Topic: Struggling to get 82 650SC idling

[cmouta]

Hey guys and gals.  I'm starting to lose it with my newly acquired bike but I'm too stubborn to take it somewhere(and I doubt there are any locally knowledgeable sohc4 places in CT)

I can't get my bike to idle for the life of me.  Always stumbles and dies within 30 seconds or less.  Maybe someone can throw out some suggestions

List of what I have done:

Cleaned/Rebuilt(did not seperate) 82 CV carbs, new screw in slow jets, clear passages. Made sure to buy correct rebuild kit for nighthawk with 118main
new fuel accelerator rod and associated hardware
oil + filter change
k&N stock replacement air filter
new spark plugs(had it idling on a few occasions on 2+3, no spark on 1+4, maybe they got too fouled?)
new to me pulser generators to get all 4 cyl running
removed vacuum fuel shutoff valve
cam chain tensioned
cleaned fuel tank, raised higher to make sure gravity isn't an issue with inline filter/extra plumbing
added new inline filter
static timing check
visually confirmed synced throttle plate movement
visually confirmed synced choke operation
confirmed spark with a spare spark plug on all leads
all exhausts get hot fairly equally
plenty of fuel in the float bowls
Sprayed carb to engine boots with carb cleaner, bike didn't stumble.

Have NOT done valves but checked them quick and they seemed alright.  should still idle at least even if they were whacked out?

I've been messing with all sorts of mixture settings and main idle adjustment.  Yesterday I was at a point where I could get it idling moving choke to no choke back and forth.  Choke on would allow throttle to work, choke off the engine would die immediately on throttle input.

The closest I got was following the clymer manual which, I think maybe incorrectly, told me the mixture screw settings should be 2.5 out.  I got it to idle at 2k rpm, although it was backfiring like crazy so i didn't let it last long.  According to this motorcycleproject.com/motorcycle/text/specs.html I should be at 1.5 out.  I was at dancing around 1.5 last night to get something going. quarter turns up, down, all around, no dice.

Help! It's getting cold in CT and I want to ride!  Thanks!

[Mainerider]

When you say cleaned the carbs, did you just do the dip tank routine?  I repair bikes as a sideline and I can say from experience that using a true ultrasonic carb cleaner can make all the difference.  Hard to diagnose accurately over the computer but dying at the slightest throttle input usually indicates a clogged idle and/or slow speed circuit. 


Had that scenario many times and the $25 carb dip tank never did the job; my $900 ultrasonic cleaner has proven extremely effective at cleaning the passageways thoroughly. As a matter of fact, I handle the carb-cleaning for a local shop here in Maine and my cleaner , along with the appropriate chemicals, has cured countless idling problems.
  Find an automotive or mc shop that uses a quality cleaner (not a $79 Harbor Freight special) and get the rack cleaned properly.  Good luck.

[cmouta]

My carb cleaning consisted of blowing carb cleaner on everything and through the passages and making sure it spews out on the ends where it was supposed to  I was hoping that along with all new jets/o-rings/etc would get the job done.  Maybe I'll call some shops around and see what people have available.  thanks!

[curemode2002]

Also with the 650's if your tach is old and a little cranky you cannot count on the RPM's to give you an accurate read especially at the low end a portable digital tach is recommended.

[cmouta]

Did a valve adjustment.  Definitely improved the smoothness of throttle. Engine doesn't sound like its coming apart any more. Pulled the plugs which were completely fouled and carboned up from almost 100% idling/warming up in the last week or so. Put new ones in but will run it tomorrow and see what happens.  Seemed like it could idle when warming up and then struggled to do so once warm...

[brewsky]

plenty of fuel in the float bowls

Maybe too much?
Did you set the float height to spec?

[cmouta]

confirmed by the MacGregor carb rebuilding PDF, my bike has the brown floats that are non adjustable.

"The brown plastic floats on the ‘80s and later bikes are not adjustable as far as float height – if you have a float level issue with these floats, it’s likely your valve is bad or the wrong one for that model"

new valves from the rebuild kit.

I might try and replace the plug wires.  I guess the inexpensive route is to make my own?  They don't seem to be arcing but the outside ones have seen better days:


hopefully will run better with these replaced(they were new two weeks ago):

[cmouta]

She runs!!! new plugs seemed to really get the job done.  Had to play around a bit to get the idle stable but as soon as she was hanging around 1500rpm I rode her around for about 10-15 minutes.  Color me excited!

[iron_worker]

If your old plugs were fouling at idle then your new plugs likely will too unless you changed heat ranges.

You may need to adjust your idle mixture or change/clean idle jets.

IW

[cmouta]

well I believe they became fouled from almost 2 weeks of screwing around with idling and timing and mixture and  absolutely no riding on top of the 12 years of sitting.  Since there are new ones in and i'm able to ride around and maintain an idle to make adjustments, I'm hoping I should be ok.  mixture screws were set today at 1.5 turns out.

[cmouta]

Not yet sure what this means ultimately, but I just realized from reading a bunch of threads on the topic that the Honda dealership has given me Canadian spec NGK "R" plugs; resistance plugs.  I believe my US factory plug caps are 5K ohms and after swapping from NGK D8EA's covered in 2 weeks of crap from trying to idle, to new clean DR8ES-L's, my bike is now able to idle properly.  However it sounds like ive basically got 10kohm ignition lines which would effectively reduce my spark plug Current by half of stock?  Should I have any other concerns from this system?  I've read that the resistance is for noise interference but might it also affect engine performance?

From my quick research, it seems the L suffix means "half heat range", so my 8 is more like a 7.5 which based on this statement from another thread:

Cold-bloodiness in this part of the world has nothing to do with plugs heatrange.

Gotta vehemently disagree with this statement.  The CB550 was un-rideable with D8 until after a ten minute warm up.
Simple change to D7 and you could start and go with a bit of choke on, no matter how cold it was.
Plug heat range most definitely matters.

could explain why I feel like I need so little choke to get my bike to idle after the plug change!