Heater sputters and spits

idle air control valve probably not working to supply enough air for idle speed during start up

Most likely, the carb is misadjusted or needs cleaning. This is a job for a licensed, respected Harley mechanic, as an amateur would most likely make it far worse. Should not be costly.

Put a spike air filter on my 06 honda shadow spirit 750cc and now it spits and sputters won't go past 35 with out spitting and sputtering

Not sure to be honest as to what the cause could be ,i would suspect a coil pack problem or even the ignition module if it has one but i think it may be built into the ECU ,although you havent stated if this is a diesel engined vehicle so having more information would help a great deal

Sounds like plugged catalytic converter, Disconnect exhaust in front of Cat. and see what happens. Check to see if you are losing fluid from radiator.

If it is old enough to have points then I would check them and make shure they are clean and gapped at .020. if that is noth the problem then it sounds like a fuel issue. Either a weak pump or a dirty carb.

I have the same problem on my 95 grand cherokee laredo. Sometimes it starts out fine and after about 10 miles it starts spitting and sputtering. Then after a while it seems to clean out and run fine again for a little while. Then other times it starts out spitting and sputtering at the begining. I changed the fuel filter and that was not it. It is a 4.0L 6cyc. Any Ideas?

Thanks,
Broken Arrow, OK

mine did the same, I found out that the high speed jet was clogged, I pulled the fuel line off the filtor(going to the carb), stuck the line into a mixture of half gas half carb cleaner, I fanned it up and in 2 or 3 minutes it started running well, hope this helps.

when the last time u did a tune up?

do a compression test