Performance Carb Upgrade

Discussion in 'Performance Mods' started by 210061741, Nov 10, 2009.

  1. 210061741

    210061741 Guest

    Ok i have done alot to make my motor breathe well.
    But i'm still running the stock carb.

    I think it's time to get a performance upgrade that is very tunable.
    I'm thinking a carb with easily available needles and jets.

    I don't see many threads relating to a good carb that is perfect for the HT's.

    Can u guys help me out here.

    $$$ isn't too much an issue.

    I just want the best i can get.

    hopefully under $100.


  2. Here is the carbs

    These are some bad to the bone carbs,they are out of stock but will have be restocked in the next couple of weeks....Just scroll down and you will see the 2 carbs....One is 50 bucks and the other is 25 bucks....
  3. motorpsycho

    motorpsycho Active Member

    ok, here's a question on the subject of high perf. carbs.
    I have the 50 c.c. slant head, and it does not have an intake manifold (tube). The carb is bolted directly to the cylinder with some long studs and nuts. The nuts sit in recesses on the outside of the carb throat and they are impossible to get at. the recesses surround the flats of the nuts. My guess is that the studs were put into the carb holes, and then screwed into the cylinder with the nuts already on them with some sort of special tool. or the studs were screwed in when they were longer, and then once they were tight, they cut the ends of the studs off. There is no way to get a socket or a wrench onto the nuts to pull the carb off. i can just barely get to the flats of the nuts with a pair of small needle nose pliers, but I can't get a good enough grip or enough leverage to loosen them up. So how can i pull this carb off to put on a better one?
    Last edited: Nov 12, 2009
  4. 210061741

    210061741 Guest

    I would use a good sharp center punch and put a divit in the center of the stud.
    Take a drill bit that is a little smaller than the stud and drill into the stud just enough to get past the nut.

    The nuts will fall off then you can remove the carb and should have enough stud hanging out of the cylinder to get ahold of it with visegrips.

    Remove the studs replace with Socket head cap screws.

    Once you drill past the nuts you outta be good to go.
    If your careful the studs are the only thing that will get drilled.
  5. bigdan

    bigdan Member

    I've heard a lot of good things about the cns carb from spooky tooth. I haven't tried it yet because I haven't been able to buy one. I emailed spooky tooth about the cns carb back in September. I received this Sept 22, from spooky tooth.
    Well, let's see, 5.5 weeks after Sept 22? That's October 30th. Today is November 16. That's 8 weeks so far and no carb. I'd given up and had actually forgotten about this until I saw your post.

    So, if spookytooth ever decides to cary this carb, I'll buy it in a heartbeat but, I'm not holding my breath.

    Listen up spooky tooth! there's $50 in my pocket right now and you can have it. All you have to do is get this carb in stock.
  6. aussie*pride*n*ride

    aussie*pride*n*ride New Member

    there is some good carbs from i have bought one of their carbs and their great, big increase in power and you have more to adjust =D try them they worked for me
  7. AussieSteve

    AussieSteve Active Member

    Which carb did you buy, Dellorto clone or Mikuni?

    Specifically, where did you get the power increase, bottom-end, mid-range, top-end, all of the above?

    Has your comfortable slow speed decreased? By how much?

    Has you top speed increased? By how much?

    I just fitted a RSE billet head and am wondering whether to also get a better carb.
    ... Steve.
  8. Fabian

    Fabian Well-Known Member

    I tried the Dellorto SHA copy and it simply did not work.
    Both the No .072 and .079 main jet were used but the engine ran very poorly with midrange and top end flutter being the result, not to mention cutting and filing of the carby throttle guide tube and throttle grip housing modification to gain an increased length of inner cable to allow the Dellorto slide to attach. A total pain the backside.

    In the end i went back to the standard NT carburettor on the Rock Solid Billet Intake Tube.
    The throttle action is once again, nice and smooth and all the carburettor surging issues are gone.
    I've looked at carburettor upgrades and have come to the conclusion that a Walbro "pumper" style carburettor used in chainsaws is the way to go.
    Lots of advantages, mainly being micro adjustable main needle and idle needle screw jets, which eliminates the need of changing fixed jets for mixture adjustment.
    It only requires a small hole drilled into the crankcase with a pressure tap and pressure line fitted, allowing pulsing of the carburettor diaphram.

