Author Topic: Irratic Idle and Flat Spot from HELL (Read 3191 times)

Maniac · « **on:** July 15, 2005, 09:56:05 AM »

Hey all,

I'm supposed to ride my Bandit to Orlando tomarrow to meet up with a buddy of mine. Right now though, I have a problem that threatens this ride...

My carbs!

As you may or may not be aware, I'm running 33mm carbs now. Currently the main jet is a 97.5, but I have a 117.0 set of mains that I had in it before. Here's the problem...

The bike will idle just fine at startup, although a little high with the choke on. After it warms up or with a little riding, the idle becomes somewhat odd. Sometimes it returns to idle, others it hovers at 4000RPM (usually this is after some revs have been hit) for a while before droping to 500 and nearly stalling.

From idle, the throttle is very odd. If you grab some throttle at idle, the engine stalls. If you ease it up, she falls flat on her face at 3000RPM and doesn't really rev until she hits 4000RPM or so, where she takes off like a bat out of hell all the way to redline.

This sounds to be pointing at the idle mixture. I started at 1.5 turns and I'm at 2.75 turns now. Best result was at about 2.25 turns or so. The needles are clipped in the middle and the floats are all set the same within 1mm of correct (some were way off). I'm suspecting I know what the problem is, though. You see, I'm running the needle/needle jets out of the 32mm carbs in the 33mm carbs. I wasn't aware they were different, they look the same at least. Could my problems be the result of a way-rich condition caused by fuel leaking up around the needle/needle jets?

As near as I can tell, the carbs are balanced (or close at least). I can go out and hit the starter and the bike will fire right up. This has been a progressive problem over the last few weeks, and I'm really at my wits end with it! Any suggestions you guys have would be really appreciated.

interfuse · « **Reply #1 on:** July 15, 2005, 12:05:43 PM »

I'm no carb expert. But I'd double check the float height. Sounds like it might be set high. 97.5, third clip, and 2.25-2.5 rotations should get you close if you've got a jet kit installed. Also one of the float valves might be sticking open.

Thief400 · « **Reply #2 on:** July 15, 2005, 01:54:27 PM »

Your WAY WAY WAY too lean everywhere!!!!!!!!!
My advise to you is to find a good carb guy in your area and have him set it up, I see too many guy here who don't have the techinical know how to jet an engine properly. I'm not coming down on you. But to jet an engine properly takes year of experance and making alot of mistakes along the way, LOL . There a a few guy here who know how to do it but to try to explain and help out someone on such a compicated subject is damn near impossible on line
Forget about checking the float hieghts, If you have them, install the 33mm needle jet and jet needles with the c clip in the 4th groove down, air screws 2 turns out and stick in the biggest mains you have. If you have a pipe and modified air box the 117.5 are too lean still. start at 130 to 140's I'm running 137.5's and i'm at 660 feet above sea level. This might get you going. These are stock Suzuki parts I'm taking about not some jet kit parts. One last thing balace the carbs.

Maniac · « **Reply #3 on:** July 15, 2005, 01:58:06 PM »

Yeah, thats the problem. I can't afford to take the bike in and get it worked on at the moment, and I'm trying to sell it so I can pay some bills.

b4cruz · « **Reply #4 on:** July 15, 2005, 02:23:00 PM »

you can always do the home depot carb ballancing tool
its messy to build and slow to reset but totally worth the afternoon
to get your carbs running nice if you don't have the money

1 - two paint sticks or yard sticks the longer the easier to reset
2 - 2 long strands of clear tubing to wrap in a U over the two sticks
3 - nice clean dark oil to fill the tubing just at the bottom of the sticks
4 - packaging tape to hold the tubing round the sticks
5 - attatch the tube ends to each of the carb vacuum holes.
6 - one stick on the left side one on the right
7 - when you have each side sucking the oil evenly so the oil
stays nuetral between the plastic tubes do the same to the
middle 2 carbs with one set

this is how they did it in thunderdome
its just too easy too cheap and way more fun
than paying a shop to do it for you

but it sounds like you may have more problems in the jet setup
than ballancing could help, but i don't know much about jetting

Maniac · « **Reply #5 on:** July 15, 2005, 02:35:54 PM »

I've actually got a set of vacuum gauges and I balanced them that way. All 4 carbs are reading the same on the gauges now, they were quite a bit different when I started. So I -think- they are balanced, I'm relativly sure it's all in the jetting now. I'll re-balance once I get the carbs reset.

When I -did- have the 117.5 mains installed the bike had no top end, though. It'd go to 8000RPM and stop revving, at the time I suspected it was to rich, I guess I was wrong.

Maniac · « **Reply #6 on:** July 15, 2005, 10:27:15 PM »

Whoa, Thief...

Dang man, excellent advice! She fired right up and runs great.