It's emissions time again.
Which means Rocinante failed emissions again.
Even with a quart of 91% rubbing alcohol in his belly.

A couple days after the new engine went in, I attempted to adjust a high idle on the side of the road, in a hurry, with my lunch sitting in the passenger seat. I grabbed my Swiss Army Knife, popped the hood, and turned the idle speed adjustment screw. Nothing happened. I turned it some more. Nothing happened. I turned it back somewhere near where it was originally and turned a different screw. Shti. I need to put things back the way they were and just break the throttle cable bracket loose to release tension on the cable tonight when I get home.

Rocinante failed on HC and CO. Fine on NO. I suspect I've messed up the mixture or enrichment. Hopeing someone here can say something like, "Turn the enrichment screw clockwise to lean it out, counter-clockwise to richen things up." Is that a pipe dream?

Here's some pictures of the area and screws.





And, while we're at it, I wonder if adjusting the dashpot to slap shut quicker might fix the stupid annoying run-on condition. Anything I can do here, screw-wise?



Fingers crossed.

SAS 1 and 2 - Not not touch SAS2. SAS 1 adjusts idle speed. (I think I have those right - check the fsm
Dash pot - this is for raising the idle speed for a/c and maybe when cold. No effect on emissions.
Mixture screw - it's under a protective anti-tamper cover to keep people like you from fooling with it. You have to pry out the press fit cover, or follow the fsm directions and pull the carb, drill a hole, and drive it out - The idle mixture adjustment is CW for leaning and CCW to richen. The basic method is to screw it in or out to maximize idle speed, reset idle speed with SAS screw, readjust mixture screw for highest speed, reset idle speed again, repeat as necessary so the highest idle speed is the spec idle speed.

I suspect, as I recall I did before, that you have a bad cat, or a fuel leak into the manifold. Post the test numbers and I'll have a better idea. The most common fuel leak is a hung or misadjusted float or a torn primary or secondary accel pump diaphragm.

While we're at it, anybody have any suggestions for getting the three main sections of a Mikuni carburetor apart once you have it stripped of all the other components? The one I'm working on doesn't want to split and I fear cracking the plastic center section.

Brian, both of the Mikunis currently sitting on my dining room table have the mixture screw uncovered/drilled out for access. My suggestion would be to turn it in all the way, counting how far it turns until it stops and RECORD that number somewhere. Just so's you can return it to there, if need be.

John B.

JBFP, never taken a Mikuni apart, wish I could help. (Been thinking about tearing this one down for a rebuild over the winter, though.)

I'll have to check the enrichment screw status later tonight. Maybe it's still intact?

Eddie, I appreciate your insights. Here's the test details:

HC = 4.26 (limit 3.00)
CO = 26.97 (limit is 25.00)
NOX = 2.44 (limit is 4.50)

Again, full tank of regular with a quart of 91% rubbing alcohol.

Truck passed smog less than six months ago with the same carb and settings. "Only" thing different this test is engine. :P

I just tore mine apart for a rebuild and I had this issue too. Did you get the screw that comes up through the throttle body? (That's what I missed.) You can try to gently wedge a knife in between the main parts and just work your way around till it pops.

On a side note, the screws holding it all together were barely tight and the gaskets were completely soaked in gas. Think I at least fixed that problem.

And fasteddy, thanks for your input. I'll have to keep that in mind once I can figure out why my Raider is acting like the battery is dead. I installed the rebuilt carb, went to start it, and got nothing. Same result after switching out the battery for a new one.