CBR600 F2 idles a bit roughly
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CBR600 F2 idles a bit roughly Phil, Non-Squid 03-21-2007
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Posted by Phil, Non-Squid on March 21, 2007, 8:57 pm
How smoothly should a carb'ed bike idle? I was B-12'ing my F2 and I've been
wondering: it does a sort of rumbly bit where it sounds like it's a bit
starved for air/fuel for a second or two, then revs up another 50-100 rpm
momentarily, then goes back to starved mode. It's been this way since I
bought it last year. All the FI bikes I've heard have a perfectly contant
idle without rumbling. The idling performs similarly at ~2000 rpm as it
does at 700 rpm, so my guess is that the idle passage(s) isn't all that bad.
What do you guys think?

BTW, my LED and battery fixer-uppers from 9 months ago have worked
beautifully. I don't worry about the RR anymore and just charge the batt
through an external harness from Radio Shack every few weeks.

--
Phil



Posted by John Johnson on March 21, 2007, 8:44 pm

> How smoothly should a carb'ed bike idle? I was B-12'ing my F2 and I've been
> wondering: it does a sort of rumbly bit where it sounds like it's a bit
> starved for air/fuel for a second or two, then revs up another 50-100 rpm
> momentarily, then goes back to starved mode. It's been this way since I
> bought it last year. All the FI bikes I've heard have a perfectly contant
> idle without rumbling. The idling performs similarly at ~2000 rpm as it
> does at 700 rpm, so my guess is that the idle passage(s) isn't all that bad.
> What do you guys think?
>
> BTW, my LED and battery fixer-uppers from 9 months ago have worked
> beautifully. I don't worry about the RR anymore and just charge the batt
> through an external harness from Radio Shack every few weeks.

A well-tuned carb setup will idle perfectly evenly. In a carbureted
engine, such stumbling or "hunting" is often either a result of clogged
passages or a result of carbs in need of synchronization. Unfortunately,
you really can't synchronize properly unless you know that your carbs
are clean.

In any case, procedures for both (sounds like you've got cleaning
already) may be found in the group's archives. I've posted on carb synch
before, for certain.

--
Later,
John

johajohn@indianahoosiers.edu

'indiana' is a 'nolnn' and 'hoosier' is a 'solkk'. Indiana doesn't solkk.

Posted by Phil, Non-Squid on March 22, 2007, 1:56 am
John Johnson wrote:
>
>> How smoothly should a carb'ed bike idle? I was B-12'ing my F2 and
>> I've been wondering: it does a sort of rumbly bit where it sounds
>> like it's a bit starved for air/fuel for a second or two, then revs
>> up another 50-100 rpm momentarily, then goes back to starved mode.
>> It's been this way since I bought it last year. All the FI bikes
>> I've heard have a perfectly contant idle without rumbling. The
>> idling performs similarly at ~2000 rpm as it does at 700 rpm, so my
>> guess is that the idle passage(s) isn't all that bad. What do you
>> guys think?
>>
>> BTW, my LED and battery fixer-uppers from 9 months ago have worked
>> beautifully. I don't worry about the RR anymore and just charge the
>> batt through an external harness from Radio Shack every few weeks.
>
> A well-tuned carb setup will idle perfectly evenly. In a carbureted
> engine, such stumbling or "hunting" is often either a result of
> clogged passages or a result of carbs in need of synchronization.
> Unfortunately, you really can't synchronize properly unless you know
> that your carbs are clean.

I just B-12 every few months, making sure to let it idle for 10 minutes to
get that stuff into the idle jets. I never notice any difference, though.
I'm going to sell the bike later this month so I thought I would get
everything to as tip-top a shape I could get it without too much labor.
I've already done enough with this one.

> In any case, procedures for both (sounds like you've got cleaning
> already) may be found in the group's archives. I've posted on carb
> synch before, for certain.

Eech... It runs well enough as it is... I'd rather leave the tank and airbox
on. My next bike will be FI all the way.

--
Phil



Posted by Potage St. Germaine on March 22, 2007, 12:22 am
wrote:
The idling performs similarly at ~2000 rpm as it
> does at 700 rpm, so my guess is that the idle passage(s) isn't all that bad.

700 RPM idle is awfully low. I would expect the specified RPM to be
around 1100.

What does the white EPA sticker say the idle RPM is supposed to be?

The sticker will probably be under the seat or on the airbox, but I
have seen EPA sticker under the sidecovers.



Posted by Phil, Non-Squid on March 22, 2007, 1:26 am
Potage St. Germaine wrote:
> wrote:
> The idling performs similarly at ~2000 rpm as it
>> does at 700 rpm, so my guess is that the idle passage(s) isn't all
>> that bad.
>
> 700 RPM idle is awfully low. I would expect the specified RPM to be
> around 1100.
>
> What does the white EPA sticker say the idle RPM is supposed to be?
>
> The sticker will probably be under the seat or on the airbox, but I
> have seen EPA sticker under the sidecovers.

I was just testing the idle to see if it would run at all at the low RPMs...
I figured if the idle passages were clogged, that's the RPM range where I'd
find it. But it was like that at any lowish RPM. Not sure at which point
the other jets and passages come into play.

BTW, my bike is heavily modded and chopped up... aftermarket fairings, the
trunk was cut out of the frame, seat is devoid of any stickers... No white
EPA sticker on mine. I typically run it smoothly between 1200 and 1500. A
bit high, I know, but it never bugged me enough to bother.
--
Phil



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