Speed carb idles high

[copmagnet80cc]

So i bought me a speed carb for my motorbike and everything fine for awhile. Im able to get it starrtedfairly easily, but when im letting it warm up and i rev up the engine it wont stop idling high and i have to adjust the idle screw to make it die down. but then itll bog down too much and have to screw it back in..im just confused if this is an air leak, a kink in my throttle line or what. I've done a little reseach but cant find a solid answer for my motor.

 

[maniac57]

First, take off the air filter a look into the carb to make sure the slide is not hanging up.
If it looks okay, I'd be looking for an air leak.

 

[MotorBicycleRacing]

So i bought me a speed carb for my motorbike and everything fine for awhile. Im able to get it starrtedfairly easily, but when im letting it warm up and i rev up the engine it wont stop idling high and i have to adjust the idle screw to make it die down.

How are you sealing the Carb on the intake?
That is where they tend to have air leaks that cause your symptoms.

 

[2door]

Air (vacuum) leak or the throttle slide not returning to the idle position due to a cable issue or a warped carburetor body.
Tightening the top cap too tight can cause the slide to not move smoothly or hang. Finger tighten that cap. No tools.

Tom

 

[copmagnet80cc]

How are you sealing the Carb on the intake?
That is where they tend to have air leaks that cause your symptoms.[/QUOT

I dont use anything to seal my carb..i havent had this problem with the stock NT carb but what size of rubber gasket should i use?

 

[MotorBicycleRacing]

Just use a 3/4" OD O ring to seal that fits into the Carb throat.

 

[2door]

I'm not a big 'O' ring fan. They rely on the carb being pressed tightly against them for a good seal. A gasoline compatible sealant is my choice. Read the label of any product you are considering. Most silicone based sealers are not gasoline resistant.
SealAll is a good one.

Rough up the intake manifold to give the sealant a good 'bite' and clean the carb throat before sealing. The chrome on the steel manifolds doesn't give a good sealing surface unless it has been sanded. Make sure the slots in the carb are filled with whatever sealer you choose.

Tom

 

[Mean.motor]

Ok so i take it this is the NT speed carb. The red air filter cap one...

My story short..
Had two identical bikes with stock carbs, changed one out to speed carb , ran like **** for about 2 or 3 weeks, then started kicking the other bikes ass.
Bought speed carb for other bike, bike ran like **** for a month and then last night, the other bike couldnt keep up with me. lol
Its just one of those things that your engine will like right away or will take some time getting used too in my opinion. I dont have air leaks.
One thing i did notice is when your throttling off the start and its bogging... pull your choke up just to the point where you feel your engine grab all the power... then as you accelerate put the choke back down when reaching top speed... i do this when racing my bro and i rip by him and he doesnt know why lol. you might have to do this for about ten mins... all depends on the weather right now.. anyways whether its right or wrong, thats my two cents.

 

[Mean.motor]

Ok so i take it this is the NT speed carb. The red air filter cap one...

My story short..
Had two identical bikes with stock carbs, changed one out to speed carb , ran like **** for about 2 or 3 weeks, then started kicking the other bikes ass.
Bought speed carb for other bike, bike ran like **** for a month and then last night, the other bike couldnt keep up with me. lol.


Its just one of those things that your engine will like right away or will take some time getting used too in my opinion. I dont have air leaks.
One thing i did notice is when your throttling off the start and its bogging... pull your choke up just to the point where you feel your engine grab all the power... then as you accelerate put the choke back down when reaching top speed... i do this when racing my bro and i rip by him and he doesnt know why lol. you might have to do this for about ten mins... all depends on the weather right now.. anyways whether its right or wrong, thats my two cents.

So i just re-read this post. Kinda chimed in so nonsense that doesnt help you out COPMAGNET
Sorry about that. Me and my brother both now have the banana pipes and the nt speed carbs, we do notice the same thing. Whether it be adjusting the idle screw, its very freakin sensitive to adjustments itll rev super high with just the littlest adjustment, or bog out if adjusted the littlest bit looser. I have found once the bike is warmed up (10 mins or so of riding) try adjusting it with the idle screw to a point of where it sounds just a bit faster then a good idle, then adjust the cable on the top of the carb or the bottom of your throttle handle to get a more dialed in approach. But once you get it good.. leave it and the next time you start your bike when its cold...its probably gunna rev high till it gets warmed up. I think its due to the banana pipe.. the backpressure in the upstroke causing it to rev high till she gets warm. It will settle down again. But if you keep tampering with your idle screw and cable tensions.. its an issue you cant beat.