yosty Posted February 19, 2009 Share Posted February 19, 2009 Hey all, I'm new to the site and I just got a DT100 for my girlfriend. It starts up great, one or two kicks. But I have to keep the choke just a little bit on to keep it idling. Also, when it's idling if i rock it left to right it stalls. I've already taken the carb apart and cleaned it. I've tried a bunch of different settings with the throttle stop and pilot air screw. I've noticed that maybe my pilot air screw doesn't come out as far as it should, it seems like some of the threads are stripped out, but I can't see why it would need more pilot air anyway if I have to choke it already. I'd like two things: -First, if anyone has any ideas about why it stalls when I shake it I'd love the advice. -Second, what's the stock settings for the pilot air screw? How many turns out? Really appreciate any help. -Yosty Link to comment Share on other sites More sharing options...
little dave Posted February 19, 2009 Share Posted February 19, 2009 my 74 dt175 did the same thing when i got it, sorta. now im not an expert at all, but I would suggest checking the float level, and cleaning the carb while you have it off. its as good of a place as any to start. also check the air filter. Link to comment Share on other sites More sharing options...
yosty Posted February 19, 2009 Author Share Posted February 19, 2009 So I just found this manual online at google books: http://books.google.com/books?id=CgqnqoODm...a3mCQ#PPA198,M1 So the stock setting for my pilot air screw on a DT100K (1983) is 2 turns out. I'm gonna go try playing with that, I'll let you all know. Link to comment Share on other sites More sharing options...
yosty Posted February 19, 2009 Author Share Posted February 19, 2009 my 74 dt175 did the same thing when i got it, sorta. now im not an expert at all, but I would suggest checking the float level, and cleaning the carb while you have it off. its as good of a place as any to start. also check the air filter. Thanks Dave, yeah I got the float level from that manual too as .83" I'll check that too. Already cleaned the carb... see above. Air filter is my own design, foam cut to fit, with UNI filter oil. I suppose that could be letting to much air through... Link to comment Share on other sites More sharing options...
little dave Posted February 19, 2009 Share Posted February 19, 2009 Air filter is my own design, foam cut to fit, with UNI filter oil. I suppose that could be letting to much air through... dos it bog when you go from idle to wot? Link to comment Share on other sites More sharing options...
linmac91 Posted February 19, 2009 Share Posted February 19, 2009 Hi, i would have to sujest that the carbie is full of water? I've seen similar symptoms and when you shake it the water sucks up the jet. I would reccomend to try and clean carb again and clean fuel tap bowl and put some meths in the tank to wash out any moisture in there..... Good luck Link to comment Share on other sites More sharing options...
Moderator Airhead Posted February 19, 2009 Moderator Share Posted February 19, 2009 All the preceding ideas are good Strip carb and clean, look for a blocked pilot jet. While its stripped, check and set the float height When its all cleaned out and blown through with compressed air if available, re fit it and set the idle mixture, pay attention to the affect the adjustment has, moving the screw should affect engine speed. set it to the recommended setting Link to comment Share on other sites More sharing options...
yosty Posted February 20, 2009 Author Share Posted February 20, 2009 I had already stripped the carb down and cleaned it with carb cleaner and compressed air. Yesterday I took the carb off again, the float was already set higher than spec (smaller measurement, about .75") Seemed strange since that should richen the mixture right? And I was already having to run it with the choke. I decided to try the stock settings: I set the float to .83" and the pilot screw to 2 turns out as per these pages: http://books.google.com/books?id=CgqnqoODm...a3mCQ#PPA198,M1 and http://books.google.com/books?id=CgqnqoODm...a3mCQ#PPA192,M1 Bike is much worse at stock settings, wont rev at all, and needs full choke to stay at idle. With the old settings it would only need a little choke and revved up fine. My current thinking is that the foam filter I made for the bike is flowing more air than the stock paper one. My next step is trying the float a little higher than it was, maybe .70" Also, the head on the pilot air screw is slowly stripping, as the threads in the carb body were eaten up by someone else that used a screwdriver that was too big. Any thoughts? dos it bog when you go from idle to wot? With the float now set at stock spec, yes. Before I changed it, no. Link to comment Share on other sites More sharing options...
yosty Posted February 20, 2009 Author Share Posted February 20, 2009 Hi, i would have to sujest that the carbie is full of water? I've seen similar symptoms and when you shake it the water sucks up the jet. I would reccomend to try and clean carb again and clean fuel tap bowl and put some meths in the tank to wash out any moisture in there..... Good luck Thanks, I dont think there's water in it, I cleaned it out two days ago and I live in the desert. Link to comment Share on other sites More sharing options...
yosty Posted February 20, 2009 Author Share Posted February 20, 2009 All the preceding ideas are good Strip carb and clean, look for a blocked pilot jet. While its stripped, check and set the float height When its all cleaned out and blown through with compressed air if available, re fit it and set the idle mixture, pay attention to the affect the adjustment has, moving the screw should affect engine speed. set it to the recommended setting I'll double check the pilot jet when I pull it again to reset the carb. Link to comment Share on other sites More sharing options...
little dave Posted February 20, 2009 Share Posted February 20, 2009 not that i recommend running this way, but how does it fare without the cleaner? with mine off, I idle fine. rev ok unless I really get on it, then it stalls at 1/2 throttle and runs a bit weak at top end. with the filter I made up for it, if its driving it wont pass 8k rpm, which is fine with me. thats a bit past redline anyway. my thinking is that your filter isnt letting in enough air. Link to comment Share on other sites More sharing options...
