Low power under load

[JPP]

So I am in test ride mode.  The engin runs smooth under idle.  I can reeve it up  to high RPM.  I put it in gear and I throttle down and the response is not very impressive.  I do get some sputter.  I dont get any of this at idle and high throttle.  So what have I not tuned correctly?  Clutch and pressure plate are new, drive shaft and rear all good, transmission rebuilt three speed no issues.  HELP.

[Don Coatney]

Have you done a compression test to check the general health of your engine?

[Reg Evans]

Maybe your vacuum advance is not working.

[MBF]

Has the carburator ever been rebuilt?  Have you checked for vacuum leaks?   Last weekend I started my big old John Deere that had been sitting it the garage for about 6 mos.  It bucked, backfired and ran like crap-we couldn't figure out why-it ran so good last year.   Drained that gastank and put in fresh gas, ran fine.   I've been careful to use non-ethanol whenever possible on this old stuff, and use a marine stabilizer too.   Today's gas doesn't last long in storage.  Just something else to check for