Carb question

Discussion in 'Engine, Fuel and Exhaust' started by shanedawg, Oct 1, 2008.

  1. shanedawg

    shanedawg Member

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    Need some advice. For a while now I have been thinking of replacing my stock carb with a S&S Super E or Mikuni. I have an 01 dyna wide glide and the guy that I bought it off of said that he put bigger jets in it. I think that he might of put to big of ones in. Because once it is good and warm and I stop to get gas or something short like that to where I shut it off for a short period of time (couple of minutes) and I go to start it I have to twist the throttle to about half and black smoke rolls from the exhaust. But if it sits for say 20 min or longer and I go to start it, it will fire right up with no smoke and no twist of the throttle. So could this be something with the jetting? Also what are the opinions of putting an S&S or Mikuni Carb on?
     
  2. glider

    glider Veteran Member

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  3. TQuentin1

    TQuentin1 Well-Known Member Staff Member Moderator

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    Shane (... and Mother wants you ... SHANE! - Great movie!!)

    You probably have the CV40 (Keihin) carb on that bike. I have a '91 Dyna and that is the carb on mine. Personally, I love this carburetor. It is simple, easy to work on, and does what it is supposed to depending on what it is you want it to do. However, someone might have fiddled with the one you have and messed it up for the way you want to ride. Before you go and buy another unknown, if you have the time, inclination and ability why don't you see if you can get this carb working the way you want.

    First thing is to get the factory service manual for your bike. This will include info on the Keihin carb which was probably stock on the bike. Also order a rebuild kit for your carb. You can get this from HD or any of the online motorcycle supply shops. Your local dealer will probably have to order it anyway. Or you can also get something like this:

    Stage 1 Carb Tuner Kit

    I also like the YOST power tube kit. Does a better job of atomizing the gas, and they include a bunch of jets in the kit:

    Yost Performance Products, Inc. - Yost Performance Products, Inc. - Products: Motorcycles (at bottom)

    Completely dissassemble and clean everything carefully. Be careful getting too aggressive with spray carb cleaner since you don't want to blow any of the little bits out of sight. A good aromatic liquid solvent will do nicely with some Q-tips and an old toothbrush. Watch out for the "rubber" parts and the solvent though. Will probably swell them.

    Decide what you want to try for jets, and replace the ones in the body if they look bad. Also, while you have the carb handy, turn the body over and find a spot on the bottom that looks like it should be a hole, but has some plastic filler sealing it (probably red or brown colored). One of the guys here thinks it may be an aluminium plug. If this is not there, but you see a small screw head in a recessed hole, great! This is your idle-air mixture screw/needle. If the plastic (or aluminium) IS still there, drill it out carefully to expose the screw. You will probably want to fiddle with that once you have the bike running. (See photo)

    I would also suggest that you replace the accelerator pump. Chances are that has never been done, and it will be itchin' to fail on you. Finally, look carefully at the slide diaphram to see if that looks old and worn. If so, replace it. OEM is fine. There are some that would suggest you drill out the hole in the top of the slider to 1/8". DON'T. It is easy to mess this up, and then your throttle response will be crappy. In fact, get a 1/8" bit and turn it around. See if it will fit in the hole in the slide. If not, great! If so, try a 9/64". If that fits, someone has screwed up the slide and I would replace it if it was mine.

    As I said above, I like this carb. It is very simple and easy to mess with. Once you get it back on the bike, you can easily rejet based on the way you ride and what you want the bike to do. You can spend lots of money on some of the aftermarket models, but once you have this carb working, it does what it is supposed to. Again though, DON'T drill out the port in the slide!! Just MHO.

    TQ
     

    Attached Files:

    Last edited: Oct 2, 2008
  4. hntwrobin

    hntwrobin Active Member

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    If you don't want to spend a lot of money redo the stock carb with the thunderslide. The mikuni is a nice carb as is the S&S Mikuni is more forgiving and can be easier to dial in. As for the yost power tube I have a friend that does dynos Dr. Dyno he once told me don't spend the money on the Yost powertube as it has no significant impact on performance. I definitely trust his word!:bigsmiley18:
     
  5. TQuentin1

    TQuentin1 Well-Known Member Staff Member Moderator

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    Shane,

    There ya go! This is the interesting thing about about this site. You will get a lot of different perspectives on any particular problem or issue that is raised by the participants. In my previous post, I was writing based on my own personal experience with the Keihin carb. I have rebuild my carb several times, and my recommendation NOT to drill the slide is based on having messed up MYSELF. I replaced the slide with another OEM slide after researching the options.

    I did decide on trying the YOST power tube (again after researching the options). The tube that comes in the kit is mechanically different from the OEM tube with MANY more ports in the tube then the OEM has. The research I did convinced me that the YOST approach atomized the gasoline more thoroughly. My own experience showed that every thing I did to the carburetor resulted in great performance from it. But this was not just one thing, I completely dissassembleed and cleaned the carb thoroughly, rejetted, replace the stock tube, new needle, drilled the slide (bad idea and I went back and replaced it), new slide spring, drilled out the access to the idle-air mixture and adjusted that, cleaned out the gas tank, replaced the tank valve with a Pingel Power Flo, and replaced hoses (cross-over and supply). All these things were done at about the same time, so pointing to any ONE thing as the reason that the carb works so well is not possible. Maybe there is synergy in all these things?

    Net result is the that I am very happy with this simple carb. My suggestion is to give it a shot before investing in a more expensive alternative.

    TQ
     
  6. glider

    glider Veteran Member

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    I agree with TQ

    Drilling the slide can cause a problem under certain conditions when the temps are lower and you hit the throttle open suddenly, there's a temporary lean condition caused by the faster opening of the slide from the larger opening and usually results in a pop back through the carb. The CV carb set up properly is hard to beat dollar for dollar.
     
  7. shanedawg

    shanedawg Member

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    Gentlemen,
    I really appreciate all the advice on this matter. I believe I am going to go ahead and rebuild and start there. How often should you rebeuild the carb? Or is it just one of those things that when you feel it needs to be done you go ahead and do it. The bike only has about 24,000 miles on it.
     
  8. glider

    glider Veteran Member

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    Usually when a problem shows up, it's time to rebuild the carb, however it's a good idea to drop the float bowl and clean it out every 15-20K miles.

    You should be able to flush it out easily even sooner without opening it up. Take a look at the drain screw in this post for doing it.

    Poor Performance With Carb Models - Harley Davidson Community
     
  9. detrimentald

    detrimentald Member

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    I dont like my S&S but it was on my sporty when I bought it used. I would have rather had the origonal CV. My advice would be to invest in something different.