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Post by B. A. M. F. on Oct 1, 2013 18:32:41 GMT -5
I've been having problems with my scoot idling after it gets warmed up. It wont. It starts and idles fine (probably a little fast even) cold but once hot it will bog down and quit when I come to a stop, so I have to hold the throttle to at least 4-5k rpms to keep it running. I know this is wreaking havoc on my clutch but I have no other option as my starter is not working either, and I cant be getting of and kicking this thing at every red light Im at...
I thought this was a carb issue so I bought a new 23mm carb because I was using a stock carb on a 50mm BBK with aftermarket exhaust (nothing fancy, just an ebay exhaust). I installed it at work today and on the ride home it did not help the problem but now it is cutting itself off while im going down the road and cutting back on a half second later. This can happen 3-6 times in a 15 second period then maybe go a few miles with no problems, maybe not...
Also now when I go to accelerate from a stop it seems to be misfiring or some thing because it will go, quit, go, quit, around 10 times in 4-5 seconds, but then it will go like normal. I have also started noticing black specks of soot on the back of the bike coming from the exhaust. I think all 3 of these problems are related (not idling when hot, misfiring when hot, and the black stuff coming from the exhaust) I still think its carb related, but 2 carbs, same result? Im stumped...
So everyone knows I've tried 2 different ignition coils and my plug (iridium) looked fine last I checked it so Im pretty sure Im getting consistent spark. I also checked the valves and they were spot on. (I reset them for good measure)
All help is appreciated! You guys rock!
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Post by jjoshua20213 on Oct 1, 2013 18:48:34 GMT -5
Somehow your running too lean. When the bike warms up so does the auto choke restricting the extra gas. Does it sound anything like this? itistheride.boards.net/thread/4271/timmingIf It does I fixed it by putting stock airbox back on |
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Post by JerryScript on Oct 1, 2013 19:11:52 GMT -5
Somehow your running too lean. When the bike warms up so does the auto choke restricting the extra gas. Does it sound anything like this? itistheride.boards.net/thread/4271/timmingIf It does I fixed it by putting stock airbox back on Wouldn't black soot indicate rich? The idle issue may be too small of an idle jet, but wouldn't soot indicate too rich at speed? I just happened to try putting the stock air box on my scooter today, after having used a straight line air filter that came with my BBK (ScrappyDogScooter's stage 3 kit). I've read conflicting reports on their effect, some saying the stock air boxes help with the pulse? I immediately had the symptoms described here. As soon as I twisted the throttle, it started to bog, and continued to go then bog, go then bog, with a frequency of about 3 seconds at low speed and 5-6 seconds at high speed WOT. No playing with the throttle helped, and I could barely top 30mph. I put the straight line air filter back on, and vroom vroom, no bogging. Have you pulled your plug and checked the color? |
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Post by B. A. M. F. on Oct 1, 2013 19:28:31 GMT -5
I have a stock air box. but your link shows a post about timing and I don't know what to make of that...
How would intake and choke affect timing? Seems to me the only part that would affect timing other than internal engine parts (i.e. timing chain, cam, etc.) would be the cdi...
maybe that's worth looking into...
or I probably am just running to rich or lean, I just couldn't figure out which...
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Post by JerryScript on Oct 1, 2013 19:43:10 GMT -5
I may be wrong here, but... When you went to a 50mm BBK, you increased the need for air. I've read over and over that an engine is essentially an air pump. Your stock air filter box may not be allowing in enough air. Someone please correct me, but isn't soot an indication of rich, which could be the result of not enough air.
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Post by urbanmadness on Oct 1, 2013 19:50:36 GMT -5
Is the bike a four stroke? If it is, it sounds like tight valves. When you put the BBK on, are you sure the valve timing is correct?
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Post by B. A. M. F. on Oct 1, 2013 20:10:41 GMT -5
if this is the case than that's great! this is my first scoot but with my cars the intake was always my first on my list. when my scoot was new I went to the local shop and asked for one and they said they don't sell them because if you didn't have a jetted carb and an exhaust, all youll do is burn up your heads, which made sense. So I put on the back of my list.
but it all makes perfect sense now! that perfectly explains why the bigger carb makes it run worse, im starving it of O2 even more.
I need to ride into work tomorrow, ill pull the plug off the front of the airbox to see if that helps for now...
thanks!
