H300F Posted April 21, 2004 Report Share Posted April 21, 2004 I have the Keihin 30mm carbs on my banshee. They worked fine for 2 or 3 months. One day after riding for 20 mins I decided to put smaller main jets in since it was running alittle rich on top. I went from 180s to 170s. After doing so, I started it up and the engine screamed close to wide open. I then checked all my clamps over about 5 times and couldn't find anything wrong. So I then put the main jets that I was previousely using back in 180s, and still the same problem. I then took it home and cleaned both carbs out really well. Bolted everything back on, and still the same exact problem. I then put the stock carbs back on, started it up and it runs fine. I then put the keihins back on, and same problem, goes wide open. I made sure the boots are seated well, sparyed wd40 on the boots (no change), checked the slides and they are not sticking (didnt check them with engine running), adjusted the air screw (nothing), set the idle screws at all different spots (no change). I am using the same jetting as I was when it ran perfect. And now it is hot out instead of being really cold, so its running richer which would not cause this problem. When I start it up, it idles high equivalent to giving it between 1/4 and 1/2 throttle, and after about 3 seconds it starts to sky rocket and then I hit the kill switch and she likes to stay running for another 3 seconds. One time it stayed running for about 10 seconds wide open, even with the plug wires off. So what can be wrong with these carbs??? Please help I am stuck. Quote Link to comment Share on other sites More sharing options...
ledofthezep Posted April 21, 2004 Report Share Posted April 21, 2004 One time it stayed running for about 10 seconds wide open, even with the plug wires off. Man...you've checked about everything I can think of...is there a choke tube connecting the keihins? Dunno, sounds like an air leak...but you've already eliminated that. I've not messed with those carbs so I couldn't tell ya. Could you have done something when you changed the jets?...have you pulled everything back apart & checked the carbs out? I dunno man, good luck. Someone with knowledge on these carbs on here should be able to help ya out. Quote Link to comment Share on other sites More sharing options...
H300F Posted April 21, 2004 Author Report Share Posted April 21, 2004 Hey, no these dont have choke tubes on them. They are similar to stock carbs though, D-slides, mains, pilots, airscrews on the backside of the carbs, screw down caps instead of threaded carb caps, 2 chokes, and the bowls have a plug to take the main jets out. And I am using the same boots as stock carbs, band clamps, fuel lines, same everything. Yeah I went over everything when I cleaned the them. Nothing seemed out of place. Quote Link to comment Share on other sites More sharing options...
H300F Posted April 21, 2004 Author Report Share Posted April 21, 2004 (edited) Oh, and yes it seems like an airleak. especially when the motor gets really wound up before I kill it, it sounds very weak and powerless like its lean. But where is the leak, I cant find it!!! And after killing it and checking the plugs, they look normal, no white. Edited April 21, 2004 by H300F Quote Link to comment Share on other sites More sharing options...
SDD Posted April 21, 2004 Report Share Posted April 21, 2004 Check for a torn carb boot and make sure the carb caps are threaded correctly. Thats a large main jet size jump for Keihin carbs. The run on condition is a problem that should be addressed. It could be caused by something getting hot enough to act as a glow plug and keep the motor burning any fuel that flows into the motor. Check for signs of detonation. Is there any carbon build up in the cylinder? Quote Link to comment Share on other sites More sharing options...
H300F Posted April 21, 2004 Author Report Share Posted April 21, 2004 (edited) Well I put the same main jets back in that it prevousely ran fine with and no change at all. And with the stock carbs it does not have any of this, it runs perfect, and im using the same boots, and the motor is only about a 1/2 year old. And the caps have 2 screws to hold them down so its impossible to put them on wrong or loose. Edited April 21, 2004 by H300F Quote Link to comment Share on other sites More sharing options...
FoxBansheeRacing Posted April 21, 2004 Report Share Posted April 21, 2004 Is it both cylinders over-revving? take the plug cap off one so only one cylinder is firing and see if its just one or both cylinders doing it. Quote Link to comment Share on other sites More sharing options...
