Author Topic: throttle doesnt return fast enough when I let go? (Read 3682 times)

ranakin400 · « **on:** July 25, 2005, 06:51:00 PM »

I recently revived a b4 thats been sitting for a while. it idles nicely and revs fine but it doesnt return fast enough. i mean i let go of the throttle and it snaps back fine on the grip but the engine doesnt rev down accordingly. it seems to take a while for the revs to come down?

any suggestions?

gsxr400 racer · « **Reply #1 on:** July 25, 2005, 07:49:59 PM »

carb sync!

Thief400 · « **Reply #2 on:** July 25, 2005, 08:39:22 PM »

Quote from: "gsxr400 racer"

carb sync!

and your idle mixture is too lean

ranakin400 · « **Reply #3 on:** July 26, 2005, 12:59:53 PM »

how do you adjust the carb sync and idle mixture?

Spacey86 · « **Reply #4 on:** July 26, 2005, 01:49:16 PM »

Ye it is all to do with the carb Sync, and mixture, i had the same problem, with mine, tryed to fix it myself(didn't really know what i was doing) screwed it up so took it to the shop. So if you are not confident to do it your self, get somebody else to do it.

Krautwagen · « **Reply #5 on:** July 27, 2005, 01:47:07 AM »

Generally you don't want to synch the carbs until you get them all tuned correctly and evenly.

It sounds to me like your pilot jets are too lean. On the bottom of the carbs there are adjustment screws. Look for the flathead screw inside of the small tube. You'll need a decent glove and a flathead screwdriver bit.
Warm up the bike
Screw each one out 1/4 turn
Recheck the throttle

Do this until it's happy. If you're too rich, when you slightly blip the throttle, it will stumble before revving up. Then you'd want to screw them in. Go about a 1/4 turn at a time.

If it's been sitting for some time, chances are that some gunk/varnish has built up in the pilot jet holes, which means you'll need a decent carb cleaning. You can try to adjust it out now, and hope that it will become too rich in the near future.

ranakin400 · « **Reply #6 on:** July 27, 2005, 01:22:19 PM »

thanks dave I ll try that

ranakin400 · « **Reply #7 on:** July 28, 2005, 02:35:38 PM »

dave are the tubes under the carbs that you are refering to very very tiny?

under each carb the casing makes these small tubes and there is also philips head screws that go perpendicular to the tubes at the top of the tubes.

To adjust the idle mixture do I put a tiny screwdriver in the tube or turn the phililps head screw at its side?

PitterB4 · « **Reply #8 on:** July 28, 2005, 03:32:14 PM »

As Dave said, the idle screws use a flathead driver. The tubes/screws point straight down and are on the exhaust or engine side of the carbs. If no one has ever messed with them, yours may be covered with a brass cap that would need to be drilled out. Here's a pic of B12 carbs with the cap drilled out. The screws on the B4 are more recessed than these:

I took that from a B12 FAQ on installing a jet kit. It gives some good carb anatomy info, though which might be useful.

ranakin400 · « **Reply #9 on:** July 28, 2005, 06:04:24 PM »

thanks. If I drill out the brass cap can I leave it off?

PitterB4 · « **Reply #10 on:** July 28, 2005, 10:19:53 PM »

gsxr400 racer · « **Reply #11 on:** July 28, 2005, 11:13:33 PM »

Be carefull you do not drill to far as the drill bit will grab the brass and hog out the hole as the fuel screw full seats or it will get stuck in there and then youll be up shit creek!