to re-jet or not to re-jet

[Guest]

So I have gotten my 82gs1100gz running and fixed the head gasket and valve cover leaks, now I have to decided weather it is worth re-jetting the carbs. I removed the stock exhaust, and currently have a MAC 4 to 2 ordered. The only thing that I can see that changes is it doesn't have the h-pipe, and it may flow a little more than stock. Is it really necessary to re-jet? If so how big of a step up do I have to make to the mains and/or the pilots? MAC doesn't seem care one way or the other,at least that's the general feeling I got from the person on the phone.

[hampshirehog]

You won't have to change your jets just with that pipe. You might - note might - gain a bit by turning your mixture screws out a tad but that's all.

[hjfisk]

If it's piped rejet it or you may have a lean condition and you will be doing the head again or worse pistons. You could start by doing some plug chops and reading the plugs but I would dare guess you could jump at least 2 jet sizes out of the gate

[adam]

So re-jetting a couple sizes up? I have always done the motor work, however this is the first time I would really be changing anything on the carbs myself. The guy I used to have to them for me isn't around anymore. So could anyone elaborate on sizing up a couple of jet sizes, and does it mean changing the pilots and mains or just one of them. I have been looking at kits and the kits all come with needles, mains, pilots and different air jets. Do I need to change all of this? I am using the stock air box and filter so will that make a difference?

[tkent02]

Is it running lean?
If so which circuits are lean?
How lean? If you don't know you have some learning to do. We can't tell from here.
Do you want the engine to run perfectly or just good enough to ride until something expensive burns up?

[adam]

It runs fine as long as the stock pipes are on but I already ordered the MAC exhaust. The stock pipes are starting to get heavily pitted and I figured it was a good reason to replace them. I was just wondering what I need to do to the carbs. Another buddy of mine that rides a heavily modified kz1000 said I would have to re-jet. I have always been the heavy lifter and motor re-builder out of my group of friends. My buddy Mike has always been the one to do the carb work, but he has decided to become a trucker and is hardly ever around any more. So I am trying to expand my knowledge a little. I am more of a hands on learner, haven't been able to learn much from books. I was just looking for a place to start seeing as I don't really know much about tuning the carbs. After reading a few posts though, I am getting a feeling that I have a long road ahead of me.

[tkent02]

Not so long. At least the carbs pop right off in a couple minutes on the 1100G. Very easy. I'd probably go with slightly bigger main jets for starters. Maybe a size or two. Probably won't take much change with the stock intake, might not take any at all, but better to start rich and work your way lean than to start lean and do some damage.

[7981GS]

The Mac 4-into-2 pipes are not nearly as restrictive as stock pipes.
Go up at least one if not two main jet sizes.

Eric