Tips on setting idle screw correctly?

chrisd1984

XS400 Addict
Messages
126
Reaction score
0
Points
16
Location
Toronto
Just wondering if anyone has concrete steps for setting this screw? I've been twiddling with it a bit and can't get the correct setting it seems. Ideally, I'd want it to be set so the bike won't stall when idling but doesn't inch forward when idling either. Any tips for this?
 
I just did this on my bike yesterday,3 1/2 turns counter clockwise from being screwed down all the way.It idles at 1200rpm.This is on my 81 xs.Your bike may vary slightly from mine though, all depends on the jetting you have.
 
The "inching forward" has nothing to do with the idle speed. The idle speed should be set to the correct RPM for your bike, per the service manual. Usually between 1200 and 1500 RPM when fully warmed up (after a 20 minute ride).

The "inching forward" is your clutch dragging.
 
Are you talking an idle screw on the carbs or the throttle cable adjusting screw which sets the idle speed when the throttle is closed?
If the former, I haven't ever touched a carb screw, so I don't know. If it's the throttle cable screw you may have the same problem I do. One has to set it to idle at the right speed when the bike is warm like Dave says. Until it warms up, however, the engine won't idle that fast during warm-up and if I let go of the throttle it will stall.

I can prevent this by turning that screw a bit, and it will then sit and warm up at 1200. But then when it is warm and I come to a stop or a light, it idles at nearly 2,000. So, instead, while warming it up, I try and use the throttle lock to increase the amount of throttle and hold it there while I use my 2 hands to put on the helmet and gloves.

When the screw on that eventually loosens off and the throttle lock starts to slip again, I take the stem off a small leaf and stick it between the end of the adjustment screw and the stop while I do the helmet and gloves. Then, when I use the throttle to start off, the leaf stem drops out and blows away - easier than rummaging for a screw driver to tighten up the throttle lock screw, most times anyway. :shrug:
 
I have the same issue as Lou ever since I adjusted my valves and synced my carbs..

But I don't do anything strange with leaves, throttle locks and all that. By the way, wouldn't it be a lot easier to put on your helmet and gloves before starting the bike, Lou? Then you can just hold your throttle instead.

Anyways, I just upped my idle screw a little so it idles nicely after 30 seconds of choke (sry I don't have a tachometer, can't tell you rpms). Then it does have a pretty high idle when I get the bike all warmed up, but who cares :shrug: I thought. I might sound a little silly at the traffic light, but when I take off I'm not so silly anymore haha :D

yea I agree, inching forward has nothing to do with your idle settings! that's definitely your clutch slipping, either your oil is too thick (which causes sticky plates) or, more likely, your cable needs adjustment
 
But I don't do anything strange with leaves, throttle locks and all that. By the way, wouldn't it be a lot easier to put on your helmet and gloves before starting the bike, Lou? Then you can just hold your throttle instead.
It makes one wish for computer-controlled fuel injection on occasion, I must admit. :laugh:
When it's over 35 C and above 85% RH, 30 seconds standing in boots, pants and jacket is 5 minutes too long. To add 30 more to put them on after would cancel the trip on those days.

The throttle lock came with the bike 30 years ago and until the set screw vibrates too loose every few days, it works great.
Leaf stems work even better - except for the bending down to pick them up part. "Old guys rule" no doubt, but we don't bend over as easily or a forgivingly as we once. This is why it's a lot of old guys who have computer-controlled F.I.
 
This adjusts idle speed.

idleairscrew.jpg


This adjusts idle mixture.

idlescrewright1.jpg


The idle mixture screws should be screwed in to a very light seat, then out. I started with 3 turns out. I adjust by ear. When the bike is warm, I accelerate hard up to about 4500 or 5000 rpm, then let off the throttle and let it engine brake. If it pops a lot, I turn the screws another 1/2 turn out and test until the popping stops. If there's no popping at 3 turns, I close it up 1/2 turn, and test again until it pops. When it starts popping a lot, I go back to the last setting before it started popping.

The idea is to get it as lean as possible, but rich enough to accelerate well.

AFTER the mixture is set and the carbs synchronized, then set the idle speed with the idle air screw. I set mine to idle around 1000 cold so that when fully hot it idles around 1200. If the idle climbs too much or the throttle lingers at high rpm (when throttle released, no load), then richen the idle mixture 1/2 turn and try it again.

Now- here's the kicker. Having done all that with the carbs and having set the valves, and replaced the points and condenser a couple of years ago, I've barely touched the carbs in 2 years. Every once in a while, I adjust the idle speed, but just me fiddling. It probably would not be necessary.
 
I am jealous, I have to take off the fuel tank to use a long mini screw driver, to adjust my idle mix. MIKUMI Now we know why you put the BS in to the carburetor name!!!! :devil:

:bs:

:smoke:
 
Unless you are using a set of xs360 carbs:D
 

Attachments

  • DSC02033.jpg
    DSC02033.jpg
    157.9 KB · Views: 10,253
Ahh. . :shootme:
You guys are adjusting the actual carbs? . :yikes:
I am simply using leaf stems against the throttle stop screw to keep the bike from stalling while it warms up.
 

Attachments

  • Idle Adjust.JPG
    Idle Adjust.JPG
    50.1 KB · Views: 1,772
Yeah I just meant the throttle idle screw - I've been playing with it and hopefully will get it soon.

That makes actually because my clutch cable is just about shot, ordered another one in this week.
 
One tip- if the idle mixture is too lean, then the rpm will increase a lot more as the bike warms. It's almost impossible to get a consistent idle unless the idle mixture is set a bit richer than factory settings.
 
Wow! Why do it the hard way? I use a double ended 1/4" screwdriver bit that I've attached a washer to. The washer acts like a thumb wheel. I can adjust my pilot screws in less than 5 minutes without removing anything from my bike.

Don't work harder, work smarter!
 
You can do what Dave did,
Wow! Why do it the hard way? I use a double ended 1/4" screwdriver bit that I've attached a washer to. The washer acts like a thumb wheel. I can adjust my pilot screws in less than 5 minutes without removing anything from my bike.
Or you can do what I do, and remove the tank. I have 2 buckets that can sit on top of each other, so I just rotate the fuel tank in a circle and get it to perch on top those two, (carefully) Hook up a longer fuel line, Just in case. Then I hook up the manometer, and adj the pilot/mix screw, and then double check the balance. as long as I have the access to the screws. There are reasons that there are alot of threads of how people have broken the mix screw. I am okay with taking my time. If I am taking the tank off, I have nothing better scheduled to do for the day.
 
i can access the mixture screws fine, not sure if i have fat hands or what, but really have to struggle to get to the idle screw ( the one Hough circled above). On my buddy's CB550, its all the way to right, he can adjust it while sitting on the seat
 
I can adjust the one I circled sitting at a stop sign, but I only need to get one finger on it to turn it either way.
 
Back
Top