re-jetting 750 twin? new exhaust

Just purchased a kerker header, and muffler 2 into 1 no idea if muffler is baffled or straight, currently I am running the stock 2 into 2. Bike runs excellent starts up at any temp. Will I need to re-jet?

I doubt that rejetting will be needed, but keep an eye on the spark plugs to tell for sure.
I have installed two into one exhaust on a 79 and a 80 750 twin while keeping the stock airbox and neither one required rejetting.

i searched for an answer and this may have somthing to do with it, i rebuilt these carbs, i was able to use the original jets and stuff, i installed new piston rings, and it runs really good, starts good, idles good, but won't rev over 4000, then it starts crappin' out, is this a problem? i'm just riding this bike around the pasture, when the rings break-in will it get better? not sure....

What do you mean by "crappin out"? Does it have no power, or start missing?

it starts missing like it's starving for gas, i was told to set the floats at 22mm but i left them at 20mm because they were both set the same, and that way originally. oh, and i have a mac 2-2 exhaust its pretty loud, so i think its pretty straight, don't know if this is harming anything

I have had good luck setting the fuel level at 25mm, I know that's not the way the manual says to set it, but it has worked for me.

Just to clarify, that is 25mm from the carb bowl gasket to the top of the float when the carb is held upside down with the float bowl removed. If you are setting them at 20mm the same way, then it seems to me that it should be running pretty rich and making the spark plugs black. Have you checked the plugs?

by the way, thanks for your help
that's the way i'm setting the floats, the plugs are darkening but no carbon build up. i would say they look good, it seems like i would really be starving for gas at 25mm, so i guess that's not my problem, i'm just not sure where to look right now

Have you gone through the ignition system to eliminate it as a possibility? Point gap, timing advancer, ignition timing, coil resistance (primary and secondary), plug wires, and plug caps?
Does it do it in all gears? If so, then it's probably the ignition, carb problems are usually load related and not rpm.

i see .3 - .4mm for the breaker point gap, but i haven't found how to check the coil, (resistance values)i can check it this weekend and get back here

Less than 4 ohms on the primary side (the 12 volt wire and the wire going to the points) and 16k-20k on the secondary side (between the two spark plug wires).
This is assuming you have a single coil with two spark plug wires, I think the 76 and 77 models had dual coils.
Check the plug caps separately, they should have 0-5k depending on whether or not they are resister type.

I just read your sig and it says you have a 77, the 77 I have had dual coils on it, I have no idea if they were stock or not, I got the bike from a junkyard.

If you have dual coils, check the resistance between each spark plug wire and the metal case of the coil, then check it between the spark plug wire and the points wire, and let me know what the readings are.

I just realized this is a total thread hijack, the original poster has never posted again

Post edited by: steell, at: 2006/06/01 03:46