Whats wrong!?

[qletsinger]

So i just replaced my cam gear, timing chain, guides and tensioner and when i started it, it would rev up until i turned off the key. I checked to make sure the throttle on the carb was not stuck open and it wasnt. I have no idea what it could be, any ideas?

 

[datzenmike]

Rev up is subjective. Like 7,000 RPM screaming, oil spraying out, rod through the block? Or 1,800- 2,200 RPM? as this is normal on a cold engine with the choke on.

 

 

Other than that look down the secondary barrel.. is the throttle plate closed?

[qletsinger]

Yes like it will rev up until it blows the rod out of the block, it is a little bit rough sounding as well. Yes the throttle plate is closed.

[datzenmike]

Well that's impossible, so look again. The primary and secondary throttle plates are down at the bottom of the carb close to the manifold. The primary is well below the choke plate.

 

Other than that look down the secondary barrel.. is the throttle plate closed?

 

One of these is open, Only has to be less that a 1/4" open in neutral to rev to the sky.

[qletsinger]

It turns out that was it! Thanks for getting back to me so quick, i really appreciate it! It was just barely open and i messed with the throttle linkage and it went right down. I also have another question i will post on here rather than starting a new topic... I had my carb rebuilt and i noticed that the air/fuel screw is just a plug and not adjustable. Can i somehow get it out and put in a screw so i can adjust it? Im running really rich and i hate watching my fuel guage go from full to empty in the blink of an eye!

[datsunaholic]

Rich at idle or rich when driving?  The air/fuel mix screw is only used at idle.  If it's rich when driving then something isn't right in the carb- wrong jets, parts missing, feedback system screwed up, choke stuck shut (or not electrically connected), etc.

[qletsinger]

Just at idle...choke isnt stuck shut, already checked that. Im just curious if you can drill out what is in there now and put in a screw?

[Tinman]

If you have the flush aluminum plug where the idle mix screw is, (factory) you can drill the plug out and the screw is recessed behind it.

You drill a hole in it at an angle and then use a tool to pry out the plug.  Do NOT just drill in straight.

 

I think it's even shown in the service manual.

[datzenmike]

Drill an 1/8" hole and screw a wood screw into the soft aluminum plug and pull out with pliers. These are set at the factory using an O₂ sensor and sealed. Can't see how it would change.

 

Anyway, warm the motor and turn the idle down slightly, if you can, so that changes are more noticeable. Turn mixture screw in and then out looking for a spot where the idle increases and smooths out. Usually about a two turn range with poor idling on either side. Set roughly in the middle and turn the idle down. Repeat by turning in (leaner) until the idle stumbles, then turn out (richer) until it stumbles. Adjust roughly in the middle between these. Again look for the fastest smooth idle and set there. Turn the idle speed down and repeat again as many times as needed until you cannot improve the idle quality. Idle mixture is now set.