need expert input on startup !!!!

ok... i have a 1980 xj650, I cleaned and rebuilt carbs, replace valve shims, and rebuilt the top end. I am having trouble getting it to idle and run correctly. mixture screws are set 2.5 turns out from bottom. I will idle wildly with a good bit of choke, dies without choke, and dies when i touch the throttle whether the choke is on or not. I have set float level and have a vacuum gauge and colortune...though they are useless until i get it idling right. My next step was to do a quick compression test. Any input would help!!! thanks guys

 

if it dies with choke on or off when you crack the throttle, it sounds like the slides are sticking.
what do the plugs look like when you let it idle for a minute?
have you checked for air leaks? did you break the rack apart when you cleaned?

 

For now, set the Pilots at 3 full turns,(or more) and adjust them later with the ColorTune. Use water on the header pipe to find the CYL that's not firing. You might still have a plugged Pilot circuit?

Get the running sync done, even with a higher idle. If you have to sync at 2,500, then start there. Sync again later. Check for possible air leaks, or a loose boot clamp? (I forgot a clamp once)

Double-check the carb sliders. I left a diaphragm folded over once. They don't lift folded over, but they still would idle.

 

all the slides were polished and operate like smooth sex I will adjust idle screws and check the boots and let you guys know what happens. Thanks for your help!!

Scott

 

ok..i adjusted screws 3.5 turns out. It no longer needs choke to start but as soon as it starts the revs start climbing until i freak and hit the kill switch. i checked float levels once already...but it feels like that may be a problem. Input????

 

okay, if the idle creeps up like that, you will need to adjust the idle screw between 2 & 3 to bring it down. that will set your baseline. take it out, ride it and see how it does. get it good and warm and then readjust the idle again to 1050.

 

Sounds like you botched the bench sync. No Prob.
Just work your way thru the running sync the best you can.
One of the outer butterflies can hold the whole rack open
Turn the sync adjuster for #1 and #4 clockwise 1/4 turn, retry.
Keep track of your turns.
Get on with the running sync.

 

i adjusted 1 and 4 sync screws like you said. seems to idle better. But i'm wondering if the readings on the vac gauge should be that crazy. Again I really appreciate your help... I'm more of a turbo honda guy and a jet engine guy..haha so i'm new to carbs!!

I posted a quick clip on youtube: idle xj650

another

 

You need a restrictor in the vac gauge line.
a "union" or butt-end connector with an inch of WD-40 red straw glued or epoxied in to restrict the vac pulses.
or rig up a quart glass bottle with 2 tubes so the pulses get absorbed into the volume. Or do both, for super smooth vac gauge readings.

http://www.xjbikes.com/Forums/viewtopic ... meter.html

You should eventually want to build this devise ^^ as it's accurate.
Your video didn't sound bad at all !!

 

I saw your comment in the second video- -
turned 1 and 4 another 1/4 turn,
NOPE !!
turn them back. you went too far. Get the sync right. Good luck.

 

alright...ill play around with the sync. I do have a wd40 tube restrictor and fuel filter baffle in place though lol