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Another Idle Adjustment Question

5K views 23 replies 11 participants last post by  slimvulcanrider 
#1 ·
My bike has been idling a bit low lately - to the point it sometimes dies when I stop. I tried adjusting the knob some. It seems to help a little but doesn't seem normal.

When I turned the idle up - it idles ok but when I'm riding it acts as if the throttle isn't releasing when I let go (like when I shift gears) - or almost like the choke is in use.

One thing I noticed is when I turn the knob the entire line/hose turns with it - is this normal? (see picture).

I haven't looked too deeply into it yet but wanted to get some opinions.

Thanks in advance
 

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#2 ·
Sounds to me like you just havnt found the sweet spot yet. If its dying when you come to a stop sign (and its already to running temp) your idled too low. If you let off the throttle and its still revving, your idled too high and its still burning the extra amount of fuel left in the carbs. And yes its normal for the cable to spin when you turn the knob. The knob is connected to the cable and on the other end of that fable is a threaded adjusting pin going into the carbs.
 
#11 ·
Well I think I am narrowing in on the "sweet spot" as you put it. Seems to be 2-1/2 to 2-3/4 turns out for me. However...... When I give it some throttle it still stays at the high RPMs before slowly coming back down (3 - 5 seconds).

And when I took it for a short ride - it's still staying "revved up" during my shifts. I get it up to around 3k and let go the throttle, clutch in to shift, RPMs still at 3k.

I'm not sure where to start looking. The throttle seems to have 3-4mm of play in it.

I do know the air filters are probably due for a good cleaning - could that have any factor in it?
 
#3 ·
Our bike should idle at 1100 rpm. Once you get it to running temp, adjust your idle to this & you should be good.
If your still dying when you come to a stop then something else is not right.
 
#6 ·
Sorry Kanuck, not correct. You would turn the screws in to make the carbs leaner. Factory settings were around 1 1/2 turns out for a leaner engine ( EPA ). We all go to about 2 1/2-3 turns out to make the mixture richer.
 
#8 ·
Haven't got to look at it yet, but mine was idling too high when I got back to town after a hard run on the slab for 15 miles in the heat.

She was slightly warmer than I'd ever seen (just on the right half of the symbol) and I dropped the idle to 1100, then shut her down.

Just went out and started her up, cool, it's idling 500-600, and needs set back up to 1100.

Maybe the adjustment just walked up on it?
 
#10 ·
Haven't got to look at it yet, but mine was idling too high when I got back to town after a hard run on the slab for 15 miles in the heat.

She was slightly warmer than I'd ever seen (just on the right half of the symbol) and I dropped the idle to 1100, then shut her down.

Just went out and started her up, cool, it's idling 500-600, and needs set back up to 1100.

Maybe the adjustment just walked up on it?
I highly doubt that. With the way the idle adjuster is setup, the engine would need to be vibrating pretty good for the adjuster to turn on its own. What were the RPM's before lower them to 1100? The bike will run slower when cold then warm. Don't readjust until the bike is at operating temp. If it struggles to stay running or won't start when cold, use the choke. Back off the choke anytime the RPM's climb passed 2000 until it stops climbing or the bike will run on its own w/o choke.
 
#9 ·
on my bike, if the engine is cool, it wont idle at all unless I pull a little choke.. will start quickly, just wont idle.

This is in SW florida, with 90+ days... takes about 2 minutes (maybe less in the heat) to get it to idle with no choke.

when it is idling with no choke, im right at 1100
 
#14 · (Edited)
I don't have a clue what those are :doh:

Are they something that suddenly go bad?
The choke operates them...Mine appear / suspect are deteriorated enough to leak.

Not that I know of...

We need some carb experts to offer their thoughts....

:smiley_th
 
#15 · (Edited)
Although no expert, I might be some help.

Rpm's staying up. If new to the VN, get a manual, adjust your throttle cables. The return cable should be adjusted first and has no play. Verify throttle closing using your finger. The opening cable should then be adjusted to the prescribed play. 3mm I think. If the rpm's still stay high, I would look for an intake leak. Though not easy, you can verify the choke plungers are bottomed when the choke is off.

Pilot air adjustment screws. JM is correct, out=richer, in=leaner. I confess, I have not mapped a CVK 34 but see no reason for these to be different. It is an air screw and you are increasing air, however that air is coming from the cylinder. You are increasing the 'draw' on the front orifice of the pilot circuit.

Idle speed changes from hot to cold. Set the idle hot, the bike should then idle low cold even on a 90* day. Exceptions are if the bike is rich enough to somewhat choke itself.

HTH..............
 
#19 ·
after a little 'research' I know what the diaphragm for the slide is now. I'm not sure how that would be checked unless I take the carburetors off the bike - is that the only way?

I think I know what the carb boots are that you are talking about. What do you guys recommend as the best way to check for a vacuum leak at the boots?
 
#20 ·
boots are easy to check... start the bike and let it warm up for a few minutes, then spray wd-40 around the rubber boots that connect the crabs to the cylinders. if the rpm stumbles or engine dies you have a vacuum leak, if not that its not a carb boot vacuum leak. The carb diaphragms can only be checked off the bike (as far as I know).
 
#22 ·
You can even use water to check for vac leaks, a pinstream is best, If there's a leak you'll get a stumble when it suck it in, and eventually with enough water ingestion you'll get steam out the pipe. Plus side with water like that, it will also clean carbon out, but that's another procedure.

If you can get a finger into the carb throat, slide or bend the boot aside just enough, quickly lift the slide all the way up and drop it. You should hear a whoosh-whoosh from the diaphragm both ways, it should not drop in free fall, should feel some light resistance when lifting. There's a youtube video somewhere close on the list.
 
#23 ·
Well I tried the WD40 test on the carb boots. I couldn't tell that it made any difference in the way the engine was running. I tried several times. After the bike started and warmed up, and also after taking it for a short ride.

Is there someplace else to check for a vacuum leak?


If you can get a finger into the carb throat, slide or bend the boot aside just enough, quickly lift the slide all the way up and drop it. You should hear a whoosh-whoosh from the diaphragm both ways, it should not drop in free fall, should feel some light resistance when lifting. There's a youtube video somewhere close on the list.
Is there a way to check that slide with everything still on the bike?
 
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