what can you tell me about reading these plugs?

[Matt_E]

Someone was exaggerating a bit.

Unless there's a significant elevation change or temperature and humidity change, you will never notice a difference.
And for what it's worth: Even then you don't necessarily notice anything. My ski (Dual 44's) runs great in 30 degree air/36 degree water and 100 degree air/70 degree water. Without having to tune.

 

[onesojourner]

cool thanks man. just wanted to be safe.

 

[Mark44]

Yo

I recommend www.mikuni.com
Click carburetors
Click manuals
Click SBN carburetor owners manual

They got excellent tuning info.

Yes 100% manual and tach! It takes years of experiance to be able to read plugs IMO

Mark44

 

[Speedfreak]

Just because the ski is running right I would still address that dark plug. Try to lean that cylinder out a bit. With that tiny bit of time on the plugs that one is still pretty dark. You will have fouling problems if you put a lot of time on the motor. Is that the front or rear plug?

 

[Mark44]

i

Just because the ski is running right I would still address that dark plug. Try to lean that cylinder out a bit. With that tiny bit of time on the plugs that one is still pretty dark. You will have fouling problems if you put a lot of time on the motor. Is that the front or rear plug?

You know all about white ashy rear plugs don't you Mr. Air leak? :biggrin:

Mark44

 

[Speedfreak]

You know all about white ashy rear plugs don't you Mr. Air leak? :biggrin:

Mark44

That was the front cylinder... you just stager your jetting to get rid of the air leak. Heck a 147.5 main is plenty of fuel for a limited with a case leak

 

[Mark44]

r

That was the front cylinder... you just stager your jetting to get rid of the air leak. Heck a 147.5 main is plenty of fuel for a limited with a case leak

:haha: :haha: :haha: :haha:

Mark44

 

[CarFanatic]

excuse my newbieness... what do you mean by tuning by rpm? I have an idea of what you mean, but would like to know exactly what your talking about.

 

[SJBrit]

excuse my newbieness... what do you mean by tuning by rpm? I have an idea of what you mean, but would like to know exactly what your talking about.

As you lean a motor from too rich to too lean, the RPMs drop right after you go through the optimum point. So, you do a WOT run and check the RPMs, then lean a little, then check again. You do that till you get an RPM drop, then you richen it back up a little, say 1/4 turn. That gets you dialled in better than anything, but you need a tach to do it.

Anyone who flies a piston plane with a carb does that routine with the mixture knob as soon as they reach their cruising altitiude.

 

[Matt_E]

The motor will run the highest RPM it can with ideal air/fuel mixture.
SO you tune the carbs by trying to achieve the highest RPM.

 

[SkiDaddy]

On a freestyle Ski running the HS adjuster (& sometimes jetting) a bit richer than would yield light tan plugs will give snappier throttle response.:sneaky: urr:

 

[Matt_E]

Why?

 

[CarFanatic]

ah, makes sense! Alot lot like tuning a nitro rc car, but a bigger scale, and more difficult. (you tune to rpm)

I'm stock now, but ths s good knowledge when I add a pipe and head. You always tune the HS needle first then adjust low speed?

 

[Dustin Mustangs]

No, just the opposite. The low speed circuit contributes through the entire power band so a change there will effect hs mixture as well (although not much). You should REALLY read that article Matt linked to on page one. It goes over all of this in great detail.

 

[Matt_E]

ah, makes sense! Alot lot like tuning a nitro rc car, but a bigger scale, and more difficult.

I'm stock now, but ths s good knowledge when I add a pipe and head. You always tune the HS needle first then adjust low speed correct?

No, absolutely not. The HS screw is the last thing to tune

1 - Tune low speed screw
2 - tune pilot
3 - tune popoff
4 - tune main jet
5 - tune high speed adjuster

 

[SJBrit]

No, absolutely not. The HS screw is the last thing to tune

1 - Tune low speed screw
2 - tune pilot
3 - tune popoff
4 - tune main jet
5 - tune high speed adjuster

Exactly. A pop-off guage is worth the modest investment.

 

[SkiDaddy]

Agreed, my post is assuming you already have everything else spot-on.:biggrin:

 

[Matt_E]

Absolutely necessary for good & accurate tuning, especially dual carbs.

 

[CarFanatic]

:banghead: man! I better start reading up if I plan to modify!!! Thanks for the help. Whats the pilot?? Man fuel injection so much easier it seems to me at least! I will read the link about the carbs now.

 

[CarFanatic]

Man I read that artical, What I dont understand is how do you change the pop off pressure? Change the spring? I also have heard of people triming the spring aswell..? My head is spinning!:frown: