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Stephan Rose - 11 May 2005 07:42 GMT

Hey,

I read in one of your other posts that you have had plenty experience
rebuilding motorcycle carbs, so thought I'd direct this question at
you, maybe you can help me out.

Couple weeks back, I had some mid-range issues. Namely, a very sudden
loss of power at around 9,000 rpms in any gear. I checked the sync on
the carbs, it was off a little. So I resynced them to where all 4
carbs are pulling the exact same amount of vacuum, and that problem
was fixed.

She's running way better now, but still not quite that smooth as I
think she could be. Any thoughts? Someone else has suggested drilling
out the anti tamper plugs and readjusting the idle screws, and I may
do that, but right now kind of wanting to keep that as a last-resort.

I've run some carb cleaner through the system, hasn't really helped
any. Spark plugs are brand new as well. Total miles on the bike are
around 16,500.

--
Stephan
2001 Yamaha YZF-R6

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nate - 11 May 2005 16:24 GMT

When you say she could be running more smoothly, are you talking about at
idle, half throttle, full throttle...? If it is at idle, your pilot circuit
could have gotten some crud in it (stuck in the pilot jets) and that could
cause it to run a little rough. At 1/2+ throttle, the same applies, but to
the main circuit, most likely your main jets.

How do the plugs look? Take a read at idle and after a a few minute ride on
the main jets (cruise at low rpms in a lower gear such that you have to give
it 1/2 throttle to keep her going). Then cut the throttle and pull the
clutch and do another read. This will be your best indication of what is
running lean/rich, etc.

I've had so much experience with motorcycle carbs lately, it's ridiculous.
Trying to get an old Suzuki GS bike back on the road :-)

Let me know if I can be of any more assistance.

> Hey,
>
[quoted text clipped - 20 lines]
> Stephan
> 2001 Yamaha YZF-R6

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Stephan Rose - 12 May 2005 03:10 GMT

>When you say she could be running more smoothly, are you talking about at
>idle, half throttle, full throttle...? If it is at idle, your pilot circuit
[quoted text clipped - 7 lines]
>clutch and do another read. This will be your best indication of what is
>running lean/rich, etc.

Plugs are brand new. Don't really think I can do that test all too
well though because its a royal pain to get to the plugs. Can't remove
them without talking half the bike apart, its impossible. And even
then its difficult, frame really gets in the way bad on plug 1 and 4.

>I've had so much experience with motorcycle carbs lately, it's ridiculous.
>Trying to get an old Suzuki GS bike back on the road :-)

And I'm being forced to learn fast lol!

>Let me know if I can be of any more assistance.

Come over and fix my carb? =)

Well, to elaborate on the problems a little bit more.

It's worst when she's cold. Gets better as she heats up.

Problems are mostly in low to mid throttle and low-mid range rpms. At
idle, I can hear the engine randomly for a split second idling faster,
than dropping back down.

Now I do remember this, a few weeks ago, when I first had the
problems, I took it by a shop and they did a quick check and we found
that the exhaust pipe on the header for cylinder number 1 was at
around 160 degrees VS 400 degrees on the other 3. So something
definitely wasn't right w/ that cylinder. This is also when I had the
sudden power loss at 9,000 rpms. But as I've said before, resyncing
the carbs solved that, and it was mainly that cylinder that I had to
make most the adjustments on. So I figured that it probably wasn't
getting a combustible mixture all the time.

However I'm wondering if maybe that cylinder still is not always
firing. If that were the case, it would explain the idle bouncing
around like that if the cylinder was randomly going on/off.

I guess maybe I should go buy a thermostat that can handle the exhaust
pipe temps and check the temperature on that pipe and see if there
still is a temperature difference.

--
Stephan
2001 Yamaha YZF-R6

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Richard - 12 May 2005 05:15 GMT

Have zero knowledge of bikes but what you are describing sounds like it
could be an ignition coil issue. Faulty or a bad connection?

Signature

Richard

'94 GT 'vert
Under Drive Pulleys
Transgo HD2 Reprogramming Kit
High Stall Torque Converter
4:10 Gears
Gripp Sub Frame Connectors (welded)
FRPP Aluminum Drive shaft
FRPP M5400-A Suspension
Laser Red

> >When you say she could be running more smoothly, are you talking about at
> >idle, half throttle, full throttle...? If it is at idle, your pilot circuit
[quoted text clipped - 51 lines]
> Stephan
> 2001 Yamaha YZF-R6

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Stephan Rose - 12 May 2005 05:50 GMT

>Have zero knowledge of bikes but what you are describing sounds like it
>could be an ignition coil issue. Faulty or a bad connection?

I've thought about that too. It does have an individual coil for each
plug, so yea it may be possible that coil 1 is possibly bad. I suppose
I need to actually tear it all apart again and check the resistance on
it.

--
Stephan
2001 Yamaha YZF-R6

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