Hello,

There are some questions to answer in order to pinpoint the problem.

When you say " it jumps the high gears" do you mean the gears slip when
you pedal or do you mean it is jumping across more than one gear at a
time when you change?

Are you using a new chain and new sprocket, old chain and sprocket or
some other combination?

If you mean it slips when you pedal, this is most often caused by using
non matched chain and sprocket. For example a new chain on an old
sprocket (by sprocket I mean cassette or free wheel). Using different
bits of chain from various sources can also be a problem. A given chain
and sprocket wear together and if too worn won't work when one or the
other is changed. I make it a point to use a new sprocket and chain on
all my builds.

What about your cable outers? do you have proper gear cable outers? They
have londitudinal wires not the spiral wrap style. They are imperative
with index shifting.

If it is jumping across gears this sounds like an adjustment problem.
Perhaps the deraileur is not lined up properly. Sight down the bike from
the rear. The deraileur should be square with the chain and also
vertically. You may need to adjust by bending the mount carefully. If it
is square then try placing the chain on the middle chain ring and the
smallest sprocket. Wind the adjuster in all the way. Now change to the
next cog. While turning the pedals by hand wind the adjuster barrel out
until the gear just changes then go about 1/2 turn more. This should put
you in the ballpark. You may need to trim slightly one way or the other
to get it exact.

Another thought. Are your shifters and deraileur matched. For example
Shimano SiS deraileurs don't work well with twist shifters.

I had some problems on my TE which I put down to frame flex and
mismatches. My total cure was to change to friction shifters. That
solved my problem. They are not as finicky as indexed shifters where
everything has to be just right.

John Lewis