carbs problems, plugs or no plugs

[vintagemcyclegu]

80 XS1100SG what would the symtom be if you were to run the engine with the plugs missing if it needed them, would it run exceptionally rich. My engine symtom, would rev fine, come down a little, run there for a bit maybe 5 or 6 seconds and than drop down to nothing and die. Looking at the plugs they are sootie as in running rich. I tryed 1.5 -2 turns out to 6-7 turns out with not much difference. What do you think. Also what are the three holes for in the stock air box one big center one and two smaller end ones. Bikes serial # 3J6-003960 only thing on the carbs is MIC mikuni KOGYO. Thanks.

[bikerphil]

If there is a crossover hole in between the main and pilot jet towers, you need the pilot jet rubber plugs. Also make sure the pilot jets are the correct type, some rebuild kits include the wrong type of pilot which will cause a rich condition. ours use the BS30/96 type as in the photo in this link.
http://www.mikesxs.net/products-39.html#products

The large center nipple on the airbox is for the crank case breather, the two smaller ones are only used for the 78-79 carbs.

[cywelchjr]

Not having the plug will not affect the idle in the least, but when you start to hit the mains in the least little bit it will flood out and bog down something terrible and will not run for anything, but will come right back down to idle and run fine at idle DAMHIK. The issue is that the idle jet is being fed properly, but the main jet is completely bypassed, and instead of the main venturi getting metered gas, it's gets as much gas as the vacuum of the venturi can suck up there, which is several times more than you can use. Look in where the idle jet is, if you need the rubber plug there will be a hole that goes at an angle towards the top of the carb and the main jet tower, and if you follow it it will come out just above the main jet. With the plug all the fuel for the idle jet comes through the main, which doesn't actually affect the idle jet, but means the main has to pass both the idle jet fuel AND the main jet fuel at speed (the idle jets work all the time to some extent, which is why you do them FIRST after setting the float height as they affect all throttle settings).

But, unless you have early 80 carbs you likely don't need them. However, the symptom could be caused by idle jets too big. If the idle screws can't kill the engine, the jets are probably too big, cause the idle screws can't shut off ALL the idle fuel, just a portion of it, and the jet has to get you into the ballpark to let the screw do it's job.

[DGXSER]

I was involved in working on one set of the 80 carbs with the crossover. Without the plugs they ran like total crap.