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Post by B. A. M. F. on Oct 1, 2013 20:12:14 GMT -5
urbanmadness, yes its a 4 stroke and valves are at .005 for both
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Post by B. A. M. F. on Oct 1, 2013 20:16:56 GMT -5
ohh sry. you said valve timing. I do not know as I had a shop install the BBK because I knew I wouldn't trust myself with timing
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Post by urbanmadness on Oct 1, 2013 20:20:02 GMT -5
sounds just a little loose, I run mine at about .003 but it should run Ok at .005 (a little loud and don't rev the snot out of it).... Have you checked for vacuum leaks? The other thing to check, is the Sheer key on the stator.... Timing might be out a little. What kind of intake and exhaust are you running? Oh and what displacement is the motor? Are you running a performance cam?
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Post by B. A. M. F. on Oct 1, 2013 20:32:50 GMT -5
As said before, stock intake/air box, 50mm BBK (83cc), and an ebay exhaust. no cam yet...
also a red hot ignition coil and iridium plug.
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Post by urbanmadness on Oct 1, 2013 22:45:09 GMT -5
Ok... I'd tear down the stock carb... make sure the diaphragm, etc is in good shape, get a jet kit. Stock idle jet and maybe a #  or maybe even #100 with the aftermarket exhaust on the Main jet to start? see if that gets her running. Make sure the intake boot isn't leaking, So you have a stock CDI module you can swap in? Also, pull the cooling shroud for the flywheel, and set it to TDC on the compression stroke, and check against valve timing to make sure you didn't sheer a woodruff key and that your valve timing is correct. I'd actually do this first as it's the cheapest. In the event that you did sheer the woodruff key, make sure that the mating surfaces of the crank and stator bell are not tore up and that you don't have any Stator bell wobble. I just read where you had a shop do the work. Did the bike run properly when you got it back? |
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Post by jjoshua20213 on Oct 2, 2013 7:27:18 GMT -5
I have a stock air box. but your link shows a post about timing and I don't know what to make of that... How would intake and choke affect timing? Seems to me the only part that would affect timing other than internal engine parts (i.e. timing chain, cam, etc.) would be the cdi... maybe that's worth looking into... or I probably am just running to rich or lean, I just couldn't figure out which... The post was asking if timing was the reason for it running like that. I never got around to posting results, but putting the stock box fixed it. I had scrappy's free flow air filter before and just couldn't get it tuned. My bike runs fine but is not 100% Black soot is an indicator of running too rich. And it is 100% possible to run lean at the first 3/4 of the throttle and rich the rest. I think it switches over to the main jet the last quarter of throttle or something like that. I know you probably already checked but make sure the filter is clean. At the end of my air box is a tube with a cap that has 4 holes in it. Try removing the cap and see if it runs slightly worse or better. If better than your too rich and need to adjust the carb. Turn the mixture screw clockwise all the way in and then turn it counter clockwise two full rotations and a half and rev the bike and let of throttle easy until it breaks into a smooth idle. Then rev it again to see if that fixed it. Counterclockwise richens the mixture, clockwise leans it. To adjust full throttle move the clip on the needle jet up or down. Down lean the mixture up richens it. www.scootusa.com/adjust_carb.htm |
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Post by JerryScript on Oct 2, 2013 12:02:16 GMT -5
Someone please correct me if I'm wrong here:
The main jet takes over as soon as there is enough vacuum to raise the needle, not at 3/4 throttle.
Raising the needle clip would lean it out, since the needle would stay in the hole longer, and lowering the needle clip would richen it since the needle would come out sooner.
I really think the OP needs a less restricted air box, then tune to the new air box needs, nothing else. But I've only been riding my chinese scooter for a little over a month, so I'm easily confused by all the different advice here.
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Post by jjoshua20213 on Oct 2, 2013 18:18:23 GMT -5
Someone please correct me if I'm wrong here: The main jet takes over as soon as there is enough vacuum to raise the needle, not at 3/4 throttle. Raising the needle clip would lean it out, since the needle would stay in the hole longer, and lowering the needle clip would richen it since the needle would come out sooner. I really think the OP needs a less restricted air box, then tune to the new air box needs, nothing else. But I've only been riding my chinese scooter for a little over a month, so I'm easily confused by all the different advice here. At high rpm the vacuum is lowest and at idle its highest, so I don'y know how that would work, but then again idk. And yea, that what I went to say. lol I was thinking in terms as the whole needle |
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or maybe even #100 with the aftermarket exhaust on the Main jet to start? see if that gets her running. Make sure the intake boot isn't leaking, So you have a stock CDI module you can swap in?