So, I just bought my first bike (1990 GS500!). I knew it had a little engine trouble, but after reading up on it, it seemed like an easy fix (famous last words...).
Basically it starts up fine, but when I give it throttle it dies. I can use the choke to get the RPMs up (say around 3000), then I have no problem applying throttle and getting to redline. So, I cleaned the jets in the carbs (which looked fairly clean to start with) and the problem still persists. I followed all the instructions here: http://www.gstwin.com/carb_work.htm.
Anyone have some hints on what to try next?
Did I post to the wrong forum?
Sorry for the lack of replies so far :(
This is a common problem for any bike that has been sitting for awhile; fuel tends to gum up and block off the narrow passages in the carburetors. You will likely need to take off the carbs and give them a thorough cleaning.
Here are some threads found by searching -- dies on throttle:
http://gstwins.com/gsboard/index.php?topic=42196.0
http://gstwins.com/gsboard/index.php?topic=27448.0
For cleaning the carbs, use carb cleaner and pass a thin wire through the passages. Also, be careful not to spray the carb cleaner on rubber/plastic parts. Search for carb cleaning and you will find many related threads. There is also this HOW TO on this site:
http://gstwin.com/carb_work.htm
Also, do you know if the previous owner was messing around with the carb jetting and/or mixture screws? That can cause problems if not done right:
http://gstwins.com/gsboard/index.php?topic=29605.msg320543#msg320543
Already did a full clean on the carbs. Maybe I start looking at making adjustments within the carb...I might have to defer to a mechanic for that though...
Quote from: MichaelWH on June 30, 2008, 09:03:14 AM
Already did a full clean on the carbs. Maybe I start looking at making adjustments within the carb...I might have to defer to a mechanic for that though...
If it were mine, I would get the bike to run before making any carb adjustments. Of course, this assumes the carbs are stock and you do not need to "fix" a problem introduced by a previous owner. Check for the brass caps over the mixture screws to help determine if the carbs are stock.
Is it possible that you missed some passages when you cleaned the carbs? :cry:
Here is a recent thread where pennstump had to clean the carbs a few times before he found the clogged pilot jets:
http://gstwins.com/gsboard/index.php?topic=42192.0
I had the same problem with my 97 GS and I "thought" i thoroughly cleaned the carbs and jets, but after looking through the many forum posts I knew something in my carbs was still blocked. sure enough, I open them up for the 4th time and the pilot jets are both clogged again(soaked them in carb cleaner for a few hours and used compressed air to clear em out). after lubricating my slides with 2 stroke motor oil (another handy suggestion I found from the main page about cleaning carbs) and reinstalling the clean jets, it ran like a champ :thumb:
I also drilled out the brass caps and set the air mixture screws at 2.5 turns out. adding allen bolts to your carbs will make any future adjustments/cleaning alot easier. I've never worked on bikes before and I can't believe all this great information allowed me to completely rebuild my carbs, do a valve adjustment (kerry's video is awesome), diagnose a lean engine and get my newly acquired bike running like a top :icon_mrgreen: awesome community!
Quote
Here is a recent thread where pennstump had to clean the carbs a few times before he found the clogged pilot jets:
http://gstwins.com/gsboard/index.php?topic=42192.0
Sounds very familiar. Pull the carbs again and make sure you cleaned everything, including the bypass ports. Also, drain the float bowls while the carbs are still on the bike, then take the carbs off. If you don't, any gunk, sludge, etc. will run into the body of the carbs. Also, know that you need the appropriate amount of back pressure, so make sure the air box is on and doesn't leak.
Good luck. :thumb: