Running rich

How do I adjust the carbs to get it to run a little more lean?

 

First we need to ask why you think it is running rich. Is it running rich at idle or at highway speeds? Have you done anything with the carbs that could have lead to this. Once we cover this ground we'll be able to pin point where you need to go.

 

Runs rich at Idle,and at lower speeds, I am not entirely sure about highways speeds, I am rather inexperienced.

 

I would check that your choke is completely off before diving into resetting the carbs. The choke on these bikes are actually enrichment circuits. They add fuel rather than restricting air. Look at the front of your carbs and pull the choke switch out. You will see the choke plungers rise. Then turn the choke off and push the choke plungers down to check for any movement and check the cable for slack.
Have you replaced your air filter lately? A dirty one will richen your mixture. Check the simple first we always say!
Is the reason you think it is running rich because you have pulled the sparkplugs and found them black?

 

were they black sooty or black wet?

 

They were black and wet, also, the bike is letting go a significant amount of white smoke when running, any ideas?

 

This is not a MaximX is it?

White smoke could be coolant getting into the combustion chamber.

How many turns open are the mixture screws? If they aren't more than 3 turns open then it sounds like possibly float level settings!?
Also if these carbs have just been built were the jets changed out?
Have there been any mods to the exhaust system?

 

It is not a maxim x, it is a xj650jmaxim, carbs have not been touched recently, does backing the mixture screws out make it run mor air or more fuel?

 

Backing them out enrichens the mixture (more fuel)

 

at the same time screwing them in leans them out too.
If you have changed or have reason to suspect that the mixture screws are out of adjustment, you need a Colortune to do this correctly.
(unless you are really experienced at setting multi-carb mixture)

Let us know how this helps

Good Luck

 

Funny how timely new threads can be. My '82 750 Maxim, which I've had for all of a few months now, has recently started running REALLY rich and kind of rough at low speeds. Choke plungers appear to be working properly. It had been running alomost flawlesly until last week, and still runs great at high RPM. Plugs on cyls 1 and 2 are carbon fouled, but 3 and 4 seem perfect. Seems odd for this to have started so suddenly and only on the left side.

My local bike shop guru suggested the possibility that the carbs may have been re jetted by a PO when aftermarket slip ons were installed and it's just way too much in the colder temps. This doesn't explain the fouling on only 2 plugs, though.

Also somewhat related to this problem: I need a new airbox cover. The one I have just broke its last attachment point (front), the rear screwholes have been missing from the start. As a temporary measure, I wired the filter itself to the intake box to insure that it is still filtering. Tried to repair the lid but the glue let go. It may well be the wrong part for all I know. Anyone have a stock cover lying around?

I'll try to get in touch with the PO and see if jetting was messed with during his ownership, but is there a way to see if an aftermarket jet kit was put in just by looking?

Which mixture screw(s) affect this rpm range?

THanks for any suggestions,

Tim

 

You and the OP need to pull your carbs off and spend an evening (or more) wandering through the carbs and cleaning them. Set the float levels when you're done.

By any chance is your bike parked on its' sidestand most of the time?. That would explain the #1 & #2 cylinders misbehaving, as the fuel will run to the left/downhill carbs when parked. Any crud in the fuel system will go where gravity tells it to.

 

Ruh Roh! I'm lazy about using the center stand...that may explain part of this. Carbs were supposedly cleaned last spring, and by the way the bike ran when I got it, I had no reason to doubt this, but it sure needs attention now. Oh well...

 

With the plugs being black and wet one or both things are true. There is either too much fuel or too little spark. So long as the wettness is not oil. When carbs get dirty they tend to push carbs to be lean due to a restricted fuel passage. Being that the cylinders do not share a coil I would leave that at a low priority. Changing the plugs would be a good idea followed by a check of the resistance on the plug caps. I would then check the fuel levels in those two carbs. I high float level would easily cause the symptoms and is to be suspected since the float valves deteriorate over time.

 

Sorta related: I could use a new airbox cover. The one I have has a broken eyelit at the front and I've temporarily rigged a safety wire to hold the filter tightly against the front, but the air box cover has no other attachment points...I suspect it isn't the correct one for my bike and it's been modified as well. Does anyone know of or have a stock, correct airbox cover for an 82 XJ 750J? Thanks.