Moderator Cynic Posted February 20, 2009 Moderator Share Posted February 20, 2009 I had already stripped the carb down and cleaned it with carb cleaner and compressed air. Yesterday I took the carb off again, the float was already set higher than spec (smaller measurement, about .75") Seemed strange since that should richen the mixture right? And I was already having to run it with the choke. I decided to try the stock settings: I set the float to .83" and the pilot screw to 2 turns out as per these pages: http://books.google.com/books?id=CgqnqoODm...a3mCQ#PPA198,M1 and http://books.google.com/books?id=CgqnqoODm...a3mCQ#PPA192,M1 Bike is much worse at stock settings, wont rev at all, and needs full choke to stay at idle. With the old settings it would only need a little choke and revved up fine. My current thinking is that the foam filter I made for the bike is flowing more air than the stock paper one. My next step is trying the float a little higher than it was, maybe .70" Also, the head on the pilot air screw is slowly stripping, as the threads in the carb body were eaten up by someone else that used a screwdriver that was too big. Any thoughts? With the float now set at stock spec, yes. Before I changed it, no. I think you are about right with the air filter letting her go lean, its not a perfect fix but as an exercise leave the float height and pilot jet at std settings and lift the needle a click and see if that has an effect, if it does then try upping it another step and check again if a couple of points up gets it somewhere near then you may be able to leave it at that. Or chuck a bigger main jet in. If you are in the desert then the oiled sponge is prob a better filter for you situation and the hot air will mean (i think) that you won't be as lean as i would be in our stinky UK wheather mix of hot,wet,cold,dry mixed any way you fancy every 20 minutes. Link to comment Share on other sites More sharing options...
yosty Posted February 20, 2009 Author Share Posted February 20, 2009 not that i recommend running this way, but how does it fare without the cleaner? with mine off, I idle fine. rev ok unless I really get on it, then it stalls at 1/2 throttle and runs a bit weak at top end. with the filter I made up for it, if its driving it wont pass 8k rpm, which is fine with me. thats a bit past redline anyway. my thinking is that your filter isnt letting in enough air. Im open to the idea but if its not passing enough air, why would I need the choke to run with the carb float set higher than stock (more fuel in the bowl)? I made it out of 1/2" thick, air conditioner foam... doesn't seem restrictive. Link to comment Share on other sites More sharing options...
yosty Posted February 20, 2009 Author Share Posted February 20, 2009 I think you are about right with the air filter letting her go lean, its not a perfect fix but as an exercise leave the float height and pilot jet at std settings and lift the needle a click and see if that has an effect, if it does then try upping it another step and check again if a couple of points up gets it somewhere near then you may be able to leave it at that. Or chuck a bigger main jet in. If you are in the desert then the oiled sponge is prob a better filter for you situation and the hot air will mean (i think) that you won't be as lean as i would be in our stinky UK wheather mix of hot,wet,cold,dry mixed any way you fancy every 20 minutes. I agree about the need for a filter in the desert. As for changing the clip on the needle, that would have been my next step except that the Mikuni VM20SS that is stock on my bike has a fixed needle clip, no way to adjust it. http://books.google.com/books?id=CgqnqoODm...a3mCQ#PPA198,M1 It seems like upping the float passed where it was should help all the jets richen up. But if that doesn't work I either need at least a bigger pilot jet or a different carb... Link to comment Share on other sites More sharing options...
Moderator Airhead Posted February 20, 2009 Moderator Share Posted February 20, 2009 Im open to the idea but if its not passing enough air, why would I need the choke to run with the carb float set higher than stock (more fuel in the bowl)? I made it out of 1/2" thick, air conditioner foam... doesn't seem restrictive. No its the opposite way round, the float set higher will make it richer, you should not mess about with float height settings, leave them as specified.. if it works well with open throttle without choke but not with marginally open throttle you should check the pilot jet is not blocked. Link to comment Share on other sites More sharing options...
yosty Posted February 20, 2009 Author Share Posted February 20, 2009 No its the opposite way round, the float set higher will make it richer, you should not mess about with float height settings, leave them as specified.. if it works well with open throttle without choke but not with marginally open throttle you should check the pilot jet is not blocked. Yeah, I think we're on the same page. The bike runs well at mid throttle with the float set higher than stock AND the choke on. This leads me to believe the air filter I made is flowing more air than stock. I'd like it to run with the choke off because whenever I'm riding around the choke rattles itself off and the bike stalls when I come off the throttle. In order of pain in the ass level, I think I need to: a- set the float higher still b- put in a more restrictive air filter c- get bigger pilot and possibly main jets d- get a different carb that has an adjustable clip position and a pilot air screw that is not on the verge of stripping. Link to comment Share on other sites More sharing options...
