Carb tuning

[spwalker09]

I'm still getting to know my GS450 and all its little quirks, and I'm gonna start to try and nail them all down...but I need you guys' help, so here it goes, starting with the carbs

Symptom #1: The bike starts cold with 1/4 turn throttle but no choke. The choke works, but when its on the bike will not start or run. Do I need to adjust it? If so, how?

Symptom #2: Esp. when cold, the bike doesn't want to keep running unless I give it some throttle. This only happens for about a minute Its tough to tell, but I think its because a cylinder is momentarily dropping. I've already cleaned out the carbs, and its much better than when I got the bike, but still this happens. Then again, this was more of a problem last night when it was 35 degrees out, and the bike had been sitting outside for a week and a half. Despite that the bike still fired on the first crank, except for the issue described above. Any thoughts?

Symptom #3: When warming up, the bike idles fine (kinda low and borderline stumbly, but doesn't stall). When the bike is warm, it doesn't want to keep idling, especially when its on the side stand. It will keep doing this when I adjust the idle stop screw (with no change in idle) and then suddenly it will start to rise up to a very high idle once I reach a certain point. Is there something else I need to look at to fix the idle?

Other than above, the bike has no driveability problems, no flat spots when driving, but I really haven't opened her up yet (I dont have a working tach for starters)

Any input would be appreciated!

 

[ryonker]

I don't want to assume this, so I will ask; have the carbs been thoroughly cleaned; disassembled dipped and blown out with air?

If not, this is where I would start.

Rick

 

[spwalker09]

I don't want to assume this, so I will ask; have the carbs been thoroughly cleaned; disassembled dipped and blown out with air?

If not, this is where I would start.

Rick

When they were cleaned back in December, they were not dipped. I did take off the bowls before I put the engine back in and they were pretty clean still. I did not take out the jets however

 

[tkent02]

I don't want to assume this, so I will ask; have the carbs been thoroughly cleaned; disassembled dipped and blown out with air?

I would start with this, and afterwards spray aerosol carb cleaner through every tiny passage in the carbs and in the float bowls, visually make sure the spray goes all the way through all the passages on each carb. Make sure the spray patterns are the same in both carbs. Do this with all the jets and screws removed. There are some very tiny holes bored in the carb body and some in the bowls themselves that allow the low power and choke circuits to work, they all need to be completely clear for the engine to run properly.

 

[Steve]

Has anyone mentioned a full, proper carb cleaning yet? That's where I would start.

While you are in the process of dipping the carbs, order a set of o-rings from cycleorings.com. Do NOT bother with "carb rebuild kits", they usually have parts of sub-standard quality, and don't even have enough to properly re-build the carbs. The only thing you might need besides the o-rings would be bowl gaskets, but if yours are not torn, that's fine. While you are ordering the o-rings for the carbs, get some for the intake boots, too.

When your carbs are back together, the proper starting technique should be a little different than what you are doing now.
1. Set the "choke" to about 1/2
2. Ensure the RUN switch is in the ON position
3. Insert ignition key, turn to ON
4. Pull clutch handle (unless you have this disabled)
5. Push the starter button
6. Adjust fast idle speed with "choke" knob or lever, whichever you have.

Notice that at no time did I mention "twist the throttle". That's because YOU DON'T twist the throttle when using the "choke".

After running between 30 seconds and a minute, it will be warm enough to ride. By the time you are in second or third gear, you can turn the "choke" off entirely.

.

 

[spwalker09]

Thanks a lot for the info Steve. I know that throttling is not the way to start a bike (hence why I knew I needed help! lol) - thanks for the vendor info - don't be surprised to see more questions from me (I'm new to bikes and taking apart carbs, but I'm mechanically inclined so it won't be too big of a challenge...I hope)

The bike was last on the road in '96, so I'm not surprised that the little details of the fuel system would be in need of attention.

Thanks again!