback first.

This is a great forum, I am learning so much every day

thanks all

Glenn
 
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