Hi! I'm new at this. I have posted a couple of times but I have some questions. I tried to attach pictures to a message with no success. I could use some help. I have my bike built and rode it for the first time today. First it idled high, then it ran with the RPM's going up and down with the throttle in one position. It dosen't take throttle but just a little. My bike has the carb with the petcock on it, where should it be turned to during operation? By the way it is a 66/80cc Skyhawk engine. I tried adjusting the richness by moving the clip up and down with no real change, The clip is back in original position. While riding, fuel drips from the carb. I read in the directions how to check retainer clip on the needle valve but I havn't checked it yet.
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- Thread starter metalmanipulator
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As for your running problems, the idle speed screw (I think) for your carb should be initially set at 3 1/2 turns out from fully turned in. I don't have that particular one on my engine so I am a bit fuzzy on it.
The surging is caused by either the float height being set too high, or there is crud between the float needle valve and needle valve seat. This would also cause the fuel drip you observed.
There also is a slight chance that the float actually has a pinhole in it and it now has fuel inside the float, preventing it from floating properly.
It could also be a horrible air leak in the carb to manifold junction or manifold to cylinder junction. I would check for that after you check out the carb and if the carb check does not help.
The surging is caused by either the float height being set too high, or there is crud between the float needle valve and needle valve seat. This would also cause the fuel drip you observed.
There also is a slight chance that the float actually has a pinhole in it and it now has fuel inside the float, preventing it from floating properly.
It could also be a horrible air leak in the carb to manifold junction or manifold to cylinder junction. I would check for that after you check out the carb and if the carb check does not help.
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You can post photos using the attachment way........ http://motorbicycling.com/f30/how-post-pictures-7572.html
if the idles hunting up and down and the engine boogs when you try to give it gas you have an air leak. probably where the carb slides onto the intake, put some silicon sealer on the intake tube and make sure the carb is pushed all the way onto the tube, make sure the intake is bolted onto the jug tight too. just don't over tighten then as they will strip out pretty ez.
If its running ok when you are moving, but "leaking fuel" noticeably from the air filter area, its possible that the float tang is bent. Inside the bowl under the carburetor, there is a plastic float ring, and a thin metal "fork" that connects that float to a little pin/valve. If its not working right (bent, hanging up, set to close with float too high or low), the engine could "flood".
First, I want to thank everyone for all the advice, alot of helpful ideas. I checked the float for leaks. I checked the needle valve, to make sure it was clean and operated properly. Everything looked good. I set the pac-man clip to the top groove, this seemed to help some, but if I turn the fuel-cock slightly closed this seemed to help with the fuel dripping and it doesnt bog when you give it throttle as bad. I just finished my first tank of gas. The power is increasing alittle, from about 3/4 throttle to full throttle it doesnt do anything. Will this eventully disappear as the engine continues to break in? Alot of getting to know my bike and some frustration, but I'm Lovin' it.
I mean no disrespect by this question: Are you turning off the starting choke/ enrichner after the engine is warmed up?
Judging by the symptoms you described, you still have a fuel delivery problem.
All indications point to too much fuel, a rich mixture.
What color is the spark plug?
White to light tan = too lean, not enough fuel.
Medium tan to dark brown = perfect.
Black = too rich.
The ideal color is the color of milk chocolate.
My next guess would be that the fuel level is set too high in the float bowl.
You can easily adjust this by carefully bending the two arms on the float/ valve fork
down, away from the carburetor body, just a teeny bit; equal on both sides as best as you can. It does not take much bending to do it and you are better off to sneak up on the ideal setting by doing it a few times then going too far the first time.
My best guesstimation is you need it 1/16 to 1/8 of an inch lower, but you will have to determine this yourself.
Judging by the symptoms you described, you still have a fuel delivery problem.
All indications point to too much fuel, a rich mixture.
What color is the spark plug?
White to light tan = too lean, not enough fuel.
Medium tan to dark brown = perfect.
Black = too rich.
The ideal color is the color of milk chocolate.
My next guess would be that the fuel level is set too high in the float bowl.
You can easily adjust this by carefully bending the two arms on the float/ valve fork
down, away from the carburetor body, just a teeny bit; equal on both sides as best as you can. It does not take much bending to do it and you are better off to sneak up on the ideal setting by doing it a few times then going too far the first time.
My best guesstimation is you need it 1/16 to 1/8 of an inch lower, but you will have to determine this yourself.
To post pictures best try resizing them smaller using a photo program, if you have one- I use 1000 on the long side of the photo- the "manage attachments" function next to the smiling face on the "advanced" toobar works great.
The petcocks on both the tank and carb are meant to be only gates and not fuel regulators, and technically should be open during operation. I did however find better performance closing the tank petcock slightly closed, at least during break-in- I think my oil mixture was lean until it built up- try a more oily mixture at first- usually you'll just get excessive smoke that way, while you get dropoff and blown motor with too lean.
It sounds like you have the newer NTS 66 carb if the petcock is also on the carb- it should work well, but steadily- I got great results after typical fall-off performance at higher revs when I put a billet intake on- it's only about 15 bucks but a little tricky to install and frame clearance may be a problem.
that's my best advice for now- a little more oily, and maybe try the petcock adjustment a little during breakin-
The petcocks on both the tank and carb are meant to be only gates and not fuel regulators, and technically should be open during operation. I did however find better performance closing the tank petcock slightly closed, at least during break-in- I think my oil mixture was lean until it built up- try a more oily mixture at first- usually you'll just get excessive smoke that way, while you get dropoff and blown motor with too lean.
It sounds like you have the newer NTS 66 carb if the petcock is also on the carb- it should work well, but steadily- I got great results after typical fall-off performance at higher revs when I put a billet intake on- it's only about 15 bucks but a little tricky to install and frame clearance may be a problem.
that's my best advice for now- a little more oily, and maybe try the petcock adjustment a little during breakin-
