Will a dellorto SHA work in high altitude?

F

fischer550

Member
I live at about 5,500 ft above sea level. Since the dellorto sha's can only be tuned by the main jet, is it possible for use in high altitude, if I can't change the needle setting is there anyway to control bottom end? Also, what size would I want, the 15.15 or the 16.16? Thank you
 
You can rejet it. I live at a good 6000 foot or so here. Depends on where I am? I run carbs bigger than that one on this engine. Asuming you got a H.T. two stroke you are refering to?
 
Ya, it's 69cc china girl with a fred top end kit (ported cylinder, fred head, boost intake, expansion chamber from arrow). I know I can rejet, but will it be enough?Because the only way to adjust an SHA is the main jet, right?
 
Just jet as needed from every where I hear. I never did jet mine when I ran it. Was a bit rich,it was just fine. I know we got more folks here that run this carb.
 
Sorry Goat, but I'm looking for a more specific answer from someone who has experience with the carb in high altitude, I don't know if simply down jetting without any other adjustments will work.
 
http://www.piratecycles1.com/dejetpa5je.html Now post your plug chops and we can tell you where you are at? There is no telling what jet comes with your carb? Sombody might swap one out at the store or the factory could put anything in it?


I prefer to be jeted my self a little on the rich side. I live around a lot of hills. Do you know the basics of carb tuning?

http://motorbicycling.com/showthread.php?t=2314
http://www.google.com/cse?cx=partne...gsc.q=how to tune a dellorto sha's&gsc.page=1
 
Last edited:
fischer550 said:
Sorry Goat, but I'm looking for a more specific answer from someone who has experience with the carb in high altitude, I don't know if simply down jetting without any other adjustments will work.
Click to expand...

Low altitude/high altitude - the only difference is the air density, the only adjustment fuel. Recommendations regarding rejetting to tune for your specific region are either so general as to be simply "ballparked" as there's always variations unaccounted for (type/cleanliness of air filter, fuel mix ratio & flow, intake/exhaust port matching and type, etc.) or fine tuned by the owner/operator to suit.

Even if folks had more specifics to offer, it wouldn't do your particular build any more then the generalized as it's your spark plug that has all the answers ;)
 
I don't think you are getting what I am trying to ask. I know I can down jet, but doesn't that only control the top half of the throttle range? So, with an SHA, if it 4 stroked on the bottom end there would be no way to fix it?
 
Being at the same elevation or even higher than you and having perfect success with mine I just don't see why you cannot make it work? Does not get better than this I reckon? This is where I learned to fine tune the 21mm PHBG. Which gave me more over all power everywhere and complimented my porting. ''No newbee will like learning this carb''

My SHA carby really was a very simple carb. Their instructions are often pretty concise here at this sight IMHO on the carbs.. From what I could tell in the first two paragraphs this carb is very highly modifiable!

The simplicity of this style carb is prolly one of the best recommendations for the average newbe in my opinion. As most of them work with very little modification as reported by most members here and the float will work with out leaking. lol

So I rec do what the majority of folks report doing here is ''down jet'' and they are done! I have yet to hear of anyone changing slides etc. Do plug chops and try a main jet first. Once again I want to say mine worked great at high altitude. In my own experiance there was no improving on it as it was flawless right out of the box. So in a nut shell I just don't see why another fellow could not make one work? Even if it came with the wrong main jet etc??

I could dig up my old carb and read off the numbers on every part in it for you. Could post you picts as well? As it worked perfect.


Here you go!
http://www.mopedarmy.com/wiki/Dellorto_SHA


Cheers!!!!

Got a memeber here that knows this carb rather well mebbe Mapbike will pipe in?:D He loves this carby. I have never heard him complain about it. I loved the simplicity of mine. Sorry I could not help.

No body here will be able really to tune you up from a long distance and a computer cord. Got folks here that will sure try. Your in a great community!
 
Last edited:
Well than there is your answer? Do you think the stock carb is better? I don't...

Then again it is what you make of it? If a fellow can fix machinery any of these carbs are a go. I will not use a carb smaller than 19mm myself for the H.T. motor. From my point of veiw what good is porting if the motor sucks wind through a tiny straw?

When fuel injection was starting to go main stream way back my Auto Mechanics teacher told me in school that all carbs are just toilets with linkage on them. Potentially cynical thing to say I suppose? Yet once again it is what ya make of it!

The smaller the carb the more simple the curcuit can be in my experiance with these type carbs.

Want a good carb get a Del PHBG 21mm. Doubt you will be able to tune it? I absolufrigginlutly love them now! You will find that is another can of worms? What I am gathering here is a lack of patience? I will help any way I think I can none the less!

Good luck!dnut
 
Last edited:
I have not ordered the carburetor yet, all I have now is the stock carburetor. That is why I am asking if it will work or not. You think the 16mm dellorto will be too small?
 
http://www.google.com/cse?cx=partne...&ss=#gsc.tab=0&gsc.q=16mm dellorto&gsc.page=1 Here is a ton of reading and opinions. I know it is a lot of reading. This will give you a point of veiw besides mine.

The stock carbies are 12mm if I remember correctly? The NT carb was my first and it worked great with some quirks. Like poorer air flow. My original point was that I can take a troublesome huge carby and make it work at my elevation perfectly. ''not all that easy to perfect'' Think Bernoulli's Principle. High elevation air lacks the same density.

Any carby that is smaller will of course be easier to tune. So surfice to say these things are all in fact doable! Just not by every average joe...
 
Last edited:
Sure! I never had 4 stroking issues. Why would I think differant for even minute if mine worked. Oh I think I said that tho.....
 
Here is my concern. Right now I have an NT, I have the needle at the leanest setting, the smallest jet I could find a 60 (.6mm) and still it 4 strokes at the bottom end. I am wondering if the SHA (jetted properly of course) will solve this problem.
 
Sweet spot on the N.T. carb for me was, always ''jetted properly of coarse'' to set the needle on the second notch from the top. I had N.T. carbs here among freinds and i included that ran them stock.


We all were oiling about 32 to 1 back then. Oils come in differant flash points. Had dirty jugs then too.

I See folks here at a high altitude that use the likes of 100 to 1 and they all had to rejet.

Thicker oil bike run leaner. ''less fuel to air''
Thinner oil and more fuel gets past the orfice in the carby ''richer fuel to air''

Thicker oil wrong flash point = dirty jug ''soot''
Oil at its proper flash point and bingo.


What kind of pipe are you running?
 
I have the 16.16 SHA carb and love it. remote choke version.

I use it with a reed valve, running a 100:1 mix ratio (ELF HTX909) at 2300ft above sea level and currently got a #45jet in it.

I used a gunson colour tune spark plug to find the bunson blue flame.

I think you can buy different slides for the SHA carb, that have different ramp angles. this will affect air flow at lower throttle settings, and i think it has an effect on the amount of vacuum it creates on the upper hole of the fuel delivery tube(i dont know the proper name).
 
You must log in or register to reply here.
Back
Top