akamor Posted July 13, 2010 Share Posted July 13, 2010 Hello All, First off, thanks to everyone that has been helping me over the past two weeks. I started off with a motorcycle that would not start and it is near running flawlessly now. I am having one problem however. I can only start the bike with the throttle open. Once the bike starts if I do not constantly apply the throttle the bike dies. Between 1200 and 2000 rpm (approximately) the bike sounds weak, however, over 2000 rpm it sounds GREAT. I think the problem lies in the idling circuit in the carburetor. For this carburetor the idling circuit has two components I believe. The air screw and idle jet. Even with throttle the bike can only start when the air screw is turned all in, however, like I said idling is bad. What should I do to adjust the idle jet? Assuming you believe the idling circuit to be the problem. Thanks, Adam Link to comment Share on other sites More sharing options...
Paulwhite Posted July 13, 2010 Share Posted July 13, 2010 have you done a spark plug check? to see what the mixture is doing? if you know the mixture is fine then the next step will be sorting out the air screw. but if it wont stay on idle then the jet might be clogged. if you take it out and blow into it then pop it back in and see what happens or are you sure that its clean? if its not that then you need to adjust the air screw i normally do mine to the bike and not what the manual says, but il tell you my way then im sure someone will give tell you what the manual sais. right. warm the bike up then turn the idle screw up so the bike is at say 1000-1500rpm then turn the air screw in as much as you can without the engine stalling, then slowly turn it out till the bike revs up as far as it can (just listen to the engine). the idea is you set the screw to just below the point where the engine is at its highest rpm and this could mean 1/8th of a turn! then turn your idle screw down to a comfortable Laval then go for a quick ride to see how it is. should sort it out lovely Link to comment Share on other sites More sharing options...
akamor Posted July 14, 2010 Author Share Posted July 14, 2010 have you done a spark plug check? to see what the mixture is doing? if you know the mixture is fine then the next step will be sorting out the air screw. but if it wont stay on idle then the jet might be clogged. if you take it out and blow into it then pop it back in and see what happens or are you sure that its clean? if its not that then you need to adjust the air screw i normally do mine to the bike and not what the manual says, but il tell you my way then im sure someone will give tell you what the manual sais. right. warm the bike up then turn the idle screw up so the bike is at say 1000-1500rpm then turn the air screw in as much as you can without the engine stalling, then slowly turn it out till the bike revs up as far as it can (just listen to the engine). the idea is you set the screw to just below the point where the engine is at its highest rpm and this could mean 1/8th of a turn! then turn your idle screw down to a comfortable Laval then go for a quick ride to see how it is. should sort it out lovely Thanks for the reply. I took the carburetors out for one last cleaning. When I put them back together I will give it a try. Stay tuned. Link to comment Share on other sites More sharing options...
akamor Posted July 15, 2010 Author Share Posted July 15, 2010 right. warm the bike up then turn the idle screw up so the bike is at say 1000-1500rpm then turn the air screw in as much as you can without the engine stalling, then slowly turn it out till the bike revs up as far as it can (just listen to the engine). the idea is you set the screw to just below the point where the engine is at its highest rpm and this could mean 1/8th of a turn! then turn your idle screw down to a comfortable Laval then go for a quick ride to see how it is. should sort it out lovely I am a little confused by your instructions. In the bikes current state my air screw is turned in all the way and my idle screws are 2.5 turns out. The bike will not idle with these settings. Should I continue turning out my idle screw until the bike will idle then follow your directions? Link to comment Share on other sites More sharing options...
Paulwhite Posted July 15, 2010 Share Posted July 15, 2010 I am a little confused by your instructions. In the bikes current state my air screw is turned in all the way and my idle screws are 2.5 turns out. The bike will not idle with these settings. Should I continue turning out my idle screw until the bike will idle then follow your directions? ok try and get the bike to idle then turn up the idle screw so it revs to about 1500rpm then once you have done that turn the air screw in (but dont let it stall) then slowly turn the air screw out till the bike revs high (there should be a point where the bike will stay at the same rpm after a certain amount of turns. you want to be just on it!) then turn down the idle screw to about 500 - 1000 rpm .....done Link to comment Share on other sites More sharing options...
akamor Posted July 15, 2010 Author Share Posted July 15, 2010 ok try and get the bike to idle then turn up the idle screw so it revs to about 1500rpm then once you have done that turn the air screw in (but dont let it stall) then slowly turn the air screw out till the bike revs high (there should be a point where the bike will stay at the same rpm after a certain amount of turns. you want to be just on it!) then turn down the idle screw to about 500 - 1000 rpm .....done How do I get it to idle in the first place is my real question I guess. Should I be adjusting the idle screw? Thanks, Adam Link to comment Share on other sites More sharing options...
