Honda Twins banner
1 - 6 of 6 Posts

·
Registered
Joined
·
148 Posts
Discussion Starter · #1 ·
hi guys,
looking for some help with the 76 cb200t again. of all the quirky little things i've seen during this project, this might be the weirdest. the idle screw on the left carb is literally falling out of the screw hole. i've lost two screws already--in two days!
here's the "story." sorry if it's longer than it needs to be, but i'm really at a loss and don't want to leave out any details that may be important. at the beginning of the riding season, i took the carbs off, sprayed them down with some carb cleaner, then compressed air, etc. nothing big, just a quick clean to get rid of any gunk that might have built up over the winter. i put the carbs back together, and, before i put them back on the bike, i set the fuel/air mix screw to the standard 1 and 1/4 turns out from seated (this has always--and continues--to be a good setting for my bike's fuel/air screws) and the idle screws back to where they were before I took the carbs apart (about 3 or 3 1/2 turns out). when i put the carbs back on the bike and started it, the bike was idling at about 2500rpms even after it was warm to riding temperature. it was almost as if someone was leaning on the throttle rather than just letting the bike sit and idle. so, i backed the idle screws out further (1/4 turn at a time, evenly on each side). to get down to 1200rpms, i wound up having them about 4 1/2 to 4 3/4 turns out. but, it ran fine, the fuel/air mix seemed right, the back pressure from the two exhaust pipes was dead even...so i didn't give it much thought.

the other day, i had the pipes off for polishing, i was cleaning the air filters, adjusting the points and doing some other things. so, while i had everything apart, i figured i'd do a real good carb cleaning (including dipping them in berryman's and so on). when i put the carbs back together, the idle issue was the same--it took about 4 1/2 t0 4 3/4 turns out on the idle screws for the idle to settle at 1200rpms. i took the bike out and got it to WOT for a couple minutes to make sure the carbs were adjusted right. the bike ran GREAT, and the carbs didn't seem to need any fine tuning at all.

so, i rode home, happy as a pig in mud, and parked her. i looked down and noticed that the idle screw from the left carb was GONE! the strange part is that the bike ran no different after it fell out. i didn't even notice. i put another one in, hoping (naively) that it had just loosened some how and fell out. took another good ride today (again, the bike ran well) and got home to the same problem: the left idle screw was GONE.

so, tonight, i put another screw in (good thing i've got all these extras!). i also replaced the springs on both idle screws. i still had to come out 4 and 1/8 turns to get to an idle speed of 1200rpms (still a lot, i think, but better than 4 and 3/4!). i also noticed tonight that the idle speed is not as sensitive to the left idle screw as it is to the right idle screw. in other words, i'll back off the right idle screw 1/4 turn and it makes a noticeable difference to the idle speed. but the adjustment to the left idle screw doesn't make a noticeable difference to the idle until i adjust it about 3/4 turns or more. i assume that's a related symptom (again, i'm just trying not to leave anything out).

any ideas or thoughts? thanks...
 

·
Registered
Joined
·
83 Posts
Hi!
Usualy does screws have springs. See if they are making pressure in all the screw length. If they are making good pressure they won´t fall of with viration.
If you can do synchronize the carbs with a vacuum synchronizer.
Regards
 

·
Registered
Joined
·
148 Posts
Discussion Starter · #3 ·
thanks--
i did put new (and slightly longer) springs in and it seems to have done the trick. the idle is good and, more importantly, the screws are staying put!
I have a new problem, though. the bike is hesitating big time when i accelerate. it hadn't been doing that before, and i'm not sure what i could have done to cause it. my guess is that maybe some dirt or something got into the carb when i was riding after the idle screw had fallen out? i know the float height is right and the fuel/air mix is good. the carbs are synchronized. not sure what else it could be. any thoughts?
 

·
Premium Member
Joined
·
239 Posts
cb200t said:
hi guys,
i also noticed tonight that the idle speed is not as sensitive to the left idle screw as it is to the right idle screw. in other words, i'll back off the right idle screw 1/4 turn and it makes a noticeable difference to the idle speed. but the adjustment to the left idle screw doesn't make a noticeable difference to the idle until i adjust it about 3/4 turns or more.
Sounds to me like your left idle screw might be "floating" on the cable...
Did you adjust your throttle cable by backing out your idle screws until they make no contact with the carb body, then make sure you have a little play in the throttle (about 1/4" turn before either 'flipper' starts to move), then resting your finger on one 'flipper' while looking at the other, turn the throttle and adjust the cables at the carb until the 'flippers' begin to move at exactly the same time, and then set the idle screws to 1200rpm and synch?
Just a thought.
 

·
Registered
Joined
·
148 Posts
Discussion Starter · #5 ·
thanks for your reply, matt. i did do something similar to what you've described. i'm not sure what you mean by the "flipper" or if these carbs have such a thing. what i did was back out on the idle screw as you describe, and then twisted the throttle to make sure that 1) there was the appropriate amount of free play in the throttle, 2) both slides began moving at the same time and moved evenly. i made a slight adjustment to the cable adjuster on the top of the left carb to make sure the slides were moving together (it seemed to be lagging behind the right carb's slide at the initial point of movement).

these things (along with new springs for the idle screws) seemed to have helped. but i'm still a little surprised at having to back out on the idle screws 4 full turns to get the idle to 1200rpms. i've checked my previous notes, and when i first got the bike, 3 full turns out (give or take a quarter turn) was enough to get the idle set at 1200rpms. not sure why i need that extra full turn now...
i'm also not sure why the bike (which is idling nicely) is hesitating so much during acceleration. for the last two weeks or so, i've gone back and forth from good, strong idle and poor acceleration to weak-sounding idle and excellent acceleration...

thanks again and, of course, any further thoughts are most welcomed.
 
1 - 6 of 6 Posts
Top