Help me figure out why my bike isn't running right.

[devinc]

Hey guys, I'm having a hard time getting my 98 running right.  It's a really long story so I'll start from the beginning. 

When I got it, it had a gutted factory pipe, an aftermarket foam filter, and had been rejetted.  I have no clue what size jets. Also as soon as a got it, I had the carbs professionally cleaned. It ran really great, it would cut out way up high in the rpm's here and there but not consistently.  The only issue was that the throttle wanted to hang a tad when I let off.  This can be quite scary when you blip the throttle before a curve.  It's definitely not the throttle cable, it's been lubed and checked a million times.  I assume it may be a vacuum leak but I just can;t figure it out.  I dug into the carbs recently and found out that those tiny little o-rings above the valve piston were missing and replaced them.  At the same time I did the 3 M3 washers on the needles while I was in there.  Put it back together and it ran really well, and didn't cut out in the higher rpm's at all. It definitely ran better but just like before, throttle hangs a little.

Today I took off the gutted factory exhaust and put on a random D&D pipe I got off Ebay.  It is about 20 inches long and not gutted.  After I got it put on I took it for a ride and it was definitely short on power.  It also cuts out in the higher rpm's pretty bad.  And as usual, throttle hangs. It sounds SWEET though!  The D&D is a gnarley sounding pipe. 

The spark plugs are black, but there's no buildup or signs that it's running really rich, just smooth and black.  I'm new to this carb business but I'm learning, I'm about to pull them off and check for anything weird.  I also want to rejet it while I'm in there.  I need jets that are going to work with a k&n lunchbox that I'm getting and the slightly-bigger-than-factory D&D pipe. 

Can you guys give me suggestions to what size jets I should buy?  I don't want to have to do this again so I'd like to get it right the first time.  I wish I knew what size jets I already have and it would make this easier.  I'm also looking for suggestions to why the throttle might be hanging....

[coll0412]

Hanging throttle means that its lean on the idle circuit, which means you need to just the idle screws out a bit. There is plenty of info in the wiki discussing this, but a good starting point is 2.5 turns out.

As far as it losing power, odds are its an issue with jetting. Again check out the wiki and see what other people have done, and in the end you may have a unique setup and may need to find what works the best for your setup.

[devinc]

Thanks a lot, I'm gonna try some new jets tomorrow and adjust the idle screws and will report back.

[bill14224]

I agree with coll's advice, and the black plugs are telling you your main jets are too big for that pipe.  Adding washers made it even richer.  You're heading in the wrong direction.

[devinc]

Ordered some 40 pilots and 147.5 mains as a well as a lunchbox today, so hopefully I'll make some progress this weekend.