throttle responds, but is slow on the descend (when throttle is not engaged)

[davekat]

OK folks,

I've been working on my bike, and I'm having trouble with the throttle. When the idle is really low (below 1000), it revs, but it seems slow on the descent, as in it takes about a second and a half to go back down. When I rev up to 3000 rpm, if my idle is above 1000 rpm, it seems to stay between 3000-2500 rpm. I have to turn the idle screw to get her to drop, but she drops too much, and she just barely stays alive, so I have to readjust the idle screw again. HEre's what's been done so far before this.

1.) Cleaned the carbs thoroughly including removing and reseating the pilot screws to 2.5 turns. I at first thought maybe she was running lean, and redid the pilots to 2.5.
2.) Synced the carbs with both a home made water bench sync and then once the idle seemed low/proper, synced again with a syncpro quad sync. The pressure in all four chambers seems to be level.
3.) Replaced the fuel lines with new fuel lines
4.) Checked the seals of the carb to the engine block, solidly placed. Checked the seals of the carbs to the airbox, and I'm having trouble with carb #2 seating it, but it seems to be seated.
5.) All tubes to the airbox are connected, and during the carb sync, the third tube (at the end of the carbs), is sealed with plastic to maintain the vaccuum. As far as I can tell, well, I have no idea how to check for vaccuum leaks, but everything is seated.

I"m lost, as to why the throttle isn't properly responding. Also, my tachometer doesn't seem to go above 3000 rpm.

Help!

[92xjunker]

Vac leak or your carbs are still dirty, ie the pilot circuit. How were the carbs cleaned?

[shpielers]

Vacuum leaks are probably causing that. Warm the bike up, and spray starter fluid or some other flammable liquid around at the connections. Where the carbs meet the head, the airbox, the vacuum lines/fuel lines, the tops of the carbs etc. Spray something, give it a few seconds, and then move on to the next spot. If the RPMs climb, you've found a leak. Figure out how to seal it, and check again.

Might want to start checking carb #2 if you had issues seating it.

The orings between the header and the carb boots flatten out with time, they may need replacing. If you find a leak in that area, that'll be why.

[davekat]

Vac leak or your carbs are still dirty, ie the pilot circuit. How were the carbs cleaned?

I opened each carb body one by one, removed the components, squirted them with carb cleaners (soaked), while squirting the carb cleaner through each one of the holes. I also used a compressed air can to blow through them. The pilot screws I removed, spring, washer, and rubber gasket assembly completely, and cleaned them in carb cleaner (not the rubber). I then reassembled and put them back in.

I'm guessing I gotta do another round of it?

[92xjunker]

Also check the boots on the airbox and the drain from it (should be capped) canned carb cleaner won't do shit, they need to soak in a carb dip type cleaner to dissolve the varnish in the passages that can't be accessed properly.

[davekat]

Also check the boots on the airbox and the drain from it (should be capped)

The airbox drain (bottom of the airbox) has a tube to it. That's supposed to be capped? Wait, just looked. It's capped.

How do you look for vaccuum leaks?

[92xjunker]

You need to check out carbs 102, save some time and look for a vac leak first.

[davekat]

Also check the boots on the airbox and the drain from it (should be capped) canned carb cleaner won't do shit, they need to soak in a carb dip type cleaner to dissolve the varnish in the passages that can't be accessed properly.

Well, the carbs were professionally cleaned a while ago, and the bike wasn't running at all since then. Carbs were empty of any kind of fluid, so I'm pretty sure there isn't any varnish, as I cleaned them again before attaching them to an empty fuel tank.

When I reopened them, they were empty.

OK, I just tried spraying carb cleaner on the air box boots, and carb number 3 (counting from left to right, facing the front of the bike), when I spray it, the idle actually changes!

I'm guessing I have to reseat the airbox?

[arsenic]

They were "professionally" cleaned? Take a few minutes to read though a few different threads and see the common experience with "professional" carb work.

[davekat]

They were "professionally" cleaned? Take a few minutes to read though a few different threads and see the common experience with "professional" carb work.

Actually, I bought them from you off of ebay. Good seeing you again Arsenic.

[92xjunker]

Vacuum leaks are probably causing that. Warm the bike up, and spray starter fluid or some other flammable liquid around at the connections. Where the carbs meet the head, the airbox, the vacuum lines/fuel lines, the tops of the carbs etc. Spray something, give it a few seconds, and then move on to the next spot. If the RPMs climb, you've found a leak. Figure out how to seal it, and check again.

Might want to start checking carb #2 if you had issues seating it.

The orings between the header and the carb boots flatten out with time, they may need replacing. If you find a leak in that area, that'll be why.

Like this ^^^^^^^^^^^^

[davekat]

Like this ^^^^^^^^^^^^

Alright, Im gonna try reseating them. Any tips on that by the way? Cause I noticed, even when the boot is ALL the way in on the carb to airbox, when I tighten the ring, it starts to squeeze off!

[92xjunker]

Doh!!!! definitely not a carb issue then.

[arsenic]

Take the air filter out of the air box. Stick one hand inside to push the boot onto the carb. While applying pressure to hold the boot in place, tighten the clamp.

[davekat]

Take the air filter out of the air box. Stick one hand inside to push the boot onto the carb. While applying pressure to hold the boot in place, tighten the clamp.

OMG, that is SOOOO MUCH BETTER than using a freaking mallet! ;P

Seriously though, you have no idea how many times I went batty getting those damn boots to seat, to the point I wondered if they were that important...