Carby thatsdax RT carb vs other SHA 15:15 clones What's the difference?

Discussion in '2-Stroke Engines' started by RadicalxEdward, Nov 3, 2014.

  1. Like the title says, what's the difference between the rt carb (which is an SHA 15:15 clone) and all the other SHA clones out there?

  2. Bzura

    Bzura Member

    If they are stamped with the name "Runtong" on the side there is no difference. Some places sell these with the jets AND cable included for the same price as other places do for them carb alone. Check the spinsor's prices on these & decide for yourself.

  3. It's funny you're the one who responded Matt. I was JUST about to post saying I got mine from and it's indeed stamped with Runtong and looks exactly the same in every way PLUS came with 5 extra jets and the cable (vs thatsdax which only includes 3 and no cable)

    Can't wait to get it installed and try it out. Tired of trying to coax any life out of my crappy NT carb.
  4. I should mention I also contacted thatsdax to ask them directly what the difference was, especially since I've seen a lot of people compliment their SHA clone whereas most people debate whether the SHA or CNS is better when it comes to generics. Their response was simply "I do not know the SHA..." literally. Not the people I wanna be buying a carb from if they don't even know what they're selling. Much rather go with someone who knows what's what.
  5. Fabian

    Fabian Well-Known Member

    The NT carburettor is not a crappy carburettor. It works perfectly fine, so long as the thing is assemble correctly, and jetted correctly.

    To eliminate air leaks between the intake tube and the carburettor clamp, just place an appropriately sized o-ring inside the carburettor clamp area.
    The carburettor clamp is one of the biggest potential sources for air leaks, which manifests itself in poor idle and poor throttle transition issues.
  6. It's also not a great carburetor in general. But my statement wasn't about NT carbs in general. It was about my specific NT carb. Which was running so rich that it would basically only run with the filter off. I was going to buy some micro drill bits to re jet it but the cost of bits and a micrometer, etc wasn't far off of a new carburetor with a full set of jets. So I decided to just do that.

    Idk if the sha jets are the same size as the nt jets. If so I may try them with it. I had a hard time deciding between the cns and sha carbs. There's pros and cons to both. But I got a good deal on the sha so I went with that.
  7. Fabian

    Fabian Well-Known Member

    At the end of the day, a float style carburettor such as the NT or the Dellorto or the CNS etc is not the most optimal solution.

    The best option is a Walbro style diaphragm carburettor with externally adjustable high and low jetting screws, allowing infinitely variable jetting with the simple twist of a screwdriver.
    The other benefit of a diaphragm carburettor is that they are far more resistant to fuel and air leaks that a traditional float style carburettor.

    My advise is not to use drill bit to open up the main jet on the NT carburettor because a standard home specification drill press does not have the accuracy to properly drill a perfect sized hole.
    You would be much better advised to purchase a range of Dellorto 5mm jets from No #70 through to N0 #84 in 2 jet size increments, like 70, 72, 74, 76 etc.

    Because i wanted nothing less than perfect jetting (when previously using the NT carburettor), i have every jet size from No #68 through to No #94 in single jet size increments i.e. 70, 71, 72, 73, 74 etc.
  8. That's absolutely true and that's exactly what I wanted to do. And perhaps after the winter I will. But the problem with that is the price. How much did you spend for that carb and all those jets?

    I paid about $25 for this carb, the air filter, throttle cable and 5 extra jets. Nothing else comes remotely close to that. I'd be paying 4-5 times that for a diaphragm carb alone.

    Not to mention at that price you're not getting 4-5 times the performance increase. You're only getting a small performance increase and a lot more tunability. Which you may not need if the cheaper carbs are close enough to begin with to optimal.
  9. Fabian

    Fabian Well-Known Member

    I have bought a few carburettors over the 6 years i've been playing with these engines, and have a few carburettors set up with 3 jet size increments that are around the average of what my engines normally use, eg, one carburettor with a No #73, No #76, No #79, No # 81

    For the most part my engines (using Australian lower eastern states 98 octane fuel, which is equivalent to American 93 octane fuel) run optimally using a Dellorto No #76 main jet. I have had one engine run optimally using a No #70 main jet and another engine run optimally using a No #86 main jet, but for the most part, they seem to run best around a No #76.
    It's a lot quicker (and less messy) to change the jetting (of a float style carburettor) by simply unbolting one carburettor and bolting on another with different jetting, then perfectly optimising the jetting once you know which way you need to go; using 1 unit jet size increments.