H300F Posted April 21, 2004 Author Report Share Posted April 21, 2004 good idea. let me give it a try. ok, wont start on either of the cylinders, only kicks over for a second. however it is revving up on both cylinders, both are pushing out the same amount of smoke and exhuast pressure. i did notice that if you catch it and shut it off before it really winds up it will shut off immediately. if you let it rev for a few more seconds up higher and then try to shut it off it has a delay to takes a few seconds to kick off. if you let it rev up high for a long amount of time it likes to keep running. Quote Link to comment Share on other sites More sharing options...
fixitrod Posted April 21, 2004 Report Share Posted April 21, 2004 If your went from 180 to 170 I bet your way lean and making it really hot in there. I believe there are three sizes between that. 172, 175 and 178 then 180. I'd put the 180's back in just to see. That will eliminate the air leak theory. I bet it's too lean. Quote Link to comment Share on other sites More sharing options...
H300F Posted April 21, 2004 Author Report Share Posted April 21, 2004 I did put them back in that same day and the problem did not change. And even when its cold it still has the same problem. And its not when i touch the throttle, it occurs by doing nothing but kicking it over. As soon as it starts it goes right up. My friend has my 180 jet so I will have to get them tomorrow and try again. Even with the chokes on it does it. Quote Link to comment Share on other sites More sharing options...
MotulMonsta Posted April 22, 2004 Report Share Posted April 22, 2004 Keihnin's have a nipple on the barrel after the slides..make shure they are sealed up. Those carbs did work right at some point in time right? When I first got my 28's they did the same thing. but it had 135's from the factory..I had to get every size from 150-180 to get it to jet right. I'm now at 165 with 30 pilots I belive...might be 35's..Anyways.. does it run better with both chokes out? Is the tor's black box disconnected? It shouldn't run at all after you kill the motor..that's bad mojo. something isn't right in your electrical wiring...unless it's detonation..REALLY bad mojo. try disconnecting the trottle cable from the thumb throttle then cycle the slides by hand..make shure they both move even and smoothly then check your idle gap..both slides should sit the exact same hight when at idle next move them up real slow paying attention that they move in unison. then try to start it up. If it does the same thing..swap carbs then try again...the whole time with the cable disconnected from the thumb throttle. Quote Link to comment Share on other sites More sharing options...
MotulMonsta Posted April 22, 2004 Report Share Posted April 22, 2004 You don't have a shitty assed terry cable throttle cable do you? Quote Link to comment Share on other sites More sharing options...
Banchetta Posted April 22, 2004 Report Share Posted April 22, 2004 Its obviously a stuck slide. If it was an air leak, then the problem would persist w/ the stock carbs as well....maybe your cable is pulled out the top of the carb or the sleeve where the cable goes into the thumb throttle.... Quote Link to comment Share on other sites More sharing options...
H300F Posted April 22, 2004 Author Report Share Posted April 22, 2004 I emailed the seller of the carbs heres his response. "Your cable adjustment is out of whack. Check how level your cables are, and run them as low as possible out of the top of the carbs. You want just a little play in them. I had this same problem with mine, and I found that my screws that go into the top of the carbs were not only set too high, but also they were not the same height. This will also affect the way the power comes on, and they wont be completely in sync with each other. Also, make sure you use those little black boots where your cable fits into the tops from your stock carbs otherwise they could hang up on you under a lot of throttle. That could get ugly." When I have the air filter off and look at the slides move, they are fine. Tomorrow I am going to take the cable off and rerun it. And its motion pro cable. Thanks for all your help. Quote Link to comment Share on other sites More sharing options...
sredish Posted April 22, 2004 Report Share Posted April 22, 2004 I would definitely check the cable, could be kinked somewhere or pulled from the top as Banchetta mentioned. Just the other day, I was tinkering with the needle and put it all back together. I kicked her over and BWAAAAAAAHHHHHHH. WTF. First I panicked and pulled the needle back out and put her where she was to begin with and started it. BWAAAAAAAHHHHHHH. Ok, then I stopped and thought about it a little. I followed the cable and sure enough, it had been pulled just alittle, but plenty to make her Wide Freaking Open, and it' enough to startle you. Good luck. Quote Link to comment Share on other sites More sharing options...
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