I have a 1999 sportster 1200 sport it has sampson exh. no baffles and a pro hypercharger on it. The hypercharger has the k and n filter and the carb has been drilled out. My problem is I can't seem to go over 3000 rpms or crack the thottle more than 1/4 of a turn. The bike acts like it dies slows right down but if I let off of the gas it comes right back. I put sea foam in the gas tank thinking it might need cleaning because I don't know how long it sat before I got it and still no better.

 

Check the plugs first thing, I'm sure it wasn't always running like this, and did you just do all the Mods or was it done when you got it?

 

I bought the bike like it is now

 

Did it just start this recently?

 

yes about 2 weeks ago. I just took all 4 spark plugs out and they look fine old but have a good color to them

 

Sounds like a fuel delivery problem, but I aint no expert,,,,yetLots of times when that happens, on a Cage, the fuel filter is getting clogged upor the fuel pump is going bad, when the load is applied it can't keep up with the demand for more fuel, when ya let off, it idles fine because ample fuel is being delivered for it to idle. If ya sit still and rev it up, does it rev up OK? Or does it rev up in neutral? Fouled plugs usualy result in popping and back firing, but that is the easiest thing to check and/or change. Sounds more like a fuel delivery problem.

 

revs fine when sitting still or in neutral. Where is the filter located

 

IN the tank.[:@]If yours is the same as later models it is located in the tank,above the Fuel petcock. Itis entirely possibe that this is a float problem in the Carb, but I would check the Filter/screen first.

 

I replaced all 4 spark plugs still did the same thing then I took off the float bowl and ta da there was a peice of clear silicone in the jet and also in the bottom of the bowl. I put it back together and just got back from doing 80mph in about 15 seconds so I would say it is fixed. Thanks for everything hope to talk to you again.

 

what are the stock jet sizes