Bike sat for 3-4 months while I played with other pet projects. It ran OK but not GREAT then. Now there's enough space in the garage to work on it again.
Not surprisingly, it didn't run when I first attempted to start it. I've cleaned the carbs, replaced the plugs, set the float height, set the mix screws to 3 (previous owner messed with them), refilled and charged the battery and roughly synced the throttle valves with a modified flashlight. Now it starts, but runs rough below 3000. It needs choke to stay running, but if I turn the idle screw to lower the idle, it will start to stall once it goes below 3000 - this is once it's warm. It also takes a LOT of turns on the idle screw to significantly change the idle speed. Bottle-sync showed no major difference in pressure between the carbs. Plugs were showing a little whiteness (leany) so I took the mix screws out a half-turn and increased the jet size to 132.5 main and pilot to 20 (it's an '04) - I had a stock upgrade kit from Buddha laying around (the bike is all stock). That seemed to reduce the backfires, but it still hates any speed below 3k.
I'm quite stumped at this point. The bike slowly stalls out when idle drops below 3k. Also, I can tell there's power missing from the rest of the band when I ride it. If, while riding it, I twist the throttle when the RPM is below 3k it will sound REALLY out of sync & unbalanced. I want to say it's only running on one cylinder, but that's not the case. I resynced them and they're as close as they can get in this state. I checked and re-checked the float heights and they're ok. Spraying carb cleaner all over the bike shows no leaks.
Any ideas? Tomorrow I'm going to start researching valve adjustment, ugh. :icon_neutral:
Are you sure the pilot jets aren't clogged? Have you checked for vacuum leaks? It never hurts to run a compression test too.
-Jessie
Yea a valve not fully closing can do that, usually worse when its warming up, it can be OK when fully hot, but then it starts out that way and can get worse with age.
Can also be an exhaust leak.
The next possibly is dirt or clogged fuel passages.
If that is all good, open air screw more. 3 is just a starting point. 5-6 is max before you have to worry about it falling off when running down the road.
Check float level too. Though new type ones dont "walk" like old ones did. But that makes it richer, so you're possibly low ... maybe not unless someone set it wrong.
Cool.
Buddha.
Thanks for the tips. I kind of figured I would need a compression test at some point, but I'll need find an adapter that will fit the GS first. I'll try to get it done this weekend.
The GS has 12mm threads.
-Jessie