overnight personality change

[Guest]

1981 gs650g
last week bike was running fine, decent power from 0-80. went to fire up earlier this week and it took forever to fire up, just kept cranking. finally started but has an attitude problem when trying to take off from a stop. no power and will stall out if anything more than 15% throttle applied. I can crawl it up to 45 on low throttle but will bog down on medium to high throttle. I pulled the slides and drain plugs out of the carbs and there doesnt seem to be anything blocking flow from the tank to the bowl. gas had a bit of a dark color to it. plugs look normal, dark color with a slightly white tip. Will idle ok now and choke seems to be working.

I have been busy with work and havent had much more chance to check it out until 6pm every night.

[Nessism]

How long since the last valve adjustment?

[2BRacing]

Did you fill up the tank recently? Maybe a bad batch of gas?

[jcskokos]

valves were in spec about 6 or 7 months ago. I dont remember the exact numbers off hand but it wasnt at the outer extremes. I tried draining the tank and refilling with new gas as well.

[roeme]

If the power loss is related to rpm, then something has gone wrong in the ignition. Maybe bad contacts. Happened to me recently.

[jcskokos]

is it possible for the battery to discharge to a point where it will fire and run but have poor engine response? I remember something similar on my 67 dodge but that is a much larger motor and coil.

[Big T]

Not really. If the battery were that low, the starter wouldn't turn

Maybe the cam chain jumped a tooth?

[tom203]

Check airbox/filter for blockage....maybe some critter has built himself a home

[jcskokos]

it will rev up without a load very easily. will it still be able to do that with a jumped tooth?
I peeked in the air box and didnt notice anything other than the filter could probably use a cleaning but its not horrible yet. I can try checking deeper with a mirror and flashlight later though.

[tom203]

With no load the "choke" system could rev it way up without the slides lifting .Any chance something has blocked the very top entrance to airfilter - just below seat?

[jcskokos]

its very possible. ive noticed a huge increase in creepy crawlies recently around the yard. ill take a look tonight.

[jcskokos]

Welcome back to GSR (Yah, your logon name expires is dont logon in a few months).

I too suspect old fuel.

But let me ask, when you say "there is fuel" do you mean is fuel in the tank, if so; I ask if you put the petcock on PRIme before trying to start.

If you mean the plugs were wet, ... well then that supports the old gas idea.

When you say you charged the battery, how do you know it was fully charged? If not fully charged, it could turn over seemily fast but voltage low enough to not operate the ignition.
You say you have spark, but maybe that was with all plugs out.

.

This is the post I remember seeing on the 4 cylinder page

[Cipher]

hey put stabil in before you stored it.............
Drain gas and try fresh stuff with a freshly charged battery.
be lazy and use a in tank carb cleaner and go for a ride requiring frequent gear and throttle changes on a safe low traffic road.

[jcskokos]

honestly this was my plan for tomorrow. hook up the slow charger tonight and try in the morning.

[Eli69]

If all else fails there may be something blocking a main jet. happened to me once.