fine tuning a sha 16.16

I have a sha 16 on my nc 50 that has a 60cc kit 2stg reeds a stock header and jamarcol slip on pipe. at an idle it loads up once it clears up the mids run like a raped ape till 30mph and the slow go to 35mph where it tops out at. my question how can I lean out the idle? I have tried several different main jets (that`s were idle circuit gets it fuel from) if I go down to were I get a good idle then I`m to lean in the mid and top end is there any to lean out the idle circuit??? with out effecting the rest of the power curve? or should I switch to a carb that has more jets and adjust ability??? which carb has the best performance gains and more jets ie start up,idle,main and a adjustable needle.

sorry for all the questions but I`m really tired of switching main jets to only go slower at top speed but idle great or vise-versa.

Thanks in advance Mad Mike from Michigan

Re: fine tuning a sha 16.16

I posted in the wrong section feel free to move it to the tuning section

Re: fine tuning a sha 16.16

campeona del mundo /

fine tuning a sha is an oxymoron. there is one jet and an idle screw...they are mediocre carbs with no tuning options. I've rocked shas on stock bikes and they are pretty good just because they are so simple and reliable. With a kit, they run rich at idle and lean at wot which is super annoying. some people have talked about drilling a couple super small holes in the slide to lean out the idle.

Re: fine tuning a sha 16.16

Or making a cutout in the slide like the way a PGBG round slide looks. This speeds up the air at low speeds making it leaner. I have experimented with this with fantastic results. Just buy some extra slides and make bigger mouse-holes at the bottom and try them out.

Re: fine tuning a sha 16.16

I'm having the same trouble with my sha16 on my Pug. My concern is that with city riding, it's spending a lot of time building up heat four-stroking, then when I hit some open road, my cylinder will be baking more than it should be.

I've had great luck with them on Tomos' but I think that's simply because I've tuned its clutch to spin up quite a bit before engaging, so the carb never really has to perform at lower speeds.

I plan on getting something more tunable for the Pug, but for the time being I think I'll try altering the slide.

Any suggestions for specific shape of the notch?

Re: fine tuning a sha 16.16

Mars you should talk to MP richard.

He had a few different slides for dellorto that had different angled notches in them. I think they are more tuneable than people give them credit for.

Re: fine tuning a sha 16.16

Pushrod Fifty /

I have a 14.12 that I improved. I cut a slot about .020" deep in the center of the slider with a hacksaw blade. It helped the low end, off idle, and it will idle for a longer period of time.

Re: fine tuning a sha 16.16

so you just are cutting or drilling hole all the way through the slide. wouldn`t turning up the idle have the same effect? does anyone have any pics of these modified slides?

Re: fine tuning a sha 16.16

SHAs are tuneable, you just have to be creative

that said im too lazy to dig deep to tune a SHA, but not lazy enough to be satisfied with them as-is.

Re: fine tuning a sha 16.16

I dunoh about asking the mental pones about mopedburetors

Re: fine tuning a sha 16.16

http://rides.webshots.com/photo/2117837810067172765IcuAIA?vhost=rides

Did this about two months ago. I took a grinder to it, ~1" diameter. Ground it down about 10-degree angle, shown here. Sanded w/600,1200, and 2000-grit. Rich spot at 1/8 -throttle disappeared.

I also opened up the bernoulli on the 14/12 entrance which I think was purposely designed to restrict, that helped more at mid-throttle.

Re: fine tuning a sha 16.16

so you put a half moon shape in the bottom of the slide? kind of hard to tell with not having a unmodified slide in front of me to compare it to. I`ll look tomorrow. thanks for posting the pic.

Re: fine tuning a sha 16.16

Pushrod Fifty /

Adjusting the idle screw will just raise the idle and keep the same proportions of gas/air mix. By cutting a slot across the slider, you will add more air to the mix at the off-idle throttle position, leaning it out. The slot would be about just in front of the first atomizer orface.

Re: fine tuning a sha 16.16

The trick is to allow for more airflow in a way that will not allow that added moving air to draw any more gas out of the (fuck, words escape me) thingy, so you don't want your notch in front of the thingy, you want it off to one side.

Re: fine tuning a sha 16.16

Pushrod Fifty /

That makes sense. I jut did mine in the middle because that is where I have seen them on other carbs.

Re: fine tuning a sha 16.16

wish this thread had more pictures/videos. would love to mod my 15.15

Re: fine tuning a sha 16.16

well I notched my metal slide and now when I come off of idle just bogs and dies unless I feather the throttle. I think I took too much off. shopping at threats again and get 2 or 3 more slides or sell it and buy a mikuni or phbg.

Re: fine tuning a sha 16.16

I like this thread. I do not like 16.16s. 14.12 and 13.13 are great carbs. I want to know more about slide filing and driling and whatnot! Mickr mentioned some good bits to me about this maybe he will weigh in.

Re: fine tuning a sha 16.16

OK - pictures are worth a thousand words but I don't have any. So:

The cutaway in a PGBG round slide - that looks like a half moon type shape on the incoming side. Which is angled though, to "ramp in" the air. You mimic this type of effect to speed up the air coming in - a venturi effect. Think a mouse hole like on Tom and Jerry - a little half moon at the bottom, but getting smaller (through an angle) as it near the edge closer to the cylinder. Putting it in front of the atomizing spray bar is not as detrimental as you might think because the little idle circuit hole below the main body helps draw air too. This cutaway in front of the spray bar, it speeds up the air and draws more fuel yes but it's a lot of air compared to an unmodified slide. The faster the air off idle, the more likely it is to get the revs up fast.

By buying a few plastic slides and trying some things, can mess around with it (just like you can buy different slides or atomizers for a PHBG).

I know Drew Olde Order (Beans) has said to put a hole up top somewhere, away from the lower venturi area and although I have never tried this, it sounds like it might have a similar effect. Putting a graded mouse-hole at the bottom (angled to speed up the air flow) mimics things I have seen before so that is why I tried it. SHA slides come flat at the bottom and two others which are angled like I am talking about (albeit angled all the way across, not in a cutaway mouse hole).

It's funny i was asking about this 5-6 months ago and just started trying things and messing around. Just file away at your slides and see what it does. it's fun.

Re: fine tuning a sha 16.16

† CH∆D † /

Good read! My stock 15.15 has a angled slide. Running good!

Re: fine tuning a sha 16.16

Will beat me to it.

Fine tuning a SHA is like "jumbo shrimp" or "living dead".

You get a jet and an idle screw.

If you are SERIOUSLY dedicated to fucking around with it you can melt out the atomizer etc but its for real not worth it.

The best way I have found to "fine tune" a SHAt is with layers of panythose.

I know it sounds ghetto but adding or removing or stretching panty hose layers is my SHA tuning secret move.

Re: fine tuning a sha 16.16

read this

they can be fine tuned, it just takes a bit of work. but because theyre simple, they can be more durable than most carbs

Re: fine tuning a sha 16.16

#CrazyWayne™ rocks. #CrazyWayne /
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