Tuning SHA14

Benjamin Hojnik /

So i've kitted my Tomos with a 42mm cylinder and a l style piston. Cylinder and head is also lowered for increased compression.

Porting is currently stock, as is the crankshaft.

Now WOT seems to be okay (spark plug is brownish color) but midrange and bottom end feels a bit rich.

How do i need to tune my slide to achieve a leaner AFR? Bigger angle on the slide ?

Crab is a chinese copy of sha14/14 (runtong i believe).

Thank you.(edited)

Re: Tuning SHA14

Jet adjusts your over all mixture, needle adjusts it through the throttle pull..

Move your needle down one notch if u think it's rich...

No clue what you mean by slide angle.

Re: Tuning SHA14

Benjamin Hojnik /

SHA carbs don't have a needle, they get tuned via main jet and slide cutaway.

By the looks of it, according to this http://www.dansmc.com/carb4.htm steeper angle means leaner mixture. That what i was looking for!

Re: Tuning SHA14

Huh, the more you know.

Re: Tuning SHA14

You can use orifice drills to make small holes in the slide that are only open at the throttle positions you are rich, as you open the throttle the holes will go into the carb body and no longer effect you're mixture. It's not so much the air the holes let in as it is the drop in differential pressure across the venturi that decreases the draw on the main jet.

Re: Tuning SHA14

Overpriced Parts /

full throttle Is full throttle,

If you rich @ bottom end @ full throttle and good at top end Making holes or slide changes wont do nothing

Those changes work at part throttle not full open throttle

Making a hole that stays uncovered at full open throttle will make the mix rich and you want lean at bottom end rpm not rich you say.

Tune for top end rpm because you don’t want to seize

so if rich at bottom rpm with full open throttle so be it,

Get screen and black cap filter and retune with that setup you may get better results over stock airbox filter, the black cap has a good inlet hole size for the 14.14 carburetor most times

Re: Tuning SHA14

> Ken Roff Wrote:

> -------------------------------------------------------

> full throttle Is full throttle,

>

> If you rich @ bottom end @ full throttle and good at top end Making

> holes or slide changes wont do nothing

Says he's OK WOT

> Those changes work at part throttle not full open throttle

>

> Making a hole that stays uncovered at full open throttle will make the

> mix rich and you want lean at bottom end rpm not rich you say.

Please explain how this is even possible? If fully open no slide should be exposed.

> Tune for top end rpm because you don’t want to seize

>

> so if rich at bottom rpm with full open throttle so be it,

Really? So be it? Something tells me your bikes are only tuned for WOT then.

> Get screen and black cap filter and retune with that setup you may get

> better results over stock airbox filter, the black cap has a good inlet

> hole size for the 14.14 carburetor most times

Normally I agree with Ken, but he's wrong here, maybe drunk but it's pretty early.

Re: Tuning SHA14

Benjamin Hojnik /

Yeah, my top end is fine, as evident by the sparkplug color and overall power/willingness to rev. Without the correct jet size, i'd hardly crack 7k rpm, now with the correct jet, it's happy all the way to 8.

I'm obviously limited here by the old contact type ignition (will get swapped for a newer contactless in the future).

The idea here is to tune for lower throttle as well, because as it sits, it already hits almost 80kph :) This category of mopeds over here is suppost to run only at 45kph :)

Re: Tuning SHA14

Benjamin Hojnik /

Maybe another dumb question, not totally related to SHA; what kind of surface temps are usually normal for forced cooled cylinders ? I'm planning on hooking a sensor probe to the cylinder head or cylinder itself to see whats happening.

Re: Tuning SHA14

i would definitely mess with the cutaway first.

its all on myrons:

i find that you get the best throttle response when you scallop out the slide and bevel it at the same time.

Re: Tuning SHA14

Overpriced Parts /

> Derek Stahl Wrote:

> -------------------------------------------------------

> > Ken Roff Wrote:

>

> > -------------------------------------------------------

>

> > full throttle Is full throttle,

>

> >

>

> > If you rich @ bottom end @ full throttle and good at top end Making

>

> > holes or slide changes wont do nothing

>

> Says he's OK WOT

>

> > Those changes work at part throttle not full open throttle

>

> >

>

> > Making a hole that stays uncovered at full open throttle will make the

>

> > mix rich and you want lean at bottom end rpm not rich you say.

>

> Please explain how this is even possible? If fully open no slide should

> be exposed.

>

> > Tune for top end rpm because you don’t want to seize

>

> >

>

> > so if rich at bottom rpm with full open throttle so be it,

>

> Really? So be it? Something tells me your bikes are only tuned for WOT

> then.

>

>

>

> > Get screen and black cap filter and retune with that setup you may get

>

> > better results over stock airbox filter, the black cap has a good

> inlet

>

> > hole size for the 14.14 carburetor most times

>

> Normally I agree with Ken, but he's wrong here, maybe drunk but it's

> pretty early.

I don’t drink ‘ my God you don’t know nothing ! I’ve been messing with two cycle bikes for 42 years are you 40 years old?

Sha carbs suck for anything less than stock applications most times but 14.14 sha are great for puch or or Tomos bikes!

Re: Tuning SHA14

> Ken Roff Wrote:

> -------------------------------------------------------

> Sha carbs suck

Like I said, I usually agree with Ken.

Re: Tuning SHA14

i carved a couple notches into the slide and opened up the stock air box a little bit.

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