No choke no go

[Guest]

Hi
Could use your infinite wisdom on solving this riddle for me, although I have an idea what the answer may be...... I have a 650e pretty much stock standard with around 70,000 miles on the clock. Over the last couple of years I've spent my time cleaning and maintaining it. When I got it there was a 4 to 1 NZ made exhaust and keen to get it looking more original I've changed this to a 2 to 1 without the balance pipe. Petcock has had a rebuild kit, new plugs, air filter has been cleaned. First start for well over a year and runs well on choke up to 3000 rpm however dies when you close the choke. Won't idle at all. So a few questions
1. Is it a carb clean down?
2. Is the different exhaust without balance pipe causing the problem?
3. Does rejetting the carb require different jets and if so how do you determine what size?

Thanks in advance
Sean

[tom203]

Question 1..,, yes. Your idle circuits are not delivering enough fuel - using "choke" compensates because it's an enricher system not a choke. These small passages get clogged up easily.
when you clean carbs, note the jet sizes. Probably nobody changed to a different main jet when they changed pipe, but who knows. The US gs650E has 97.5 mikuni main- yours should be close.
Follow this guide to do the carb cleaning properly - you need to do a thorough job

http://zeus.mtsac.edu/~cliff/storage/gs/Mikuni_BS-CV_Carburetor_Rebuild_Tutorial.pdf

Edit: there might be a person in your area who can clean carbs ultrasonically- done right with right equipment will yield good results and avoid harsh chemicals.

[phydeauxmutt]

1. Yes
2. No
3a. Yes
3b. Experiment.

1. Yes, it sounds like it's time for a carb cleaning and replacing the o-rings. Member Robert Barr runs a service at cycleorings.com where he sells o-ring kits for the carbs at a fantastic price. He also has available the o-rings for the intake tubes, where they mate with the head. He also has stainless bolts to replace the stock items that hold those tubes to the head. Many have postulated that the OEM screws are made of aged cheese and need to be replaced.

2. No, the lack of a balance tube has no effect on your situation.

3. Yes, "jetting" involves changing jets, but depending on your mufflers and intake system, you might not need jets, only some adjustments. If the mufflers are rather quiet, that is a hint that they are a bit restrictive, and probably don't flow any more air than the stock mufflers. If your intake is still the stock airbox, and not individual pod filters, even better. The reason to "jet" the carbs is because restrictions have been removed and more air can flow, which requires more fuel. If your airflow is about the same, there will be no need to change the jets. Reading your spark plugs will be your best clue what is going on inside the engine.