Paulwhite Posted July 15, 2010 Share Posted July 15, 2010 How do I get it to idle in the first place is my real question I guess. Should I be adjusting the idle screw? Thanks, Adam right can you get the engine started with the throttle and or choke? if you can then get it started and screw the idle screw in till you can let go of the throttle and it idles, then you can sort it out. Link to comment Share on other sites More sharing options...
akamor Posted July 15, 2010 Author Share Posted July 15, 2010 right can you get the engine started with the throttle and or choke? if you can then get it started and screw the idle screw in till you can let go of the throttle and it idles, then you can sort it out. Ok, that makes sense. I am going to unscrew the idle screw a ridiculous amount then incrementally screw it in until the engine will idle. Is it common practice to leave the carburetor on the motorcycle while making these adjustments. I suppose it would be possible with a small enough ratchet to remove the float bowls and make the adjustments? What do you think? Thanks, Adam Link to comment Share on other sites More sharing options...
Paulwhite Posted July 15, 2010 Share Posted July 15, 2010 Ok, that makes sense. I am going to unscrew the idle screw a ridiculous amount then incrementally screw it in until the engine will idle. Is it common practice to leave the carburetor on the motorcycle while making these adjustments. I suppose it would be possible with a small enough ratchet to remove the float bowls and make the adjustments? What do you think? Thanks, Adam im not quite sure what your trying to do? the idle screw should push the part that your throttle cable connects to (so it opens the throttle slightly), so you shouldnt need to take the carb appart. dont suppose you could post a pic then i can see exactly where ur comming from? Link to comment Share on other sites More sharing options...
akamor Posted July 15, 2010 Author Share Posted July 15, 2010 im not quite sure what your trying to do? the idle screw should push the part that your throttle cable connects to (so it opens the throttle slightly), so you shouldnt need to take the carb appart. dont suppose you could post a pic then i can see exactly where ur comming from? Oops, I think there has been quite a misunderstanding on my end. What you are calling the idle screw I call the throttle stop screw. Yes, that is on the outside of the carburetor and can easily be adjusted. Currently, I have that screwed in all the way. My understanding is that the idle circuit INSIDE the carburetor has two components. I have been talking about the idle jet and air screw which are pictured here: http://www.dansmc.com/pilot_group1.jpg. My air screw, which is actually accessible from outside of the carburetor is completely seated. My idle jet is 2.5 turns out. I do not believe that I have an air air jet. In this configuration my bike will not idle. When I unseat the air screw the problem becomes even worse. My plan was to adjust the idle jet by unscrewing it more because I thought this would richen the mixture. Once the bike could actually idle I was then going to follow your directions with the air screw and throttle stop screw. Thanks and sorry, Adam Link to comment Share on other sites More sharing options...
Paulwhite Posted July 15, 2010 Share Posted July 15, 2010 right put the idle jet in all the way and close up the carb (and dont touch it again ), turn out the air screw by 3 turns and if the throttle stop is in all the way turn it out to about half way and try that for now then it should idle ok, then turn the air screw out till the bike revs high (till turning the air screw has no efect) then you need to turn it back in a tiny bit at a time till the revs drop then turn it out till you hit the point where the revs go up. and then that should sort it Link to comment Share on other sites More sharing options...
akamor Posted July 15, 2010 Author Share Posted July 15, 2010 right put the idle jet in all the way and close up the carb (and dont touch it again ), turn out the air screw by 3 turns and if the throttle stop is in all the way turn it out to about half way and try that for now then it should idle ok, then turn the air screw out till the bike revs high (till turning the air screw has no efect) then you need to turn it back in a tiny bit at a time till the revs drop then turn it out till you hit the point where the revs go up. and then that should sort it I will do this the moment I get home. Can you explain to me the purpose of the idle jet. My understanding was that it controls fuel supply during idle. Turning out = more fuel, Turning = less fuel. Is this correct? Can you explain why turning in the idle jet could potentially fix the bad idle? Thanks, Adam Link to comment Share on other sites More sharing options...
