81 GS650L, Choke doesn't do much/anything

[DaveP]

I have been pretty lucky with the condition of this bike so far. It hadn't run for a few years before I got it, but it was kept in the garage all of the time. The tank is very clean, definitely no rust or debris coming from the tank to clog things up. Fuel petcock and hoses were replaced with OEM.

Float heights were checked while taking the carbs apart and also when putting them back together. The way the floats were set, there was more fuel in the bowl than there is now. Originally the floats were measuring correctly at the shoulder (step) of the float vs. the body of the float. I raised the float (lowered the fuel level) so that the measurement was at the proper location. Verified float heights with clear tubing from the float bowl drain before ganging the carbs back up and reinstalling to the bike. Clear tube measured fuel height at 5mm below bottom edge of carb body. When checking again this way, the fuel level was still high, so I raised the floats (lowered the fuel level) a bit more.

Not sure on fuel mileage yet and have been filling up from a portable gas can. I've only ridden this bike about 50 miles since it has been back together. I ride my fuel injected bike more since I can just get on and go.

Intake boots are original, but o-rings were replaced. One of four intake o-rings was cracked already when the boot was removed. All original o-rings were brittle and came out in pieces. Intake boots are supple, but I didn't pull on them the way that was shown in the video.

Idle does rise a bit during riding. 1,100 RPM pretty steady most of the time. Has hung up around 1,500 RPM as you disengage the clutch to come to a stop. Will then settle back towards 1,100 RPM.

Intake boots: http://twowheeljunkie.wordpress.com/.../intake-boots/
Carb cleaning and float height: http://twowheeljunkie.wordpress.com/...-float-tested/

[barnbiketom]

Nice work!! I had a gs400 and poor running. No effect while spraying ether..carb spray or propane. New boots still solved my hanging intermittent idle..and every bike since gets new ones. I will be following this with interest..tommie

[DaveP]

Did the carb cleaner spray test today to see if I could detect any vacuum leaks at the intake boots. No change in idle while spraying all around the intakes...

[DaveP]

Finally pulled out the spark plugs this weekend to see how they looked:



The appearance of the spark plugs would suggest that it is running rich instead of lean and not a clogged carburetor issue. They are all fairly consistent too.

Could it be that the air filter is not letting through enough air? Or just the idle mixture screw settings. I believe they are all three turns out.

[mrbill5491]

Finally pulled out the spark plugs this weekend to see how they looked:



The appearance of the spark plugs would suggest that it is running rich instead of lean and not a clogged carburetor issue. They are all fairly consistent too.

Could it be that the air filter is not letting through enough air? Or just the idle mixture screw settings. I believe they are all three turns out.

Yeeeoow those are way rich. Check the air filter to see it is clogged. Don't think its the idle mixture screws unless you let it idle for long periods. Once you get on the throttle, the other circuits over ride the idle circuit. Here is one thing you can do is put in a fresh set of plugs and do a plug chop to get a better idea what maybe is going on. Ride the bike so it gets up to operating temps and find a long piece of hiway and run it up to about 70 for about 5-7 miles, pull in the clutch and kill the motor and coast to a stop.Pull the plugs and see what color it is then. Might need to let it cool down for a bit. So bring some refreshment with ya lol.

[tom203]

When you had carbs apart, did you note main jet size? Sometimes a PO will get ambitious .Those plugs are running really rich. Since the "choke" circuit seems to be doing nothing at cold start, I'd suspect the main circuit- did you reinstall those rubber plugs over pilot jets?

[DaveP]

I checked the markings on each component and everything was to original spec. The rubber plugs over the pilot jets were replaced as most were dry and would not stay in by themselves.

I don't think the PO was very ambitious with any modifications. Anything stamped with a MFG date was still original other than tires and brake pads and those were 10+ years old.