Motor missing- solution?

[sailor202]

79 xs1100 special -- was rebuilt by high school tech shop. Since then have spent tons on trying to find out what is wrong with it. Starts fine, idles fine 0-60 fine, 60-70 coughs and sputters, 70-140 fine. Coughs and sputters both up and down. Have tried new igniter,coil,carbs, am at a loss, need some suggestions. Am looking for a motor to replace it for now, if you've got one for sale, let me know. Glen

[skids]

I would check the pickup coil wires under the left engine cover. Remove the cover, pull off the vacuum hose that goes from the ignition cover to the No 2 carb and plug the carb nipply with a piece of hose and a golf tee. Start the bike. Pull the wires that goe to the pickup coils and look for "hour-glassing" which indicates a break in the conductors inside. If there is a bad wire, it will probably kill the engine. There are many tech tips here about repairing the wires...use the search option.

If the wires are OK, look for problems with the exhaust system, like cracks, crapped-out baffles, or maybe they didn't use crush gaskets at the head pipes.

If all of the above is good and the carbs are CLEAN, then you can mess with the diaphragm needle settings.

[79XS11F]

How can your motor be missing .. it's way to heavy for someone to run off with

[79XS11F]

as per skids .. check out the pick-ups and if they are OK check coils and mid range carb operation.
Rob

[petejw]

as above,

but does it do it consistently,
or when its only warmed up or when its cold?

does it do it at cruise or while accelerating up or
down thru that speed range?

i wouldnt b changing the motor out just yet,
have u got good compression, the tranny in good nic,
other than the trouble ur having is anything else occurring?