36mm Mikuni Flat slide main jet size?
- Thread starter Nick
- Start date
motoddrob
Hero member
- Location
- S/W Australia
I just changed main jets from 122.5 up to 127.5. Track use so wot most of the time.
piranha-bro2
Hero member
- Location
- Melbourne
Have you based the too-rich analysis on wide open throttle, eg on a dyno, moving on a long straight for long enough to determine the rich condition? Just asking cos you don't specify. Too many owners think main jets when their bike is sooting up plugs tootling around town. 3/4 to full throttle is main jet territory. Apologies if you already know all this - thought it worth asking.Hi,
My Jota is apart (again) and appears to be running too rich. Can folk tell me what size main jet they're running?
Cheers
Nick
I have a chart of about 20 triples showing jetting specs - all running differing configs of cc, cams. pistons, CRs, headers etc in combo with RS Mikunis.
Last edited:
motoddrob
Hero member
- Location
- S/W Australia
I also went from 17.5 pilot up to 20s
After a normal legal ride (slow) about 60 kays. Pulled the plugs and they were quite rich so went back to 17.5
Next ride was 2 days on track.
After 3 sessions the #1 plug had good colour the others showing slightly richer.
I think it's time to strip the carbs and run them through the ultrasonic cleaner.
After a normal legal ride (slow) about 60 kays. Pulled the plugs and they were quite rich so went back to 17.5
Next ride was 2 days on track.
After 3 sessions the #1 plug had good colour the others showing slightly richer.
I think it's time to strip the carbs and run them through the ultrasonic cleaner.
Hi,
Thanks for all the replies - I'll post my jet sizes when I strip the carbs, maybe this evening.
The question has arisen from a trip to the cylinder head man whose first reaction on seeing the head was 'over fueling' which I interprete as rich.
When the bike last ran it started smoking excessively. All three cylinders were black with maybe the alternator side most oily. Mr cylinder head also pronounced all exhaust guides knackered.
So the diagnosis isn't from a dyno run but everyday riding...I'm not the slowest rider but far from the fastest!
Nick
Thanks for all the replies - I'll post my jet sizes when I strip the carbs, maybe this evening.
The question has arisen from a trip to the cylinder head man whose first reaction on seeing the head was 'over fueling' which I interprete as rich.
When the bike last ran it started smoking excessively. All three cylinders were black with maybe the alternator side most oily. Mr cylinder head also pronounced all exhaust guides knackered.
So the diagnosis isn't from a dyno run but everyday riding...I'm not the slowest rider but far from the fastest!
Nick
piranha-bro2
Hero member
- Location
- Melbourne
Nick, you'll obviously need to sort the Mr head probs before worrying about jetting. Once everything's tidied up I highly recommend a dyno run to set main jet with an air-fuel ratio meter up the claka - it's really the only way to get a true reading and indicate correct main jet size. Alternatively you can buy a portable A/F meter and go for a flat chat run somewhere!So took a look and mine are currently 125.
I hear what folk are saying about state of tune and so forth but maybe follow Piet's lead and reduce mine down to 122 (this is the lowest value quoted here).
Many thanks as always
Nick
Basing your main jet size on other owner's settings is ballpark at best, but really just second guessing.
motoddrob
Hero member
- Location
- S/W Australia
I ran mine for years with 17.5 pilots.
I raised the needle 1 notch.
Always ran well with good colour on the plugs. It wasn't until I started doing track days i notice the 122.5 main jets were lean as hence now running 127.5.
Mixture screws set half to 3/4 turns out
I raised the needle 1 notch.
Always ran well with good colour on the plugs. It wasn't until I started doing track days i notice the 122.5 main jets were lean as hence now running 127.5.
Mixture screws set half to 3/4 turns out