81 GS650G Jetting question, Spark Plug question

[gmoore1785]

First of all, love the site. I've gotten a ton of questions answered by lurking other people's posts. It's time to finally get some questions asked to pertain to my bike specifically. I know this topic is talked about quite a bit...

I have an 81 GS650G built by a shop locally.
Air box removed, UNI pod filters, stock exhaust, 127.5 main jets/42 pilot jets. To the best of my knowledge no official jet kit was installed.

I rode it for about 1 and a half seasons in Illinois fine, although it never seemed like it's full potential.

This year I decided to clean and fully rebuild carbs, line the gas tank completely, re-build petcock, new battery, new plugs. My carb rebuild kit came with stock jets (110 main, 42 pilot) and it wouldn't start with those. I put the 127.5 main jets in and it fired up right away. Although its running great, my plugs are black dry and sooty. Also, after about 1 hour on the highway it acted like it was out of gas and would only start back up if I pulled the choke out all the way and rode with it out (died every time I got back down to first gear or stopped).

Turns out there was a leak with the intake boots so I ordered those. But my real question is still about the jetting. With stock exhaust should I go down on the mains? 117.5 mains, 45 pilot? Right now as it sits the pilot is still stock and the mains are up at 127.5. I haven't read any clear answers for this question. Should I buy several sets and just tinker? I think I'm rich at 127.5 and having the air screw 2 turns out.

Any help would be great guys. These jets are about $25 for 4 so I really wanna get it close to right the first time. I don't entirely trust the guys that converted this bike from stock to what it is now, it was a great deal though.

*picture of my spark plug after an hour on the highway* http://i.imgur.com/x1Vqowj.jpg

 

[tom203]

"My carb rebuild kit came with stock jets (110 main, 42 pilot) and it wouldn't start with those."

you could have no main jet installed and it should still start if the enricher circuit was truly clean. Putting in the 127 main lets it start probably because there's likely lots of slop between it and the stock needle so extra fuel can get sucked up- this gets the blame for the black and sooty plugs too when running.
If you want to stick with pods,you need the dynajet kit to get the correct needle profile. Otherwise it's unlikely to run happily without a lot of fiddling.

 

[duaneage]

The 650 engine definitely runs best with the airbox assembly. You will get 42-45 MPG and it will run like an electric motor if you put it back to stock. I would gravitate towards getting the airbox back on it. The L and G models use the same airbox, I have the rear section but not the front. Perhaps in parts Wanted someone could help you out.

YMMV and there are plenty of Pod Fans who disagree but there is little extra power to be gained from pods on the 650G/