Carb help needed.

[70ATC90]

Still having troubles with the 90. Bought a new carb from DrATV that said it was jetted for a 90, but it still does the same thing. Bogges and dies with any throttle, also still running really rich. I even bolted the stock exhaust back on and it didn't help. What else can I do? Do I need a different size pilot screw? Is this a sign of a serious engine problem? Should I just take it to the honda shop and have a professional look at it?:confused: :confused: :confused:

[SYKO]

valves may need to be adjusted, I know alot of times that can fix all kinds of problems

[RedRider_AK]

Plug chop? Why did you "put the stock exhaust back on"? What did you have on there before?

[70ATC90]

Plug chop? Why did you "put the stock exhaust back on"? What did you have on there before?

Cobra with a leak. *Edited**Edited**Edited**Edited* never done this on a 4 stroke, how do I know when Its at the top of its compression stroke? And for those of you who know, where is the mark on the side cover that I line the "T" up with on the rotor?

[super90]

It could be valves, sticking float, or just jetted wrong. Try going down a couple jet sizes or drilling them, though I never got how people did that. And are you talking about the cam as in rotor?

[RedRider_AK]

Hey man. I said I'd try to help out later, here I am.

If it runs at all, I don't think it's jumped time, so don't worry about the valvetrain right now. If you're having trouble starting it, check the plug. If it's really soaked in gas, you are definetely running too rich, and possibly flooding the intake. Good idea would be to check out the float, all those carb parts, make sure they're sealing well. Be sure the float pivot pin is straight and maybe even grease it to help it move more smoothly. My ATC110 had a problem with flooding out because someone had hacked up the pin and that kept the needle valve from closing.

If it's running rich, then putting the stock pipe wouldn't help much, if at all, because the Cobra is a much more "straight-thru" design, which means it flows better than stock. More flow = leaner running, so if you're running rich, you want as free of a pipe as you can get. Also, try running it without the air filter, just to see if it works a little better. Just don't ride it like that! :lol:

If none of this solves any problems, we will get more in-depth into your motor, but it's easier to try the simple stuff first.

[70ATC90]

Okay. I adjusted the valves, the idle seemed to get faster. But stronger for sure. I ran it without an air filter and when I pulled the plug it was still blackened with carbon. Looked at the float and it was moving freely. Put a much smaller main jet in (size 70). None of this is helping, it still doesn't want to stay running and dies when I give it gas. What else can I try?

[4cylinders]

hey, if it has points, check them out.

[RedRider_AK]

Yeah, the ATC 90 has points. I'd also check them, just to be sure. If they're not timed right or pitted, that could cause poor running.

[70ATC90]

Okay, the valve clearance on a 90 is .005 right? Does anyone know they clearance for the points?

[jason 32]

do a compression check-
im bettin it needs new rings-
the stock exhaust will clog it up more ,and will run richer-from lack of air flow
-check the timing on the stater side, not sure if there is a advance on the stater-,check the points---,and the mechanical advance if applicable--

[70ATC90]

do a compression check-
im bettin it needs new rings-
the stock exhaust will clog it up more ,and will run richer-from lack of air flow
-check the timing on the stater side, not sure if there is a advance on the stater-,check the points---,and the mechanical advance if applicable--

Compression is strong. I think i've narrowed it down to the carb just being jetted wrong. Heres the part that puzzles me, I have a K&N cone filter on it in the place of the stock air box, shouldn't that make it run leaner?? Anyway, to make it run leaner I need a smaller pilot jet right?

[3WheelsOn2]

Yeah, Better flow from the air filter makes it run leaner.

[RedRider_AK]

Your ports (intake and exhaust) and valves might not be flowing very well, causing an overall rich running condition, even with the K&N Filter and Cobra pipe. I'd try to see if they're really carbonized and clean them up. It might just be that the ATC 90 didn't need a lot of gas to work correctly, and the carb is jetted for "modern" 90cc engines that rev higher and put out more power.

[70ATC90]

Your ports (intake and exhaust) and valves might not be flowing very well, causing an overall rich running condition, even with the K&N Filter and Cobra pipe. I'd try to see if they're really carbonized and clean them up. It might just be that the ATC 90 didn't need a lot of gas to work correctly, and the carb is jetted for "modern" 90cc engines that rev higher and put out more power.

Yeah I thought that too, but even when I had the Cobra pipe on it, it was still running just as rich. I have an intake for an ATC 110 I'm gonna bolt on and see if it helps. I also have a pilot jet for an ATC 70 on the way. Lets hope for the best.

[70ATC90]

But heres another question, does raising and lowering the position of the pilot jet do anything?

[RedRider_AK]

No, I believe it doesn't. The Pilot jet doesn't have a needle that operates it, thus it wouldn't make a difference. Also, how are you going to "lower" the pilot jet itself, not screw it in all the way? I think it'll just vibrate out unless you actually tighten it up.

[70ATC90]

It has lots of threads on it and doesn't get loose until the last 3 or so. But you were right, i didn't do anything. The pilot jet for the 70 came today, i'll probably throw it in tonight and see what happens.

[70ATC90]

Okay nevermind, didn't do anything, couldn't even get it to run. Screw it, I'm just gonna take it to a small engine repair shop.