Should I replace my jets?

[romack991]

Today was official read up on carb information day because I was really tired of not know how to really tune my boat. Also my boat used to always start with a push of a button and did not need to be choked or primed. Now it does and it's really annoying to me. The settings I have are just what Paul suggested to me with maybe a 1/8 turn tweaking. Reading up I noticed a rule of thumb that you want to have your pilots sized so that your adjustors are set between 1 and 1 1/2 turns out (to have best adjustment capabilities).

Currently I have:
Pilot (Low Speed) 125
Main (High Speed) 150
Low Speed 2 1/2 turns out
High Speed 1 1/2 turns out
1.5 N&S
95g Spring

Should I bump up the pilot jet to get my low speed adjustor back down between 1 to 1 1/2 turns?

This was more of a theoretical question, but my set up is SportPorted 61x cylinder, stock cases, Stock F/A, Boysen Reeds, Limited B-Pipe.

 

[Matt_E]

I may be wrong - but I don't think the low speed adjusters have much to do with the pilot jets.
AFAIK, the low speed adjusters adjust idle mixture. The low speed jets control low speed throttle mixture. You can't compensate one with the other - as opposed to High Speed jets and high speed adjuster.
Am I wrong?

 

[romack991]

Gas runs through the pilot jet before the adjustor so I thought it would have an impact. I'm don't know, its just how I thought it would work, I'm just trying to get a good handle on the carb operation. Mikuni does have you setup your adjuster and popoff before the pilot jet.

 

[Mile9c1]

Look at the chart on Mikuni's website, it tells you what controls what.

 

[romack991]

yeah, i guess i just had my own thoughts how things worked. low speed adjustment is used in conjunction with the idle screw to set idle and make it smooth.

Guess theres no need in changing the pilot jet since the ski is nicely tuned right now.

 

[romack991]

So the low adjuster is basically determined by the engine setup and idle screw and changing jets/n&s/spring wont have an effect?? Is that correct? Just doesnt seem right to me.

 

[Mile9c1]

Look at the cutaway. It must be that the low speed screw can't flow as much as the pilot jet, so the pilot jet will have no affect on the idle.

 

[romack991]

well I hooked up my tiny tach this weekend and set idle at 1000RPM, then just adjusted the lower screw until it ran smoothly. Since I thought I was getting a few lean cut outs the day before running WOT I richened the high speed some and planned on tuning it with the tach. well you must have tachs that record the highest rpm or my eyes suck because there was no way to read the tach with it was secured to my handlebars running WOT. Since I couldnt do that, I went the reading plugs method and they were a real nice light brown. So I figured I must have been running a little lean and left the screws where they were. Never had any hesitations or cutouts during off idle, low to high transistions, or high speed so I think I'm pretty good now. Also I went out and tapped the start/stop button tonight after the ski had sat for 2 days and it fired up instantly. So I'm think I'm good for the time being.