[Darrie]

Plagarised from the OORacing site ... a tuning guide that may help:

Carb jetting at the bottom end of the range

In general, a FOUR stroke carb has an Air Screw adjustment - which will be on the manifold side of the carb slide.
Most of the time, the air screw is set about 1-1/2 turns out from fully seated - this is a good base line starting point.
At first, adjust the Air Screw in 1/2 turn increments so you can see the difference. Then start being more finite by making 1/4 turn adjustments. You'll eventually get to where you only need to make adjustments in 1/8 turn increments.
Get your ride idling in neutral (warm it up fully first)
Quickly nail the throttle, going from idle to wide open in a smooth manner, but quick manner.
Just stabbing the throttle as fast as you can may cause enough disruption in the flow of the intake that the engine can't keep up - eventually, when the carb's tuned correctly, you should be able to nail it and have the engine react correctly. You'll see how this works as you tune the carb.
What does the engine do? Does it hesitate and then rev up? As it comes back down to idle, does it seem to hang at a higher idle for a minute and then settle down to normal idle?
If it does this you're too lean on the Air Screw adjustment. You need to richen it up by turning the Air Screw IN 1/2 turn and then repeat the test. Adjust as necessary, repeating the test until you have a nice response.
Or
Does it sound like it bogs a bit? As it comes back down to idle, does it seem to drop to a low idle (or even die) and then come back to normal? If it does this, it's Too Rich. Turn the Air Screw out 1/2 turn. Adjust as necessary, repeating the test until you have a nice response

 

[Suzukibike12]

It sounds like you've got yourself an air leak. Spray the carb to manifold and the manifold to head. Like someone else said on here, get the spray nozzle so you can be more accurate with it. If you are looking to seal it up than just tighten it on there like normal and run a bead all around the edge where it meets the head. If that doesn't work than it is your carb. I wouldn't recommend using high temp silicone on the carb to manifold.

 

[mfw]

I made my own gaskets and put them on every connection. Still hanging throttle. So, I am going to re adjust the card to factory specs. My carb only has 1 adjustment screw. The other just looks like a brass plate.

. Anyone in LAs Vegas that would be willing to look at it for me? Thanks
\
MFW

 

[Darrie]

I believe that brass thingy is actually a "tamper proof" airscrew version that has only a slightly slotted edge - honda has the adjustment tool but costs !!!. I've seen advice to back it out with a pair of tweezers and then cut a slot in it to use a screwdriver for adjustments, or even making a tool by pulling an eraser out of a pencil and flattening one side of the metal piece to replicate the tool and using that. Not sure how successful either is.

Alternately take the carb to a honda dealer, get them to back it out and install an earlier model airscrew. Then you can tune more easily.
Hope this helps, Darrie

 

[mfw]

Well, i finally dug back into this problem. I back out the non adjustable screw and cleaned everything really well and put it back in. Still have the problem. Bought a new carb and put it on. Problem fixed. Should have just bought one in the first place.

MFW

 

[wazzajohno]

New Carb

Well, i finally dug back into this problem. I back out the non adjustable screw and cleaned everything really well and put it back in. Still have the problem. Bought a new carb and put it on. Problem fixed. Should have just bought one in the first place.

MFW

Where did you get the new carb? I am having the same trouble and there are some $25-$40 carbs on ebay. Would this save me some headaches or create new ones?

 

[CJK]

Well, i finally dug back into this problem. I back out the non adjustable screw and cleaned everything really well and put it back in. Still have the problem. Bought a new carb and put it on. Problem fixed. Should have just bought one in the first place.

MFW

I am having the same issue. The carb cleaner makes the engine rev higher. Should I start with carb or remove the head and change the gaskets?

 

[PocketBikeRacingTsmmr]

The raise in idle would suggest an air leak ..
Start by changing the O ring between the intake manifold and carburetor itself..put a light coat of grease on the o ring when installing.
If that doesn't fix it then go to the Gasket between the manifold and head

 

[Kenton Gates]

So, I am new to the Crf bikes. I picked up a 2006 50 CRF and I noticed that its slow to return to idle after letting off the throttle. I am use to the two adjustment screws on the CT 70 carbs. This only has one. Also, I completely pulled apart the carb and cleaned the one jet using the tool. Not sure if there is another adjustment or what the issue is.... Thanks for any help.

MFW

For me personally I pulled the idle screw all the way out and cleaned the gunk off the tip of the screw and sprayed carb cleaner in the whole then it idled down great

 

[tmas]

For me personally I pulled the idle screw all the way out and cleaned the gunk off the tip of the screw and sprayed carb cleaner in the whole then it idled down great

Thread is from 2014. 7 years ago.
tmas