finally starts and idles, but throttle response is weird

So, I bought my first motorcycle two months ago - a 1981 xj650 maxim that supposedly was running just fine before it sat for "a few months" and now wouldn't run. Also, the front brake was seized. No major cosmetic damage, just a bit of grinding on the engine bar on one side along with a damaged footpeg rubber. Little rust - looks recent and minor, the PO probably just left it sitting in the weather for a while, it looks like the owner before (PO's mom) took pretty good care of it. Picked it up and I have a project!

Done so far:
-New battery
-New front brake pads and brake fluid
-Opened up and cleaned the front brake caliper - lots of sediment/reddish brown gunk, piston looked OK, put everything back together, bled the brakes and they seem to work just fine.
-New engine oil and filter - the oil drain plug had some thick gunk stuck on it, wiped clean. Oil itself seems ok - but there may be some sediment in the bottom. I plan on giving her another oil change/new filter after about 500 miles to try and clear that out.
-Just got brake shoes for the back (not yet installed)
-New final drive oil (going to do at the same time as the brake shoes)
-Drained the tank and added fresh gas with some seafoam
-New spark plugs
-Cleaned out the carbs with rebuild kits - those were gross. I didn't know gas would turn green... Spent two afternoons cleaning and I am relatively sure that I got them clean - however, it is my first time working on bikes/carbs so I may have missed something. Also, I now realize that I did not pull the enrichment circuit valves (from the top of the carbs), and I did not check the float heights. (noobie mistakes)

After cleaning the carbs, the bike earned the name Swamp Thing.

After cleaning the carbs, the bike was still difficult to start. I noticed that the covers over the mixture screws had already been removed so I set out to put them back to the 2 3/4 turns out from the bottom that I have seen recommended. Two of the screws were set the same, one was set close, and one was WAY off.

Today, I have been playing with the mixture screws and am getting frustrated. I bottomed out all the mixture screws, then backed them out to:

2 1/2 - bike starts, any throttle = engine dies

2 3/4 - bike starts, any throttle = rpm's shoot up, I hit the kill switch at about 3500, it sounded like it wanted to keep rising

2 ~5/8 - bike starts, good throttle response to about 2500, then any more throttle = rpms fly up to 4000-4500 and hangs for a second when I close the throttle, then drops ok back to idle

I don't really know how to proceed from here. Also worth noting - I have not ridden the bike yet, waiting to get the brake shoes installed before I start thinking of considering it roadworthy.

One other thing - when I pull the rear wheel to change brake shoes, does disconnecting the drive shaft dump out all of my final drive oil or does it remain contained? I am wondering if I should drain that oil before removing the wheel or if it doesn't matter.

Thanks in advance for your help.

 

oil is separe from the wheel. y ou can pull the wheel off all you want. there's no oil to lose.

 

Thanks!

Any ideas on the throttle response?

 

pull the wheel off. youi don't disconnect the drive shaft.

sounds like you've got throttles binding. and the diaphgram assemblies might be sticking. check the throttle plates for binding. and polish the bores and throttle sliders that go up and down. i used a light sand papers on the sliders.

also check your floats. should be 17 mm sitting on there own weight. anything higher then 18 and your not geting enough fuel for choke starts.

easiest way is to get a clear tube. pull the drain screws out. you can screw the tube in the hole a little bit. it's tight enough to hold and you can see your fuel level. put the fuel switch on prime and let the carbs and hose fill up with fuel. 3mm from base of carb with carbs being straight and level.

the problems your experience are what usually happens to me when i disconnect the fiuel switch and let the gas run out of the carbs before doing whatever i'm doing with the carbs. i'd fire up the bike and let her idle with the choke on to get maximum fuel pulled out of the bowl.

so i don't think you've got enough fuel in the carbs.

youi'll need to pull them back off and check and double check everything. make sure you got stock jets in the right holes. all passages are clear. throttle aren't binding. and throttle slides go up and down with no stiffness what so ever. and the diaphrams are seated properly with the notch in the right place.

once everything is confirmed and looking good. the carbs might also be way out of whack and need to be syncronized with each other

 

Thanks again, Snowwy, looks like I have a project for tomorrow.

The throttle sliders were moving smooth and the diaphragms were set in their grooves when I pulled them to clean. I also checked the synch (by eye) and they all looked like they were in line. When I moved the throttle lever (where the cable connects) the throttle plates all turned, there was a little resistance, but not too much. At the handlebar it feels fine.

I will double check the sliders, jets, float heights, synch and double/triple check the cleaning.

 

you can't go by eye sync.

some have been using a paperclip. not sure of the method.

i bought 20 ft roll of tube from home depot for $3. cut in half. so you have 2 ten feet sections. filled with ATF and hooked each open end to a vacuum port on the carb intakes and used for a vacuum sync tool. youi can't get a sync tool any cheaper then that.

i draped em over the handle bars with a tie down strap hooks for weights so the line was straight. i also used a board in back of the motor to keep the vacuum lines from touching the motor. so they don't melt.

 

Thanks everybody! Took the carbs apart this afternoon and found a few new nooks and crannies to clean up, evened out the float levels and did a proper bench synch. Bike is running MUCH more smoothly now. Now to get the new brake shoes installed and get her on the road!

Thanks for the help!