Paulwhite Posted July 15, 2010 Share Posted July 15, 2010 oh and forgot to mention once the air screw is done turn out the throttle stop till its ticking over nicely and quietly. then we can see if the mixture is ok Link to comment Share on other sites More sharing options...
Paulwhite Posted July 15, 2010 Share Posted July 15, 2010 the idle jet controlls the fuel flow on low throttle so it needs to be on the carb properly for it to work as it should if you unscrew the jet then it wont work properly causing little or no idle. Link to comment Share on other sites More sharing options...
akamor Posted July 15, 2010 Author Share Posted July 15, 2010 the idle jet controlls the fuel flow on low throttle so it needs to be on the carb properly for it to work as it should if you unscrew the jet then it wont work properly causing little or no idle. The manual for the bike says it should be at 1.5 turns. Obviously that was not working. Why do you say it should be screwed in completely, why the manual says it should be out 1.5 turns. I am not doubting you, because the manual has not helped me one bit, but I would like to understand this process better. Link to comment Share on other sites More sharing options...
akamor Posted July 15, 2010 Author Share Posted July 15, 2010 the idle jet controlls the fuel flow on low throttle so it needs to be on the carb properly for it to work as it should if you unscrew the jet then it wont work properly causing little or no idle. Perhaps I misread my manual actually. I have attached a snapshot of the tune-up page. I highlighted in red the section I am referring to. It says to adjust the pilot screw which is fitted to each carburetor. Is that not the same as the idle jet? Where would the pilot screws be located? Are they inside or outside of the carburetor? What is their purpose? Link to comment Share on other sites More sharing options...
Paulwhite Posted July 15, 2010 Share Posted July 15, 2010 The manual for the bike says it should be at 1.5 turns. Obviously that was not working. Why do you say it should be screwed in completely, why the manual says it should be out 1.5 turns. I am not doubting you, because the manual has not helped me one bit, but I would like to understand this process better. are you sure the manual is talking about the jet? and not the air screw? it sounds like the manual is on about the air screw with it being 1.5 turns wich would be the factory setting for the carb. Link to comment Share on other sites More sharing options...
akamor Posted July 15, 2010 Author Share Posted July 15, 2010 are you sure the manual is talking about the jet? and not the air screw? it sounds like the manual is on about the air screw with it being 1.5 turns wich would be the factory setting for the carb. Oh ok. So the idle jet, which is inside of the carburetor, should be seated. The pilot screw is actually the air screw, and that is what needs to be adjusted? Is that correct? That would make a lot more sense because now I would not need to remove the carburetor each time I had to make a simple adjustment since the air/pilot screw is outside of the float bowl. Your really saving me here. Thanks, Adam Link to comment Share on other sites More sharing options...
Paulwhite Posted July 15, 2010 Share Posted July 15, 2010 Oh ok. So the idle jet, which is inside of the carburetor, should be seated. The pilot screw is actually the air screw, and that is what needs to be adjusted? Is that correct? That would make a lot more sense because now I would not need to remove the carburetor each time I had to make a simple adjustment since the air/pilot screw is outside of the float bowl. Your really saving me here. Thanks, Adam yes m8 the pilot screw is the air screw ! so if you follow the manual and lightly seat the "pilot screw" (air screw) on both carbs then un-do them by 1.5 tuns (try and be exact) then this will put them back to factory settings and sort it out Link to comment Share on other sites More sharing options...
akamor Posted July 15, 2010 Author Share Posted July 15, 2010 yes m8 the pilot screw is the air screw ! so if you follow the manual and lightly seat the "pilot screw" (air screw) on both carbs then un-do them by 1.5 tuns (try and be exact) then this will put them back to factory settings and sort it out Gothca. Thanks for all of your help. When I get home today I will try it out. Will keep you updated. Adam Link to comment Share on other sites More sharing options...
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