I've a question about possible problems arising from replacing the stock handlebar with a SM2 bar. I did this replacement about 5 months ago and the bike has run ok since then. However, recently despite the warming weather, the bike seems to be running much leaner. The choke isnt as effective and even after its run for 10 minutes and the choke is switched off, the engine pops/blows back through the air filter. Its also producing less power and sounds harsher when in high revs.

What could have changed?? I have been adjusting the carb throttle stop to try and get it to idle, but I think its somehow a problem with mal-adjusted cables.

Other symptoms are engine/rev racing when not in gear and less engine braking power when downshifting.

Ive observed that when I give it some throttle I can see the little u-clip on the side of the carb move, but for some reason if i hold the throttle (the u-clip holds as well), but the engine begins to race....

Is this a jetting problem?

Many thanks,
Fin

Hmm...you have a 2002, stock, and so far you've only changed to SM2 bars, which means that you only messed with throttle and choke cables (http://gstwins.com/gsboard/index.php?topic=25156.msg259894#msg259894), but you could have bumped the synchronizing screw...
Did you take the carbs off to reinstall the throttle cables?  If so, you may not have seated, or be getting a good seal around, the carbs.
When was your last valve adjustment?  Do you still have that ticking sound? http://gstwins.com/gsboard/index.php?topic=24087.msg246666#msg246666

Loosen all of the throttle cable adjusters, and just pull up on the sheath of the forward (pull) cable until the cable is barely taught, spin down the locknut, but do not tighten.  Now do the same with the other (push) cable.  Now turn the handlebars full left and check your slack; you should be able to see the cable just move when you wiggle the throttle.  Same thing with the handlebars full right.  Adjust the slack at the tightest point.

Something that may contribute to your throttle cable issues will be the idle screw,  If it is set too high, then your cables will be too tight when you try to lower the idle.

Do the same thing for your choke cable.

Ok thanks Scratch, I've never really figured out how to use the throttle adjustments - but I'll give your method a try. I havent gotten round to adjusting the valves yet, as this throttle/choke prob is effecting my riding more, plus school.

To change my handlebar, I didnt do anything except take all the gear off the old bar and slide it on the new one a la pablo's site. This might have changed up the tensioning on the cables...

Can things go wrong when adjusting the idle with the plastic knob sticking out from the bottom of the right carb? I never thought to be careful of other bits in an around the knob, I've just stuck my gloved hand in there and rotated it anti/clockwise.

I replaced the plugs today and its seemed to have cured half the problem! It doesnt race now in neutral, but it still wont idle properly. If the idle is set to anything more than "stall"  it races/hangs big time.

I took a look at the air filter and it is def. dirty.

I also switched the fuel selector to prime - would that change things?

-Fin

I just tried working the throttle cables at the grip:

the forward one -  screwed in all the way- all it does is twist the grip towards full throttle a VERY small bit, like 1/20 of an inch

the rear one - tried loosened all the way- makes the throttle really sticky (wont return to closed), screwed all the way in, makes the throttle grip snap back normally.

I dont have much to work with there.


The ideal situation it seems to me would be to be able to warm the bike up, set the idle screw so it doesnt race above 2-3k, THEN, adjust the throttle stop to give it some throttle to keep it from stalling- WHICH is essentially what I have to do when I'm stopped at a light- keep a little throttle on - if I can adjust the grip to stay with a little throttle on then things would be fine!

Should I pull the tank off and adjust at the carb?

Whoops, yeah, my adjustments start down on the carb.  Sorry for not clarifying that.  Loosen 'em all up again.  Sorry, sorry sorry.

Maybe, I should start you from the beginning.

First we need to set your idle.  After a long ride on a cold day, at least 15 minutes of riding, to get the bike fully up to operating temperature, then set the idle to manufacturer specs (for a 2002 Canadian GS, I'm not completely sure, but I'd probably still set it to 1200rpms).

Now we can get your throttle cable slack set.

BTW, did you check your choke cable, and set it's slack?

And lastly, it is normal to use throttle to keep the rpms up when the bike hasn't warmed all the way up.  It usually takes 10-15 minutes for mine to hold a decent idle without throttle.  And that's jetted.

Ok so warm up the bike, set the idle and bring 'er home and take the tank off? I cant get at the carb side throttle cables unless the tank is off?

Im still not clear on why, when I screw the idle adjust (in) to make it idle higher, I get this racing/hanging problem.

Its really BAD, like when shes set to idle at 1200-1500 (after warming up), its not ridable. It just revs outta control when I give it a little throttle.

So I'm not sure how I'm going to get it warmed and idling properly in the first place 

I checked the choke cable and it seems to be fine - as in it moves the choke slide from stop to stop

When was your last valve adjustment?
How many km's on your bike now?
We may need to set your idle to 1100 for now.
What are your float levels at?

Finmac,

Have you figured out your hanging idle problem yet? My bike seems to be doing the same exact thing.