idle problem

When my xj 550 gets warm, the idle jumps up to about 2500 - 3000. I sprayed the whole thing , well just the intake boots, down with wd, looking for leaks, but found none. # 3 cylinder is running cooler than the rest at idle, so I changed the battery, as it has a tendency to run cooler than the rest with a weak battery, and i had a new one laying around to put in. then earlier today, I adjusted the mixtures, 2 3/4 turns out , then tried to tweak for optimal idle. Well, after the bike warmed up nicely, the idle went back up again. This time, I noticed if I put my hand on the brake, or foot on brake, or turned high beams on, or hit turn signal, the idle would come back down , so I am figuring it is electrical at this point. I turned the idle screw out about an eighth turn to bring the idle back to normal. Any ideas, suggestions, comments ????????

 

drop how many rpm and from where?

 

at idle, when nice and warm, idles around 2500 - 3000 (parked) when I put the electrical load on, it drops down to about 1250 - 1500, the more load, the more the drop

 

Boys & Girls:

Here we go, again! What defines this issue? Basically ... "Load"

Place "Load" on electrical system ... performance decreases.
The "Load" is NOT being -- Regulated. Insufficient power is being delivered to the system to be regulated. Consequently, the whole load is being supplied by the available amperage in the battery.

As the load increases ... (lighting, brake lights ... etc.) - the revs fall-off.
Sure they do!
The COILS primary circuit is undoubtedly under-powered.

Hook-up a voltmeter to the battery.
A new battery should be at 12V or maybe even 12.5
Start the bike.
The voltage should NOT show a significant drop.
Add some power increasing the rpm's gradually through the 1,000 - 1,500 range.
The Voltage should gradually INCREASE with the additional rpm's.
At 15-hundred -- maybe 17-50 ... the Voltage should be 14.5V - Steady.

Observations:
Voltage drops steadily ...
BRUSHES.
Voltage increases marginally ... fluctuates BELOW 12V then, falls-off (with a possible brief jump to restore power consumption ...
REGULATOR > Possibly arcing brushes > Brushes.

Check brushes.
Check Regulators plastic connection block to wiring harness for high-temp around the Red wire.

Brushes not within Service limit.
Replace brushes.
Connection melted around the blade connector on the Voltage Regulator's Plastic Quik-connect.
Replace regulator -- AFTER troubleshooting electric problems related to power supplied to regulator.

If you left the battery hooked-up and supplied a charging current to the battery which was high-amp ... Battery charger on BOOST -- Car battery with car RUNNING ...

Stick a fork in the regulator ... it's cooked!

 

new battery 12.7 volts
idle @ 1000 rpm 12.7 volts +/- a few points
idle @ 1250 +/- 14.5 volts +/- a few points
idle @ 1500 rpm 14.5 volts +/- a few points
3000 rpm 14.7 volts

shoule I assume the brushes are starting to go, and start by pulling the cover and checking them

 

oh, i forgot to say, this holds true:

Hook-up a voltmeter to the battery.
A new battery should be at 12V or maybe even 12.5 I had 12.7
Start the bike.
The voltage should NOT show a significant drop. didnt
Add some power increasing the rpm's gradually through the 1,000 - 1,500 range.
The Voltage should gradually INCREASE with the additional rpm's. it did
At 15-hundred -- maybe 17-50 ... the Voltage should be 14.5V - Steady.yeppers

 

No. Those numbers are good.

I guess we should peek at the coils. Integrity of the casings.
Condition of the wire grounding the coils to the frame. (Clean the eyelet and shine the grounding spot to bare metal.

Test the coil primary's and secondary's.
"The Book" says:
Primary's at: 2.5 ohms (+/-) 10%
High-tension secondary's: 11,000 ohms (Std OEM Coils - Higher on aftermarket performance coils if so equipped.)

I doubt it's the coils. They usually work off a bike that's been outside at a bone-yard for years! Only takes a few minutes to check them, though ... so, why not!

 

well, I won a set of coils on ebay the other day, should be here within a day or so, so I will check them and make sure they are good, and then check mine and see what they are. Would do it now, but my multimeter is at work, maybe tomorro at lunchtime. At least if mine are going I have a replacement set.

I should mention that after I did the carbs yeaterday and the new battery, while idling for an extended period, is when the rpms went up. A little later in the day, I took it for a 10 mile ride for ice cream, and when I stopped, the idle was at normal. Also when I returned it was normal too. I took it to work today (I take it everyday almost) and idle was normal both on way there and on way home (only 3 mile ride tho), but it wasnt running high at the stop lights

It used to only idle high after cruising around at 65 - 70 for 15 or 20 miles, then it started to idle high after just a few minutes at 45 - 55 , however last nite and today it was idling normal. Guess I gotsta take it for a longer ride at higher rpms to see how it acts now.

 

are your carbs synced? i would also check your throttle shaft seals to see if they are old and cracked... i had the same preoblem on my bike when it was synced... i had to deliberatly de-tune them until i got parts to keep the idle below 4000 you have two problems going on, your high idle is not related to your idle drop when putting load on the electrical circuit.

 

Spot ON.......