Carb jets

[flextrainer]

just checking to see what the best experiences with carb jet combinations are. I am currently running a 35 pilot and an 86 main. I also have a 30 & a 38 pilot. I haven't quite got the perfect combo yet, but I feel like I'm close. Would like to see what everyone else thinks and has found works well. I have an open element air filter and more open than stock but not wide open exhaust.

[zombie]

The easiest way to ball park is start w/ the idle jet. Which type of circuit adjust do you have (fuel or air) Use your mix screw to tell you if you need to go richer or leaner. for example if you have a fuel adj. turning your screw out should stall the idle. If it does not, you can go richer. Also the same for the main. Adjust your needle up or down , and note the results. Plug Chops will tell you more than anything else though. You want a tan plug at all three operating ranges. Slinger may have some basic settings, but each scoot has variables that will affect the results. Ie: rollers, tires, ect... . The burn conditions are directly related to the condition of all the parts as a whole. What you are trying to achieve is a tip temperature of 450-500 degrees to get that clean burn. The amount of fuel simply controls that temp. I can tell you what I have in my 2t, approx. 40 idle- 98 main, also 44 choke jet. Mine is tuned pretty much b*lls to the wall

[flextrainer]

Thanks zombie you're always a great help. I think I'm gonna go back to my stock intake. I think the one I have on it now may be the problem since I've tried a bunch of combos and none of them seem to be the perfect combo. It seems to run rich sometimes and lean sometimes and it always has a miss on opening and in the mid range. I thought it could be the carb, but I tried a different and it has the same problem. The intake is quite a bit bigger and must be causing a problem somehow. It is getting to me because I've never had a problem I couldn't fix especially with the help of this forum. One question I do have is if I turn the screw and it doesn't stall ( it doesn't until close to three turns out now) it needs to go richer in the pilot right. That is what I thought, but when I go richer in the pilot (or main) the bog on opening is worse and the screw (fuel) has to be turned all the way in. By the way once I get this straightened out have you had any experience with performance ckutches. mine is starting to slip and I was thinking of an upgrade. Are they really worth the dough

[zombie]

What you said makes PERFECT sense. If the intake is too large you will lose vacuum efficiency. Sorta like sucking through a straw compared to a paper towel holder. There HAS to be a median though. Jetting is sssooo hard to get right! I have turned to CUSTOM jetting. I use torch tip cleaners to wallow out the jets. If you go too far, High tin solder will close them up again to re-try. To ID the low end miss you can put in a NEW spark plug, and run it at ONLY the missing rpm range. See if you are either rich or lean. Don't get tempted to open it up to the good range. Here's a link to a site that may help determin where your problem is. The mix system your carb has will determine the answer you need. The Idle circuit is the link to look at. It all depends on which system you have. Keep Posting!!!

[flextrainer]

Thanks again zombie. Good idea about running in the dead spot I'll try but it is hard to hit and stay in. it is the worst when getting off and back on the throttle and when opening the throttle fast from a stop.It is in the transition from pilot to main(probably because of the dramatic drop in vacuum from the too large intake). I can't see the link you posted can you post it again for me please. One last thing are the torch tip cleaners you have numbered with sizes cause mine aren't and I don't have the time ususlly to take the carb on and off several times.

[zombie]

sorry bro , my bad ! I forgot to post the link.     http://www.ducatimeccanica.com/dellorto_guide/dellorto.html   The theory will apply to ALL carbs. we run. You have to figure which system you have. The tip cleaners are numbered. They are standard sizes to what they are made for. You have to get a new plug to see what is happening in that rpm range. Ask shaka! 1 plug will tell the tale if you keep it in the "bad " spot for just a little while. 1 km will do. After the scoot is warm 3-4 minutes will do the job. We would ALL like to have instant numbers, and I think thats why there are sssooo many posts on the 50cc link. It all depends on EVERYTHING your scoot is running. A new 500 has NOTHING on a tuned 50. Just MY opinion. I saw a signature once that said; ALL capitals is cruise control for cool. I only try to STRESS the important parts. YOU'LL GET IT!!!

[flextrainer]

Well, I changed the intakes and picked up a little in the bottom and middle but lostsome up top. The dead spot on takeoff is gone too , so I guess I'll just have to take that trade off.

[Shaka]

Sometimes there is a trade-off!  It seems to me, you should be able to get it tuned with the intake, you may be limited by the range of the stock carb though!  Here's a real good link I found for tuning Delorto Phbg style carbs:  http://www.mopedarmy.com/wiki/How_To_Tune_PHBG_Carburetors

[zombie]

Yeah, I would say you can get it back. Maybe just moving your needle a notch will get it. You may be suprised how well these things respond to a tiny change