Low idle RPM and engine cuts off when revving too gently

[manlio]

Hi there,

my Rock has almost 36,000 m and is ready for full service. However, lately I have experienced something new: when I rev up too gently from idling (at a light or a stop) the engine dies. If I give the throttle a firmer, more aggressive turn, the engine will just rev up normally. It's driving me nuts.
I also noticed yesterday that generally the idle RPM seems too low, with the needle between the 600 and 800 lines on the tach.
I assume these two things may be related.
Any idea of what this may be and how to solve it?

thanks a lot, as usual,

Manlio

[rdsmith3]

The usual suspects for servicing would be adjusting the valves and synchronizing the throttle bodies. Do you know when the fuel filter was last changed?

[NoRRmad]

Idle RPM should be 1100.

You might want to do a throttle-body sync and adjust the Big Brass Screws on the throttle body (with the twist-grip untouched.)

[andre]

Sorry I can't help with your problem, but I wanted to let you know that to me, the opposite happens .... if I rev it up gently it has no problem, if I rev it up harder sometimes it dies .....
good luck
Andre

[boxermania]

Check the basic maintenance vdeos a couple of posts down

[jfslater98]

The idle for these bikes is recommended to be 1100. So you're just about at "stall speed" where you are now. If you're doing the 36K yourself, poke around teh interwebz for throttle body synchronization instructions. The Big Brass Air Screws sound like they need to be let out a little bit.

Or let your mechanic know what's going on. Good luck, keep us posted!

[manlio]

the fuel filter was replaced at the 24,000 miles service, the throttle and body sync with valve adjustments at 32,000, when a canister-ectomy was also performed.
I trust you guys are right, so that the 36,000 miles service should take care of it. Even though I am mystified that after only 4,000 miles the valves and throttle sync are so out of tune to create this issue that I have never experienced before.

will keep you posted. thanks for the help

[macx]

Another possible suspect might be the tps adjustment, altho there should
be no reason for that to change any more than the other things that had
recent adjustment or attention unless something's loose.

You mention the cannister removal - if this started after that, especially
fairly soon after that, a small vacuum leak might also be a possible suspect.
This could also explain the low idle due to a leaned out air fuel mix from
the extra air from a vacuum leak.

Seems like you might not be getting enuf fuel at idle and under gentle
acceleration, but more vigorous application of the throttle would provide
extra fuel.

[CycleRob]

when I rev up too gently from idling (at a light or a stop) the engine dies. If I give the throttle a firmer, more aggressive turn, the engine will just rev up normally

This points directly to a TB synch. If the right TB butterfly is opening before the left side TB -or- the blue painted idle stop screws were tampered with your bike will run as described. The fact the idle is low is also a clue something isn't right.
There are other possibilities like one too tight valve clearance or a burnt valve that will also give a low idle and poor response.

I have seen guys synchronize just the idle settings without checking or doing the "on throttle" (OT) adjustments. On most multi cylinder bikes the OT adjustment is the same as the idle synch, but NOT on our Air/Oil/Hex Heads.

.

[scubas42]

I have had some throttle cable problems lately and in my searching your problems came up several times. I'm sure there are other people here who could help you more but you might want to check the accelorator and both throttle body cables for wear and make sure the ends are seated right. Good luck.