Author Topic: 5k Idle, Ive checked the usual stuff (Read 2009 times)

ncstatecamp · « **on:** May 28, 2013, 01:05:30 PM »

got my wiring done and she fires right up, with one miner issue... she revs immediately to 5k and wont go down. Ive sprayed the boots no leaks there, bench synced with a 3/16 drill bit, air screws are 540 (1.5 turns) degrees out from seated and the idle screw isnt even touching. Its a 750k2. The carbs are rebuilt to manual specs (it was awhile ago but they just sat clean and dry). It will rev up just fine as well. If I put on the choke it slows it down a tad but rumbles a bit. Currently no airbox just for tuning purposes. Any ideas?

iron_worker · « **Reply #1 on:** May 28, 2013, 01:13:32 PM »

How many threads are showing above the locknut on the sync adjusters? (top of the carb) It should only be 1 or *maybe* 2 threads. Any more and you may not be allowing the slides to fully seat onto the floor of the carb throat. Using the drill bit method you may have set all of the slides the same but you may have also set them all too high.

Also check that the throttle cables are free and not somehow binding.

IW

ncstatecamp · « **Reply #2 on:** May 28, 2013, 01:20:46 PM »

So this is the culprit then?

TwoTired · « **Reply #3 on:** May 28, 2013, 01:23:38 PM »

Quote from: ncstatecamp on May 28, 2013, 01:05:30 PM

bench synced with a 3/16 drill bit,

Probably the problem right there.

With the main idle knob backed out, can all the slides get fully closed? Fairly easy to see if there are no filters on the carbs.
The slide cutaway will not fully close, but the engine side must have shut off control via the idle knob.

flybox1 · « **Reply #4 on:** May 28, 2013, 01:33:07 PM »

Quote from: TwoTired on May 28, 2013, 01:23:38 PM

Quote from: ncstatecamp on May 28, 2013, 01:05:30 PM
bench synced with a 3/16 drill bit,

Probably the problem right there.

With the main idle knob backed out, can all the slides get fully closed? Fairly easy to see if there are no filters on the carbs.
The slide cutaway will not fully close, but the engine side must have shut off control via the idle knob.

+1
need to set the idle screw so the slave slide is down on on the bit before you bench sync 1, 3 and 4.
if no slave carb, then you need to turn the idle set screw in +/- 2 turns, and bench sync from there, so that when you are done, turning the idle set screw out lowers the slides completely.

ncstatecamp · « **Reply #5 on:** May 28, 2013, 01:40:49 PM »

So I have the idle screw not touching and the lock nut/setting nut as far out and it still won't seat, none are holding it back.

flybox1 · « **Reply #6 on:** May 28, 2013, 01:44:27 PM »

exactly. reread my post.
you bench sync'd the carbs with the idle set screw OUT. positioned like that, it cant drop the slides lower than where you set them during the bench sync ....it needs to be in a few turns and set the slides from there.

74750k4 · « **Reply #7 on:** May 28, 2013, 01:47:37 PM »

With my new "street/touring" DP117KHD cam, my idle cannot be any lower than 2000, or it dies. The carbs were working fine on the stock cam. Tried air screws in/out helps only very marginally. Any setting below 2000 RPM kills the engine. I have Kibblewhite HD valve springs. That shouldn't be causing enough extra friction to kill it, should it? Maybe new idle jets are in my future??? I know I need bigger mains, because in higher gears at WOT around 7000-up, it sputters unless I back off a bit, then it regains the lost fuel mix, and acceleration continues.

flybox1 · « **Reply #8 on:** May 28, 2013, 01:52:42 PM »

ncstatecamp · « **Reply #9 on:** May 28, 2013, 01:53:55 PM »

Looking at the pics I posted how far off are the slides? I mean they have to be slightly open for a bit of air to come through right?

flybox1 · « **Reply #10 on:** May 28, 2013, 02:00:42 PM »

when the idle screw is all the way out, the slides should be all the way down (no light)
when your bike is to operating temp, you will set the idle with the idle set screw, and at that time, there will be space for air to come through.

your idle set screw WILL be touching, and should even turned in a little when you get your bike to idle nicely.

