Bicycle Tutor

Hi - I have a Cannondale CAD2 Road bike and am having problems with the rear wheel. All gears fall in lovely other than the smallest cog on the rear I have tried to adjust the alignment to no avail. Thing is I have only just built the bike from scratch could the smallest cog be out of alignment to make it jump? It just doesn't seem that the chain falls right into the teeth?
Thanks

If everything is new then you really should have no serious problems. Have you got the "Hi" limit screw on the dérailleur set properly?
Make sure the dérailleur is being allowed to move to its limit. Also check alignment of the dérailleur. - Vertical and and not twisted.
Check you don't have a stiff chain link. Wind the chain backwards and if the dérailleur "jumps" then look to see what's causing it.
By jumping, the chain could be catching the next gear and trying to change on its own.

Due to slow Internet server I posted the same as above so please ignore this. Pity I can't delete it under editing.

Thanks for your reply tried both of the above still the same problem. The cassette is still jumping. The cassette isn't new and was put on the wheel by an elderly gent. Could the last cog have not been put on right? It seems to be out of sink.

It is possible you have a missing spacer or something. See if you can measure the gap between the cogs to make sure the last one is the same.
Is it just not shifting well, or is is jumping when you put force on it? If the latter, then it might be the cassette/chain are worn and need replacing.