A tunable color-center laser and a molecular-beam electric-resonance optothermal spectrometer have been used to record the infrared spectra of the C-H stretching vibrations of HCCH-NH3, HCCD-NH3, NCH-NH3, and HCCCCH-NH3. The hydrogen-bonded C-H stretching vibrations of NCH-NH3, HCCH-NH3, and HCCCCH-NH3 are redshifted by 200.88126(30), 75.1042(38), and 127.4(1) cm(-1) from the respective free monomer modes. The non-hydrogen-bonded C-H stretches are less perturbed by complexation, being blueshifted by 0.2992(3) cm(-1) in HCCCCH-NH3 and redshifted by 1.179(1) cm(-1) in HCCD-NH3. Consistent with the much larger perturbation of the monomer vibration for the bonded C-H stretch, the B rotational constants increase by 1%-2% for the bonded C-H stretch excited NCH-NH3 and HCCH-NH3 complexes, but change by less than 0.1% for the nonbonded C-H stretches in HCCCCH-NH3 and HCCD-NH3. The decoupling of the two C-H stretches in HCCH-NH3 is not sufficient to allow the observation of the nonbonded C-H stretch in the complex, which correlates to the Raman-active symmetric C-H stretch of acetylene. Also, no spectra were observed for the weaker N-H stretching vibrations of the complexes, consistent with the very weak intensities of these modes in the monomer. The homogeneous linewidths of the transitions, assumed to be a measure of the vibrational predissociation rate, are approximately two orders of magnitude larger for the bonded C-H stretches than for the nonbonded C-H stretches. The similarity in homogeneous widths for the nonbonded C-H stretches in HCCD-NH3 and HCCCCH-NH3, of 7-12 MHz, suggests that the rate of vibrational energy flow along acetylene chains is only weakly dependent on chain length.