ncstatecamp · « **Reply #11 on:** May 28, 2013, 02:04:25 PM »

Ah alright that makes sense. Do I need to pull them to get them adjusted? I just tried adjusting them (everything's loose) and nothings moving

flybox1 · « **Reply #12 on:** May 28, 2013, 02:07:43 PM »

best to remove them. is your carb #2 your slave carb?

ncstatecamp · « **Reply #13 on:** May 28, 2013, 02:10:49 PM »

I don't think I have one, but I don't really know how to tell

iron_worker · « **Reply #14 on:** May 28, 2013, 02:12:30 PM »

750K2 won't have a slave carb. I think those came in the 77-78 models once emissions regulations started to become more strict. They tried to prevent tampering with the carbs by making one of them non-adjustable.

IW

flybox1 · « **Reply #15 on:** May 28, 2013, 02:15:06 PM »

thanks IW

ok, NC, once you get your carbs off, turn your idle set screw in 2 full turns from its 'just touching' position, and then, do your bench sync with your 3/16" bit.
when you are finished, all slides should bottom out when you turn the idle screw all the way out.
if they do, then you are good to put them back on and hopefully vac sync.

edit ...and i cant see any pictures, either

TwoTired · « **Reply #16 on:** May 28, 2013, 02:42:24 PM »

I'll just ask, since I can't see any pics.
You sure the slides weren't put in backwards? The bottom cutaway should face the air inlet/air cleaner.

bjbuchanan · « **Reply #17 on:** May 28, 2013, 05:32:43 PM »

I've always wondered how you could put the slides in backwards. Not being smart, but there is the little locator tab and the obvious cut out for it, not to mention the slide can't go in 180 opposite because it won't seat

TwoTired · « **Reply #18 on:** May 28, 2013, 05:54:49 PM »

Quote from: bjbuchanan on May 28, 2013, 05:32:43 PM

I've always wondered how you could put the slides in backwards. Not being smart, but there is the little locator tab and the obvious cut out for it, not to mention the slide can't go in 180 opposite because it won't seat

Some have swapped the slides from 3&4 with 1&2, this makes all the slides installed backwards even though the locator tab and slide slot are aligned. Of course, they don't seat properly and racing idle is but one symptom.

ekpent · « **Reply #19 on:** May 28, 2013, 09:27:14 PM »

Be nice if your picture worked to see the amount of threads showing on the slide adjusters at the carb tops. Anyways to fix it you will need to loosen the 4 locknuts on the carb tops and back those adjusters off to give you enough headroom in the slide position to allow the idle screw to function again. Shouls have just a couple threads showing above the lock nut as has already been mentioned.

lucky · « **Reply #20 on:** May 29, 2013, 07:23:26 PM »

I think the clue is in the first post when he said he used a 3/16" drill bit!
That would open up the slide at least .180 thousandths!!!!
.008 thousands will make a big difference.

ncstatecamp · « **Reply #21 on:** May 30, 2013, 04:01:20 PM »

Idk why my pics weren't working.... Here's what I've got now (if the pic work....) though I'm worried bc now I have no threads showing, like the lock nuts might fall out... And before I think I used an 1/8 now a 3/16

ncstatecamp · « **Reply #22 on:** May 30, 2013, 04:04:24 PM »

Damn tapatalk app

flybox1 · « **Reply #23 on:** May 30, 2013, 05:32:56 PM »

Ok. Those pictures came thru.
Turn all the cap screws in so that 2-3 threads are showing on each. As is you won't have any adjustment room during a vacuum sync.
Once you have them all looking the same, do your bench sync. 2 turns in from lightly seated on your idle set screw, and with the 1/8 bit.

ncstatecamp · « **Reply #24 on:** May 30, 2013, 05:51:25 PM »

Got it set back up, runs at idle 1200 just fine any lower it cuts out. Now I just need to make some adapters to vac sync

ncstatecamp · « **Reply #25 on:** May 30, 2013, 05:53:25 PM »

It also might just be my meters a bit off. Anybody know the thread size and rate?

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Author Topic: 5k Idle, Ive checked the usual stuff (Read 2009 times)