    A much better system though, and what all of us have been waiting for is the release of the new Rock Solid Engines fuel injection and digital ignition system that's fitted to the billet engine.
    Simply plug in your laptop and easily control all parameters relevant to engine operation.

    Last edited: Nov 27, 2009
  9. AussieSteve

    AussieSteve Active Member

    Hello mate, you don't sleep either? One of these days I'll get 8 hours sleep - my body won't know what hit it.
    I spoke to Tony about the Dellorto (clone) carb and for low to mid-range performance he recommended sticking with the NT carb and jetting down to #73, even after I said that I wanted to order the Dellorto. (Not much of a salesman, is he?)
    So far, I've gone down from #79 to #76 with good results but I should have listened to Tony in the first place - the #76 is still slightly rich. #73 tomorrow.
    Now off to bed.
    ... Steve
  10. 210061741

    210061741 Guest

    Has anyone tried the new HT carbs with SPEED marked on them?

    They also have a red air cleaner.
  11. aussie*pride*n*ride

    aussie*pride*n*ride New Member

    ok i bought the dertollo carb and i particular noticed at low end the idling was much stable and running perfect take of and starting has improved and also their is no "fuel starving" at top speeds i noticed exatclty a 7 km increase in speed:) worth buying
  12. bigdan

    bigdan Member

    I bought the 14mm dellorto SHA replica and absolutely hate it. It ran very rich out of the box. I bought a set of jets but they were all bigger than the stock jet (that was my bad I should have paid closer attention). So, I soldered and drilled the smallest jet. No matter what I did, I could not get the thing tuned across the entire RPM range. It was either lean in the high end or rich in the low end. I finally gave up and switched back to the stock carb which is still a little lean at WOT but much better than the dellorto knock off.

    Spooky Tooth finally got the CNS carb in stock so, I ordered that thing immediately. I should have it by Tuesday or Wednesday. I'll post my results as soon as I get the new carb installed.
  13. Fabian

    Fabian Well-Known Member

    Hi bigdan

    Your experience with the Dellorto SHA replica is exactly the same as my experience: ran far too rich even with a smaller than standard jet, being a No .072

    The carburation was never smooth through the rev range; only being relatively good at low rpms but everywhere else it was overly rich.
    In the end i gave up on the thing and went back to a standard NT carburettor on a Rock Solid Engines, billet intake tube.
    This combination works reasonably well but it's still a little on the rich side from 4,000 rpm.

    Programmable laptop interfaced digital fuel injection is the only way to go and the only person selling a perfected system will be Rock Solid Engines.
    Release date is to be January 2010.

    Last edited: Dec 5, 2009
  14. AussieSteve

    AussieSteve Active Member

    Hello bigdan, I'll be watching with interest to see how the CNS carb goes.
    Rock Solid Engines have a Mikuni for these engines, so if the CNS carb doesn't seem too good I might lash out and buy one - see if it's better.

    Has anyone else bought the Mikuni?

    ... Steve
  15. jlebh1

    jlebh1 Member

    ive bought the CNS style one from zbox when they had them but there not so great either, they give you a bit more bottom end but the top end is lost.
  16. 210061741

    210061741 Guest

    Anyone try the racing carb from pirate cycles?
  17. AussieSteve

    AussieSteve Active Member

    Do you know what make it is? They only describe it as 'The Racing Carburetor'.
    A pic:-

    This put me off, (the red is mine):-
    Won't fit most bikes without mods and might be hard/impossible to get jets and spares. Still, I wonder how they perform. (I'll try almost anything to make my engine run more like a Japanese one.)

    ... Steve
    Last edited: Dec 8, 2009
  18. 210061741

    210061741 Guest

    That i'm not sure of either.
    I think the extra length is required cause of the air cleaner.
    If you can fit a dellorto i think it would fit.
    I'll give Justin a call and see if i can find out.

    All these carbs need tuned.
    And truthfully i get my 48cc going 45mph 36t singlespeed with the stock carb.

    Idles terrible cause i got to run it rich but once i'm movin watch out.

    Thats really what we need ... a more tunable Carb.
    So we can really dial in the mix.
  19. jlebh1

    jlebh1 Member

    thats the mikuni type one ive got its not that great.
  20. 210061741

    210061741 Guest

    I seem to hear that about all of em.
    A few have good luck.

    Thats why i wonder about the new stock grubee SPEED Carb.
    Possibly better???