special06shee Posted March 4, 2012 Report Share Posted March 4, 2012 Hi guys.. I have a fresh 4 mil dune/ play port with boost ports dune by fast racing. Pwk35- toomey t5 - cfm airbox- noss head with 21cc domes for pump fuel. Im at around 600 ft elevation. My jetting is currently 150 main 52 pilots cel needle middle clip and 11/2 out air fuel screw. Runs great on the big end but at 1/4-1/2 throttle if you roll in it or stap it it stutters and wont take it. Did plug chops with 155/ 52 pilots and it was rich so i dropped the main to 150. Tryied different pilots 50/48 and played with the needle a bit but cant seem to clear the mid up. Any help would be great. I could call Jeff at fast but i just dont want to be a pain in the ass even though i know he does not mind!!! He is a super dude and always is willing to help but i know he is crazy busy. Thanks Quote Link to comment Share on other sites More sharing options...
Judge1 Posted March 4, 2012 Report Share Posted March 4, 2012 Try a 152 main. Quote Link to comment Share on other sites More sharing options...
special06shee Posted March 4, 2012 Author Report Share Posted March 4, 2012 Forgot to state i originally started with 165 mains and worked my way down to the 150 that is in it and the stutter has been there along Quote Link to comment Share on other sites More sharing options...
Titan up Posted March 4, 2012 Report Share Posted March 4, 2012 Well if the problem is at 1/4-1/2 throttle, it's not the main...Pilot might be too rich, which you could back the air screws out another turn, to lean it out some..I think most likely it's your needle clip position. The needle is probably rich, but to be safe I always like to prove that out. If it were me I would raise the needle by lowering the clip 2 spots and try that first..I imagine it will make it worse and if it does, then bingo, put the clip one from the top, or even at the top spot, bringing the needle way down and see if that cleans it up. Explain the CFM air box. I don't think I've seen one. How much does it restrict air flow? lid no lid? One big filter, 2 filters? Quote Link to comment Share on other sites More sharing options...
special06shee Posted March 4, 2012 Author Report Share Posted March 4, 2012 Cfm air box is an aluminum box.. It holds two smaller style k&n pod filter.. And no it does not have a lid.. Went with this set up because i like the idea of having the extra protection in the envirorment i ride in.. And also thought fitting the factory box in would be next to impossiable with the bigger carbs and intake set up. Its a pretty nice set up.. Just hope this is not my problem!! Thanks for the advise.. Will try it out today!! Quote Link to comment Share on other sites More sharing options...
troyzstang Posted March 4, 2012 Report Share Posted March 4, 2012 I think you need to ditch that air box. And sell it to me Quote Link to comment Share on other sites More sharing options...
RadarRacing Posted March 4, 2012 Report Share Posted March 4, 2012 Im 100% with Titan. Needle position. 1/4 th to 1/2 is a huge part effected by needle clip position. I like to do a 1/2 throttle plug chop just like you would do a W.O.T. chop but I keep the needle a little richer than what the plug would be on a wide open throttle chop. I would imagine you are at least 2 or 3 clips off on needle. Richen the needle up (DROP CLIP/RAISE NEEDLE) and starting with new plugs ride a good ways at only 1/3 to 1/2 throttle in a higher gear preferably. You probably wanna check a plug after only 200 feet or so and make sure it isnt grey or white (LEAN) Hopefully your plug will show pretty rich. If the plug is looking rich then lean out the needle as needed tiill the stumble goes away at part throttle. I do think however you may be slightly large on the pilot as well and would change to a 45 or 48 and then tune. Changing one size on the pilot will do basically nothing if the needle is way too rich. Quote Link to comment Share on other sites More sharing options...
special06shee Posted March 4, 2012 Author Report Share Posted March 4, 2012 Well after test and tuning today i found out that the 1/4-1/2 throttle stutter is accually a lean spot. I started with the cel needle with the clip in the middle and it would not take it.. So i accually lowered the needle to lean it out because i was so conviced that it was rich.. But it made it so much worse!!! Could not believe it. So i then raised the needle all the way up and it is so much better but not perfect.. Still needs more fuel in the mid. I put a size bigger mains in thinking that might help but all that did was make the big end not as stout.. So i guess i just have to find a little richer needle then the CEL. Anyone know of a richer needle off the top of their head? Thanks for the tech help guys!!! Quote Link to comment Share on other sites More sharing options...
Titan up Posted March 4, 2012 Report Share Posted March 4, 2012 There are 3 things to look at on needles....Taper, diameter and a length dim... A "CCL" needle would be a slighter richer needle with the "length dim" being 1.8mm shorter...Each clip position is .9mm apart so in theory this would give you 2 more clip positions..(*I'm not 100% certain about this because the overall length of the needle is the same on ALL of the needles*) thats just the way I interpret the chart. If it were me I would leave the length and dia the same and just increase the taper angle..You'll have more adjustability and it covers 1/4-to over 3/4 throttle....a "D" @ 1* 45' or a "E" @ 2* of taper... So DEL or an even richer EEL needle I think would get you where you need to be. Google Keihin needle charts and you'll see what I'm talking about....My 4mm cub 35pwk's I ran an EEK needle and there was a big difference between the 3rd and 4th clips. Good job tuning and figuring out what you need. Quote Link to comment Share on other sites More sharing options...
badshee1998 Posted March 4, 2012 Report Share Posted March 4, 2012 Are you running air stryker carbs?? If so jeff told me you have to really drop the pilot down on those carbs.. Quote Link to comment Share on other sites More sharing options...
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