Moderator Airhead Posted February 20, 2009 Moderator Share Posted February 20, 2009 Yeah, I think we're on the same page. The bike runs well at mid throttle with the float set higher than stock AND the choke on. This leads me to believe the air filter I made is flowing more air than stock. I'd like it to run with the choke off because whenever I'm riding around the choke rattles itself off and the bike stalls when I come off the throttle. In order of pain in the ass level, I think I need to: a- set the float higher still b- put in a more restrictive air filter c- get bigger pilot and possibly main jets d- get a different carb that has an adjustable clip position and a pilot air screw that is not on the verge of stripping. No mate were not quite on the same page, I have said you should stick to the factory float height setting, you seem determined to keep altering it in an effort to overcome a problem caused by something else! Like I said twice before, I suspect the pilot jet is blocked, you also indicate you have issues with your pilot air mixture screw, so the best thing to do now is buy one of These they're only $17.50 and you will then have all manner of new bits with which you can re build your carb, go to siriusconinc website, you will find them under Keyster carb kits Yamaha. If you still have problems then...that is the time to start altering needle height and mixture screw settings in my opinion Link to comment Share on other sites More sharing options...
yosty Posted February 20, 2009 Author Share Posted February 20, 2009 No mate were not quite on the same page, I have said you should stick to the factory float height setting, you seem determined to keep altering it in an effort to overcome a problem caused by something else! Like I said twice before, I suspect the pilot jet is blocked, you also indicate you have issues with your pilot air mixture screw, so the best thing to do now is buy one of These they're only $17.50 and you will then have all manner of new bits with which you can re build your carb, go to siriusconinc website, you will find them under Keyster carb kits Yamaha. If you still have problems then...that is the time to start altering needle height and mixture screw settings in my opinion I hear you about the float height. I rechecked all the jets, all seem good. I think that the extra air flow is the culprit. So I'm going to rejet the carb. Stock was 17.5 pilot and 130 main. I just ordered a 20 pilot and 135 and 140 mains. Also, ordered a 44mm POD filter to fit my 43mm flange. Hopefully that will get it set right with the stock float height. That kit is awesome, thanks I didn't know about Keyster. I'm not going to get it though because I think I need non stock jetting. Also, the problem with my pilot air screw is that the threads in the carb body have been stripped by someone messing around with a screwdriver that was too big. So to fix that I need a new carb body as well as a new screw... Either this rejet will work or I'll buy a replacement carb. Link to comment Share on other sites More sharing options...
Moderator Airhead Posted February 21, 2009 Moderator Share Posted February 21, 2009 I hear you about the float height. I rechecked all the jets, all seem good. I think that the extra air flow is the culprit. So I'm going to rejet the carb. Stock was 17.5 pilot and 130 main. I just ordered a 20 pilot and 135 and 140 mains. Also, ordered a 44mm POD filter to fit my 43mm flange. Hopefully that will get it set right with the stock float height. That kit is awesome, thanks I didn't know about Keyster. I'm not going to get it though because I think I need non stock jetting. Also, the problem with my pilot air screw is that the threads in the carb body have been stripped by someone messing around with a screwdriver that was too big. So to fix that I need a new carb body as well as a new screw... Either this rejet will work or I'll buy a replacement carb. I still think that youre 'barking up the wrong tree' with the air filter. The reason i say this is when the throttle is closed (which is where you say you have the problem) there is very little air going through the venturi, so how can a less restrictive filter be a problem here, Are you sure that the throttle stop screw hasnt been backed off too much Or maybe the bypass hole is blocked, its a small hole just behind the throttle slide on the engine side, this is where fuel/air is charged into the engine when the throttle is closed Link to comment Share on other sites More sharing options...
yosty Posted February 21, 2009 Author Share Posted February 21, 2009 I still think that youre 'barking up the wrong tree' with the air filter. The reason i say this is when the throttle is closed (which is where you say you have the problem) there is very little air going through the venturi, so how can a less restrictive filter be a problem here, Are you sure that the throttle stop screw hasnt been backed off too much Or maybe the bypass hole is blocked, its a small hole just behind the throttle slide on the engine side, this is where fuel/air is charged into the engine when the throttle is closed I've gone through the carb twice now looking for problems and making sure its clean. I've messed with all combinations of throttle stop and pilot air at two different float levels. With the floats set as they were it only idled with the choke on. Even when I turned the pilot air screw all the way in. To me this sounds like a lean condition, which I think I can fix with a larger pilot jet. Is that sound judgement? Link to comment Share on other sites More sharing options...
Recommended Posts