    From past experience, i have paid around $3.50 (per jet, in Australian money, and i must have around 30 jets, so it works out to around $100AU for all of my jets.

    My current engine uses a No #77.
    The only reason why i am using the NT carburettor is because i've been too lazy to put the Walbro style diaphragm carburettor back on the engine, but i'll endeavour to put it back on in the next week or two.
  10. I'm amazed you can get jets that cheap in Australia. Seems like everything is taxed to hell over there. What's $10 here ends up costing $100 over there for the same thing. Lol

    Either way $100 just on jets is ridiculous. I guess if you have the money to dump into it it's personal choice but if price isn't a major concern why not just buy a real motorcycle or something.
  11. Fabian

    Fabian Well-Known Member

    I order all of my jets from America, which makes it a far more economical proposition. If i were to buy a single 5mm Dellorto jet in a motorcycle shop (somewhere within my immediate location), they want $17AU per jet, which is approx $15 American, and that's nothing less than f*$king outrageous.

    I have owned many motorcycles, and raced (in a recreational manner) more than a few motorcycles.

    Having said that, the joy of a motorised bicycle far exceeds any of the motorcycles i have ever owned.
    I subscribe to the view that smiles per mile is more important than outright miles per hour.
    Last edited: Nov 8, 2014
  12. Fabian

    Fabian Well-Known Member

    You are 100% correct in your assessment of the situation in Australia.
    Some time ago, i shipped a bunch of parts for my radio controlled helicopter (from Singapore) and as an example, one item was around $5AU. The same exact part in the local hobby shop had a sticker price of $23AU - - - Absolutely f*#king outrageous.

    Another example: i bought two small silicone bicycle lights (a little flashing device just for visibility) for $20AU each. Only reason why i bought the things is because they were reduced to clear, from a price of $35AU each.
    Imagine my horror when i got on Chain Reaction Cycles (American site) and saw the exact same item advertised for $6.49AU. I fell on the floor and cried because i got shafted so bad, and i am being absolutely honest.

    We get shafted to the worst degree in Australia, and the same goes for automobiles. A car that sells for $35,000AU in Australia, made by Holden, which is a subsiduary of GM America, sells for $20,000 American at the American dealerships, despite the vehicle being made in Australia.

    How the f*#k can they sell the same car for nearly twice the price in Australia, when it is made in Australia and doesn't have any shipping costs associated with sending the vehicle to America.
    Next question that always gets asked when Holden says that they only make $5 per vehicle (ok i am over exaggerating). How can they can ship the vehicle to America and sell it for half the price that Australians pay. Holden's standard response is that the cost of labour is so high in Australia. If that's the case, then there is no way that they can sell the thing for half the price in America, and still make a profit.

    No question about it, we Australians get shafted; in a big way.
    Last edited: Nov 8, 2014
  13. dirtwarrior

    dirtwarrior Member

    Off topic a little but can a Walbro style diaphragm carburettor be easily used on a 4 stroke
  14. Neardood

    Neardood Guest

    For anyone thinking of getting a runtong dellorto clone, I have some advice: When you order it, get heaps of different Jets for it (I paid $8.25AUD), because the one it comes with will almost certainly be wrong.

    My only engine mod is the carbie as the NT one leaked like a siv. With the runtong attached I would get up to a certain revs and it was almost like it had a limiter. It would abruptly start four-stroking at exactly 30kmh, indicating poor scavanging due to waaayyy too much fuel.

    I drilled out the jet in it to 1mm as that was the smallest bit I had (Yes I know I should have made it smaller), and it did run for about a minute before it flooded itself. After that I ordered a set of 5 (60,65 ect) and found the #60 works best on my motor. I'm not far above sea level either.

    I wouldn't recommend this carb for hardcore tuners at it has literally one adjustment: The idle speed. Everything else is governed by the jet size.